Paracetamol: new vistas of an old drug

Perioperative pain management for shoulder surgery: evolving techniques

Improving management of postoperative pain following shoulder surgery is vital for optimizing patient outcomes, length of stay, and decreasing addiction to narcotic medications. Multimodal analgesia (ie, controlling pain via multiple different analgesic methods with differing mechanisms) is an ever-evolving approach to enhancing pain control perioperatively after shoulder surgery. With a variety of options for the shoulder surgeon to turn to, this article succinctly reviews the pros and cons of each approach and proposes a potential pain management algorithm.

Pain Chemogenomics Knowledgebase (Pain-CKB) for Systems Pharmacology Target Mapping and Physiologically Based Pharmacokinetic Modeling Investigation of Opioid Drug-Drug Interactions

More than 50 million adults in America suffer from chronic pain. Opioids are commonly prescribed for their effectiveness in relieving many types of pain. However, excessive prescribing of opioids can lead to abuse, addiction, and death. Non-steroidal anti-inflammatory drugs (NSAIDs), another major class of analgesic, also have many problematic side effects including headache, dizziness, vomiting, diarrhea, nausea, constipation, reduced appetite, and drowsiness. There is an urgent need for the understanding of molecular mechanisms that underlie drug abuse and addiction to aid in the design of new preventive or therapeutic agents for pain management. To facilitate pain related small-molecule signaling pathway studies and the prediction of potential therapeutic target(s) for the treatment of pain, we have constructed a comprehensive platform of a pain domain-specific chemogenomics knowledgebase (Pain-CKB) with integrated data mining computing tools. Our new computing platform describes the chemical molecules, genes, proteins, and signaling pathways involved in pain regulation. Pain-CKB is implemented with a friendly user interface for the prediction of the relevant protein targets and analysis and visualization of the outputs, including HTDocking, TargetHunter, BBB predictor, and Spider Plot. Combining these with other novel tools, we performed three case studies to systematically demonstrate how further studies can be conducted based on the data generated from Pain-CKB and its algorithms and tools. First, systems pharmacology target mapping was carried out for four FDA approved analgesics in order to identify the known target and predict off-target interactions. Subsequently, the target mapping outcomes were applied to build physiologically based pharmacokinetic (PBPK) models for acetaminophen and fentanyl to explore the drug-drug interaction (DDI) between this pair of drugs. Finally, pharmaco-analytics was conducted to explore the detailed interaction pattern of acetaminophen reactive metabolite and its hepatotoxicity target, thioredoxin reductase.

Comparison of Intravenous Nalbuphine and Paracetamol on Maternal Hemodynamic Status, Neonatal APGAR Score, and Postoperative Pain given before Induction of General Anesthesia for Elective Cesarean Section

Background:

Stress response to endotracheal intubation and surgery is associated with exaggerated hemodynamic response and an increase in catecholamine levels which is deleterious to both the mother and fetus. We aimed to compare the effects of intravenous nalbuphine and paracetamol on maternal hemodynamic status, neonatal APGAR score, and postoperative pain using the visual analog scale for elective cesarean section under general anesthesia.

Study Design:

This was a prospective, randomized, double-blinded clinical study.

Materials and Methods:

Sixty full-term pregnant patients, belonging to the American Society of Anaesthesiologist physical status Classes I and II, scheduled for elective cesarean section under general anesthesia were enrolled for the study. The patients were randomly allocated into two groups of 30 patients each to receive paracetamol (15 mg.kg^{− 1}) in Group Pand nalbuphine (0.2 mg.kg⁻¹) in Group N before induction of general anesthesia. Maternal heart rate, blood pressure, and oxygen saturation were recorded before infusion of study drugs, after induction, after intubation, and during surgery across all periods. APGAR score of neonates was recorded by a pediatrician. Time to reach visual analogue score-1 was recorded.

Results:

Significant attenuation of maternal hemodynamic response was observed with nalbuphine compared to the paracetamol group (P < 0.05). The time to achieve visual analogue score-1 in the postoperative period was higher in the nalbuphine group. APGAR score at 1 min was significant between the groups and at 5 min, nonsignificant difference was observed (P > 0.05).

Conclusion:

Nalbuphine and paracetamol are effective in perioperative hemodynamic stability of mother and APGAR score of neonates. However, nalbuphine had better hemodynamic stability as compared to paracetamol with a comparable APGAR score at 5 min.

Effects of short-term exposure of paracetamol in the gonads of blue mussels Mytilus edulis

A growing body of literature suggests that pharmaceutical contamination poses an increasing risk to marine ecosystems. Paracetamol or acetaminophen is the most widely used medicine in the world and has recently been detected in seawater. Here, we present the results of 7 days' exposure of blue mussel adults to 40 ng/L, 250 ng/L and 100 μg/L of paracetamol. Histopathology shows that haemocytic infiltration is the most observed condition in the exposed mussels. The mRNA expression of VTG, V9, ER2, HSP70, CASP8, BCL2 and FAS in mussel gonads present different patterns of downregulation. VTG and CASP8 mRNA expression show downregulation in all exposed mussels, irrespective of sex. The V9, HSP70, BCL2 and FAS transcripts follow a concentration-dependent variation in gene expression and may therefore be considered good biomarker candidates. ER2 mRNA expression shows a downregulated trend, with a clearer dose-response relationship in males. In conclusion, this study suggests that paracetamol has the potential to alter the expression of several genes related to processes occurring in the reproductive system and may therefore impair reproduction in blue mussels.

Interleukin-22 ameliorated acetaminophen-induced kidney injury by inhibiting mitochondrial dysfunction and inflammatory responses

Acetaminophen (APAP) overdose can lead to acute, severe kidney injury, which has recently attracted considerable attention among researchers and clinicians. Unfortunately, there are no well-established treatments for APAP-induced renal injury, and the molecular mechanism of APAP-induced kidney injury is still unclear. Herein, we explored the protective effects of interleukin (IL)-22 on APAP-induced renal injury and the underlying molecular basis. We found that IL-22 could significantly alleviate the accumulation of reactive oxygen species (ROS) and ameliorate mitochondrial dysfunction, reducing APAP-induced renal tubular epithelial cell (TEC) death in vitro and in vivo. Furthermore, IL-22 could downregulate the APAP-induced NLRP3 inflammasome activation and mature IL-1β release in kidney injury. Additionally, the APAP-mediated upregulation of the serum levels of IL-18, TNF-α, IL-6, and IL-1β was obviously decreased, suggesting IL-22 has inhibitory effects on inflammatory responses. Conclusively, our study demonstrated that IL-22 exerted ameliorative effects on APAP-induced kidney injury by alleviating mitochondrial dysfunction and NLRP3 inflammasome activation, suggesting that IL-22 represents a potential therapeutic approach to treat APAP-induced kidney injury. KEY POINTS: • IL-22 could ameliorate APAP that triggered oxidative stress and mitochondrial dysfunction. • IL-22 could reduce APAP that caused inflammatory responses. Graphical abstract.

Hepatotoxicity and nephrotoxicity following long-term prenatal exposure of paracetamol in the neonatal rat: is betaine protective?

Background

Paracetamol is one of the widely used antipyretic and analgesic drug around the world. Many researchers showed that paracetamol caused to hepatotoxicity or nephrotoxicity.

Objective

In the present study, we aimed to determine whether betaine has protective effects on hepatotoxicity and nephrotoxicity in neonate rats, following to long term maternal paracetamol exposure.

Materials and methods

Randomly chosen neonates, from the neonate pools, were divided into three groups; Control (n=13), APAP (n=13), and APAP+Betaine (n=13). Physiological saline, paracetamol (30 mg/kg/day), and paracetamol (30 mg/kg/day)+betaine (800 mg/kg/day) were orally administered to the relevant groups during the pregnancy period (approximately 21 day). Following to the birth, neonates were decapitated under anaesthesia and tissue samples were taken for biochemical and histological analyses.

Results

The statistical analysis showed that, malondialdehyde and nitric oxide levels increase significantly in APAP group, while paraoxonase, arylesterase activity and glutathione levels decrease. After the betaine administration, glutathione levels, paraoxonase and arylesterase activities increased while malondialdehyde and nitric oxide levels decreased in APAP+betaine group. These biochemical findings also were supported by histological results.

Conclusion

In this study, our biochemical and histological findings indicate that betaine can protect the tissue injury caused by paracetamol.

Ferroptosis driven by radical oxidation of n-6 polyunsaturated fatty acids mediates acetaminophen-induced acute liver failure

Acetaminophen (APAP) overdose is a common cause of drug-induced acute liver failure. Although hepatocyte cell death is considered to be the critical event in APAP-induced hepatotoxicity, the underlying mechanism remains unclear. Ferroptosis is a newly discovered type of cell death that is caused by a loss of cellular redox homeostasis. As glutathione (GSH) depletion triggers APAP-induced hepatotoxicity, we investigated the role of ferroptosis in a murine model of APAP-induced acute liver failure. APAP-induced hepatotoxicity (evaluated in terms of ALT, AST, and the histopathological score), lipid peroxidation (4-HNE and MDA), and upregulation of the ferroptosis maker PTGS2 mRNA were markedly prevented by the ferroptosis-specific inhibitor ferrostatin-1 (Fer-1). Fer-1 treatment also completely prevented mortality induced by high-dose APAP. Similarly, APAP-induced hepatotoxicity and lipid peroxidation were prevented by the iron chelator deferoxamine. Using mass spectrometry, we found that lipid peroxides derived from n-6 fatty acids, mainly arachidonic acid, were elevated by APAP, and that auto-oxidation is the predominant mechanism of APAP-derived lipid oxidation. APAP-induced hepatotoxicity was also prevented by genetic inhibition of acyl-CoA synthetase long-chain family member 4 or α-tocopherol supplementation. We found that ferroptosis is responsible for APAP-induced hepatocyte cell death. Our findings provide new insights into the mechanism of APAP-induced hepatotoxicity and suggest that ferroptosis is a potential therapeutic target for APAP-induced acute liver failure.

Clinical evaluation of postoperative analgesia, cardiorespiratory parameters and changes in liver and renal function tests of paracetamol compared to meloxicam and carprofen in dogs undergoing ovariohysterectomy

Background

In veterinary medicine, the administration of nonsteroidal anti-inflammatory analgesics (NSAIDs) for the control of postsurgical pain in dogs and cats is common given the anti-inflammatory, analgesic, and antipyretic effects of these drugs. This study compared the serum biochemical changes and postoperative analgesic effects of paracetamol, meloxicam, and carprofen in bitches submitted to an ovariohysterectomy using the Dynamic Interactive Visual Analog Scale (DIVAS) and Pain Scale of the University of Melbourne (UMPS) scoring systems.

Methods

Thirty bitches of different breeds underwent elective ovariohysterectomies and were randomly assigned to one of three treatment groups: a paracetamol group [15 mg kg^-1 intravenous (IV)], a carprofen group (4 mg kg^-1 IV), and a meloxicam group (0.2 mg kg^-1 IV). All treatments were administered 30 minutes prior to surgery. Paracetamol was administered every 8 hours postoperatively for 48 hours total, while carprofen and meloxicam were intravenously administered every 24 hours. An evaluation of post-surgical pain was done with the DIVAS and the UMPS. The first post-surgical pain measurement was performed 1 hour after surgery and then 2, 4, 6, 8, 12, 16, 20, 24, 36, and 48 hours after surgery.

Results

All groups exhibited a gradual reduction in pain throughout the postoperative period in both scales; however, neither scale significantly differed between the three treatment groups (P > 0.05) during the 48 postoperative hours.

Conclusions

Paracetamol was as effective as meloxicam and carprofen for post-surgical analgesia in bitches subjected to elective ovariohysterectomy. The present study demonstrates that paracetamol may be considered a tool for the effective treatment of acute perioperative pain in dogs. Furthermore, this drug led to no adverse reactions or changes in the parameters assessed in the present study, indicating its safety.

Modification of TRPV4 activity by acetaminophen

N-Acetyl-p-aminophenol (APAP/acetaminophen) is a widely used analgesic/antipyretic with weaker inhibitory effects on cyclooxygenase compared to those of non-steroidal anti-inflammatory drugs. The effect of APAP is mediated by its metabolites, N-arachidonoyl-phenolamine and N-acetyl-p-benzoquinone imine, which activate transient receptor potential (TRP) channels, including TRP vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) or cannabinoid receptor type 1. However, the exact molecular mechanism underlying the cellular actions of APAP remains unclear. Recently, we observed that APAP promotes cell migration through TRPV4; in this study, we examined the effect of APAP on Ca²⁺-channel activity of TRPV4.

In the rat cell line PC12 expressing TRPV4, GSK1016790A (GSK), a TRPV4 agonist, stimulated an increase in [Ca²⁺]_i; these effects were abrogated by HC-067047 treatment. This GSK-induced Ca²⁺ entry through TRPV4 was inhibited by APAP in a dose-dependent manner, whereas APAP alone did not affect [Ca²⁺]_i. The specificity of the effect of APAP on TRPV4 was further confirmed using HeLa cells, which lack endogenous TRPV4 but stably express exogenous TRPV4 (HeLa-mTRPV4). GSK-induced [Ca²⁺]_i elevation was only observed in HeLa-mTRPV4 cells compared to that in the control HeLa cells, indicating the specific action of GSK on TRPV4. APAP dose-dependently suppressed this GSK-induced Ca²⁺ entry in HeLa-mTRPV4. However, it is unlikely that the metabolites of APAP were involved in these effects as the reaction in this study was rapid.

The results suggest that APAP suppresses the newly identified target TRPV4 without being metabolized and exerts antipyretic/analgesic and/or other effects on TRPV4-related phenomena in the body. The effect of APAP on TRPV4 was opposite to that on TRPV1 or TRPA1, as the latter is activated by APAP.

Lethal methemoglobinemia in the invasive brown treesnake after acetaminophen ingestion

The invasive brown treesnake (Boiga irregularis) has extirpated much of Guam's native birdlife and poses significant threats to other parts of the western Pacific. Acetaminophen (APAP) is a proven lethal oral toxicant in reptiles but the physiological mechanism is unknown. The effects of a lethal APAP oral dose on methemoglobin (MetHb, non-oxygen carrying form) levels and other blood parameters were examined in brown treesnakes. Co-oximetry was used to measure MetHb (%) and other hemoglobin species. Assessment of red blood cell integrity, white blood cell differential counts, and plasma biochemical analyses were conducted to evaluate tissue damage, stress, and liver function. Changes in oxygen carrying capacity were noted in APAP-treated snakes indicated by a 50-60% increase in methemoglobin levels and a 40% decrease in oxyhemoglobin (oxygen-carrying form) levels compared to controls. APAP-treated snakes had decreased lymphocyte and increased monocyte counts while also having increased levels of blood analytes associate with impaired liver function and muscle damage. The proximate cause of death in APAP-treated snakes was likely acute methemoglobinemia and respiratory failure due to severe hypoxia with no observed signs of distress or pain. An orally-ingested lethal dose of APAP appears to be a humane method for lethal control of this species.

Evaluation of hepatic and renal effects in rat dams and their offspring after exposure to paracetamol during gestation and lactation

Paracetamol (PAR) is the analgesic and antipyretic of choice for pregnant and nursing women. PAR may reach the fetus and/or neonate through the placenta and/or milk and effect development. This study evaluated possible hepatic and renal effects in rat dams and their offspring exposed to PAR using a human-relevant route of administration and doses from Gestational Day 6 to Postnatal Day (PND) 21. Dams were gavaged daily with PAR (35 or 350mg kg-1) or water (CON). Dams and pups were killed on PND21 and 22 respectively, and blood was collected for biochemical analysis (aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea and creatinine). The kidneys and liver were isolated and processed for histopathological assessment and evaluation of oxidative stress markers. Compared with the CON groups, pups exposed to 350mg kg-1 PAR had increased renal reduced glutathione (GSH), whereas dams exposed to both doses of PAR increased serum AST. PAR administration did not affect parameters of general toxicity or renal and hepatic oxidative stress. In conclusion, maternal exposure to human-relevant doses of PAR by gavage was not associated with hepatic or renal toxicity in the pups or dams, but PAR was not devoid of effects. Exposure to PAR increased renal GSH in pups, which could suggest an adaptive antioxidant response, and affected maternal serum AST activity.

Analgesic use in contemporary burn practice: Applications to burn mass casualty incident planning

BACKGROUND

Determining the amount of analgesics required will help burn centers improve their ability to plan for a burn mass casualty incident (BMCI). We sought to quantify the amount of analgesics needed in an inpatient burn population. We hoped that assessing the analgesic use in daily burn care practice will potentially help estimate opioid needs in a burn mass casualty incident (BMCI).

METHODS

We included patients with burns covering equal to or less than 30% total body surface area (TBSA), admitted from spring 2013 to spring 2015. Patient records were reviewed for analgesics and adjuncts, pain scores, age and TBSA. The doses of the different opioids administered were converted into morphine equivalent doses (MED).

RESULTS

We enrolled 141 acute burn survivors with a mean TBSA of 8.2±0.6%. The lowest daily average MED per person was 24.6±2.0mg MED, recorded on the day of injury. The daily average MED per person increased until it peaked at 52.5±5.6mg MED at day 8 post-burn. Then, it declined to 24.6±3.4mg MED by day 14. Bivariate regression analysis of average MED by TBSA showed a significant positive correlation (p<0.001). The analysis of average MED by age showed a significant negative correlation (p<0001).

CONCLUSION

Our study quantified opioid requirements in an inpatient burn population and identified TBSA (positively) and age (negatively) as significant predictors.

Structural and Dynamic Characterizations Highlight the Deleterious Role of SULT1A1 R213H Polymorphism in Substrate Binding

Sulfotransferase 1A1 (SULT1A1) is responsible for catalyzing various types of endogenous and exogenous compounds. Accumulating data indicates that the polymorphism rs9282861 (R213H) is responsible for inefficient enzymatic activity and associated with cancer progression. To characterize the detailed functional consequences of this mutation behind the loss-of-function of SULT1A1, the present study deployed molecular dynamics simulation to get insights into changes in the conformation and binding energy. The dynamics scenario of SULT1A1 in both wild and mutated types as well as with and without ligand showed that R213H induced local conformational changes, especially in the substrate-binding loop rather than impairing overall stability of the protein structure. The higher conformational changes were observed in the loop3 (residues, 235-263), turning loop conformation to A-helix and B-bridge, which ultimately disrupted the plasticity of the active site. This alteration reduced the binding site volume and hydrophobicity to decrease the binding affinity of the enzyme to substrates, which was highlighted by the MM-PBSA binding energy analysis. These findings highlight the key insights of structural consequences caused by R213H mutation, which would enrich the understanding regarding the role of SULT1A1 mutation in cancer development and also xenobiotics management to individuals in the different treatment stages.

Pharmacology of Common Analgesic and Sedative Drugs Used in the Neonatal Intensive Care Unit

In this review of analgesic and sedation medication in neonates, important classes of old and newer medications commonly used in the neonatal intensive care unit setting are discussed. In addition to drug metabolism, efficacy, and safety for individual drugs, new insights into multimodal analgesic approaches suggest ways in which multiple analgesic drug classes can be combined to maximize efficacy and minimize toxicity. Opiate pharmacogenetics and the potential for a precision therapeutics approach is explored, with a final description of gaps in knowledge and a call for future research of pain and sedation control in the neonatal population.

Embryonic development, locomotor behavior, biochemical, and epigenetic effects of the pharmaceutical drugs paracetamol and ciprofloxacin in larvae and embryos of Danio rerio when exposed to environmental realistic levels of both drugs

For several years, the scientific community has been concerned about the presence of pharmaceuticals in the wild, since these compounds may have unpredictable deleterious effects on living organisms. Two examples of widely used pharmaceuticals that are present in the environment are paracetamol and ciprofloxacin. Despite their common presence in the aquatic environment due to their poor removal by sewage treatment plants, knowledge concerning their putative toxic effects is still scarce. This work aimed to characterize the effects of paracetamol (0.005, 0.025, 0.125, 0.625, and 3.125 mg/L) and ciprofloxacin (0.005, 0.013, 0.031, 0.078, 0.195, and 0.488 μg/L) in zebrafish embryos and larvae, exposed to environmentally relevant levels, close to the real concentrations of these pharmaceuticals in surface waters and effluents. The adopted toxic end points were developmental, a behavioral parameter (total swimming time), and a biomarker-based approach (quantification of the activities of catalase, glutathione-S-transferase, cholinesterases, glutathione peroxidase, and lipid peroxidation levels) combined with epigenetic analysis (immunohistochemical detection of 5-methylcytidine). Exposure to paracetamol had effects on all of the adopted toxic end points; however, ciprofloxacin only caused effects on behavioral tests and alterations in biomarkers. It is possible to ascertain the occurrence of oxidative stress following exposure to both drugs, which was more evident regarding paracetamol, an effect that may be related to the observed epigenetic modifications.

Comparing cost and effectiveness of IVPCA morphine with perioperative multimodal analgesia of oral etoricoxib and oxycontin: A retrospective study

Introduction

Good pain control modality for post total knee replacement promotes patient's comfort and facilitates functional recovery, which may prevent post-operative complications; and shorten hospital stay. Therefore, manage pain efficiently and effectively have financial implications to the hospital. This retrospective study analyzed the clinical outcomes and costs of the intravenous (IV) patient-controlled analgesia (PCA) with a new perioperative multimodal analgesia (PMA) of using etoricoxib and oxycontin.

Methods

This retrospective study analyzed a total of 102 inpatients, 53 received both IVPCA and regular oral analgesics from September 2016 to February 2017, while 49 received preemptive oral etoricoxib before surgery and duly together with oxycontin and paracetamol after surgery from September 2017 to February 2018. Pain scores as the primary outcome were measured by Numeric Rating Scale (0–10) at rest (NRS-R) and on movement (NRS-M). They were analyzed by one-way analysis of covariance (ANCOVA). Other outcomes included side effects from analgesics, range of motion (ROM^o), patient satisfaction, length of hospital stay and costs of medications.

Results

Patients in PMA group achieved better outcomes than PCA group. NRS-M of PMA group shown lower mean pain score and (standard error) than PCA group (2.96 [0.31] vs 4.26 [0.29]; p = 0.003), side effects from analgesics (18% vs 45%), ROM≥ 90° (55.1% vs 30.2%), patient satisfaction (8.97 vs 7.5 out of 10; p = 0.005), and length of hospital stay (6 days vs 8 days; p < 0.001). Moreover, the medication cost of PMA was 59.9% lower than PCA regimen.

Conclusions

This PMA approach achieved better outcomes and saved hospital costs.

A Single δ9-Tetrahydrocannabinol (THC) Dose During Brain Development Affects Markers of Neurotrophy, Oxidative Stress, and Apoptosis

δ⁹-tetrahydrocannabinol (THC) is one of the most used drugs during pregnancy and lactation and efficiently crosses the placental and blood–brain barriers. Despite the recent legalization initiatives worldwide, the adverse outcome pathway (AOP) of THC following exposure during brain development is incompletely understood. We have previously reported that a single injection of THC on postnatal day (PND) 10 altered adult spontaneous behavior and habituation rates in adult mice. Similar behavioral alterations have been reported following PND 10 exposure to the commonly used over-the-counter analgesic acetaminophen (AAP; also known as paracetamol); as both THC and AAP interact with the endocannabinoid system, we hypothesize that this system might be involved in the AOP of both these pharmaceuticals/drugs. Here, we report that a single THC dose on PND 10 decreased transcript levels of tropomyosin receptor kinase b (Trkb) 24 h after exposure in both the frontal and parietal cortex, and in the hippocampus in mice. An increase in the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) ratio were also found in both the parietal cortex and hippocampus following neonatal exposure to THC. In addition, THC exposure increased transcript levels of cannabinoid receptor type 1 (Cb1r) in the parietal cortex and increased the apoptosis regulator BAX in the frontal cortex. This study is important for mainly 3 reasons: 1) we are starting to get information on the developmental neurotoxic AOP of PND 10 exposure to THC, where we suggest that transcriptional changes of the neurotrophic receptor Trkb are central, 2) our PND 10 exposure model provides information relevant to human exposure and 3) since PND 10 exposure to AAP also decreased Trkb transcript levels, we suggest THC and AAP may share key events in their respective AOP through endocannabinoid-mediated alterations of the brain-derived neurotrophic factor (BDNF)-TRKB signaling pathway.

Potential Novel Strategies for the Treatment of Dental Pulp-Derived Pain: Pharmacological Approaches and Beyond

The diagnosis and management of pain is an everyday occurrence in dentistry, and its effective control is essential to ensure the wellbeing of patients. Most tooth-associated pain originates from the dental pulp, a highly vascularized and innervated tissue, which is encased within mineralized dentin. It plays a crucial role in the sensing of stimuli from the local environment, such as infections (i.e. dental caries) and traumatic injury, leading to a local inflammatory response and subsequently to an increase in intra-pulp pressure, activating nerve endings. However, thermal, chemical, and mechanical stimuli also have the ability to generate dental pulp pain, which presents mechanisms highly specific to this tissue and which have to be considered in pain management. Traditionally, the management of dental pulp pain has mostly been pharmacological, using non-steroidal anti-inflammatory drugs (NSAIDs) and opioids, or restorative (i.e. removal of dental caries), or a combination of both. Both research areas continuously present novel and creative approaches. This includes the modulation of thermo-sensitive transient receptor potential cation channels (TRP) by newly designed drugs in pharmacological research, as well as the use of novel biomaterials, stem cells, exosomes and physical stimulation to obtain pulp regeneration in regenerative medicine. Therefore, the aim of this review is to present an up-to-date account of causes underlying dental pain, novel treatments involving the control of pain and inflammation and the induction of pulp regeneration, as well as insights in pain in dentistry from the physiological, pharmacological, regenerative and clinical perspectives.

The Crystal Structure of Orthocetamol Solved by 3D Electron Diffraction

Orthocetamol is a regioisomer of the well-known pain medication paracetamol and a promising analgesic and an anti-arthritic medicament itself. However, orthocetamol cannot be grown as single crystals suitable for X-ray diffraction, so its crystal structure has remained a mystery for more than a century. Here, we report the ab-initio structure determination of orthocetamol obtained by 3D electron diffraction, combining a low-dose acquisition method and a dedicated single-electron detector for recording the diffracted intensities. The structure is monoclinic, with a pseudo-tetragonal cell that favors multiple twinning on a scale of a few tens of nanometers. The successful application of 3D electron diffraction to orthocetamol introduces a new gold standard of total structure solution in all cases where X-ray diffraction and electron-microscope imaging methods fail.

Mangiferin ameliorates acetaminophen-induced hepatotoxicity through APAP-Cys and JNK modulation

An overdose of the most popular analgesic, acetaminophen (APAP), is one of the leading causes of acute liver failure. It is well established that glutathione is exhausted by APAP-reactive intermediate N‑acetyl‑p‑benzoquinone-imine (NAPQI). This leads to elevated phosphorylated-c-Jun N-terminal kinase (p-JNK), which further activates reactive oxygen species (ROS), initiates an inflammatory response, and finally leads to severe hepatic injury. The present study was conducted to investigate the protective role of mangiferin (MAN), a naturally occurring xanthone and anti-oxidant, on APAP-induced hepatotoxicity. C57BL/6 mice were pretreated with or without MAN at 1 h prior to APAP challenge. MAN was administered at a dose of 12.5-50 mg/kg along with APAP at a dose of 400 mg/kg. According to the ALT/AST ratio, 25 mg/kg MAN was the most potent dose for further experiments. Serum ALT and AST depletion were observed in APAP + MAN (25 mg/kg)-treated mice at 6, 12, and 24 h. Early (1 h after APAP treatment) GSH depletion by APAP overdose was restored by MAN treatment, which reduced APAP-Cys adduct formation and promoted protection. p-JNK downregulation and AMPK activation were observed in MAN-treated mice, which could mechanistically reduce oxidative stress and inflammation. MAN up-regulated liver GSH and SOD and reduced lipid peroxidation. HO-1 protein and p47 phox mRNA expression indicated that MAN regulated oxidative stress along with JNK deactivation. The expression of inflammatory response genes TNF-α, IL-6, MCP-1, CXCL-1, and CXCL-2 reached the basal levels after MAN treatment. mRNA, protein, and serum levels of IL-1β were reduced, and NF-κB expression was similar to that of the MAN-treated APAP mice. MAN post-treatment (1 h after APAP treatment) also protected the mice from hepatotoxicity. In conclusion, MAN had a protective and therapeutic role in APAP-induced hepatotoxicity by improving the metabolism of acetaminophen and APAP-Cys adduct formation followed by JNK-mediated oxidative stress and inflammation.

The Influence of Acetaminophen on Task Related Attention

Our study was designed to examine whether the pain reliever acetaminophen impacts the normal ebb-and-flow of off-task attentional states, such as captured by the phenomenon of mind wandering. In a placebo-controlled between-groups design, participants performed a sustained attention to response task while event-related potentials (ERPs) to target events were recorded. Participants were queried at random intervals for their attentional reports – either “on-task” or “off-task.” The frequency of these reports and the ERPs generated by the preceding target events were assessed. Behaviorally, the frequency of off-task attentional reports was comparable between groups. Electrophysiologically, two findings emerged: first, the amplitude of the P300 ERP component elicited by target events was significantly attenuated during off-task vs. on-task attentional states in both the acetaminophen and placebo groups. Second, the amplitude of the LPP ERP component elicited by target events showed a significant decrease during off-task attentional states that was specific to the acetaminophen group. Taken together, our findings support the conclusion that acetaminophen doesn’t impact our relative propensity to drift into off-task attentional states, but it does affect the depth of neurocognitive disengagement during off-task attentional states, and in particular, at the level of post-categorization stimulus evaluations indexed by the LPP.

Rational Design of Multitarget-Directed Ligands: Strategies and Emerging Paradigms

Due to the complexity of multifactorial diseases, single-target drugs do not always exhibit satisfactory efficacy. Recently, increasing evidence indicates that simultaneous modulation of multiple targets may improve both therapeutic safety and efficacy, compared with single-target drugs. However, few multitarget drugs are on market or in clinical trials, despite the best efforts of medicinal chemists. This article discusses the systematic establishment of target combination, lead generation, and optimization of multitarget-directed ligands (MTDLs). Moreover, we analyze some MTDLs research cases for several complex diseases in recent years and the physicochemical properties of 117 clinical multitarget drugs, with the aim to reveal the trends and insights of the potential use of MTDLs.

Exposure to acetaminophen impairs vasodilation, increases oxidative stress and changes arterial morphology of rats

Acetaminophen (APAP) is one of the most widely consumed drugs in the world. Studies have shown renal and hepatic damage as the direct result of high oxidative stress induced by APAP. Since the cardiovascular system is sensitive to oxidative stress and literature describes increased cardiovascular dysfunction in APAP consumers, this work aimed to evaluate harmful effects of APAP on the vascular system. Rats were exposed to APAP (400 mg/kg/day in drinking water) for 14 days. Plasma and aortas were collected and stored in - 80 °C and a selection of arteries was prepared for isometric tension recordings, morphological, immunohistochemical and protein expression analysis. The APAP-treated group presented increased transaminases (ALT/AST) and malondialdehyde levels in the plasma compared to controls. Lipid peroxidation, glutathione reductase and superoxide dismutase levels were increased in the plasma and arteries of the APAP group. Nevertheless, glutathione level was reduced as compared to control group. The vasodilation response to acetylcholine and sodium nitroprusside (0.1 nM to 10 µM) was also impaired after APAP treatment; however, the vascular relaxation was restored after treatment with vitamin C (100 µM). Arteries from the APAP group presented reduced wall thickness, collagen deposition, elastic fibers and increased immunoreactivity to nitrotyrosine. eNOS and sGC protein expression remained unchanged and were at similar levels as controls. These findings showed higher oxidative stress and impaired vasodilation in rats exposed to APAP. Furthermore, arteries presented reduced cell layers, collagen, elastin deposition and significantly increased immunoreactivity to nitrotyrosine after APAP treatment.

Opioid Prescribing Can Be Reduced in Oral and Maxillofacial Surgery Practice

PURPOSE

Pain management is one of the most critical aspects of practice in oral and maxillofacial surgery. The purpose of this study was to measure the change in strong (stronger than codeine 30 mg) opioid use after introducing the standardized protocol ("office protocol") designed for opioid-free postoperative pain management.

MATERIALS AND METHODS

This is a retrospective cohort study of patients who had surgical procedures performed at the NorthShore Center for Oral and Facial Surgery (Gurnee, IL). Data of patients who underwent qualified surgical procedures and filled prescriptions for strong opioids before and after introduction of the office protocol were analyzed. The primary predictor variable was introduction of the office protocol. The primary outcome variable was filling of a strong opioid prescription that was correlated to pain control as assessed by patients. Age and gender distributions also were analyzed. Proportions and associated 95% confidence intervals were used to compare the number of hydrocodone or oxycodone (strong) prescriptions filled by patients during a 3-year interval.

RESULTS

In March 2016, the office protocol for pain management, designed to decrease opioid use, was introduced. In 2015 (before introduction of the office protocol), 2,016 adult patients (15 to 85 yr old) underwent qualified surgical procedures at the author's practice, 1,184 (59%) of whom required and filled strong opioid prescriptions. In 2017 (2 yr after introduction of the office procedure) that number decreased to 19%, whereas the number of qualified surgical procedures performed remained relatively the same between the years. Postoperative pain control was not qualitatively measured but was assumed adequate and correlated with the filling of a strong opioid prescription or requiring a refill, which would be recorded as part of total prescriptions filled.

CONCLUSION

A 3-fold decrease in hydrocodone or oxycodone prescription fill was seen at the 2-year interval. As alternatives, nonsteroidal anti-inflammatory drugs, acetaminophen, and a homeopathic recovery kit (Vega Recovery Kit, StellaLife, Glenview, IL) were used for pain management for patients undergoing various oral surgery procedures.

Chronic Pain and Chronic Opioid Use After Intensive Care Discharge - Is It Time to Change Practice?

Almost half of patients treated on intensive care unit (ICU) experience moderate to severe pain. Managing pain in the critically ill patient is challenging, as their pain is complex with multiple causes. Pharmacological treatment often focuses on opioids, and over a prolonged admission this can represent high cumulative doses which risk opioid dependence at discharge. Despite analgesia the incidence of chronic pain after treatment on ICU is high ranging from 33-73%. Measures need to be taken to prevent the transition from acute to chronic pain, whilst avoiding opioid overuse. This narrative review discusses preventive measures for the development of chronic pain in ICU patients. It considers a number of strategies that can be employed including non-opioid analgesics, regional analgesia, and non-pharmacological methods. We reason that individualized pain management plans should become the cornerstone for critically ill patients to facilitate physical and psychological well being after discharge from critical care and hospital.

Acetaminophen Mitigates Myocardial Injury Induced by Lower Extremity Ischemia-Reperfusion in Rat Model

OBJECTIVE

The injury-reducing effect of acetaminophen, an effective analgesic and antipyretic on ischemia-reperfusion continues to attract great attention. This study analyzed the protective effect of acetaminophen on myocardial injury induced by ischemia-reperfusion in an experimental animal model from lower extremity ischemia-reperfusion.

METHODS

Twenty-four Sprague-Dawley female rats were randomized into three groups (n=8) as (i) control group (only laparotomy), (ii) aortic ischemia-reperfusion group (60 min of ischemia and 120 min of reperfusion) and (iii) ischemia-reperfusion + acetaminophen group (15 mg/kg/h intravenous acetaminophen infusion starting 15 minutes before the end of the ischemic period and lasting till the end of the reperfusion period). Sternotomy was performed in all groups at the end of the reperfusion period and the heart was removed for histopathological examination. The removed hearts were histopathologically investigated for myocytolysis, polymorphonuclear leukocyte (PMNL) infiltration, myofibrillar edema and focal hemorrhage.

RESULTS

The results of histopathological examination showed that acetaminophen was detected to particularly diminish focal hemorrhage and myofibrillar edema in the ischemia-reperfusion + acetaminophen group (P<0.001, P=0.011), while there were no effects on myocytolysis and PMNL infiltration between the groups (P=1.000, P=0.124).

CONCLUSION

Acetaminophen is considered to have cardioprotective effect in rats, by reducing myocardial injury induced by abdominal aortic ischemia-reperfusion.

A hepatocyte-targeting near-infrared ratiometric fluorescent probe for monitoring peroxynitrite during drug-induced hepatotoxicity and its remediation

A novel hepatocyte-targeting near-infrared ratiometric fluorescent probe named Gal-NIR is developed for detecting ONOO⁻. The probe can target the hepatocyte and assess drug-induced liver injury and its remediation in living cells and mice.

Calixapap: Calixarene-based Cluster of Acetaminophen as a Novel Antiradical Agent

In this paper, the synthesis and free-radical scavenging capacity of novel calix[4]arene-based cluster of paracetamol was reported. The phenolic structures of acetaminophen and calix[4]arene prompted us for designing a synthetic route for calix[4]arene-based cyclic tetramer of paracetamol. The present chalice-shaped cluster is the first example of calixarene/acetaminophen hybrid and paracetamol can be considered as ¼ of the synthetic cyclic tetramer. Free-radical scavenging tests were determined by the 2,2-diphenyl-1-picrylhydrazyl radical in methanol. The results of antiradical-testing showed the enhanced free-radical scavenging capacity (~ 10-fold) for the prepared chaliced-shaped cluster with respect to the corresponding single therapeutic drug unit (acetaminophen). It is maybe attributed to the multivalency, spatial preorganization, and synergistic effect of four impacted drug units in the cluster structure (clustering effect).

Phylogenetic origins for severe acetaminophen toxicity in snake species compared to other vertebrate taxa

While it has been known for a while that some snake species are extremely sensitive to acetaminophen, the underlying mechanism for this toxicity has not been reported. To investigate if essential detoxification enzymes are missing in snake species that are responsible for biotransformation of acetaminophen in other vertebrate species, livers were collected from a variety of snake species, together with samples from alligator, snapping turtle, cat, rat, and cattle. Subcellular fractions were analyzed for enzymatic activities of phenol-type sulfotransferase and UDP‑glucuronosyltransferase, total glutathione S‑transferase, and N‑acetyltransferase. The results showed that none of the snake species, together with the cat samples, had any phenol-type glucuronidation activity, and that this activity was much lower in alligator and turtle samples than in the mammalian species. Combined with the lack of N‑acetyltransferase activity in snakes and cats, this would explain the accumulation of the aminophenol metabolite, which induces methemoglobinemia and subsequent suffocation of snakes and cats after acetaminophen exposure. While previous investigations have concluded that in cats the gene for the phenol-type glucuronosyltransferase isoform has turned into a pseudogene because of several point mutations, evaluation of genomic information for snake species revealed that they have only 2 genes that may code for glucuronosyltransferase isoforms. Similarity of these genes with mammalian genes is <50%, and suggests that the expressed enzymes may act on other types of substrates than aromatic amines. This indicates that the extreme sensitivity for acetaminophen in snakes is based on a different phylogenetic origin than the sensitivity observed in cats.

Effects of the human SULT1A1 polymorphisms on the sulfation of acetaminophen,O-desmethylnaproxen, and tapentadol

BACKGROUND

Non-opioid and opioid analgesics, as over-the-counter or prescribed medications, are widely used for the management of a diverse array of pathophysiological conditions. Previous studies have demonstrated the involvement of human cytosolic sulfotransferase (SULT) SULT1A1 in the sulfation of acetaminophen, O-desmethylnaproxen (O-DMN), and tapentadol. The current study was designed to investigate the impact of single nucleotide polymorphisms (SNPs) of the human SULT1A1 gene on the sulfation of these analgesic compounds by SULT1A1 allozymes.

METHODS

Human SULT1A1 genotypes were identified by database search. cDNAs corresponding to nine SULT1A1 nonsynonymous missense coding SNPs (cSNPs) were generated by site-directed mutagenesis. Recombinant wild-type and SULT1A1 allozymes were bacterially expressed and affinity-purified. Purified SULT1A1 allozymes were analyzed for sulfation activity using an established assay procedure.

RESULTS

Compared with the wild-type enzyme, SULT1A1 allozymes were shown to display differential sulfating activities toward three analgesic compounds, acetaminophen, O-desmethylnaproxen (O-DMN), and tapentadol, as well as the prototype substrate 4NP.

CONCLUSION

Results obtained indicated clearly the impact of genetic polymorphisms on the drug-sulfation activity of SULT1A1 allozymes. Such information may contribute to a better understanding about the differential metabolism of acetaminophen, O-DMN, and tapentadol in individuals with different SULT1A1 genotypes.

Comparison of the Effects of Two Different Analgesics on Bone Regeneration During Mandibular Distraction Osteogenesis

INTRODUCTION

Mandibular distraction osteogenesis (DO) is frequently used in the management of bone defects and craniofacial deformities, with analgesics commonly administered to relieve acute postoperative pain. This experimental animal study investigated the effects of 2 analgesics, acetaminophen and acemetacin, on bone regeneration after DO.

MATERIALS AND METHODS

This study was conducted with 14 mature male New Zealand rabbits (2.8-3.2 kg) randomized into 2 groups of 7. Mandibular osteotomies were performed under optimal operating conditions, and a custom-made distractor was applied to the mandible of each subject, with distraction initiated after a 5-day latency period at a rate of 1.0 mm/d (2 × 0.5 mm/d) for 10 days. Analgesics were administered via oral gavage during the latency period and for the first 5 days of the distraction period for 10 days in total, with group I receiving acetaminophen (200 mg/kg/d) and group II receiving acemetacin (5 mg/kg/d). Subjects were sacrificed and their mandibles dissected at the end of 4 weeks postoperatively. Bone mineral density (BMD) and bone mineral content (BMC) were measured using dual-energy X-ray absorptiometry (DEXA), and histomorphometric analysis was performed to evaluate the quality of newly formed bone. Paired group comparisons of non-normally distributed numerical variables were made using the Mann-Whitney U test, with a P value of <0.05 considered statistically significant.

RESULTS

No significant differences in BMC and BMD values of intact bone, newly formed bone, or bone around the pin site were observed between the 2 groups. Histometric analysis also indicated acetaminophen and acemetacin to have similar effects on bone regeneration during distraction.

CONCLUSION

Acemetacin may be an alternative to acetaminophen for treating pain associated with DO, given the similarities in the effects of the 2 analgesics on bone regeneration. However, this finding should be supported by further experimental and human studies.

Cannabinoids and Pain: New Insights From Old Molecules

Cannabis has been used for medicinal purposes for thousands of years. The prohibition of cannabis in the middle of the 20th century has arrested cannabis research. In recent years there is a growing debate about the use of cannabis for medical purposes. The term ‘medical cannabis’ refers to physician-recommended use of the cannabis plant and its components, called cannabinoids, to treat disease or improve symptoms. Chronic pain is the most commonly cited reason for using medical cannabis. Cannabinoids act via cannabinoid receptors, but they also affect the activities of many other receptors, ion channels and enzymes. Preclinical studies in animals using both pharmacological and genetic approaches have increased our understanding of the mechanisms of cannabinoid-induced analgesia and provided therapeutical strategies for treating pain in humans. The mechanisms of the analgesic effect of cannabinoids include inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings, modulation of postsynaptic neuron excitability, activation of descending inhibitory pain pathways, and reduction of neural inflammation. Recent meta-analyses of clinical trials that have examined the use of medical cannabis in chronic pain present a moderate amount of evidence that cannabis/cannabinoids exhibit analgesic activity, especially in neuropathic pain. The main limitations of these studies are short treatment duration, small numbers of patients, heterogeneous patient populations, examination of different cannabinoids, different doses, the use of different efficacy endpoints, as well as modest observable effects. Adverse effects in the short-term medical use of cannabis are generally mild to moderate, well tolerated and transient. However, there are scant data regarding the long-term safety of medical cannabis use. Larger well-designed studies of longer duration are mandatory to determine the long-term efficacy and long-term safety of cannabis/cannabinoids and to provide definitive answers to physicians and patients regarding the risk and benefits of its use in the treatment of pain. In conclusion, the evidence from current research supports the use of medical cannabis in the treatment of chronic pain in adults. Careful follow-up and monitoring of patients using cannabis/cannabinoids are mandatory.