Tramadol suppresses growth of orthotopic liver tumors via promoting M1 macrophage polarization in the tumor microenvironment

Tumor-associated macrophages (TAMs) are major infiltrating immune cells in liver cancer. They are polarized to anti-tumor M1 type or tumor-supporting M2 type in a dynamic changing state. Tramadol, a synthetic opioid, exhibits tumor-suppressing effect in several cancers, but whether it plays a role in TAMs polarization is uncertain. In the present study, the potential influence of tramadol on TAMs polarization was explored in liver cancer. An orthotopic murine Hepa 1-6 liver cancer model was constructed. The potential function of tramadol was evaluated by cell viability assay, EdU incorporation assay, flow cytometry, immunofluorescence, quantitative real-time polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA) assay, T cell proliferation and suppression assays and western blot. We found that tramadol suppressed proliferation and tumor formation of murine Hepa 1-6 cells in vitro and in vivo. Tramadol reprogramed the immune microenvironment to favor M1 macrophage polarization in orthotopic Hepa 1-6 tumors. Moreover, tramadol facilitated M1 macrophage polarization and inhibited M2 macrophage polarization of bone marrow-derived macrophages (BMDMs) and human THP-1 macrophages in vitro. Furthermore, tramadol-treated BMDMs promoted proliferation and activation of splenic CD4+ and CD8+ T cells. Tramadol induced cellular ROS production and mitochondrial dysfunction of BMDMs. Finally, tramadol activated NF-κB signaling in BMDMs and THP-1 macrophages, while inhibition of NF-κB signaling by JSH-23 attenuated the influence of tramadol on macrophage polarization. In conclusion, these data elucidated a novel anti-tumor mechanism of tramadol in liver cancer. Tramadol might be a promising treatment strategy for liver cancer patients.

Evaluation of histological and ultrastructural changes provoked by prenatal tramadol on postnatal cortical cerebellar neuronal development in rats: possible implication of Ki67, GFAP and MicroRNA-7/P53 signalling trajectories

Tramadol is a novel centrally acting analgesic. Despite, its implementation during pregnancy may impair neuronal survival and synaptic development in neonatal cerebella. The current investigation assessed the histological and ultrastructural alterations in postnatal cortical cerebellar neuronal development induced by prenatal tramadol. 30 offsprings were divided to control group I: fifteen pups born to mothers given saline from D10 till D21 of gestation. Tramadol-treated group II: fifteen pups born to mothers received tramadol HCL (50 mg/kg/day) from D10 till D21 of gestation. Pups were categorized into three subgroups (a, b, and c) and offered for sacrifice on the seventh, fourteenth and twenty-first post-natal days. Light microscopic examination revealed the overcrowding and signs of red degeneration affecting purkinje cell layer. Neurodegenerative signs of both purkinje and granule cell neurons were also confirmed by TEM in form of chromatin condensation, dilated Golgi channels, disrupted endoplasmic reticulum, marked infolding of the nuclear envelope and decrease in granule cell precursors. In addition, the astrocytic processes and terminal nerve axons appeared with different degrees of demyelination and decreased number of oligodendrocytes and degenerated mitochondria. Furthermore, group II exhibited an increase in P53 immune expression. The area percentage of apoptotic cells detected by TUNEL assay was significantly increased. Besides to the significant decrease of Ki67 immunoreactivity in the stem neuronal cell progenitors. Quantitative PCR results showed a significant decline in micro RNA7 gene expression in tramadol treated groups resulting in affection of multiple target genes in P53 signaling pathways, improper cortical size and defect in neuronal development.

Effect of Intraligamentary Tramadol Hydrochloride on Anesthetic Success During Endodontic Management of Mandibular Molars: A Randomized Clinical Controlled Trial

OBJECTIVE

Tramadol hydrochloride has shown local anesthetic properties similar to lidocaine, apart from a central analgesic effect. The present study evaluated the effect of the administration of tramadol alone or in addition to 2% lidocaine, as supplementary intraligamentary injections.

METHODS

One hundred and five patients, with a failed primary inferior alveolar nerve block (IANB), were randomly allocated to one of the three supplementary intraligamentary groups: 2% lidocaine with 1: 80,000 epinephrine; tramadol hydrochloride (50 mg/mL); and 2% lidocaine with 1: 80,000 epinephrine plus tramadol hydrochloride. Patients received 1.2 mL doses (0.6 mL of each root). Patients reporting pain ≤54 on Heft Parker visual analogue scale (Heft-Parker VAS), were categorized as successful anesthesia. A finger pulse oximeter was used to measure the heart rates. The anesthetic success rates, gender, and type of tooth were compared using the Pearson chi-square test. The heart rates and age were statistically evaluated using the one-way analysis of variance test. The level of significance was set at 0.05 (p=0.05).

RESULTS

The initial IANB was successful in 31% of cases. There were significant differences in the anesthetic success rates of different supplementary intraligamentary injections (χ2= 33.6, p<0.001, df=2). The 2% lidocaine-plus-tramadol resulted in significantly higher success rates than the two groups. There were no significant changes in the baseline heart rates of all groups (p>0.05).

CONCLUSION

The addition of tramadol to 2% lidocaine with 1: 80,000 epinephrine, given as supplementary intraligamentary injection, can help in achieving successful anesthesia during the endodontic management of mandibular molars with irreversible pulpitis resistant to IANB injections.

Effects of tramadol via a µ-opioid receptor on pancreatic ductal adenocarcinoma in vitro and in vivo

INTRODUCTION

Tramadol, a weak opioid anesthetic, is used for pain management in patients with cancer, but the effects of tramadol on cancer via µ-opioid receptor are still unknown. We assessed the effects of tramadol on pancreatic ductal adenocarcinoma using transgenic mice (LSL-KrasG12D/+; Trp53flox/flox; Pdx-1cre/+ ).

METHODS

Six-week-old transgenic mice were orally administered 10 mg/kg/day tramadol (n=12), 10 mg/kg/day tramadol and 1 mg/kg/day naltrexone (n=9), or vehicle water (n=14) until the humane endpoint. Cancer-related pain and plasma cytokine levels were assessed by the mouse grimace scale and cytokine array, respectively. Tumor status was determined histopathologically. Tramadol's effects on proliferation and invasion in pancreatic ductal adenocarcinoma cell lines were studied in vitro.

RESULTS

Tramadol with/without naltrexone improved mouse grimace scale scores while decreasing inflammatory cytokines such as tumor necrosis factor-α and interleukin-6. Proliferative Ki-67 and cyclins decreased by tramadol, while local M1-like tumor-associated macrophages increased by tramadol, which was blocked by naltrexone. Meanwhile, tramadol with/without naltrexone reduced juxta-tumoral cancer-associated fibroblasts and M2-like tumor-associated macrophages. Tumor-associated neutrophils, natural killers, and cytotoxic T cells were not altered. Tramadol decreased the proliferative and invasive potentials of pancreatic ductal adenocarcinoma cell lines via decreasing cyclins/cyclin-dependent kinases, which was partially reversed by naltrexone.

CONCLUSIONS

These findings imply that tramadol might be a useful anesthetic for pancreatic ductal adenocarcinoma: inhibiting the proliferation and invasion along with increasing antitumor M1-like tumor-associated macrophages via the µ-opioid receptor, while improving cancer-associated pain possibly through the antitumor effects with the decrease of inflammatory cytokines.

Nitric oxide and potassium channels but not opioid and cannabinoid receptors mediate tramadol-induced peripheral antinociception in rat model of paw pressure withdrawal

Tramadol, an analgesic classified as an "atypical opioid", exhibits both opioid and non-opioid mechanisms of action. This study aimed to explore these mechanisms, specifically the opioid-, cannabinoid-, nitric oxide-, and potassium channel-based mechanisms, which contribute to the peripheral antinociception effect of tramadol, in an experimental rat model. The nociceptive threshold was determined using paw pressure withdrawal. To examine the mechanisms of action, several substances were administered intraplantarly: naloxone, a non-selective opioid antagonist (50 µg/paw); AM251 (80 µg/paw) and AM630 (100 µg/paw) as the selective antagonists for types 1 and 2 cannabinoid receptors, respectively; nitric oxide synthase inhibitors L-NOArg, L-NIO, L-NPA, and L-NIL (24 µg/paw); and the enzyme inhibitors of guanylatocyclase and phosphodiesterase of cGMP, ODQ, and zaprinast. Additionally, potassium channel blockers glibenclamide, tetraethylammonium, dequalinium, and paxillin were used. The results showed that opioid and cannabinoid receptor antagonists did not reverse tramadol's effects. L-NOarg, L-NIO, and L-NPA partially reversed antinociception, while ODQ completely reversed, and zaprinast enhanced tramadol's antinociception effect. Notably, glibenclamide blocked tramadol's antinociception in a dose-dependent manner. These findings suggest that tramadol's peripheral antinociception effect is likely mediated by the nitrergic pathway and sensitive ATP potassium channels, rather than the opioid and cannabinoid pathways.

Analgesic and Psychotropic Effects of a New Bradykinin Antagonist

A bradykinin B1 receptors antagonist PAV-0056, an 1,4-benzodiazepin-2-one derivative, intragastrically administrated to mice at doses of 0.1 and 1 mg/kg causes analgesia in the "formalin test" not inferior to that of diclofenac sodium (10 mg/kg) and tramadol (20 mg/kg). PAV-0056 at doses of 0.1 and 10 mg/kg has no anxiolytic and central muscle relaxant effects in mice and does not damage the gastric mucosa in rats. Based on the results of the conditioned place preference test, PAV-0056 also does not induce addiction in mice.

Intradermal Sterile Water Injection: Safe and Effective Alternative for Relief of Acute Renal Colic in the Emergency Department

BACKGROUND

The optimal pain relief method for acute renal colic in the emergency department remains controversial.

OBJECTIVE

We compared the safety and efficacy of intradermal sterile water injection (ISWI) to treatment with intramuscular (IM) diclofenac, intravenous (IV) opioids, and IV paracetamol in patients with acute renal colic.

METHODS

This randomized, single-blind study included 320 patients with renal colic to one of four treatment groups. The first group received ISWI at four different points around the most painful flank area. Patients in the DI, PARA, and TRAM groups received 75 mg IM diclofenac, 1 g IV paracetamol, and 100 mg IV tramadol, respectively. Pain intensity was measured using a visual analog scale (VAS) before treatment and 15, 30, and 60 min after treatment.

RESULTS

VAS scores 15 and 30 min after treatment were significantly lower in group ISWI than in groups DI, PARA, and TRAM. However, there were no significant differences in the decrease in the pain score at baseline and at 60 min after treatment. In addition, fewer patients required rescue analgesia in group ISWI than in group TRAM. However, no significant differences were observed between group ISWI and group DI or PARA in terms of the need for rescue analgesia. Finally, there were significantly fewer adverse events in group ISWI than in groups DI and TRAM.

CONCLUSIONS

ISWI had similar efficacy, faster pain relief, and lower need for rescue analgesia compared with diclofenac, paracetamol, and tramadol for the management of acute renal colic. In addition, ISWI was well-tolerated and had no adverse effects.

Concomitant use of pre-emptive analgesia with local and general anesthesia in rat uterine pain surgical model

Preemptive analgesia is used for postoperative pain management, providing pain relief with few adverse effects. In this study, the effect of a preemptive regime on rat behavior and c-fos expression in the spinal cord of the uterine surgical pain model was evaluated. It was a lab-based experimental study in which 60 female Sprague-Dawley rats; eight to 10 weeks old, weighing 150-300 gm were used. The rats were divided into two main groups: (i) superficial pain group (SG) (with skin incision only), (ii) deep pain group (with skin and uterine incisions). Each group was further divided into three subgroups based on the type of preemptive analgesia administered i.e., "tramadol, buprenorphine, and saline subgroups." Pain behavior was evaluated using the "Rat Grimace Scale" (RGS) at 2, 4, 6, 9 and 24 h post-surgery. Additionally, c-fos immunohistochemistry was performed on sections from spinal dorsal horn (T12-L2), and its expression was evaluated using optical density and mean cell count 2 hours postoperatively. Significant reduction in the RGS was noted in both the superficial and deep pain groups within the tramadol and buprenorphine subgroups when compared to the saline subgroup (p ≤ .05). There was a significant decrease in c-fos expression both in terms of number of c-fos positive cells and the optical density across the superficial laminae and lamina X of the spinal dorsal horn in both SD and DG (p ≤ .05). In contrast, the saline group exhibited c-fos expression primarily in laminae I-II and III-IV for both superficial and deep pain groups and lamina X in the deep pain group only (p ≤ .05). Hence, a preemptive regimen results in significant suppression of both superficial and deep components of pain transmission. These findings provide compelling evidence of the analgesic efficacy of preemptive treatment in alleviating pain response associated with uterine surgery.

Cross state-dependent memory retrieval between tramadol and ethanol: involvement of dorsal hippocampal GABAA receptors

RATIONALE

Tramadol and ethanol, as psychoactive agents, are often abused. Discovering the molecular pathways of drug-induced memory creation may contribute to preventing drug addiction and relapse.

OBJECTIVE

The tramadol- and ethanol-induced state-dependent memory (SDM) and cross-SDM retrieval between tramadol and ethanol were examined in this study. Moreover, because of the confirmed involvement of GABAA receptors and GABAergic neurotransmission in memory retrieval impairment, we assessed cross-SDM retrieval between tramadol and ethanol with a specific emphasis on the role of the GABAA receptors. The first hypothesis of this study was the presence of cross-SDM between tramadol and ethanol, and the second hypothesis was related to possible role of GABAA receptors in memory retrieval impairment within the dorsal hippocampus. The cannulae were inserted into the hippocampal CA1 area of NMRI mice, and a step-down inhibitory avoidance test was used to evaluate state dependence and memory recovery.

RESULTS

The post-training and/or pre-test administration of tramadol (2.5 and 5 mg/kg, i.p.) and/or ethanol (0.5 and 1 g/kg, i.p.) induced amnesia, which was restored after the administration of the drugs 24 h later during the pre-test period, proposing ethanol and tramadol SDM. The pre-test injection of ethanol (0.25 and 0.5 g/kg, i.p.) with tramadol at an ineffective dose (1.25 mg/kg) enhanced tramadol SDM. Moreover, tramadol injection (1.25 and 2.5 mg/kg) with ethanol at the ineffective dose (0.25 g/kg) promoted ethanol SDM. Furthermore, the pre-test intra-CA1 injection of bicuculline (0.0625, 0.125, and 0.25 μg/mouse), a GABAA receptor antagonist, 5 min before the injection of tramadol (5 mg/kg) or ethanol (1 g/kg) inhibited tramadol- and ethanol-induced SDM dose-dependently.

CONCLUSION

The findings strongly confirmed cross-SDM between tramadol and ethanol and the critical role of dorsal hippocampal GABAA receptors in the cross-SDM between tramadol and ethanol.

Coenzyme Q10 attenuates neurodegeneration in the cerebellum induced by chronic exposure to tramadol

BACKGROUND

Chronic use of tramadol can cause neurotoxic effects and subsequently cause neurodegeneration in the cerebellum. The main damage mechanisms identified are oxidative stress and inflammation. Currently, we investigated the effects of coenzyme Q10 (CoQ10) in attenuates of neurodegeneration in the cerebellum induced by chronic exposure to tramadol.

MATERIAL AND METHODS

Seventy-two male mature albino rats were allocated into four equal groups, including; non-treated group, CoQ10 group (which received CoQ10 at 200 mg/kg/day orally for three weeks), tramadol group (which received tramadol hydrochloride at 50 mg/kg/day orally for three weeks), and tramadol+CoQ10 group (which received tramadol and CoQ10 at the same doses as the previous groups). Tissue samples were obtained for stereological, immunohistochemical, biochemical, and molecular evaluations. Also, functional tests were performed to evaluate behavioral properties.

RESULTS

We found a significant increase in stereological parameters, antioxidant factors (catalase, glutathione, and superoxide dismutase), and behavioral function scores in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05). In addition, malondialdehyde levels, the density of apoptotic cells, as well as the expression of pro-inflammatory (tumor necrosis factor-alpha, interleukin 1 beta, and interleukin 6) and autophagy (lysosome-associated membrane protein 2, autophagy-related 5, beclin 1, and autophagy-related 12) genes were considerably reduced in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05).

CONCLUSION

We conclude that the administration of CoQ10 has neuroprotective effects in the cerebellum of rats that have chronic exposure to tramadol.

Neuro-protective effect of pre-treatment with Sorghum bicolor and vitamin C on tramadol induced brain oxidative stress and anxiety-like behaviour in male albino rats

The study focused on the neuroprotective role of Sorghum bicolor and vitamin C in the amelioration of oxidative stress and anxiety-like behavoiur induced by tramadol in male albino rats. The study design involved 7 groups and a control group with 5 male albino rats in each group. Tramadol (40 mg/kg) treatment was administered for 21 days. Tramadol 40mg/kg was administered in all groups. Pretreatment with varying doses of Sorghum bicolor and Vitamin C was done in three of the groups. Behavioral assessment of anxiety and locomotors actions of the groups were compared using Elevated Plus Maze (EPM) and Open Field Test (OFT). In conclusion, Sorghum bicolor and Vitamin C tramadol ameliorated oxidative stress and anxiety-like behaviour induced by tramadol. Pretreatment with Sorghum bicolor or vitamin C (100mg) can also reduced anxiogenic responses in male albino rats that are induced by chronic tramadol use.

Tramadol induces apoptosis, inflammation, and oxidative stress in rat choroid plexus

BACKGROUND

The choroid plexus (CP) is the principal source of cerebrospinal fluid (CSF). It can produce and release a wide range of materials, including growth and neurotrophic factors which have a crucial role in the maintenance and proper functioning of the brain. Tramadol is a synthetic analog of codeine, mainly prescribed to alleviate mild to moderate pains. Nevertheless, it causes several side effects, such as emotional instability and anxiety.

METHODS

In this study, we focused on alterations in the expression of inflammatory and apoptotic genes in the CP under chronic tramadol exposure. Herein, rats were treated daily with tramadol at 50 mg/kg doses for three weeks. CSF samples were collected, with superoxide dismutase (SOD) and glutathione (GSH) measured in the CSF.

RESULTS

We found that tramadol reduced the SOD and GSH levels in the CSF. Furthermore, the stereological analysis revealed a significant increase in the CP volume, epithelial cells, and capillary number upon tramadol administration. Tramadol elevated the number of blob mitochondria in CP. Also, we observed the upregulation of inflammatory and apoptosis genes following tramadol administration in the CP.

CONCLUSIONS

Our findings indicate that tramadol induces neurotoxicity in the CP via apoptosis, inflammation, and oxidative stress.

Immunomodulation by tramadol combined with acetaminophen or dexketoprofen: In vivo animal study

Among other functions, macrophages remove foreign particles, including medications, from the circulation, making them an important target for immunomodulatory molecules. Currently, growing evidence suggests that analgesics affect the activity of immune cells not directly related to pain, and thus may induce unwanted immunosuppression in patients at risk. However, the immunomodulatory effects resulting from macrophage targeting by these drugs are understudied. Therefore, the current study investigated the immune effects induced in healthy mice by repeated administration of tramadol alone or in combination with acetaminophen or dexketoprofen. We observed that drug administration decreased the percentage of infiltrating macrophages in favor of resident macrophages in peritoneal exudates. While all drugs reduced the number of infiltrating macrophages that phagocytosed sheep red blood cells (SRBC), their administration increased the effectiveness of phagocytosis, and treatment with acetaminophen with or without tramadol elevated the expression of MHC class II by Mac3+ macrophages. Interestingly, SRBC-pulsed macrophages from mice treated with tramadol combined with acetaminophen potently activated SRBC-specific B cells in humoral response, and administration of these drugs to recipients of contact hypersensitivity effector cells augmented the resulting cellular immune response. In addition, tramadol administered alone or with dexketoprofen enhanced the spontaneous release of pro-inflammatory cytokines by macrophages. Our current research findings demonstrate that tramadol therapy in combination with acetaminophen or dexketoprofen has a relatively low risk of causing immunosuppressive side effect because the drugs slightly reduce the inflammatory reaction of macrophages but do not impair their ability to activate the adaptive immune responses.

The toxic profile of tramadol combined with nicotine on the liver and testicles: evidence from endoplasmic reticulum stress

BACKGROUND

Tramadol is one of the most commonly abused substances in the Middle East. Furthermore, smoking is extremely common among the population.

METHODS

An experimental study was performed on Sprague-Dawley rats to explore the effects of both nicotine and tramadol on the liver and testes. The tramadol was administered at 10 and 20 mg/kg, respectively, while the nicotine was administered at 125 mg/kg. Histological examination and androgen receptor ELISA assay showed mild effects on the liver and proofed safety on the testis. Western blot analysis of BIP (immunoglobulin heavy-chain binding protein) and CHOP (CCAAT-enhancer-binding protein homologous protein) revealed that fewer problems were induced by adding nicotine to tramadol. Autophagy marker LCIII and apoptosis marker caspase-8 showed similar effects to CHOP and BIP on liver samples. The real-time PCR of BIP expression showed similar but not identical results.

CONCLUSIONS

The results showed mild endoplasmic reticulum stress, autophagy, and apoptosis in the liver samples. Histological examination revealed stable spermatogenesis with average androgen receptor blood levels in the different groups.

Exploring Perceptions About Paracetamol, Tramadol, and Codeine on Twitter Using Machine Learning: Quantitative and Qualitative Observational Study

BACKGROUND

Paracetamol, codeine, and tramadol are commonly used to manage mild pain, and their availability without prescription or medical consultation raises concerns about potential opioid addiction.

OBJECTIVE

This study aims to explore the perceptions and experiences of Twitter users concerning these drugs.

METHODS

We analyzed the tweets in English or Spanish mentioning paracetamol, tramadol, or codeine posted between January 2019 and December 2020. Out of 152,056 tweets collected, 49,462 were excluded. The content was categorized using a codebook, distinguishing user types (patients, health care professionals, and institutions), and classifying medical content based on efficacy and adverse effects. Scientific accuracy and nonmedical content themes (commercial, economic, solidarity, and trivialization) were also assessed. A total of 1000 tweets for each drug were manually classified to train, test, and validate machine learning classifiers.

RESULTS

Of classifiable tweets, 42,840 mentioned paracetamol and 42,131 mentioned weak opioids (tramadol or codeine). Patients accounted for 73.10% (60,771/83,129) of the tweets, while health care professionals and institutions received the highest like-tweet and tweet-retweet ratios. Medical content distribution significantly differed for each drug (P<.001). Nonmedical content dominated opioid tweets (23,871/32,307, 73.9%), while paracetamol tweets had a higher prevalence of medical content (33,943/50,822, 66.8%). Among medical content tweets, 80.8% (41,080/50,822) mentioned drug efficacy, with only 6.9% (3501/50,822) describing good or sufficient efficacy. Nonmedical content distribution also varied significantly among the different drugs (P<.001).

CONCLUSIONS

Patients seeking relief from pain are highly interested in the effectiveness of drugs rather than potential side effects. Alarming trends include a significant number of tweets trivializing drug use and recreational purposes, along with a lack of awareness regarding side effects. Monitoring conversations related to analgesics on social media is essential due to common illegal web-based sales and purchases without prescriptions.

Use of tramadol as analgesic alternative in Harris hawk (Parabuteo unicinctus)

BACKGROUND

The Harris hawk is a bird of prey susceptible to traumatic injuries because it is useful for several purposes such as conservancy, biological control and falconry. Once received in rehabilitation centres or specialized clinics, it is necessary to provide proper analgesia.

OBJECTIVES

The aim of this study is to demonstrate the analgesic efficacy of tramadol in Harris hawks (PISADOL 50 PiSA Agropecuaria, S.A. de C.V. Calle 1 Norte, Manzana 2-25 Parque Industrial Tula Atitalaquia, Hgo, México), by the assessment of nociceptive threshold.

METHODS

A total of 24 adult Harris hawks were selected from a rehabilitation centre. The birds were randomly divided into four groups: control (saline solution), 5.0, 15.0 and 30.0 mg/kg of intramuscular tramadol. Nociception was produced with electrical stimuli of 9 V, applied in propatagial skin at 1, 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300 and 360 min, assessing the nociceptive threshold and sedative effects produced by each treatment.

RESULTS

No difference was observed between control and tramadol group 5 mg/kg. At 15 mg/kg, the pain threshold increased from 20 to 240 min, with minimal sedative effects. At 30 mg/kg, there was a marked increase in pain threshold from 10 to 300 min, and sedative effects like wing and head drooping for a period of 90 min.

CONCLUSIONS

Tramadol can be an analgesic alternative for Harris's hawks, as it decreases the response to painful stimuli in this species when administered by intramuscular route.

Tramadol/paracetamol treatment attenuates the development of collagen antibody-induced arthritis and interferes with prednisolone treatment in mice

The collagen antibody-induced arthritis (CAIA) model is highly effective in inducing arthritis, making it an attractive model for screening therapeutic compounds such as glucocorticoids (GCs). The severity of discomfort in this model makes it desirable to administer analgesics, but it is a prerequisite that these do not interfere with the model or tested therapeutics. In the present study, we studied the effect of 1 mg/mL tramadol and 3.5 mg/mL paracetamol (TP) on CAIA in male BALB/cAnNCrl mice and the possible interference of TP analgesia with the activity of the GC drug prednisolone (Pred). Our results showed that TP abolished the Pred-induced amelioration of CAIA, as well as several other Pred-induced effects, such as the reduction in thymus weight and the increase in insulin level. This most likely results from the effects of TP on the hepatic metabolism of this drug, since it strongly increased the Cyp3a11 expression in the liver. Altogether, we conclude that TP analgesia is not suitable for the CAIA model in male BALB/cAnNCrl mice, in particular when evaluating the effects of GCs such as Pred.

10-dehydrogingerdione amends tramadol-elicited neurotransmitters disturbance and apoptosis in the brain of male rats by repleting non-enzymatic antioxidants

Tramadol is analgesic medication to relief acute and chronic pain, referred to as alternative to opioid drugs however its abuse or overdosage may resulted in neuronal toxicity. This is attributed to severe fluctuations of neurotransmitters pattern along with cerebral inflammation and oxidative damage. Present work was undertaken to illustrate the cytoprotective effect of 10-dehydrogingerdione (10-DHGD) on the brain tissues of experimental rats due to Tramadol intake and its underlying mechanism. 24 male wistar rats were randomized into 4 equal groups. Group (1), received tramadol in a dose level 20 mg/kg intrapertioneal (i.p) daily for 30 days and referred to Tramadol group. Group (2), received both of 10-DHGD (10 mg/kg, orally) one hour before tramadol intake (dose as mentioned before) daily for 30 days. Group (3) received 10-DHGD only (10 mg/kg, orally) and daily for 30 days. Group (4), received no drugs and referred to control group for comparison. Tramadol significantly reduced Norepinephrin (NE), dopamine, serotonin and glutathione (reduced) contents of Cerebral cortex. lipid peroxidation, nuclear factor kappa B (NFkB), inducible nitric oxide synthase (INOS) levels and caspase-3 immunoreactivity showed however significant increase. Of note, 10-DHGD significantly increased neurotransmitters, glutathione contents while Malondialdehyde (MDA), Nitric oxide (NO), NFkB, INOS additionally caspase-3 immunoexpression showed significant decrease i.e counteracted to certain extent tramadol effect. These findings may refer to the cytoprotective potential of 10-DHGD against the neurotoxicity exerted by tramadol intake, most probably mediated via enhancement of endogenous antioxidants system.

Evaluation of the effect of tramadol, paracetamol and metamizole on the severity of experimental colitis

Application of dextran sodium sulfate (DSS) is often used to induce experimental colitis. Current state of the art is to refrain from the use of analgesics due to their possible interaction with the model. However, the use of analgesics would be beneficial to reduce the overall constraint imposed on the animals. Here, we analyzed the effect of the analgesics Dafalgan (paracetamol), Tramal (tramadol) and Novalgin (metamizole) on DSS-induced colitis. To study the effect of those analgesics in colitis mouse models, acute and chronic colitis was induced in female C57BL6 mice by DSS administration in the drinking water. Analgesics were added to the drinking water on days four to seven (acute colitis) or on days six to nine of each DSS cycle (chronic colitis). Tramadol and paracetamol had minor effects on colitis severity. Tramadol reduced water uptake and activity levels slightly, while mice receiving paracetamol presented with a better overall appearance. Metamizole, however, significantly reduced water uptake, resulting in pronounced weight loss. In conclusion, our experiments show that tramadol and paracetamol are viable options for the use in DSS-induced colitis models. However, paracetamol seems to be slightly more favorable since it promoted the overall wellbeing of the animals upon DSS administration without interfering with typical readouts of colitis severity.

Effect of apatinib on the pharmacokinetics of tramadol and O-desmethyltramadol in rats

Since the combination of anticancer drugs and opioids is very common, apatinib and tramadol are likely to be used in combination clinically. This study evaluated the effects of apatinib on the pharmacokinetics of tramadol and its main metabolite O-desmethyltramadol in Sprague-Dawley (SD) rats and the inhibitory effects of apatinib on tramadol in rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant human CYP2D6.1. The samples were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The in vivo results showed that compared with the control group, apatinib increased the AUC(0-t), AUC(0-∞) and Cmax values of tramadol and O-desmethyltramadol, and decreased the values of VZ/F and CLz/F. In addition, the MRT(0-t), MRT(0-∞) values of O-desmethyltramadol were increased. In vitro, apatinib inhibited the metabolism of tramadol by a mixed way with IC50 of 1.927 µM in RLMs, 2.039 µM in HLMs and 15.32 µM in CYP2D6.1. In summary, according to our findings, apatinib has a strong in vitro inhibitory effect on tramadol, and apatinib can increase the analgesic effect of tramadol and O-desmethyltramadol in rats.

Role of apoptosis and autophagy in mediating tramadol-induced neurodegeneration in the rat hippocampus

BACKGROUND

Tramadol (TRA) is an analgesic prescribed for treating mild to moderate pains, the abuse of which has increased in recent years. Chronic tramadol consumption produces neurotoxicity, although the mechanisms are unclear. The present study investigated the involvement of apoptosis and autophagy signaling pathways and the mitochondrial system in TRA-induced neurotoxicity.

MATERIALS AND METHODS

Sixty adult male Wistar rats were divided into five groups that received standard saline or TRA in doses of 25, 50, 75, 100, or 150 mg/kg intraperitoneally for 21 days. On the 22nd day, the Open Field Test (OFT) was conducted. Jun N-Terminal Kinase (JNK), B-cell lymphoma-2 (Bcl-2), Beclin1, and Bcl-2-like protein 4 (Bax) proteins and tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) were measured in rat hippocampal tissue.

RESULTS

TRA at doses 75, 100, and 150 mg/kg caused locomotor dysfunction in rats and increased total and phosphorylated forms of JNK and Beclin-1, Bax, and Caspase-3. TRA at the three higher doses also increased the phosphorylated (inactive) form of Bcl-2 level while decreasing the unphosphorylated (active) form of Bcl-2. Similarly, the protein levels of TNF-α and IL-1β were increased dose-dependently. The mitochondrial respiratory chain enzymes were reduced at the three higher doses of TRA.

CONCLUSION

TRA activated apoptosis and autophagy via modulation of TNF-α or IL-1β/JNK/Bcl-2/Beclin1 and Bcl-2/Bax signaling pathways and dysfunction of mitochondrial respiratory chain enzymes.

Evaluation of the changes induced by tramadol and the possible protective effect of vitamin C on the kidney

OBJECTIVE

Addiction is a widespread public health problem despite all efforts to prevent and treat it. Over the past few years, tramadol abuse has been sharply increasing in Middle Eastern countries. This research aims to identify the tramadol-induced histological changes in rat kidneys and any potential protective effects of vitamin C on these changes.

MATERIALS AND METHODS

This is an experimental study conducted at Prince Sattam bin Abdul Aziz University. Thirty-three adult albino rats were randomly divided into three groups. Control, Tramadol, and vitamin C groups. The Tramadol group received 25 mg/ Kg a day of tramadol orally via gastric gavage for three weeks. In the vitamin C + tramadol treated group, 100 mg/Kg/b.wt of vitamin C was administered intravenously to the animals 30 minutes before receiving the same dose of tramadol RESULTS: Specimens from the kidney of every rat were excised for histological examination by the light and electron microscope. Tramadol damage to the kidney's glomeruli and proximal and distal convoluted tubule hypertrophy were among its long-term harmful consequences. When vitamin C was added to tramadol, the distal and proximal convoluted tubules, and the renal glomeruli, improved.

CONCLUSIONS

When vitamin C was given to the tramadol group, the drug's harmful effects on the kidney were reduced.

The opioid tramadol blocks the cardiac sodium channel Nav1.5 in HEK293 cells

AIMS

Opioids are associated with increased risk of sudden cardiac death. This may be due to their effects on the cardiac sodium channel (Nav1.5) current. In the present study, we aim to establish whether tramadol, fentanyl, or codeine affects Nav1.5 current.

METHODS AND RESULTS

Using whole-cell patch-clamp methodology, we studied the effects of tramadol, fentanyl, and codeine on currents of human Nav1.5 channels stably expressed in HEK293 cells and on action potential (AP) properties of freshly isolated rabbit ventricular cardiomyocytes. In fully available Nav1.5 channels (holding potential -120 mV), tramadol exhibited inhibitory effects on Nav1.5 current in a concentration-dependent manner with an IC50 of 378.5 ± 33.2 µm. In addition, tramadol caused a hyperpolarizing shift of voltage-gated (in)activation and a delay in recovery from inactivation. These blocking effects occurred at lower concentrations in partially inactivated Nav1.5 channels: during partial fast inactivation (close-to-physiological holding potential -90 mV), IC50 of Nav1.5 block was 4.5 ± 1.1 μm, while it was 16 ± 4.8 μm during partial slow inactivation. The tramadol-induced changes on Nav1.5 properties were reflected by a reduction in AP upstroke velocity in a frequency-dependent manner. Fentanyl and codeine had no effect on Nav1.5 current, even when tested at lethal concentrations.

CONCLUSION

Tramadol reduces Nav1.5 currents, in particular, at close-to-physiological membrane potentials. Fentanyl and codeine have no effects on Nav1.5 current.

Comparison of Preoperative Analgesics on the Efficacy of Inferior Alveolar Nerve Block with Patients Having Symptomatic Irreversible Pulpitis: A Double-Blinded, Randomized Controlled Trial

OBJECTIVE

The objective of this study was to evaluate the effectiveness of preoperative analgesics on inferior alveolar nerve blocks (IANB) during root canal treatment in patients with symptomatic irreversible pulpitis of the mandibular molars.

METHODS

This study was a randomized, double-blinded, superiority trial with a parallel study design. A total of 120 subjects with symptomatic irreversible pulpitis were randomly assigned to one of four groups: group A (con- trol, Vitamin E, Evion 400 mg), group B (Diclofenac sodium, Voltral SR100 100 mg), group C (Piroxicam, Feldene 20 mg), and group D (Tramadol, Tramal 50 mg). The patients recorded preoperative pain levels, and after admin- istration of local anaesthesia intraoperative pain levels using the Heft-Parker visual analogue scale before and after the oral administration of the analgesics. Statistical analysis was performed using the Kruskal-Wallis test.

RESULTS

All the analgesic groups showed a significant effect on the efficacy of the inferior alveolar nerve block in contrast to the control group (p<0.05). However, no significant difference was found between the drug groups on the effectiveness of the inferior alveolar nerve block (p>0.05). No side effects were reported in the present study.

CONCLUSION

Preoperative analgesics significantly increase the effectiveness of inferior alveolar nerve block in patients with symptomatic irreversible pulpitis. Therefore, preoperative analgesics should be considered to increase the effectiveness of inferior alveolar nerve block in patients with symptomatic irreversible pulpitis on the mandibular molars. (EEJ-2023-02-033).

A buprenorphine depot formulation provides effective sustained post-surgical analgesia for 72 h in mouse femoral fracture models

Adequate pain management is essential for ethical and scientific reasons in animal experiments and should completely cover the period of expected pain without the need for frequent re-application. However, current depot formulations of Buprenorphine are only available in the USA and have limited duration of action. Recently, a new microparticulate Buprenorphine formulation (BUP-Depot) for sustained release has been developed as a potential future alternative to standard formulations available in Europe. Pharmacokinetics indicate a possible effectiveness for about 72 h. Here, we investigated whether the administration of the BUP-Depot ensures continuous and sufficient analgesia in two mouse fracture models (femoral osteotomy) and could, therefore, serve as a potent alternative to the application of Tramadol via the drinking water. Both protocols were examined for analgesic effectiveness, side effects on experimental readout, and effects on fracture healing outcomes in male and female C57BL/6N mice. The BUP-Depot provided effective analgesia for 72 h, comparable to the effectiveness of Tramadol in the drinking water. Fracture healing outcome was not different between analgesic regimes. The availability of a Buprenorphine depot formulation for rodents in Europe would be a beneficial addition for extended pain relief in mice, thereby increasing animal welfare.

Ethnopharmacological evaluation of Poppy seed oil in combination with Tramadol on behavioral paradigm and on dopamine, and cytokines levels

OBJECTIVE

The present study was taken up to evaluate the combination of two drugs in the management of behavioral disorders such as locomotor activity, muscle relaxation, analgesic, and anxiolytic activity.

MATERIALS AND METHODS

In the methodology, Wistar rats weighing (150-180 g) were divided into six groups of 6 each (n=6). All the animals (groups II to VI) were subjected to stress and analyzed for anxiolytic activity using an elevated plus maze. The animals were treated for 28 days with poppy seed oil in lower and higher doses (1,000 and 2,000 mg/kg), tramadol in lower and higher doses (1.5 and 3 mg/kg) as individual groups, and one group with a combination of both drugs in lower doses.

RESULTS

The results depicted showed that the combined treatment had significantly (**p <0.001) improvised behavior deficits, extemporized, and diminished anxiety-like attitude in rats, and showed the analgesic property in a significant manner. The pro-inflammatory cytokines TNF-α and IL-1β were evaluated in the serum and were observed to be lessened the values of both in a significant manner with the co-administration of both the test drugs. The dopamine concentrations were also determined in the serum, which disclosed a decline (**p <0.001) significantly.

CONCLUSIONS

It was concluded from the results that a combined effect of drugs might be beneficial in the management of behavioral disorders and pain management.

Reinforcing effect of tramadol in the rat

Tramadol is one of the most commonly prescribed analgesic opioids in various pharmacopeias. Tramadol has been linked to abuse in recent clinical investigations. However, the behavioral effects and neural substrates of the drug have not been well characterized in preclinical studies. As a result, the present study investigated the effects of tramadol on behavioral sensitizations in rats. Its impacts on cellular and molecular alterations in the brain were also investigated. In conditioned place preference (CPP) paradigm, tramadol induced behavioral as well as motor sensitizations. These effects were dramatically reduced by intraperitoneal administration of naltrexone, an opioid receptor antagonist. Tramadol caused changes in several molecular markers (pERK1/2, Δ-FosB, PKCγ, PKMζ GAD67) in the anterior cingulate cortex, which could indicate an increase in excitation within this structure. Tramadol is demonstrated in the present study to be a reinforcing drug in rats, as it increased both behavioral and motor sensitizations. Tramadol's effects are most likely due to the high levels of excitation it causes in the brain, which is mostly caused by the activation of opioid receptors.

Comparison of the analgesic effects of morphine and tramadol after tumor surgery in dogs

BACKGROUND

Pain thresholds may differ between animal species. It may even vary among individuals of the same species. Therefore, assessing pain in animals is challenging.

AIMS

The objective of the present study was to compare the analgesic effects of tramadol with morphine.

METHODS

The study was carried out on randomly selected 20 dogs with tumors in different breeds and gender. After induction of anesthesia with propofol, dogs were intubated, and anesthesia was maintained with sevoflurane. Intravenous fentanyl citrate was used for intraoperative analgesia after stabilization of the anesthesia. When the tumors were surgically removed and the operation was completed, dogs were divided into two groups to give the postoperative analgesic agent. The first 10 dogs to be investigated were identified as the morphine group and the second 10 dogs as the tramadol group. Postoperative pain scores, heart rates, respiratory rates, and body temperatures were recorded at 0, 4, 8, 12, 16, 20, and 24 hours after the operation.

RESULTS

Pain scores were lower in the morphine group than in the tramadol group during all postoperative processes.

CONCLUSION

As a result, it was determined that tramadol has immediate analgesic effects than morphine; however, morphine provides better analgesia than tramadol.

Amplification by tramadol of PGD2-induced osteoprotegerin synthesis in osteoblasts: Involvement of μ-opioid receptor and 5-HT transporter

Tramadol, a weak μ-opioid receptor (MOR) agonist with inhibitory effects on the reuptake of serotonin (5-hydroxytryptamine; 5-HT) and norepinephrine, is an effective analgesic to chronic pains. Osteoprotegerin produced by osteoblasts is essential for bone remodeling to suppress osteoclastic bone resorption. We previously reported that prostaglandin D₂ (PGD₂) induces osteoprotegerin synthesis whereby p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) are involved in osteoblast-like MC3T3-E1 cells. Herein, we investigated the mechanism underlying the effect of tramadol on the PGD₂-induced osteoprotegerin synthesis in these cells. Tramadol enhanced the PGD₂-induced release and mRNA expression of osteoprotegerin. Naloxone, a MOR antagonist, reduced the amplification by tramadol of the PGD₂-stimulated osteoprotegerin release. Not the selective norepinephrine reuptake inhibitor reboxetine but the selective serotonin reuptake inhibitors fluvoxamine and sertraline upregulated the PGD₂-induced osteoprotegerin release, which was further amplified by morphine. Tramadol enhanced PGD₂-stimulated phosphorylation of p38 MAP kinase and SAPK/JNK, but not p44/p42 MAP kinase. Both SB203580 and SP600125 suppressed the tramadol effect to enhance the PGD₂-stimulated osteoprotegerin release. Tramadol enhanced the PGE₂-induced osteoprotegerin release as well as PGD₂. These results suggest that tramadol amplifies the PGD₂-induced osteoprotegerin synthesis at the upstream of p38 MAP kinase and SAPK/JNK in the involvement of both MOR and 5-HT transporter in osteoblasts.

Evaluation of the paw withdrawal latency for the comparison between tramadol and butorphanol administered locally, in the plantar surface of rat, preliminary study

The aim of the study was to evaluate the analgesic efficacy of tramadol compared to butorphanol administered locally in ventral surface of the hind paw of rats. Prospective, randomized experimental study; twenty-one adult male Wistar rats were selected. Heart rate (beats minute^-1), respiratory rate (breaths minute^-1), and paw withdrawal latency (onset of radiant heat until paw withdrawal/seconds) were measured prior (T⁰) and after (T⁵, T¹⁰, T¹⁵, T²⁰) intraplantar injection with saline solution 0,9% (group S), butorphanol 1 mg kg^-1 (group B), and tramadol 1 mg kg^-1 (group T). Shapiro-Wilk normality test and Friedman test were used to analyze the data expressed by median and range. Statistical significance was set at p < 0.05. Statistical analysis of heart rate showed that there were significant differences between groups at different monitoring times. There were no significant differences in respiratory rate after intraplantar injection in any of the treatment groups. The paw withdrawal latency values at T5, T10, and T15 minutes after intraplantar injection in the group B were significantly higher compared to baseline value and to the values of the other groups. The paw withdrawal latency were no significant changes in the measurements of intragroup in S and T. Intraplantar administration of butorphanol provides a good analgesia and significantly increases paw withdrawal latency compared to tramadol. Intraplantar injection of butorphanol could be useful and safe and safe technique to achieve local analgesia for minor surgical procedures in rats.

The comparison of ketamine with tramadol for postoperative pain relief on children following adenotonsillectomy or tonsillectomy: A meta-analysis of randomized controlled trials

INTRODUCTION

The comparison of ketamine with tramadol for pain control remains controversial in pediatric adenotonsillectomy or tonsillectomy. We conduct a systematic review and meta-analysis to explore the efficacy of ketamine vs tramadol for pain relief in children following adenotonsillectomy or tonsillectomy.

METHODS

We have searched PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through October 2019 for randomized controlled trials (RCTs) assessing the effect of ketamine vs tramadol for pediatric adenotonsillectomy or tonsillectomy. This meta-analysis is performed using the random-effects model.

RESULTS

Six RCTs are included in the meta-analysis. Overall, compared to ketamine group for pediatric adenotonsillectomy or tonsillectomy, tramadol is associated with substantially lower CHEOPS at 1 h (SMD = 1.56; 95% CI = 0.20-2.92; P = .02; low quality) and longer first time of additional pain medication (SMD = -0.47; 95% CI = -0.74 to -0.19; P = .0008; low quality), but demonstrates no obvious effect on CHEOPS at 6 h (SMD = 0.51; 95% CI = -1.17 to 2.19; P = .55; low quality), sedation scale at 1 h (SMD = -0.80; 95% CI = -3.07 to 1.48; P = .49; low quality) or additional pain medication (RR = 1.31; 95% CI = 0.85-2.02; P = .23; moderate quality).

CONCLUSIONS

Tramadol may be better to alleviate the postoperative pain after pediatric adenotonsillectomy or tonsillectomy.

Tiletamine/zolazepam and dexmedetomidine with tramadol provide effective general anesthesia in rats

Background

Tiletamine/zolazepam is a dissociative anesthetic combination commonly used in small animals but information is limited in rats. The alpha-2 agonist, dexmedetomidine, has gained popularity in laboratory animal anesthesia. Tramadol is a weak opioid mu agonist. The aim of this study was to assess whether the tiletamine/zolazepam/dexmedetomidine (ZD) combination effectively provides a surgical anesthesia plane comparable to tiletamine/zolazepam/dexmedetomidine with tramadol (ZDT) in a minor procedure in rats.

Methods

Rats were induced with ZD or ZDT. After the loss of paw withdrawal, a small incision was made on the rats' left thighs as a surgical stimulus. Rats were maintained under a surgical anesthesia plane by assessing the loss of the paw withdrawal reflex for 45 minutes, then atipamezole was administered. Monitored anesthesia parameters included: (a) physiological parameters - pulse rate (PR), respiratory rate (RR), tissue oxygen saturation (%SpO2), and body temperature; (b) duration parameters - induction time, onset and duration of surgical anesthesia plane, onset of recovery, and recovery time.

Results

PR was significantly lower at 10 minutes in ZD and 5 minutes in ZDT groups. No difference was observed for RR, %SpO2, and body temperature. Likewise, there were no differences for duration parameters: induction time was less than 3 minutes; onset and duration of surgical anesthesia plane were approximately 5 and 45 minutes, respectively; onset of recovery (time to move) was 51 minutes; and recovery time was 52 minutes, respectively.

Conclusion

These data suggest the ZD combination provides a surgical anesthesia plane comparable to ZDT in a rat incisional pain model.

Antinociceptive effects of rotigotine-loaded microspheres and its synergistic interactions with analgesics in inflammatory pain in rats

Rotigotine-loaded microspheres (RoMS) are sustained-release formulations with prolonged anti-Parkinson's effects. Given that pain is a non-motor symptom of Parkinson's disease, this study investigated the antinociceptive effects of RoMS and their synergistic effects with analgesics on inflammatory pain. A model of inflammatory pain was prepared by intraplantarly injecting male Sprague-Dawley rats with carrageenan. The antinociceptive effects of RoMS, acetaminophen, and tramadol, both alone and in combination, were evaluated using the hind paw withdrawal latency in the hot plate test and Randall-Selitto test. The rotigotine concentrations in serum and tissues were assayed using ultra-performance liquid chromatography-tandem mass spectrometry. Isobolographic analysis was performed to evaluate the nature of the interactions of RoMS with acetaminophen or tramadol. The results showed that hind paw withdrawal latency to thermal and mechanical stimuli was significantly increased on day 3 and 7 after administered RoMS. Rotigotine could be detected in serum and tissues 3 and 7 days after an intramuscular injection of RoMS. However, the rotigotine concentration fell the detection limit of the assay on day 14 after administration. RoMS produced synergistic antinociceptive effects in the inflammatory pain model when RoMS is combined with acetaminophen or tramadol. These findings suggest that RoMS can relieve inflammatory pain in rats. Furthermore, the combination of RoMS with acetaminophen or tramadol produces synergistic antinociception, which may be clinically worthy because combination therapies may reduce the drug doses required for antinociception.

The plausible mechanisms of tramadol for treatment of COVID-19

Currently, no single medication has been approved for the management of coronavirus disease-2019 (COVID-19) caused by the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, drug repositioningby investigating the use of existing drugs for management of COVID-19 patients is considered a desperate need. Tramadol is a commonly prescribed analgesic drug for treatment of moderate to severe pain with less potential for dependence and respiratory depression. Multiple evidence support that tramadol is a promising drug for treatment of COVID-19 patients. Herein, we discuss the possible beneficial effects of using tramadol against SARS-CoV-2 infection and their underlying mechanism of action. The anti-inflammatory effect of tramadol may help to suppress the COVID-19 related cytokine storm through decreasing interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). Besides, tramadol activates natural killer (NK) and T-cells and enhances IL-2 secretion, which produce immune-enhancing effect against SARS-CoV-2. Recent studies confirmed that COVID-19 patients with acute respiratory failure showed increased fibrin formation and polymerization that may lead to thrombosis. Tramadol owing to its hypocoagulable effect may protect against venous thromboembolism in these patients. Moreover, tramadol can exert a cardioprotective effect via decreasing lactate dehydrogenase (LDH) level which is elevated in most of patients with COVID-19. Furthermore, the severity and mortality of COVID-19 have been correlated with old age patients, which may be due to the lack of antioxidant mechanisms and increased oxidative damage. Tramadol could protect COVID-19 patient from disease complications by increases the antioxidant enzymes superoxide dismutase and glutathione peroxidase while diminished malondialdehyde. More interestingly, tramadol as an effective analgesic and antitussive may have a beneficial effect on COVID-19 patients suffering from cough, headache, ache, and pain. The tramadol anti-psychotic effect may also protect against psychiatric disorders associated with SARS-CoV-2 infection. Moreover, tramadol has bactericidal activity against a wide range of pathogens including Pseudomonas aeruginosa which is common in severe COVID-19 patients leading to pneumonia with worse clinical outcomes. Therefore, we hypothesize that tramadol might be a promising adjuvant therapeutic option against SARS-CoV-2 infection. Based on that, tramadol should be considered as adjuvant therapy for COVID-19 clinical trials.

Effects of orally administered gabapentin, tramadol, and meloxicam on ocular variables in healthy dogs

OBJECTIVE

To determine the effects of gabapentin, tramadol, and meloxicam on tear production, intraocular pressure (IOP), pupillary diameter, tear break-up time, and corneal touch threshold in healthy dogs when given orally for 3 days.

ANIMALS

9 healthy research Beagles.

PROCEDURES

A randomized, blinded, case-crossover study with a 6-sequence, 3-treatment, and 3-period design was performed. A 7-day acclimation period was followed by 3 treatment phases, each with a 3-day treatment period followed by a 7-day washout period for 3 different drugs. Block randomization was used to group dogs for treatments with drug A (gabapentin), B (tramadol), or C (meloxicam). Measurements of tear production, IOP, pupillary diameter, tear break-up time, and corneal touch threshold were performed on a schedule. A generalized mixed-effects linear regression model was created for each ocular variable, accounting for repeated measures within individuals.

RESULTS

Intraocular pressure was the only variable to have differed substantially between the first 5 and last 2 days of the acclimation period. When treatment phase, day, time of day, dog identification, baseline value, and eye were accounted for, the mean IOP was lower for dogs during treatment phases with gabapentin or tramadol, compared with meloxicam, but this difference was not considered clinically meaningful.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that a minimum 5-day acclimation period is necessary for IOP measurements to return to baseline in dogs. The statistically identified effect of gabapentin and tramadol on IOP in dogs of the present study warrants further investigation. It is possible that at higher dosages, or in dogs with glaucoma, this effect may become clinically significant.

Tramadol Promotes Oxidative Stress, Fibrosis, Apoptosis, Ultrastructural and Biochemical alterations in the Adrenal Cortex of Adult Male Rat with Possible Reversibility after Withdrawal

Tramadol is a centrally acting analgesic drug, used for the management of moderate to severe pain in a variety of diseases. The long-term use of tramadol can induce endocrinopathy. This study aimed to evaluate the effect of tramadol dependence on the adrenal cortex and the effect of its withdrawal. Thirty adult male rats were divided into three experimental groups: the control group, the tramadol-dependent group that received increasing therapeutic doses of tramadol orally for 1 month, and the recovery group that received tramadol in a dose and duration similar to the previous group followed by a withdrawal period for another month. Specimens from the adrenal cortex were processed for histological, immunohistochemical, enzyme assay, and quantitative real-time PCR (RT-qPCR) studies. Tramadol induced a significant increase in malondialdehyde level and a significant decrease in the levels of glutathione peroxidase and superoxide dismutase. A significant decrease in the levels of adrenocorticotrophic hormones, aldosterone, cortisol, corticosterone, and dehydroepiandrosterone sulfate was also detected. Severe histopathological changes in the adrenal cortex were demonstrated in the form of disturbed architecture, swollen cells, and shrunken cells with pyknotic nuclei. Inflammatory cellular infiltration and variable-sized homogenized areas were also detected. A significant increase in P53 and Bax immunoreaction was detected and confirmed by RT-qPCR. The ultrastructural examination showed irregular, shrunken adrenocorticocytes with dense nuclei. Dilated smooth endoplasmic reticulum, mitochondria with disrupted cristae, and numerous coalesced lipid droplets were also demonstrated. All these changes started to return to normal after the withdrawal of tramadol. Thus, it was confirmed that the long-term use of tramadol can induce severe adrenal changes with subsequent insufficiency.

Sigma-1 receptor antagonists: promising players in fighting neuropathic pain

Sigma-1 receptors (S1Rs) are strongly correlated to neuropathic pain (NP), since their inactivation may decrease allodynia or dysesthesia, promoting analgesic effects. In the recent patent landscape, S1R antagonists endowed with nanomolar S1Rs affinity emerged as potent antinociceptive agents. So far, three patented compounds have been proposed for counteracting NP. Particularly PV-752 and AV1066, disclosed by the University of Pavia (Italy) and Anavex, respectively, showed good analgesic activity in preclinical studies. Moreover, E-52862 developed by Esteve (Spain) has been proved to be effective, both in preclinical and Phase II clinical trials, against several symptoms of NP. These patents ascertain S1R antagonists as potential drugs, alone or in combination with other analgesic drugs, for managing NP in humans.

Behavioral effects of citalopram, tramadol, and binary mixture in zebrafish (Danio rerio) larvae

Pharmaceuticals are emerging as environmentally problematic compounds. As they are often not appropriately removed by sewage treatment plants, pharmaceutical compounds end up in surface water environments worldwide at concentrations in the ng to μg L^-1 range. There is a need to further explore single compound and mixture effects using e.g. in vivo test model systems. We have investigated, for the first time, behavioral effects in larval zebrafish (Danio rerio) exposed to a binary mixture of an antidepressant drug (citalopram) and a synthetic opioid (tramadol). Citalopram and tramadol have a similar mode of action (serotonin reuptake inhibition) and are known to produce drug-drug interactional effects resulting in serotonin syndrome (SS) in humans. Zebrafish embryo-larvae were exposed to citalopram, tramadol and 1:1 binary mixture from fertilization until 144 h post-fertilization. No effects on heart rate, spontaneous tail coiling, or death/malformations were observed in any treatment at tested concentrations. Behavior (hypoactivity in dark periods) was on the other hand affected, with lowest observed effect concentrations (LOECs) of 373 μg L^-1 for citalopram, 320 μg L^-1 for tramadol, and 473 μg L^-1 for the 1:1 mixture. Behavioral EC₅₀ was calculated to be 471 μg L^-1 for citalopram, 411 μg L^-1 for tramadol, and 713 μg L^-1 for the 1:1 mixture. The results of this study conclude that tramadol and citalopram produce hypoactivity in 144 hpf zebrafish larvae. Further, a 1:1 binary mixture of the two caused the same response, albeit at a higher concentration, possibly due to SS.

Opioid-induced hypoadrenalism resulting in fasting hypoglycaemia

An 18-year-old woman with a history of hollow visceral myopathy presented with a small-bowel obstruction. High-dose opioid analgesia was required subsequently during hospital admission. She suffered two episodes of documented fasting hypoglycaemia, despite adjustment of parenteral carbohydrate administration. Investigations for non-insulin-mediated hypoglycaemia revealed a low morning cortisol of 109 nmol/L and an inappropriately low Adrenocorticotropic hormone (ACTH) level of 2.2 pmol/L. A diagnosis of secondary adrenal insufficiency was confirmed on repeat cortisol and ACTH testing. The 250 µg short Synacthen test cortisol response was normal, suggestive of acute rather than chronic ACTH deficiency. This pattern was consistent after further opioid exposure. Adrenal recovery occurred shortly after opioid cessation. Opioid-induced hypoadrenalism is likely an under-recognised clinical entity with potentially serious adverse patient outcomes. There are reported cases involving commonly prescribed opioids including fentanyl and tramadol. However, we believe this is the first reported clinical case of acute transient opioid-induced secondary hypoadrenalism associated with fasting hypoglycaemia.

Desmetramadol Has the Safety and Analgesic Profile of Tramadol Without Its Metabolic Liabilities: Consecutive Randomized, Double-Blind, Placebo- and Active Comparator-Controlled Trials

Desmetramadol is an investigational analgesic consisting of (+) and (-) enantiomers of the tramadol metabolite O-desmethyltramadol (M1). Tramadol is racemic and exerts analgesia by monoaminergic effects of (-)-tramadol and (-)-M1, and by the opioid (+)-M1. Tramadol labeling indicates cytochrome P450 (CYP) isozyme 2D6 ultrarapid metabolizer can produce dangerous (+)-M1 levels, and CYP2D6 poor metabolizers insufficient (+)-M1 for analgesia. We hypothesized that desmetramadol could provide the safety and analgesia of tramadol without its metabolic liabilities. We conducted consecutive double-blind, randomized, placebo-controlled, 3 segment cross-over trials A and B to investigate the steady-state pharmacokinetics and analgesia of 20 mg desmetramadol and 50 mg tramadol in 103 healthy participants without (n = 43) and with (n = 60) cotreatment with the CYP inhibitor paroxetine. In the absence of CYP inhibition (trial A), 20 mg desmetramadol and 50 mg tramadol dosed every 6 hours gave equivalent steady-state (+)-M1, similar adverse events, and analgesia significantly greater than placebo, but equal to each other. In trial B, CYP inhibition significantly depressed tramadol steady-state (+)-M1, reduced its adverse events, and led to insignificant analgesia comparable with placebo. In contrast, CYP inhibition in trial B had no deleterious effect on desmetramadol (+)-M1 or (-)-M1, which gave significant analgesia as in trial A and superior to tramadol (P = .003). Desmetramadol has the safety and efficacy of tramadol without its metabolic liabilities. CLINICALTRIALS.GOV REGISTRATIONS: NCT02205554, NCT03312777 PERSPECTIVE: To our knowledge, this is the first study of desmetramadol in humans and the first to show it provides the same safety and analgesia as tramadol, but without tramadol's metabolic liabilities and related drug-drug interactions. Desmetramadol could potentially offer expanded safety and usefulness to clinicians seeking an alternative to schedule II opioids.

Projected Prevalence of Actionable Pharmacogenetic Variants and Level A Drugs Prescribed Among US Veterans Health Administration Pharmacy Users

IMPORTANCE

Implementation of pharmacogenetic testing to guide drug prescribing has potential to improve drug response and prevent adverse events. Robust data exist for more than 30 gene-drug pairs linking genotype to drug response phenotypes; however, it is unclear which pharmacogenetic tests, if implemented, would provide the greatest utility for a given patient population.

OBJECTIVES

To project the proportion of veterans in the US Veterans Health Administration (VHA) with actionable pharmacogenetic variants and evaluate how testing might be associated with prescribing decisions.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included veterans who used national VHA pharmacy services from October 1, 2011, to September 30, 2017. Data analyses began April 26, 2018, and were completed February 6, 2019.

EXPOSURES

Receipt of level A drugs based on VHA pharmacy dispensing records.

MAIN OUTCOMES AND MEASURES

Projected prevalence of actionable pharmacogenetic variants among VHA pharmacy users based on variant frequencies from the 1000 Genomes Project and veteran demographic characteristics; incident number of level A prescriptions, and proportion of new level A drug recipients projected to carry an actionable pharmacogenetic variant.

RESULTS

During the study, 7 769 359 veterans (mean [SD] age, 58.1 [17.8] years; 7 021 504 [90.4%] men) used VHA pharmacy services. It was projected that 99% of VHA pharmacy users would carry at least 1 actionable pharmacogenetic variant. Among VHA pharmacy users, 4 259 153 (54.8%) received at least 1 level A drug with 1 188 124 (15.3%) receiving 2 drugs, and 912 189 (11.7%) receiving 3 or more drugs. The most common incident prescriptions during the study were tramadol (923 671 new recipients), simvastatin (533 928 new recipients), citalopram (266 952 new recipients), and warfarin (205 177 new recipients). Gene-drug interactions projected to have substantial clinical impacts in the VHA population include the interaction of SLCO1B1 with simvastatin (1 988 956 veterans [25.6%]), CYP2D6 with tramadol (318 544 veterans [4.1%]), and CYP2C9 or VKORC1 with warfarin (7 163 349 veterans [92.2%]).

CONCLUSIONS AND RELEVANCE

Clinically important pharmacogenetic variants are highly prevalent in the VHA population. Almost all veterans would carry an actionable variant, and more than half of the population had been exposed to a drug affected by these variants. These results suggest that pharmacogenetic testing has the potential to affect pharmacotherapy decisions for commonly prescribed outpatient medications for many veterans.

Revisiting Tramadol: A Multi-Modal Agent for Pain Management

Tramadol-an atypical opioid analgesic-has a unique pharmacokinetic and pharmacodynamic profile, with opioidergic, noradrenergic, and serotonergic actions. Tramadol has long been used as a well-tolerated alternative to other drugs in moderate pain because of its opioidergic and monoaminergic activities. However, cumulative evidence has been gathered over the last few years that supports other likely mechanisms and uses of tramadol in pain management. Tramadol has modulatory effects on several mediators involved in pain signaling, such as voltage-gated sodium ion channels, transient receptor potential V1 channels, glutamate receptors, α₂-adrenoceptors, adenosine receptors, and mechanisms involving substance P, calcitonin gene-related peptide, prostaglandin E₂, and proinflammatory cytokines. Tramadol also modifies the crosstalk between neuronal and non-neuronal cells in peripheral and central sites. Through these molecular effects, tramadol could modulate peripheral and central neuronal hyperexcitability. Given the broad spectrum of molecular targets, tramadol as a unimodal analgesic relieves a broad range of pain types, such as postoperative, low back, and neuropathic pain and that associated with labor, osteoarthritis, fibromyalgia, and cancer. Moreover, tramadol has anxiolytic, antidepressant, and anti-shivering activities that could improve pain management outcomes. The aim of this review was to address these issues in the context of maladaptive physiological and psychological processes that are associated with different pain types.

Tramadol induces changes in Δ-FosB, µ-opioid receptor, and p-CREB level in the nucleus accumbens and prefrontal cortex of male Wistar rat

BACKGROUND

Besides the analgesic effect of tramadol, prolonged exposure to tramadol can induce adaptive changes thereby leading to dependence and tolerance. Tramadol induces its effect via µ-opioid receptor (MOR). However, tramadol has other targets such as serotonin and epinephrine transporters.

OBJECTIVE

CREB and ΔFosB are transcriptional factors, which are involved in the behavioral abnormalities underlying drug abuse. In this study, the effects of acute and chronic tramadol treatments on MOR, ΔFosB, and CREB levels were studied.

METHODS

For this purpose, 36 male Wistar rats were used. The animals were divided into two main groups. A total of 18 animals received tramadol (0, 5, and 10 mg/kg) acutely and 18 animals received the same doses for the following 14 days. One hour after the last injection, the NAC and PFC were dissected and kept at -80°C in liquid nitrogen. Using western blotting technique, the levels of MOR, ΔFosB, and p-CREB were evaluated.

RESULTS

In the NAC, acute tramadol exposure increases the levels of MOR and p-CREB. Moreover, chronic tramadol administration in this region results in elevated levels of MOR, ΔFosB and p-CREB compared with saline-treated rats. The levels of MOR and p-CREB in the PFC increased in both acute and chronic tramadol exposure. Also, ΔFosB levels increased only following chronic tramadol administration. The results revealed that adaptive changes occurred during drug exposure.

CONCLUSION

We concluded that both CREB and ΔFosB played a role in tramadol dependence. Additionally, increased MOR levels during tramadol treatments might be due to receptor desensitization.

Evaluation of Tramadol-Midazolam-Ketamine Anaesthesia in Rabbits

Selected anaesthetic indices of, and the heart rate, respiratory rate and rectal temperature responses of 6 healthyrabbits to the intramuscular administration of 2mg/kg midazolam and 25 mg/kg ketamine alone (MK) and combined with4mg/kg tramadol (MKT) were evaluated over a 60-min observation period. Time to loss of righting reflex with MKT(1.7±0.3min) was significantly (p˂0.05) shorter than with MK (4.2±1.5min). Duration of recumbency with MKT(76.8±5.1min) and MK (77.8±3.6min) were similar. Time to standing with MKT (9.3±1.1min) was shorter than with MK(15.2±2.4 min). Mean heart rates ranged from 204.7±13.0 to 257.5±3 beats/min with MK, and from 207.3±4.6 to 238.8±8.7beats/min with MKT. Mean respiratory rates ranged from 33.8±6.2 to 64.3±15.0 breaths/min with MK; from 36.2±2.5 to54.0±8.6 breaths/min with MKT. Mean temperature ranged between 38.0±0.2 and 38.9±0.2oC with MK and between37.9±0.3 and 39.1±0.1oC with MKT. Neither MK nor MKT produced analgesia. It was concluded that although the inclusionof tramadol did not produce analgesia, it produced a faster onset of action than midazolam-ketamine alone. Midazolamketamine-tramadol will be useful for non-painful procedures where rapid drug action is needed.

Analgesic effect of morphine and tramadol in standard toxicity assays in mice injected with venom of the snake Bothrops asper

Routine laboratory animal tests necessary to assess the toxicity of snake venoms and the preclinical neutralizing ability of antivenoms and other inhibitory substances induce significant pain and distress. This has prompted initiatives to introduce the routine use of analgesia. In this study, the analgesic effect of morphine and tramadol was assessed in tests assessing the lethal, hemorrhagic, myotoxic and edema-forming activities of the venom of the viperid snake Bothrops asper. The Mouse Grimace Scale (MGS) and mouse-exploration activity were used to assess pain and its inhibition by the analgesics. Results demonstrate that tests assessing lethality and myotoxicity induce higher levels of pain than assays quantifying hemorrhagic and edema-forming activities. Our observations also indicate that pretreatment of mice with both analgesics, at the doses used, were similarly effective in reducing the MGS magnitude and increase mouse-exploration activity after the administration of B. asper venom. Moreover, the analgesic effect of both drugs was more evident in the myotoxic and lethality assays. Combined with previous observations showing that these analgesics do not alter the extent of toxic effects induced by B. asper venom, our results strongly indicate that the use of analgesia (using either morphine or tramadol) should be considered in the routine assessment of venom toxicity and antivenom efficacy.

Protocol for a randomised, double-blind, placebo-controlled trial to explore the effect of tramadol in the prevention of postpartum depression (ETPPD)

INTRODUCTION

Postpartum depression is one of the most commonly experienced psychological disorders for women patients undergoing caesarean section, which accounts for about one-third of puerpera worldwide. Tramadol, a commonly used analgesic with an inhibitory effect on the reuptake of norepinephrine and serotonin, is an effective and well-tolerated agent for analgesia after caesarean section. Based on the role of changes in the postpartum levels of serotonin and norepinephrine in postpartum depression, we speculated that postoperative intravenous analgesia using tramadol may decrease the incidence of postpartum depression for caesarean patients. Therefore, this trial aimed to explore the effect of tramadol in the prevention of postpartum depression.

METHODS AND ANALYSIS

A randomised double-blind placebo-controlled trial will be performed and 1230 singleton parturients will be randomised to receive patient-controlled intravenous analgesia with tramadol or hydromorphone, or patient-controlled epidural analgesia with ropivacaine. The primary outcome of this trial will be the incidence of postpartum depression at 4 weeks after the caesarean section, together with the collection of the relevant data during hospitalisation and at 3 months after the caesarean section. Subgroup data according to the preoperative depression score will be analysed. Demographic characteristics, postoperative analgesic effects and postoperative recovery score will also be summarised and presented.

ETHICS AND DISSEMINATION

The current trial protocol was approved by the Institutional Ethics Committee of Xinqiao Hospital (ID: 2017-026), Third Military Medical University, Chongqing, China. The results of this trial will be disseminated at scientific meetings and in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT03309163; Pre-results.

Evaluation of an Experimental Pain Model by Noncompartmental Analysis of Results from a Randomized Placebo Controlled Trial

BACKGROUND

Understanding analgesic pharmacodynamics (PD) in the elderly is key to optimising pain management. Electrically stimulated pain models (ESPM) permit assessment of pain responses in humans. C and A-delta sensory fibres convey pain and respond to low frequency electrical stimulus (5 and 250 Hz, respectively). Human research suggests pain tolerance threshold (PTT) is similar or decreases with age.

OBJECTIVES

To determine whether an ESPM is able to detect a difference in PTT in elderly (>/= 75 years) and young (20-40 years) subjects after single dose administration of a placebo and tramadol, a low potency analgesic.

STUDY DESIGN

Two-cohort, randomized, placebo-controlled, cross-over study.

METHODS

A noncompartmental analysis of data at 17 timepoints on 5 Hz and 250 Hz PTT over 24 h.

RESULTS

Young (16) and elderly (13) patients showed similar baseline (E0) PTT between active and placebo both overall and by age group in both frequencies. Net drug effect took into account negative and positive changes from E0. In the elderly, net peak effect on PTT produced by active treatment was significantly greater for both 5 Hz (34%) and 250 Hz (30%). Net area under the 24-h effect-time curve during active treatment was significantly higher for both 5 Hz (163 %) and 250 Hz (175%) stimulations in the elderly. No clinically significant difference was observed in the young.

LIMITATIONS

High variability in young subjects, despite efforts to remove outliers limited our ability to draw conclusions in that age group. Generalizability of results obtained from an experimental pain model in volunteers to treatment of elderly patients may be limited.

CONCLUSION

ESPM can detect a difference for pain tolerance threshold between placebo and tramadol administration in the elderly. Although both 5 Hz and 250 Hz stimulations can detect a difference, the effect size for 5 Hz is larger and seems more precise and reliable, particularly in the elderly.

KEY WORDS

Electrical pain model, elderly, geriatric, tramadol, placebo, opioid, area under the effect curve, noncompartmental analysis.

Analgesic Efficacy of Subcutaneous-Oral Dosage of Tramadol after Surgery in C57BL/6J Mice

This study investigated the analgesic activity of tramadol in female C57BL/6J mice by using a single subcutaneous injection (25 mg/kg) of tramadol combined with the same dose given in drinking water for 24 h. We then evaluated the pharmacokinetics of tramadol and its active metabolite O-demethyltramadol (M1). To evaluate pain and analgesic efficacy, we performed clinical and behavioral assessment, burrowing tests, and activity analysis and measured body weight, food and water intake in mice that were untreated (control) or underwent analgesia only (T); anesthesia and surgery (AS); or anesthesia, surgery, and analgesia (AS+T). The plasma concentration of tramadol decreased rapidly whereas, for more than 18 h, the M1 level remained stable and above its minimal analgesic concentration for humans. Total food and water intake over 24 h was comparable among all groups. Although T mice consumed tramadol-treated water in sufficient amount and frequency, AS and AS+T animals showed decreased drinking frequency during the first 4 h after surgery. Compared with control and T groups, composite pain scores and burrowing latencies increased significantly in both AS and AS+T mice after surgery, suggesting postsurgical pain. However, AS and AS+T mice did not differ significantly after surgery. In conclusion, although naïve animals ingested a sufficient amount of the drug and plasma levels appeared sufficiently high, mice markedly reduced water intake immediately after surgery. Consequently, even in combination with an initial drug injection, the subsequent voluntary tramadol intake was insufficient to reduce signs of postsurgical pain significantly after laparotomy.

The effects of tramadol administration on hippocampal cell apoptosis, learning and memory in adult rats and neuroprotective effects of crocin

Tramadol, a frequently used pain reliever drug, present neurotoxic effects associated to cognitive dysfunction. Moreover, crocin has been reported to have neuroprotective effects. The aim of this study was to assess crocin's capacity to protect learning, and memory abilities on tramadol-treated rats. A total of 35 rats were divided into five groups: Control, Saline, tramadol (50 mg/kg), tramadol + crocin(30 mg/kg), crocin groups and treated orally for 28 consecutive days. Morris water maze (MWM) and passive avoidance (PA) tests were done, followed by dissection of the rat's brains for toluidine blue and TUNEL staining. In MWM test, tramadol group spent lower time and traveled shorter distance in the target quadrant (Q1) (P < 0.05). On the other side, the traveled distance in tramadol-crocin group was higher than tramadol (P < 0.05). In PA test, both the delay for entering the dark, and the total time spent in the light compartment decreased in tramadol comparing to the control group (P < 0.05), while it increased in tramadol-crocin compared with the tramadol group (P < 0.05). In tramadol-treated animals, the dark neurons (DNs) and apoptotic cells in CA1, CA3 and DG increased (P < 0.05), while concurrent intake of crocin decreased the number of DNs and apoptotic cells in these areas (P < 0.05). Crocin was able to improve learning and memory of tramadol-treated rats and also decreased DNs and apoptotic cells in the hippocampus. Considering these results, the potential capacity of crocin for decreasing side effects of tramadol on the nervous system is suggested.