Pain: current aspects on peripheral and central sensitization

Acupuncture for pediatric chronic pain: A systematic review

OBJECTIVES

To survey, analyze and discuss the scientific evidence supporting the use of acupuncture and related techniques in the management of chronic pain in the pediatric population.

SOURCES

A survey of databases (MEDLINE, Scopus and Scielo) was carried out with search strategies, following the PRISMA statement, without limits on publication dates and languages. Clinical studies (clinical trials, single-arm, and case series) were accepted for review if they included participants aged up to 22 years. Study quality was assessed by MMAT, and the randomized clinical trial was analyzed under the STRICTA criteria.

SUMMARY OF THE FINDINGS

2369 articles were retrieved. After excluding repetitions, 1335 underwent the initial selection. Only 16 articles were selected for full reading, of which 5 were included in the review, being two case series, two single-arm studies, and one randomized clinical trial. The articles were considered of good quality by the adopted criteria.

CONCLUSION

The analyzed studies showed important clinical results such as the reduction of pain intensity, and improvement in school attendance and social life. However, there are many limitations in study design and sample size. Therefore, there is weak evidence to support the use of acupuncture in the context of pediatric chronic pain, but the positive results reinforce the need for further investigation of the topic with the conduct of larger and well-designed studies, to obtain more data and greater scientific conviction of the findings.

Effect of Transcutaneous Electrical Nerve Stimulation on Pain-related Quantitative Sensory Tests in Chronic Musculoskeletal Pain and Acute Experimental Pain: Systematic Review and Meta-analysis

This report provides a systematic review of the literature to analyze the effects of transcutaneous electrical nerve stimulation (TENS) on analgesia on sensitization measures, in studies with chronic musculoskeletal pain and in studies with acute experimental pain. The protocol was registered at PROSPERO (CRD42020213473). The authors searched Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, EMBASE, Latin American and Caribbean Health Sciences Literature via Biblioteca Virtual de Saúde, Physiotherapy Evidence Database, PubMed, ScienceDirect, Web of Science, Google Scholar, and hand-searched reference lists were also conducted. Among 22,252 manuscripts found, 58 studies were included in the systematic review and 35 in the meta-analysis. Thirty-four studies assessed pain intensity; 24 studies investigated hyperalgesia; temporal summation was only evaluated in 2 studies; and conditioned pain modulation was not observed in the included studies. Meta-analyses favored TENS, despite its limitations and heterogeneity. Primary hyperalgesia in studies with musculoskeletal pain presented a high level of evidence, while other outcomes presented moderate evidence in the studies that were included. It is not possible to infer results about both temporal summation and conditioned pain modulation. Moderate evidence suggests that TENS promotes analgesia by reducing both central and peripheral sensitization, as shown by the reduction in primary and secondary hyperalgesia, pain intensity at rest, and during movement in experimental acute pain and chronic musculoskeletal pain. Overall, both types of studies analyzed in this review presented meta-analyses favorable to the use of TENS (compared to placebo TENS), showing reductions in both primary and secondary hyperalgesia, as well as decreases in pain intensity at rest and in motion. PERSPECTIVE: This article presents data from the literature on the effect of TENS through sensitization assessments in individuals with chronic musculoskeletal pain, or acute experimental pain. These data contribute to knowledge about pain neuroscience research, using TENS technology.

Can Anthocyanins Reduce Delayed Onset Muscle Soreness or Are We Barking Up the Wrong Tree?

Exercise-induced muscular overload can trigger delayed onset muscle soreness (DOMS). DOMS is related to the indiscriminate use of analgesics and nonsteroidal anti-inflammatory drugs without proper guidance, decreased physical exercise adherence and degenerating sports performance, increased risk of injury, and reduced muscle strength and function. Dietary anthocyanins have been extensively studied as potential natural treatments for DOMS, but the indication, dosage, and form of use remain highly variable. Therefore, this review aims to synergize and present evidence relating to the effect of anthocyanins on DOMS in clinical studies. Notably, the results of anthocyanin supplementation for DOMS were found to be inconclusive. The use of protocols with lower anthocyanin doses yielded better results than those with high-dose supplements, suggesting that anthocyanin-rich foods are more accessible as therapeutic tools, leading to the conclusion that these foods could be used to prevent and treat DOMS. However, consumption protocols for this purpose are not yet well established, and the answer is dependent on the methodological quality of future studies.

Peripheral Neuropathies Derived from COVID-19: New Perspectives for Treatment

Peripheral neuropathies constitute a group of disorders affecting the peripheral nervous system. Neuropathies have multiple causes such as infections (i.e., COVID-19), diabetes, and nutritional (low vitamin levels), among others. Many micronutrients, such as vitamins (A, C, D, E, B6, B12, and folate), certain minerals (Fe, Mg, Zn, Se, and Cu), and ω-3 fatty acids have immunomodulatory effects. Therefore, they may play an instrumental role in the treatment of COVID-19 infection. However, many COVID-19 patients can undergo neuropathy. In this context, there is a wealth of information on a variety of first-, second-, and third-line treatment options. This review focuses on the application of nutraceutical strategies in order to improve the symptomatology of neuropathy and neuropathic pain in patients that suffered from COVID-19. Our aim is to provide an alternative vision to traditional medical-pharmacological treatment through nutraceuticals.

Evaluation of the immediate effects of a single transcranial direct current stimulation session on astrocyte activation, inflammatory response, and pain threshold in naïve rats

Transcranial direct current stimulation (tDCS) has demonstrated clinical benefits such as analgesia, anti-inflammatory, and neuroprotective effects. However, the mechanisms of action of a single tDCS session are poorly characterized. The present study aimed to evaluate the effects of a single tDCS session on pain sensitivity, inflammatory parameters, and astrocyte activity in naive rats. In the first experiment, sixty-day-old male Wistar rats (n=95) were tested for mechanical pain threshold (von Frey test). Afterward, animals were submitted to a single bimodal tDCS (0.5mA, 20minutes) or sham-tDCS session. According to the group, animals were re-tested at different time intervals (30, 60, 120minutes, or 24hours) after the intervention, euthanized, and the cerebral cortex collected for biochemical analysis. A second experiment (n=16) was performed using a similar protocol to test the hypotheses that S100B levels in the cerebrospinal fluid (CSF) are altered by tDCS. Elisa assay quantified the levels of tumor necrosis factor-alfa (TNF-α), interleukin-10 (IL10), S100 calcium-binding protein B (S100B), and Glial fibrillary acidic protein (GFAP). Data were analyzed using ANOVA and independent t-test (P<0.05). Results showed that tDCS decreased pain sensitivity (30 and 60min), cerebral TNF-α and S100B levels (30min). CSF S100B levels increased 30minutes after intervention. There were no differences in IL10 and GFAP levels. TCDS showed analgesic, anti-inflammatory, and neuroprotective effects in naive animals. Therefore, this non-invasive and inexpensive therapy may potentially be a preemptive alternative to reduce pain, inflammation, and neurodegeneration in situations where patients will undergo medical procedures (e.g., surgery).

Pain modulated by Bothrops snake venoms: Mechanisms of nociceptive signaling and therapeutic perspectives

Snake venoms are substances mostly composed by proteins and peptides with high biological activity. Local and systemic effects culminate in clinical manifestations induced by these substances. Pain is the most uncomfortable condition, but it has not been well investigated. This review discusses Bothrops snakebite-induced nociception, highlighting molecules involved in the mediation of this process and perspectives in treatment of pain induced by Bothrops snake venoms (B. alternatus, B. asper, B. atrox, B. insularis, B. jararaca, B. pirajai, B. jararacussu, B. lanceolatus, B. leucurus, B. mattogrossensis, B. moojeni). We highlight, the understanding of the nociceptive signaling, especially in snakebite, enables more efficient treatment approaches. Finally, future perspectives for pain treatment concerning snakebite patients are discussed.

Li-ESWT treatment reduces inflammation, oxidative stress, and pain via the PI3K/AKT/FOXO1 pathway in autoimmune prostatitis rat models

BACKGROUND

Due to limited data on the pathogenesis of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) and the suboptimal therapeutic effect, the development of new and effective treatment modalities was needed urgently. Low-intensity extracorporeal shock wave therapy (Li-ESWT) has been reported for the treatment of CP/CPPS. However, the underlying mechanism remains to be elucidated.

OBJECTIVE

To interrogated the efficacy and the mechanism of Li-ESWT in the treatment of CP/CPPS.

MATERIALS AND METHODS

According to different treatments, RWPE-1 cells (human prostate epithelial cells) were randomly divided into three groups: control group, LPS(lipopolysaccharide) group, or Li-ESWT group (LPS induced RWPE-1 managed by Li-ESWT). Following the Li-ESWT treatment, the levels of oxidative stress was assayed. We then established a rat model of experimental autoimmune prostatitis (EAP) by injecting prostatic protein homogenate mixed with complete Freund's adjuvant. The Sprague-Dawley rats were randomly divided into the control group, EAP group, or Li-ESWT group. Von Frey Filament was used to quantify pelvic hyperalgesia in the rats. Prostates tissues from each group were collected for immunohistochemistry, oxidation stress, and western blot analysis.

RESULTS

Histological analysis showed reduced inflammation and expression of cytokines (TNF-α, IL-1β, IL-6, COX-2, SP) in prostate tissues from the Li-ESWT group compared with those from the EAP group (all P < 0.05). Similarly, there was reduced pelvic pain and allergic symptoms in the Li-ESWT group compared with the EAP group (all P < 0.05). Besides, Li-ESWT treatment could decrease oxidative stress in the prostate and in RWPE-1 cells, respectively (both P < 0.05). Moreover, the Li-ESWT up-regulated the expression of CAT through the inhibition of phosphorylation of AKT/FOXO1 signaling pathway.

DISCUSSION AND CONCLUSIONS

Li-ESWT may reduce inflammation, oxidative stress and pain in rats with autoimmunity-induced prostatitis via the PI3K/AKT/FOXO1 pathway. It implies that Li-ESWT can present a potential therapeutic option for the treatment of CP/CPPS.

The interrelatedness of chronic cough and chronic pain

Since chronic cough has common neurobiological mechanisms and pathophysiology with chronic pain, both clinical disorders might be interrelated. Hence, we examined the association between chronic cough and chronic pain in adult subjects in the Rotterdam Study, a large prospective population-based cohort study.Using a standardised questionnaire, chronic pain was defined as pain lasting up to 6 months and grouped into a frequency of weekly/monthly or daily pain. Chronic cough was described as daily coughing for at least 3 months duration. The longitudinal and cross-sectional associations were investigated bi-directionally.Of 7141 subjects in the study, 54% (n=3888) reported chronic pain at baseline. The co-prevalence of daily chronic pain and chronic cough was 4.4%. Chronic cough was more prevalent in subjects with daily and weekly/monthly chronic pain compared with those without chronic pain (13.8% and 10.3% versus 8.2%; p<0.001). After adjustment for potential confounders, prevalent chronic pain was significantly associated with incident chronic cough (OR 1.47, 95% CI 1.08-1.99). The association remained significant in subjects with daily chronic pain (OR 1.49, 95% CI 1.06-2.11) with a similar effect estimate, albeit non-significant in those with weekly/monthly chronic pain (OR 1.43, 95% CI 0.98-2.10). After adjustment for covariables, subjects with chronic cough had a significant risk of developing chronic pain (OR 1.63, 95% CI 1.02-2.62) compared with those without chronic cough.Chronic cough and chronic pain confer risk on each other among adult subjects, indicating that both conditions might share common risk factors and/or pathophysiologic mechanisms.

Myrciaria dubia Juice (camu-camu) Exhibits Analgesic and Antiedematogenic Activities in Mice

The Myrciaria dubia (Myrtaceae) fruit is traditionally used to treat malnutrition due to its high levels of vitamin C and phenolic compounds. Because of its composition, this plant is very promising in the research of novel natural treatment for pain disorders. This study analyzed the phytochemical profile of M. dubia juice and assessed its antinociceptive and antiedematogenic potential. The phytochemical profile was determined through high-performance liquid chromatography (HPLC), the oral antinociceptive effect of M. dubia 50% juice (Md50) was evaluated by formalin, hot plate and Complete Freund's Adjuvant tests and the antiedematogenic activity by paw edema. HPLC revealed the presence of ascorbic acid, rutin, and ellagic acid as major compounds. Md50 showed an antinociceptive effect in the acute and chronic phases of the formalin test. In the hot plate test, Md50 also induced an antinociceptive effect of 0.5 up to 6 h, showing antinociceptive and antiedematogenic potential without changing the spontaneous locomotion of animals. All protocols were submitted and approved by the Ethics Committee for use of Animals of the Lutheran University of Brazil (protocol No. 2013-30P).

Usnic Acid Potassium Salt: Evaluation of the Acute Toxicity and Antinociceptive Effect in Murine Model

To obtain usnic acid potassium salt (PS-UA), the usnic acid (UA) was extracted and purified from the lichen Cladonia substellata, and modified to produce PS-UA. The structure was determined by ¹H-NMR, IR and elemental analysis, ratified through computational models, as well as identification the site of K⁺ insertion in the molecule. Antinociceptive activity was detected through contortions in mice induced by acetic acid and formalin (phases I and II) after treatments with 10 and 20 mg/kg of PS-UA, indicating interference in both non-inflammatory and inflammatory pain. After oral administration at doses of 500, 1000 and 2000 mg/kg, no deaths of mice with treatments below 2000 mg/kg were observed. Except for body weight gain, food and water consumption decreased with treatments of 1000 and 2000 mg/kg, and the number of segmented leukocytes was higher for both treatments. Regarding serum levels, cholesterol and triglycerides decreased, however, there was an increase in hepatic transaminases with both treatments. Liver and kidney histological changes were detected in treatments of 2000 mg/kg, while the spleen was preserved. The PS-UA demonstrated antinociceptive activity while the acute toxicity at the concentration of 2000 mg/kg was the only dose that presented morphological changes in the liver and kidney.

Immune System Involvement in Specific Pain Conditions

Chronic pain is a significant problem worldwide and is the most common disability in the United States. It is well known that the immune system plays a critical role in the development and maintenance of many chronic pain conditions. The involvement of the immune system can be through the release of autoantibodies, in the case of rheumatoid arthritis, or via cytokines, chemokines, and other inflammatory mediators (i.e. substance P, histamine, bradykinin, tumor necrosis factor, interleukins, and prostaglandins). Immune cells, such as T cells, B cells and their antibodies, and microglia are clearly key players in immune-related pain. The purpose of this review is to briefly discuss the immune system involvement in pain and to outline how it relates to rheumatoid arthritis, osteoarthritis, fibromyalgia, complex regional pain syndrome, multiple sclerosis, and diabetic neuropathy. The immune system plays a major role in many debilitating chronic pain conditions and we believe that animal models of disease and their treatments should be more directly focused on these interactions.

Scapholunate interosseous ligament dysfunction as a source of elbow pain syndromes: Possible mechanisms and implications for hand surgeons and therapists

Elbow pain syndromes are common upper extremity musculoskeletal disorders, and they are usually associated with repetitive occupational exposure. Ligaments are often one of the sources of musculoskeletal disorders because of their mechanical and neurological properties. The wrist ligaments are some of the ligaments most vulnerable to occupational exposure. Since most occupational tasks require wrist extension for handling tools and loading, the scapholunate interosseous ligament (SLIL) bears greater strain during loading, which results in creep deformation and hysteresis. Ligamentous creep may result in diminished ability to detect signal changes during joint movements, which impairs neuromuscular control established by ligamentomuscular reflex arcs elicited from mechanoreceptors in the ligaments. Changes in muscle activation patterns of forearm muscles due to diminished ligamentomuscular reflexes may initiate a positive feedback loop, leading to musculoskeletal pain syndromes. The relationship between elbow pain syndromes and SLIL injury will be presented through two hypotheses and relevant pain mechanisms: 1. Repetitive tasks may cause creep deformation of the SLIL, which then impairs ligamentomuscular reflexes, leading to elbow pain disorders. 2. Lateral epicondylalgia may increase the risk of SLIL injury through the compensation of the lower extensor carpi radialis muscle activity by higher extensor carpi ulnaris muscle activity, which may alter carpal kinematics, leading to SLIL degeneration over time. The differential diagnosis is usually complicated in musculoskeletal pain disorders. The failure of treatment methods is one of the issues of concern for many researchers. A key element in developing treatment strategies is to understand the source of the disorder and the nature of the injury. We proposed that the differential diagnosis include SLIL injuries when describing elbow pain syndromes, particularly, lateral epicondylalgia.

Evidence and consensus recommendations for the pharmacological management of pain in India

Despite enormous progress in the field of pain management over the recent years, pain continues to be a highly prevalent medical condition worldwide. In the developing countries, pain is often an undertreated and neglected aspect of treatment. Awareness issues and several misconceptions associated with the use of analgesics, fear of adverse events - particularly with opioids and surgical methods of analgesia - are major factors contributing to suboptimal treatment of pain. Untreated pain, as a consequence, is associated with disability, loss of income, unemployment and considerable mortality; besides contributing majorly to the economic burden on the society and the health care system in general. Available guidelines suggest that a strategic treatment approach may be helpful for physicians in managing pain in real-world settings. The aim of this manuscript is to propose treatment recommendations for the management of different types of pain, based on the available evidence. Evidence search was performed by using MEDLINE (by PubMed) and Cochrane databases. The types of articles included in this review were based on randomized control studies, case-control or cohort studies, prospective and retrospective studies, systematic reviews, meta-analyses, clinical practice guidelines and evidence-based consensus recommendations. Articles were reviewed by a multidisciplinary expert panel and recommendations were developed. A stepwise treatment algorithm-based approach based on a careful diagnosis and evaluation of the underlying disease, associated comorbidities and type/duration of pain is proposed to assist general practitioners, physicians and pain specialists in clinical decision making.

The respiratory physiotherapy causes pain in newborns? A systematic review

Abstract Introduction: Neonatal respiratory physicaltherapy plays an important role in prevention and treatment of respiratory pathologies. In preterm neonates, immaturity of respiratory system can let development of various respiratory diseases. Meanwhile, it is discussed if respiratory physiotherapy can cause pain. Objective: Investigate presence of pain in neonates undergone to respiratory physiotherapy by a systematic review. Methods: Scientific search in electronic databases: Medline, Lilacs, Bireme, PEDro, Pubmed, Scielo and Capes thesis and dissertations base. Portuguese, English and Spanish, publication year from 2000 to 2012. Results: Thriteen studies were included, but one of them was excluded due to fulltext unavaiable. Therefore, twelve articles were included, nine (81,8%) confirm pain in newborn (NB), from these, in eight (72,7%) intervention was suction and in only one vibrocompression. Four articles studied term and premature newborns. Mechanical ventilatory assistance was used in seven of the studies analyzed. Conclusion: Results suggest that suction and vibrocompression were pain causers in NB. However, evidenced the necessity of well delineated methods to evaluate if physicaltherapy techniques can cause pain in neonates.

The effects of different TENS frequencies applied to LU7 acupoint on cold-induced pain test

Introduction Pain represents a frequent phenomenon among the general population with great socio-economic impact. TENS is one of the most common forms of electroanalgesia. However, totally effective stimulation parameters remain uncertain. Thus, this study aims to assess the effects of 4 Hz, 10 Hz and 100 Hz TENS applied to the LU7 (Lieque) acupoint on cold-induced pain in young healthy subjects. Methods 100 volunteers, divided into five groups (three TENS groups, one electrode group and one placebo group), completed six experimental cycles. Each cycle comprised three phases: pretreatment, treatment and post-treatment. In each cycle, pain was induced by immersion of the hand into ice water and the pain threshold latency was measured. For the analysis of results, we used the one-way ANOVA test, followed by the Student-Newman-Keuls post hoc test. The level of significance was p < 0.05. Results The 4 Hz TENS group the pain showed elevation of the pain threshold during the treatment phase, when compared to pretreatment (p < 0.05). This elevation was maintained in the post-treatment phase. The other groups showed no changes in the pain threshold. Conclusion 4 Hz TENS applied with 1x1 cm electrodes to LU7 acupoint increases hypothermia-induced pain threshold latency in young healthy subjects.

Spirituality of chronic orofacial pain patients: case-control study

The objective of this study was to investigate spirituality and blood parameters associated with stress in patients with facial musculoskeletal pain. Twenty-four women with chronic facial musculoskeletal pain (CFMP) and 24 healthy women were evaluated with a protocol for orofacial characteristics, research diagnostic criteria for temporomandibular disorders and the Spiritual Perspective Scale. Blood samples were collected to analyze blood count, cortisol, ACTH, C3, C4, thyroid hormones, total immunoglobulin, C-reactive protein and rheumatoid factor. The study group was more spiritualized than control group. Individuals with a high score of spirituality had less myofascial pain, less bruxism and fewer complaints. They also had lower levels of ACTH and IgE. Spirituality was higher in the study group and can be considered an important tool for coping with CFMP.

Antinociceptive, anti-inflammatory and antioxidant activities of aqueous extract from Remirea maritima (Cyperaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Remirea maritima Aubl., popularly known as "capim-da-praia", is popularly employed in the treatment of diarrhea, kidney disease, fever, and for analgesic and anti-inflammatory purposes through the preparation of teas. Few studies have focused on the chemical composition and its biological properties.

AIM OF THE STUDY

This work evaluated the antinocipetive, anti-inflammatory and antioxidant activities of the aqueous extract from Remirea maritima Aubl. as well as the isolation and identification of the chemical compounds.

MATERIALS AND METHODS

Compounds were isolated from aqueous extract of Remirea maritima through preparative HPLC and the structures were identified by means of NMR and MS analysis. The tests for antinociceptive, anti-inflammatory, and antioxidant activities, along with motor coordination test (Rota rod), were performed over the aqueous extract.

RESULTS

The phytochemical investigation of aqueous extract of Remirea maritima resulted in the isolation of three flavone glycosides. The structures of these compounds were determined by means of MS and 1D and 2D NMR data as vitexin-2″-O-β-D-glucopyranoside, isovitexin-2″-O-β-D-glucopyranoside, and luteolin-7-O-glucuronide. Acute pretreatment with aqueous extract (100, 200 or 400mg/kg, i.p.) caused a significant decrease (p<0.001) in the number of abdominal writhes. In the formalin test, higher doses significantly inhibited the late (inflammatory pain) phase of formalin-induced licking (p<0.05 or 0.001). In the hot plate test, there was no significant difference in nociceptive behavior, discarding the possible central effect of the aqueous extract. In the rota rod test, it was verified that the aqueous extract in all concentration evaluated does not alter the motor coordination of mice, such antinociceptive results were unlikely to be caused by motor abnormality. In the peritonitis test, induced by carrageenan, the treatment with aqueous extract produced a significant reduction in leukocyte migration in all concentration evaluated. Additionally, a significant reduction of lipoperoxidation (TBARS test) and in nitric oxide formation (.NO Scavenging assay) was observed in antioxidant activity assay.

CONCLUSION

The biological and phytochemical investigations of the aqueous extract of Remirea maritima resulted in the identification of three flavone glycosides that have been described here for the first time in Remirea and effective analgesic activity in various pain models, probably mediated via the inhibition of peripheral mediators which could be related to its strong antioxidant effect observed in vitro.

Evaluation of preemptive effect of epidural S(+)-ketamine for hysterectomy: plasmatic concentrations of interleukins

BACKGROUND AND OBJECTIVES

Some studies showed that ketamine inhibits the production of cytokines. The objective of this study was to evaluate the preemptive analgesic effect of epidural S(+)-ketamine in hysterectomy and plasmatic cytokines (IL-6, TNF-α and IL-10).

METHOD

A double-blinded study with 29 patients was conducted. Patients in Group 1 received 13 mL of 0.25% bupivacaine with 25mg of S(+)- ketamine 30 minutes before surgical incision and 15 mL of saline solution via the epidural route 30 minutes after. Patients in Group 2 received 15 mL of saline solution 30 minutes before the surgical incision, followed by 13 mL of 0.25% bupivacaine with 25mg of S(+)-ketamine 30 minutes after. Postoperative analgesia was made with epidural bupivacaine and fentanyl. Dipyrone 1 g was used whenever required. The following paramenters were evaluated: concentration of cytokines, intensity of pain, time of first request of analgesic and total quantity of analgesic used.

RESULTS

Time for the first request for analgesics was 61.5 minutes in Group 1 and 69.0 in Group 2, without difference between these groups. There was no difference for total dose of fentanyl used in Group 1 (221.4 μg) and Group 2 (223.3 μg). A similar analgesic effect was obtained in both groups, except in T12 (Group 1 = 2.4±3.2; Group 2 = 5.5±3.4). No differences in concentration of cytokines were observed.

CONCLUSIONS

The epidural injection of 25mg S(+)-ketamine before incision reduced the pain intensity only 12 hours after surgical incision and did not alter concentration of cytokines.

Painful peripheral neuropathies

BACKGROUND AND OBJECTIVES

Painful neuropathies are common and often difficult to treat. The objective of this report was to review the subject to facilitate diagnosis and pain relief.

CONTENTS

The classification, causes, type of fibers involved, manifestations, diagnosis, adjuvant tests, questionnaires used in the diagnosis, and treatment are described.

CONCLUSIONS

The subject is very broad and involves several causes and treatments that often should be combined to obtain adequate pain control.

Antinociceptive effect of topiramate in models of acute pain and diabetic neuropathy in rodents

This study assesses the antinociceptive effect induced by different dosages of topiramate (TP), an anticonvulsant drug that is orally administered in models of neuropathic pain and acute pain in rats and mice, respectively. Orally administered TP (80 mg/Kg) in mice causes antinociception in the first and second phases of a formalin test, while in doses of 20 and 40 mg/Kg it was only effective in the second phase. TP (80 mg/Kg, p.o) also exhibited antinociceptive action in the hot plate test, however, it did not have an effect in the capsaicin test in mice, nor in the model of neuropathic pain in diabetic rats. The antinociceptive effect caused by TP (80 mg/Kg, p.o) in the formalin test was reversed by prior treatment with naloxone (opioid antagonist), but not with glibenclamide (antagonist of the potassium channel), ondansetron (antagonist of the serotonin 5HT3 receptor) or cyproheptadine (antagonist of the serotonin 5HT2A receptor).The data show that TP has an important antinociceptive effect in the models of nociception induced by chemical (formalin) or thermal (hot plate) stimuli, and that the opioid system plays a part in the antinociceptive effect, as shown by formalin.