Paracetamol: new vistas of an old drug

Long-term adverse effects of paracetamol - a review

Paracetamol (acetaminophen) is the most commonly used drug in the world, with a long record of use in acute and chronic pain. In recent years, the benefits of paracetamol use in chronic conditions has been questioned, notably in the areas of osteoarthritis and lower back pain. Over the same period, concerns over the long-term adverse effects of paracetamol use have increased, initially in the field of hypertension, but more recently in other areas as well. The evidence base for the adverse effects of chronic paracetamol use consists of many cohort and observational studies, with few randomized controlled trials, many of which contradict each other, so these studies must be interpreted with caution. Nevertheless, there are some areas where the evidence for harm is more robust, and if a clinician is starting paracetamol with the expectation of chronic use it might be advisable to discuss these side effects with patients beforehand. In particular, an increased risk of gastrointestinal bleeding and a small (~4 mmHg) increase in systolic blood pressure are adverse effects for which the evidence is particularly strong, and which show a degree of dose dependence. As our estimation of the benefits decreases, an accurate assessment of the harms is ever more important. The present review summarizes the current evidence on the harms associated with chronic paracetamol use, focusing on cardiovascular disease, asthma and renal injury, and the effects of in utero exposure.

Efficacy of Preoperative Administration of Acetaminophen and Melatonin on Retrobulbar Block Associated Pain in Cataract Surgery

Background

Retrobulbar block is one of the chosen methods for local anesthesia in cataract surgery. Since it is a painful procedure, using analgesic and sedative drugs is recommended. Current medications have side effects and evaluating of new drugs or new uses of existing safer drugs is necessary.

Objectives

The aim of this study was to compare the administration of melatonin and acetaminophen on pain and hemodynamic changes during retrobulbar block.

Methods

In a double-blinded randomized trial, 180 patients undergoing cataract surgery were randomly divided into three groups: Melatonin group (received melatonin 6 mg), acetaminophen group (received acetaminophen 500 mg), and control group (received placebo). All drugs were administered orally 60 min before arrival to the operating room by nurses blinded to the drugs administered. All patients received fentanyl 0.5 μg/kg before retrobulbar block intravenously. Hemodynamic variables and pain score in each patient were evaluated on arrival in the operating room, during retrobulbar block, during surgery, 20 min after operation, at the end of surgery, and in the recovery room. In case of pain score more than three, additional fentanyl was administered. All data were recorded in structured data sheets.

Results

Data analysis indicated no significant differences among the groups at baseline on any of the demographic variables. Both acetaminophen and melatonin reduced the pain score significantly compared with control during retrobulbar block (P < 0.05 and P < 0.01, respectively). Administration of additional fentanyl was significantly lower in the melatonin group than the control group (P < 0.05). Hemodynamic changes were not significantly different among all groups.

Conclusions

For the first time, as far as we have studied, the analgesic effect of acetaminophen on the retrobulbar block was indicated. We also showed that melatonin can reduce pain during retrobulbar block leading to reduction of additional fentanyl during operation. It seems that both melatonin and acetaminophen may have a beneficial effect on pain control in the retrobulbar block.

The Influence of Diabetes Mellitus on Glucuronidation and Sulphation of Paracetamol in Patients with Febrile Neutropenia

BACKGROUND AND OBJECTIVES

Numerous studies have confirmed the influence of diabetes mellitus on the pharmacokinetics of drugs. Paracetamol (APAP) is an antipyretic that is commonly used in febrile neutropenia (FN) therapy. APAP is chiefly metabolised by glucuronidation and sulphation. This study assessed the influence of diabetes on the pharmacokinetics of paracetamol and its metabolites: glucuronide (APAP-glu) and sulfate (APAP-sulfate) in FN patients.

METHODS

Patients with FN received single intravenous dose 1000 mg of APAP. The FN patients were allocated to one of two groups: diabetics (DG, n = 7) or non-diabetics (NDG, n = 11). The plasma concentrations of paracetamol and its metabolites were measured with the validated high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection.

RESULTS

Pharmacokinetic parameters (mean [SD]) of APAP in the DG and NDG groups were as follows: C_max (maximum comcentration) = 21.50 [11.23] vs. 23.42 [9.79] mg/L, AUC_0-t (area under the concentration-time curve) = 44.23 [17.93] vs. 41.43 [14.57] mg·h/L, t_1/2kel (elimination half-life) = 2.28 [0.80] vs. 2.11 [0.80] h. In both groups the exposure to APAP was comparable. The study did not reveal differences between the two groups in the pharmacokinetics of APAP-glu and APAP-sulfate. The C_max and AUC_0-t ratio between the metabolites and APAP were similar.

CONCLUSIONS

No differences in the pharmacokinetics of APAP, APAP-glu and APAP-sulfate in patients with FN indicates that diabetes does not influence glucuronidation and sulfatation of paracetamol.

Simple and Economical Analytical Voltammetry in 15 μL Volumes: Paracetamol Voltammetry in Blood Serum as a Working Example

Reported is a three-electrode mini-cell for voltammetry in 15 μL solutions. The key device component is a rolled platinum foil of an inverted omega-shaped cross section, which functions as both the electrolyte container and the counter-electrode. The analytical assembly was completed with properly sized working and reference electrodes in the two terminals of the quasi-tubular Pt trough. Its applicability in electrochemical assays of 15 μL solutions was verified by redox mediator voltammetry at graphite and noble metal sensors and by trace lead stripping voltammetry. Real sample analysis was adequate for drug detection in a volunteer's blood, drawn before and 1 or 4 h after ingestion of paracetamol. In line with its known pharmacokinetics, lack of drug as well as drug presence and clearance were proven correctly in the three samples. The mini-cell here is easy to assemble and operate, indefinitely reusable, and offers valuable economy in chemical usage and minimal waste. This is primarily a versatile device for electrochemical laboratory analysis of samples that are available only in small quantities, and cost-effective quantitative screens for expensive high-molecular-weight compounds, products of microsynthesis, physiological microdialysis collections, and finger-prick blood sampling are seen as feasible targets.

Use of Intravenous Acetaminophen in Children for Analgesia After Spinal Fusion Surgery: A Randomized Clinical Trial

OBJECTIVES

Opioid pharmacotherapy is the cornerstone of postoperative analgesia. Despite its effectiveness, it has a variety of potential adverse effects. Therefore, a multimodal approach with non-opioid analgesics would be optimal. The aim of this study was to determine if intravenous (IV) acetaminophen would reduce opioid requirements and improve clinical outcomes in children after surgery.

METHODS

A single-center, randomized, double-blind study was conducted in 57 children (10-18 years old) undergoing posterior spine fusion surgery between July 2011 to May 2014. All subjects received either acetaminophen or placebo at the end of surgery, followed by repeated doses every 6 hours for a total of 8 doses.

RESULTS

In the first 24 postoperative hours, the average opioid consumption was lower for the active group compared with the placebo group (p = 0.02). The total unadjusted time to patient controlled analgesia (PCA) discontinuation was also longer in the placebo group than the active group (90 hours vs. 73 hours, p = 0.02); however, this was not statistically significant after normalizing for body weight. Additionally, time to first solid intake was longer without the use of acetaminophen (69 hours vs. 49 hours, p = 0.01).

CONCLUSIONS

Postoperative use of IV acetaminophen was associated with earlier time to diet advancement and discontinuation of IV analgesics and may result in lower opioid consumption.

Updates on Multimodal Analgesia for Orthopedic Surgery

Pain control after orthopedic surgery is challenging. A multimodal approach provides superior analgesia with fewer side effects compared with opioids alone. This approach is particularly useful in light of the current opioid epidemic in the United States. Several new nonopioid agents have emerged into the market in recent years. New agents included in this review are intravenous acetaminophen, intranasal ketorolac, and newer nonsteroidal anti-inflammatory drugs, and the established medications ketamine and gabapentinoids. This article evaluates the evidence supporting these drugs in a multimodal context, including a brief discussion of cost.

The dark side of ibuprofen in the treatment of patent ductus arteriosus: could paracetamol be the solution?

INTRODUCTION

Patent ductus arteriosus (PDA) persistence is associated, in prematures, to several complications. The optimal PDA management is still under debate, especially regarding the best therapeutic approach and the time to treat. The available drugs are not exempt from contraindications and side effects; ibuprofen itself, although representing the first-choice therapy, can show nephrotoxicity and other complications. Paracetamol seems a valid alternative to classic nonsteroidal anti-inflammatory Drugs, with a lower toxicity. Areas covered: Through an analysis of the published literature on ibuprofen and paracetamol effects in preterm neonates, this review compares the available treatments for PDA, analyzing the mechanisms underlining ibuprofen-associated nephrotoxicity and the eventual paracetamol-induced hepatic damage, also providing an update of what has been yet demonstrated and a clear description of the still open issues. Expert Opinion: Paracetamol is an acceptable alternative in case of contraindication to ibuprofen; its toxicity, in this setting, is very low. Lower doses may be effective, with even fewer risks. In the future, paracetamol could represent an efficacious first-line therapy, although its safety, optimal dosage, and global impact have to be fully clarified through long-term trials, also in the perspective of an individualized and person-based therapy taking into account the extraordinary individual variability.

Effects of opioid- and non-opioid analgesics on responses to psychosocial stress in humans

Both preclinical and clinical evidence suggests that the endogenous opioid system is involved in responses to stress. For example, in animal models opioid agonists reduce isolation distress whereas opioid antagonists increase isolation distress. We recently reported that the mixed mu agonist and kappa antagonist buprenorphine dampened responses to acute psychosocial stress in humans. Now we extend this to study the effects of a pure mu-opioid agonist, hydromorphone, and a non-opioid analgesic, acetaminophen, on response to social stress. We compared the effect of hydromorphone (2 and 4 mg), acetaminophen (1000 mg) to a placebo using a between subject design. Healthy adult volunteers were randomly assigned to receive placebo (N = 13), 2 mg hydromorphone (N = 12), 4 mg hydromorphone (N = 12), or 1000 mg acetaminophen (paracetamol; N = 13) under double-blind conditions before undergoing a stress task or a control task on two separate sessions. The stress task, consisting of a standardized speaking task and the non-stressful control task were presented in counterbalanced order. Dependent measures included mood ratings, subjective appraisal of the stress (or no-stress) task, salivary cortisol, pupil diameter, heart rate, and blood pressure. The stress task produced its expected increase in heart rate, blood pressure, salivary cortisol, pupil diameter, and subjective ratings of anxiety and negative mood. Hydromorphone dose-dependently dampened cortisol responses to stress, and decreased ratings of how "challenging" participants found the task. Acetaminophen did not affect physiological responses, but, like hydromorphone, decreased ratings of how "challenging" the task was. The hydromorphone results support the idea that the mu-opioid system is involved in physiological responses to acute stress in humans, in line with results from preclinical studies. The non-opioid analgesic acetaminophen did not dampen physiological responses, but did reduce some components of psychological stress. It remains to be determined how both opioid and non-opioid systems mediate the complex physiological and psychological responses to social stress.

Prenatal paracetamol exposure and child neurodevelopment: A review

BACKGROUND

The non-prescription medication paracetamol (acetaminophen, APAP) is currently recommended as a safe pain and fever treatment during pregnancy. However, recent studies suggest a possible association between APAP use in pregnancy and offspring neurodevelopment.

OBJECTIVES

To conduct a review of publications reporting associations between prenatal APAP use and offspring neurodevelopmental outcomes.

METHODS

Relevant sources were identified through a key word search of multiple databases (Medline, CINAHL, OVID and TOXNET) in September 2016. All English language observational studies of pregnancy APAP and three classes of neurodevelopmental outcomes (autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and intelligence quotient (IQ)) were included. One reviewer (AZB) independently screened all titles and abstracts, extracted and analyzed the data.

RESULTS

64 studies were retrieved and 55 were ineligible. Nine prospective cohort studies fulfilled all inclusion criteria. Data pooling was not appropriate due to heterogeneity in outcomes. All included studies suggested an association between prenatal APAP exposure and the neurodevelopmental outcomes; ADHD, ASD, or lower IQ. Longer duration of APAP use was associated with increased risk. Associations were strongest for hyperactivity and attention-related outcomes. Little modification of associations by indication for use was reported.

CONCLUSIONS

Together, these nine studies suggest an increased risk of adverse neurodevelopmental outcomes following prenatal APAP exposure. Further studies are urgently needed with; precise indication of use and exposure assessment of use both in utero and in early life. Given the current findings, pregnant women should be cautioned against indiscriminate use of APAP. These results have substantial public health implications.

Effects of human SULT1A3/SULT1A4 genetic polymorphisms on the sulfation of acetaminophen and opioid drugs by the cytosolic sulfotransferase SULT1A3

Sulfoconjugation has been shown to be critically involved in the metabolism of acetaminophen (APAP), morphine, tapentadol and O-desmethyl tramadol (O-DMT). The objective of this study was to investigate the effects of single nucleotide polymorphisms (SNPs) of human SULT1A3 and SULT1A4 genes on the sulfating activity of SULT1A3 allozymes toward these analgesic compounds. Twelve non-synonymous coding SNPs (cSNPs) of SULT1A3/SULT1A4 were investigated, and the corresponding cDNAs were generated by site-directed mutagenesis. SULT1A3 allozymes, bacterially expressed and purified, exhibited differential sulfating activity toward each of the four analgesic compounds tested as substrates. Kinetic analyses of SULT1A3 allozymes further revealed significant differences in binding affinity and catalytic activity toward the four analgesic compounds. Collectively, the results derived from the current study showed clearly the impact of cSNPs of the coding genes, SULT1A3 and SULT1A4, on the sulfating activity of the coded SULT1A3 allozymes toward the tested analgesic compounds. These findings may have implications in the pharmacokinetics as well as the toxicity profiles of these analgesics administered in individuals with distinct SULT1A3 and/or SULT1A4 genotypes.

Effect profile of paracetamol, Δ9-THC and promethazine using an evoked pain test battery in healthy subjects

BACKGROUND

A battery of evoked pain tasks (PainCart) was developed to investigate the pharmacodynamic properties of novel analgesics in early-phase clinical research. As part of its clinical validation, compounds with different pharmacological mechanisms of actions are investigated. The aim was to investigate the analgesic effects of classic and nonclassic analgesics compared to a sedating negative control in a randomized placebo-controlled crossover study in 24 healthy volunteers using the PainCart.

METHODS

The PainCart consisted of pain tasks eliciting electrical, pressure, heat, cold and inflammatory pain. Subjective scales for cognitive functioning and psychotomimetic effects were included. Subjects were administered each of the following oral treatments: paracetamol (1000 mg), Δ9-THC (10 mg), promethazine (50 mg) or matching placebo. Pharmacodynamic measurements were performed at baseline and repeated up to 10 h postdose.

RESULTS

Paracetamol did not show a significant reduction in pain sensation or subjective cognitive functioning compared to placebo. Promethazine induced a statistically significant reduction in PTT for cold pressor and pressure stimulation. Furthermore, reduced subjective alertness was observed. Δ9-THC showed a statistically significant decrease in PTT for electrical and pressure stimulation. Δ9-THC also demonstrated subjective effects, including changes in alertness and calmness, as well as feeling high and psychotomimetic effects.

CONCLUSIONS

This study found a decreased pain tolerance due to Δ9-THC and promethazine, or lack thereof, using an evoked pain task battery. Pain thresholds following paracetamol administration remained unchanged, which may be due to insufficient statistical power. We showed that pain thresholds determined using this pain test battery are not driven by sedation.

SIGNIFICANCE

The multimodal battery of evoked pain tasks utilized in this study may play an important role in early-phase clinical drug development. This battery of pain tasks is not sensitive to the effects of sedation alone, and thus suitable to investigate the analgesic potential of novel analgesic compounds.

The hemodynamic effects of intravenous paracetamol (acetaminophen) vs normal saline in cardiac surgery patients: A single center placebo controlled randomized study

The hemodynamic effects of intravenous (IV) paracetamol in patients undergoing cardiac surgery are unknown. We performed a prospective single center placebo controlled randomized study with parallel group design in adult patients undergoing elective cardiac surgery. Participants received paracetamol (1 gram) IV or placebo (an equal volume of 0.9% saline) preoperatively followed by two postoperative doses 6 hours apart. The primary endpoint was the absolute change in systolic (SBP) 30 minutes after the preoperative infusion, analysed using an ANCOVA model. Secondary endpoints included absolute changes in mean arterial pressure (MAP) and diastolic blood pressure (DPB), and other key hemodynamic variables after each infusion. All other endpoints were analysed using random-effect generalized least squares regression modelling with individual patients treated as random effects. Fifty participants were randomly assigned to receive paracetamol (n = 25) or placebo (n = 25). Post preoperative infusion, paracetamol decreased SBP by a mean (SD) of 13 (18) mmHg, p = 0.02, compared to a mean (SD) of 1 (11) mmHg with saline. Paracetamol decreased MAP and DBP by a mean (SD) of 9 (12) mmHg and 8 (9) mmHg (p = 0.01 and 0.02), respectively, compared to a mean (SD) of 1 (8) mmHg and 0 (6) mmHg with placebo. Postoperatively, there were no significant differences in pressure or flow based hemodynamic parameters in both groups. This study provides high quality evidence that the administration of IV paracetamol in patients undergoing cardiac surgery causes a transient decrease in preoperative blood pressure when administered before surgery but no adverse hemodynamic effects when administered in the postoperative setting.

Point-of-Care Determination of Acetaminophen Levels with Multi-Hydrogen Bond Manipulated Single-Molecule Recognition (eMuHSiR)

This work aims to face the challenge of monitoring small molecule drugs accurately and rapidly for point-of-care (POC) diagnosis in current clinical settings. Overdose of acetaminophen (AP), a commonly used over the counter (OTC) analgesic drug, has been determined to be a major cause of acute liver failure in the US and the UK. However, there is no rapid and accurate detection method available for this drug in the emergency room. The present study examined an AP sensing strategy that relies on a previously unexplored strong interaction between AP and the arginine (Arg) molecule. It was found that as many as 4 hydrogen bonds can be formed between one Arg molecule and one AP molecule. By taking advantages of this structural selectivity and high tenability of hydrogen bonds, Arg, immobilized on a graphene surface via electrostatic interactions, was utilized to structurally capture AP. Interestingly, bonded AP still remained the perfect electrochemical activities. The extent of Arg-AP bonds was quantified using a newly designed electrochemical (EC) sensor. To verify the feasibility of this novel assay, based on multihydrogen bond manipulated single-molecule recognition (eMuHSiR), both pharmaceutical and serum sample were examined. In commercial tablet measurement, no significant difference was seen between the results of eMuHSiR and other standard methods. For measuring AP concentration in the mice blood, the substances in serum, such as sugars and fats, would not bring any interference to the eMuHSiR in a wide concentration range. This eMuHSiR method opens the way for future development of small molecule detection for the POC testing.

Extracts from guava fruit protect renal tubular endothelial cells against acetaminophen‑induced cytotoxicity

Acetaminophen (APAP) is an analgesic and antipyretic agent primarily used in the clinical setting. However, high doses of APAP can cause oxidative stress. Guavas have been reported to provide anti‑inflammatory, anti‑microbial, anti‑oxidative and anti‑diarrheal functions. In addition, guavas have been reported to prevent renal damage due to progression of diabetes mellitus. Therefore, the aim of the present study was to investigate whether guavas can reduce APAP‑induced renal cell damage. In the present study, extracts from guavas were obtained and added to APAP‑treated renal tubular endothelial cells. The present results demonstrated that APAP induces cytotoxicity in renal tubular endothelial cells, while guava extracts inhibited this cytotoxicity. In addition, the study demonstrated that the protective effects of guava extracts against APAP‑induced cytotoxicity may be associated with inhibition of oxidative stress and caspase‑3 activation.

In Utero Exposure to Aspirin and Risk of Asthma in Childhood

BACKGROUND

Aspirin is widely used in general population and low-dose aspirin is commonly prescribed to prevent recurrent pregnancy loss associated with antiphospholipid syndrome and preeclampsia, often used throughout pregnancy. But aspirin is associated with asthma pathogenesis. We aim to examine whether in utero exposure to aspirin at different fetal stages is associated with asthma in childhood.

METHODS

We used data from the Collaborative Perinatal Project. Maternal exposure to aspirin before and during pregnancy was recorded at each prenatal visit. Children were followed up to 7 years of age. A total of 19,928 singleton children without maternal history of asthma were included. We used multilevel multiple logistic regression models to control for potential confounders.

RESULTS

In utero exposure to aspirin was associated with an increased risk of childhood asthma (adjusted odds ratio [aORs] = 1.3, 95% confidence interval [CI] = 1.1, 1.6). aORs for exposure in first, second, and third trimesters were 1.1 (95% CI = 0.87, 1.3), 1.2 (95% CI = 1.0, 1.4), and 1.4 (95% CI = 1.1, 1.6), respectively. Furthermore, aORs of asthma were 1.3 (95% CI = 1.0, 1.7) and 1.3 (95% CI = 1.0, 1.7) for aspirin use for 2 to 7 days or more than 7 days in third trimester, respectively.

CONCLUSION

In utero exposure to therapeutic dose of aspirin even just briefly in late pregnancy is associated with childhood asthma by 7 years of age. More research is needed to carefully examine the association between low-dose aspirin with extended exposure period and long-term child outcomes.

Evaluation of a 12-Hour Sustained-Release Acetaminophen (Paracetamol) Formulation: A Randomized, 3-Way Crossover Pharmacokinetic and Safety Study in Healthy Volunteers

Acetaminophen (paracetamol) is a first-line treatment for mild and moderate pain. A twice-daily sustained-release (SR) formulation may be more convenient for chronic users than standard immediate-release (IR) acetaminophen. This randomized, 3-way crossover study evaluated pharmacokinetics and safety of single-dose 1500- and 2000-mg SR acetaminophen formulations and 2 doses of IR acetaminophen 1000 mg given 6 hours apart in healthy adults (n = 14). Primary outcome was time that plasma acetaminophen concentration was ≥4 μg/mL (TC≥4μg/mL ). Key secondary outcomes were area under the plasma concentration-time curve (AUC) from time 0 to time t, when plasma acetaminophen was detectable (AUC0-t ), AUC from 0 to infinity (AUC0-inf ), and maximum plasma acetaminophen concentration (Cmax ). TC≥4μg/mL from 2000-mg SR acetaminophen was similar to that from 2 doses of IR acetaminophen, whereas TC≥4μg/mL for 1500-mg SR acetaminophen was significantly shorter than that for IR acetaminophen (P = .004). The extent of acetaminophen absorption from 2000-mg SR and 2 doses of the IR formulation was similar and within bioequivalence limits with regard to AUC0-12 , AUC0-t , and AUC0-inf . The extent of acetaminophen absorption from 1500-mg SR was significantly lower than that from IR acetaminophen. The 2000-mg SR represents a potential candidate formulation for 12-hour dosing with acetaminophen.

Antipyretic therapy: clinical pharmacology

Fever depends on a complex physiologic response to infectious agents and other conditions. To alleviate fever, many medicinal agents have been developed over a century of trying to improve upon aspirin, which was determined to work by inhibiting prostaglandin synthesis. We present the process of fever induction through prostaglandin synthesis and discuss the development of pharmaceuticals that target enzymes and receptors involved in prostaglandin-mediated signal transduction, including prostaglandin H₂ synthase (also known as cyclooxygenase), phospholipase A₂, microsomal prostaglandin E₂ synthase-1, EP receptors, and transient potential cation channel subfamily V member 1. Clinical use of established antipyretics will be discussed as well as medicinal agents under clinical trials and future research.

A galactose-mediated targeting nanoprobe for intracellular hydroxyl radical imaging to predict drug-induced liver injury

Drug-induced liver injury (DILI) is a serious concern in modern medicine due to its unpredictability. Currently, biochemical serum markers are being used in DILI detection. However, these biomarker-based methods lack sensitivity and specificity. A high intracellular level of hydroxyl radicals (˙OH) has been regarded as an early indicator of DILI. Therefore, we proposed an ˙OH-responsive and hepatocyte-targeted nanoprobe via conjugation of carboxyfluorescein-labeled DNA and pegylated galactose on the surface of gold nanoparticles. The nanoprobe could bind to a hepatocyte-specific asialoglycoprotein receptor through galactose, and it could be internalized into liver cells. In the presence of high levels of ˙OH in DILI, the DNA could be cleaved to release carboxyfluorescein, leading to remarkable fluorescence enhancement for ˙OH detection. Confocal fluorescence imaging demonstrated that the nanoprobe could be successfully applied in monitoring high ˙OH levels resulting from acetaminophen or triptolide-induced liver injury, which may provide a simple but powerful protocol for the prediction of DILI.

A galactose-mediated targeting nanoprobe has been developed for the accurate imaging of ˙OH to predict drug-induced hepatotoxicity at an early stage.

The Analgesic Acetaminophen and the Antipsychotic Clozapine Can Each Redox-Cycle with Melanin

Melanins are ubiquitous but their complexity and insolubility has hindered characterization of their structures and functions. We are developing electrochemical reverse engineering methodologies that focus on properties and especially on redox properties. Previous studies have shown that melanins (i) are redox-active and can rapidly and repeatedly exchange electrons with diffusible oxidants and reductants, and (ii) have redox potentials in midregion of the physiological range. These properties suggest the functional activities of melanins will depend on their redox context. The brain has a complex redox context with steep local gradients in O₂ that can promote redox-cycling between melanin and diffusible redox-active chemical species. Here, we performed in vitro reverse engineering studies and report that melanins can redox-cycle with two common redox-active drugs. Experimentally, we used two melanin models: a convenient natural melanin derived from cuttlefish (Sepia melanin) and a synthetic cysteinyldopamine-dopamine core-shell model of neuromelanin. One drug, acetaminophen (APAP), has been used clinically for over a century, and recent studies suggest that low doses of APAP can protect the brain from oxidative-stress-induced toxicity and neurodegeneration, while higher doses can have toxic effects in the brain. The second drug, clozapine (CLZ), is a second generation antipsychotic with polypharmacological activities that remain incompletely understood. These in vitro observations suggest that the redox activities of drugs may be relevant to their modes-of-action, and that melanins may interact with drugs in ways that affect their activities, metabolism, and toxicities.

AM404, paracetamol metabolite, prevents prostaglandin synthesis in activated microglia by inhibiting COX activity

BACKGROUND

N-arachidonoylphenolamine (AM404), a paracetamol metabolite, is a potent agonist of the transient receptor potential vanilloid type 1 (TRPV1) and low-affinity ligand of the cannabinoid receptor type 1 (CB1). There is evidence that AM404 exerts its pharmacological effects in immune cells. However, the effect of AM404 on the production of inflammatory mediators of the arachidonic acid pathway in activated microglia is still not fully elucidated.

METHOD

In the present study, we investigated the effects of AM404 on the eicosanoid production induced by lipopolysaccharide (LPS) in organotypic hippocampal slices culture (OHSC) and primary microglia cultures using Western blot, immunohistochemistry, and ELISA.

RESULTS

Our results show that AM404 inhibited LPS-mediated prostaglandin E2 (PGE2) production in OHSC, and LPS-stimulated PGE2 release was totally abolished in OHSC if microglial cells were removed. In primary microglia cultures, AM404 led to a significant dose-dependent decrease in the release of PGE2, independent of TRPV1 or CB1 receptors. Moreover, AM404 also inhibited the production of PGD2 and the formation of reactive oxygen species (8-iso-PGF2 alpha) with a reversible reduction of COX-1- and COX-2 activity. Also, it slightly decreased the levels of LPS-induced COX-2 protein, although no effect was observed on LPS-induced mPGES-1 protein synthesis.

CONCLUSIONS

This study provides new significant insights about the potential anti-inflammatory role of AM404 and new mechanisms of action of paracetamol on the modulation of prostaglandin production by activated microglia.

Acetaminophen Relieves Inflammatory Pain through CB1 Cannabinoid Receptors in the Rostral Ventromedial Medulla

Acetaminophen (paracetamol) is a widely used analgesic and antipyretic drug with only incompletely understood mechanisms of action. Previous work, using models of acute nociceptive pain, indicated that analgesia by acetaminophen involves an indirect activation of CB₁ receptors by the acetaminophen metabolite and endocannabinoid reuptake inhibitor AM 404. However, the contribution of the cannabinoid system to antihyperalgesia against inflammatory pain, the main indication of acetaminophen, and the precise site of the relevant CB₁ receptors have remained elusive. Here, we analyzed acetaminophen analgesia in mice of either sex with inflammatory pain and found that acetaminophen exerted a dose-dependent antihyperalgesic action, which was mimicked by intrathecally injected AM 404. Both compounds lost their antihyperalgesic activity in CB₁^-/- mice, confirming the involvement of the cannabinoid system. Consistent with a mechanism downstream of proinflammatory prostaglandin formation, acetaminophen also reversed hyperalgesia induced by intrathecal prostaglandin E₂ To distinguish between a peripheral/spinal and a supraspinal action, we administered acetaminophen and AM 404 to hoxB8-CB₁^-/- mice, which lack CB₁ receptors from the peripheral nervous system and the spinal cord. These mice exhibited unchanged antihyperalgesia indicating a supraspinal site of action. Accordingly, local injection of the CB₁ receptor antagonist rimonabant into the rostral ventromedial medulla blocked acetaminophen-induced antihyperalgesia, while local rostral ventromedial medulla injection of AM 404 reduced hyperalgesia in wild-type mice but not in CB₁^-/- mice. Our results indicate that the cannabinoid system contributes not only to acetaminophen analgesia against acute pain but also against inflammatory pain, and suggest that the relevant CB₁ receptors reside in the rostral ventromedial medulla.SIGNIFICANCE STATEMENT Acetaminophen is a widely used analgesic drug with multiple but only incompletely understood mechanisms of action, including a facilitation of endogenous cannabinoid signaling via one of its metabolites. Our present data indicate that enhanced cannabinoid signaling is also responsible for the analgesic effects of acetaminophen against inflammatory pain. Local injections of the acetaminophen metabolite AM 404 and of cannabinoid receptor antagonists as well as data from tissue-specific CB₁ receptor-deficient mice suggest the rostral ventromedial medulla as an important site of the cannabinoid-mediated analgesia by acetaminophen.

Paracetamol: overdose-induced oxidative stress toxicity, metabolism, and protective effects of various compounds in vivo and in vitro

Paracetamol (APAP) is one of the most widely used and popular over-the-counter analgesic and antipyretic drugs in the world when used at therapeutic doses. APAP overdose can cause severe liver injury, liver necrosis and kidney damage in human beings and animals. Many studies indicate that oxidative stress is involved in the various toxicities associated with APAP, and various antioxidants were evaluated to investigate their protective roles against APAP-induced liver and kidney toxicities. To date, almost no review has addressed the APAP toxicity in relation to oxidative stress. This review updates the research conducted over the past decades into the production of reactive oxygen species (ROS), reactive nitrogen species (RNS), and oxidative stress as a result of APAP treatments, and ultimately their correlation with the toxicity and metabolism of APAP. The metabolism of APAP involves various CYP450 enzymes, through which oxidative stress might occur, and such metabolic factors are reviewed within. The therapeutics of a variety of compounds against APAP-induced organ damage based on their anti-oxidative effects is also discussed, in order to further understand the role of oxidative stress in APAP-induced toxicity. This review will throw new light on the critical roles of oxidative stress in APAP-induced toxicity, as well as on the contradictions and blind spots that still exist in the understanding of APAP toxicity, the cellular effects in terms of organ injury and cell signaling pathways, and finally strategies to help remedy such against oxidative damage.

Analgesics and Sport Performance: Beyond the Pain-Modulating Effects

Analgesics are used widely in sport to treat pain and inflammation associated with injury. However, there is growing evidence that some athletes might be taking these substances in an attempt to enhance performance. Although the pharmacologic action of analgesics and their use in treating pain with and without anti-inflammatory effect is well established, their effect on sport performance is debated. The aim of this review was to evaluate the evidence of whether analgesics are capable of enhancing exercise performance and, if so, to what extent. Paracetamol has been suggested to improve endurance and repeated sprint exercise performance by reducing the activation of higher brain structures involved in pain and cognitive/affective processing. Nonsteroidal anti-inflammatory drugs affect both central and peripheral body systems, but investigation on their ergogenic effect on muscle strength development has provided equivocal results. The therapeutic use of glucocorticoids is indubitable, but clear evidence exists for a performance-enhancing effect after short-term oral administration. Based on the evidence presented in this review article, the ergogenic benefit of analgesics may warrant further consideration by regulatory bodies. In contrast to the aforementioned analgesics, there is a paucity of research on the use of opioids such as tramadol on sporting performance.

LEVEL OF EVIDENCE

III.

Principles of Burn Pain Management

This article describes pathophysiology of burn injury-related pain and the basic principles of burn pain management. The focus is on concepts of perioperative and periprocedural pain management with extensive discussion of opioid-based analgesia, including patient-controlled analgesia, challenges of effective opioid therapy in opioid-tolerant patients, and opioid-induced hyperalgesia. The principles of multimodal pain management are discussed, including the importance of psychological counseling, perioperative interventional pain procedures, and alternative pain management options. A brief synopsis of the principles of outpatient pain management is provided.

Effect of acetaminophen on osteoblastic differentiation and migration of MC3T3-E1 cells

BACKGROUND

N-acetyl-p-aminophenol (APAP, acetaminophen, paracetamol) is a widely used analgesic/antipyretic with weak inhibitory effects on cyclooxygenase (COX) compared to non-steroidal anti-inflammatory drugs (NSAIDs). The mechanism of action of APAP is mediated by its metabolite that activates transient receptor potential channels, including transient receptor potential vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) or the cannabinoid receptor type 1 (CB1). However, the exact molecular mechanism and target underlying the cellular actions of APAP remain unclear. Therefore, we investigated the effect of APAP on osteoblastic differentiation and cell migration, with a particular focus on TRP channels and CB1.

METHODS

Effects of APAP on osteoblastic differentiation and cell migration of MC3T3-E1, a mouse pre-osteoblast cell line, were assessed by the increase in alkaline phosphatase (ALP) activity, and both wound-healing and transwell-migration assays, respectively.

RESULTS

APAP dose-dependently inhibited osteoblastic differentiation, which was well correlated with the effects on COX activity compared with other NSAIDs. In contrast, cell migration was promoted by APAP, and this effect was not correlated with COX inhibition. None of the agonists or antagonists of TRP channels and the CB receptor affected the APAP-induced cell migration, while the effect of APAP on cell migration was abolished by down-regulating TRPV4 gene expression.

CONCLUSION

APAP inhibited osteoblastic differentiation via COX inactivation while it promoted cell migration independently of previously known targets such as COX, TRPV1, TRPA1 channels, and CB receptors, but through the mechanism involving TRPV4. APAP may have still unidentified molecular targets that modify cellular functions.

Investigation of Drug-Induced Hepatotoxicity and Its Remediation Pathway with Reaction-Based Fluorescent Probes

Drug-induced liver injury (DILI) is considered a serious problem related to public health, due to its unpredictability and acute response. The level of peroxynitrite (ONOO^-) generated in liver has long been regarded as a biomarker for the prediction and measurement of DILI. Herein we present two reaction-based fluorescent probes (Naph-ONOO^- and Rhod-ONOO^-) for ONOO^- through a novel and universally applicable mechanism: ONOO^--mediated deprotection of α-keto caged fluorophores. Among them, Rhod-ONOO^- can selectively accumulate and react in mitochondria, one of the main sources of ONOO^-, with a substantial lower nanomolar sensitivity of 43 nM. The superior selectivity and sensitivity of two probes enable real-time imaging of peroxynitrite generation in lipopolysaccharide-stimulated live cells, with a remarkable difference from cells doped with other interfering reactive oxygen species, in either one- or two-photon imaging modes. More importantly, we elucidated the drug-induced hepatotoxicity pathway with Rhod-ONOO^- and revealed that CYP450/CYP2E1-mediated enzymatic metabolism of acetaminophen leads to ONOO^- generation in liver cells. This is the first time to showcase the drug-induced hepatotoxicity pathways by use of a small-molecule fluorescent probe. We hence conclude that fluorescent probes can engender a deeper understanding of reactive species and their pathological revelations. The reaction-based fluorescent probes will be a potentially useful chemical tool to assay drug-induced hepatotoxicity.

Endocannabinod Signal Dysregulation in Autism Spectrum Disorders: A Correlation Link between Inflammatory State and Neuro-Immune Alterations

Several studies highlight a key involvement of endocannabinoid (EC) system in autism pathophysiology. The EC system is a complex network of lipid signaling pathways comprised of arachidonic acid-derived compounds (anandamide, AEA) and 2-arachidonoyl glycerol (2-AG), their G-protein-coupled receptors (cannabinoid receptors CB1 and CB2) and the associated enzymes. In addition to autism, the EC system is also involved in several other psychiatric disorders (i.e., anxiety, major depression, bipolar disorder and schizophrenia). This system is a key regulator of metabolic and cellular pathways involved in autism, such as food intake, energy metabolism and immune system control. Early studies in autism animal models have demonstrated alterations in the brain's EC system. Autism is also characterized by immune system dysregulation. This alteration includes differential monocyte and macrophage responses, and abnormal cytokine and T cell levels. EC system dysfunction in a monocyte and macrophagic cellular model of autism has been demonstrated by showing that the mRNA and protein for CB2 receptor and EC enzymes were significantly dysregulated, further indicating the involvement of the EC system in autism-associated immunological disruptions. Taken together, these new findings offer a novel perspective in autism research and indicate that the EC system could represent a novel target option for autism pharmacotherapy.

Population pharmacokinetics of intravenous acetaminophen in Japanese patients undergoing elective surgery

INTRODUCTION

Intravenous (i.v.) acetaminophen is administered during surgery for postoperative analgesia. However, little information is available on the pharmacokinetics of i.v. acetaminophen in Japanese patients undergoing surgery under general anesthesia.

METHODS

The study was approved by the Institutional Review Board and registered at UMIN-CTR (UMIN000013418). Patients scheduled to undergo elective surgery under general anesthesia were enrolled after obtaining written informed consent. During surgery, 1 g of i.v. acetaminophen was administered over 15, 60, or 120 min. Acetaminophen concentrations (15 or 16 samples per case) were measured at time points from 0-480 min after the start of administration (liquid chromatography-mass spectrometry/tandem mass spectrometry; limit of quantitation 0.1 μg/mL). The predictive performance of three published pharmacokinetic models was evaluated. Population pharmacokinetics were also analyzed using a nonlinear mixed-effect model based on the NONMEM program.

RESULTS

Data from 12 patients who underwent endoscopic or lower limb procedures were analyzed (male/female = 7/5, median age 55 years, weight 63 kg). Anesthesia was maintained with remifentanil and propofol or sevoflurane. The pharmacokinetic model of i.v. acetaminophen reported by Würthwein et al. worked well. Using 185 datapoints, the pharmacokinetics of i.v. acetaminophen were described by a two-compartment model with weight as a covariate but not age, sex, or creatinine clearance. The median prediction error and median absolute prediction error of the final model were -1 and 10%, respectively.

CONCLUSION

A population pharmacokinetic model of i.v. acetaminophen in Japanese patients was constructed, with performance within acceptable ranges.

Repurposing AM404 for the treatment of oral infections by Porphyromonas gingivalis

Porphyromonas gingivalis is a major pathogen involved in oral diseases such as periodontitis and peri‐implantitis. Management of these diseases typically includes mechanical debridement of the colonized surfaces followed by application of antiseptics or antibiotics. Disadvantages associated with the use of antiseptics and the growing worldwide problem of antibiotic resistance have necessitated the search for alternative agents. In this study, the antibacterial and antibiofilm properties of AM404, an active metabolite of paracetamol, were tested against P. gingivalis and other bacterial pathogens. The activity of AM404 was tested against 10 bacteria, including both oral and nonoral human pathogens. The minimal inhibitory concentration (MIC) of AM404 was determined by measuring optical density (OD) values. The minimum biofilm inhibitory concentration (MBIC) was detected by crystal violet staining. The activity of structural analogs of AM404 was tested by MIC determinations. The effect of AM404 on P. gingivalis biofilms formed on titanium disks as a model for dental implants was evaluated by colony forming unit counting. Potential cytotoxicity of AM404 towards HEK‐293 (human embryonic kidney cells), HepG2 (human hepatoma cells), IEC‐6 (rat intestinal cells), and Panc‐1 cells (pancreatic cancer cells) was assessed by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assays. To get more insight in the mode of action of AM404, we used the fluorescent dyes N‐phenyl‐1‐napthylamine and SYTOX green to investigate outer and inner membrane damage of P. gingivalis induced by AM404, respectively. Of all tested pathogens, AM404 only inhibited growth and biofilm formation of P. gingivalis. Moreover, it showed potent activity against P. gingivalis biofilms formed on titanium surfaces. A structure–activity analysis demonstrated that the unsaturated carbon chain is essential for its antibacterial activity. Importantly, AM404 was not toxic towards the tested mammalian cells up to concentrations approaching 4× the MIC. Membrane damage assays using fluorescent probes N‐phenyl‐1‐napthylamine and SYTOX green revealed that membrane permeabilization presumably is the primary antibacterial mode of action of AM404. Collectively, our results suggest that AM404 has the potential to be used for the development of new drugs specifically targeting P. gingivalis‐related infections.

Comparative Study of the Effect of Intravenous Paracetamol and Tramadol in Relieving of Postoperative Pain after General Anesthesia in Nephrectomy Patients

Aim:

The aim of this study was to compare the effect of intravenous paracetamol and tramadol in relieving of postoperative pain after general anesthesia for nephrectomy in prospective donor patients for kidney transplantation.

Materials and Methods:

A randomized study was conducted on 100 adult patients scheduled for nephrectomy aged from 35 to 55 years of both sexes and divided into two groups and were administered intravenous paracetamol and tramadol for postoperative pain relief and assessed with visual analog scale score and variations in vital parameters to assess extent of pain relief.

Results:

After statistical interpretation of collected data, the observations were extrapolated. There was a statistically significant difference in the pain intensity scores obtained between the paracetamol and tramadol groups.

Conclusion:

On the basis of the present study, it is concluded that tramadol due to its lesser onset of action time was superior to paracetamol in providing acute postoperative pain relief.

Effectiveness of postoperative intravenous acetaminophen (Acelio) after gastrectomy: A propensity score-matched analysis

The aim of this study was to investigate the efficacy of postoperative scheduled intravenous acetaminophen to reduce the opioid use and enhance recovery after gastrectomy.Opioid use is reportedly associated with delayed recovery of gastrointestinal (GI) peristalsis and postoperative nausea/vomiting (PONV) despite of acceptable efficacy for pain control.Of 147 and 96 consecutive patients who underwent gastrectomy for gastric cancer before and after introduction of postoperative scheduled intravenous acetaminophen, propensity score matched population was created and short-term clinical outcomes were compared.Significant defervescence was demonstrated in Acetaminophen group (A-group) compared with control group (C-group) during the perioperative period (P < 0.001), whereas no significant difference was observed in postoperative inflammatory parameters. The incidence of postoperative complications was similar between the groups. The number of patient-controlled analgesia (PCA) pushes was significantly reduced in the A-group (P = 0.007) and the frequency of use of other nonopioid analgesics was also significantly reduced in the A-group (P < 0.001). Both daily and cumulative opioid use was significantly reduced in the A-group (P < 0.001). The time to first flatus and defecation was decreased in the A-group (P < 0.001 and P = 0.038, respectively). The incidence of PONV was significantly reduced from 26.0% to 12.5% after introduction of intravenous acetaminophen (P = 0.017), and hospital stay tended to be decreased in the A-group (13.2 vs 14.7 days, P = 0.069)Postoperative scheduled intravenous acetaminophen decreased opioid use and may be associated with enhanced recovery after gastrectomy.