(–)-(1R,2R)-3-(3-Dimethylamino-1-ethyl-2-methyl-propyl)-phenol Hydrochloride (Tapentadol HCl): a Novel μ-Opioid Receptor Agonist/Norepinephrine Reuptake Inhibitor with Broad-Spectrum Analgesic Properties

Ultramicronized N-palmitoylethanolamine associated with analgesics: Effects against persistent pain

Current epidemiological data estimate that one in five people suffers from chronic pain with considerable impairment of health-related quality of life. The pharmacological treatment is based on first- and second-line analgesic drugs, including COX-2 selective and nonselective nonsteroidal anti-inflammatory drugs, paracetamol, antidepressants, anti-seizure drugs and opioids, that are characterized by important side effects. N-palmitoylethanolamine (PEA) is a body's own fatty-acid ethanolamide belonging to the family of autacoid local injury antagonist amides. The anti-inflammatory and pain-relieving properties of PEA have been recognized for decades and prompted to depict its role in the endogenous mechanisms of pain control. Together with its relative abundance in food sources, this opened the way to the use of PEA as a pain-relieving nutritional intervention. Naïve PEA is a large particle size lipid molecule with low solubility and bioavailability. Reducing particle size is a useful method to increase surface area, thereby improving dissolution rate and bioavailability accordingly. Micron-size formulations of PEA (e.g., ultramicronized and co-(ultra)micronized) have shown higher oral efficacy compared to naïve PEA. In particular, ultramicronized PEA has been shown to efficiently cross the intestinal wall and, more importantly, the blood-brain and blood-spinal cord barrier. Several preclinical and clinical studies have shown the efficacy, safety and tolerability of ultramicronized PEA. This narrative review summarizes the available pharmacokinetic/pharmacodynamic data on ultramicronized PEA and focuses to its contribution to pain control, in particular as 'add-on' nutritional intervention. Data showing the ability of ultramicronized PEA to limit opioid side effects, including the development of tolerance, have also been reviewed.

Direct, Stereodivergent, and Catalytic Michael Additions of Thioimides to α,β-Unsaturated Aldehydes - Total Synthesis of Tapentadol

Direct and stereodivergent Michael additions of N-acyl 1,3-thiazinane-2-thiones to α,β-unsaturated aldehydes catalyzed by chiral nickel(II) complexes are reported. The reactions proceed with a remarkable regio-, diastereo-, and enantioselectivity, so access to any of the four potential Michael stereoisomers is granted through the appropriate choice of the chiral ligand of the nickel(II) complex. Simple removal of the heterocyclic scaffold furnishes a wide array of either syn or anti enantiomerically pure derivatives, which can be exploited for the asymmetric synthesis of biologically active compounds, as demonstrated in a new approach to tapentadol. In turn, a mechanism, based on theoretical calculations, is proposed to account for the stereochemical outcome of these transformations.

Tapentadol Versus Oxycodone for Opioid-Related Adverse Drug Events and Clinical Outcomes After Inpatient Surgery

Oxycodone is a commonly prescribed opioid for postoperative pain. However, there has been a marked increase in the use of tapentadol over the previous decade due to a perceived superior safety profile of tapentadol compared to oxycodone. There is limited real-world evidence on the safety of tapentadol compared to oxycodone after surgery. The primary objective was to examine the impact of tapentadol compared to oxycodone use on the incidence of opioid-related adverse drug events after surgery. Data for adult surgical patients receiving tapentadol or oxycodone during hospitalization between January 1, 2018, and December 31, 2021, were collected from electronic medical records of 3 tertiary metropolitan hospitals in Australia. The primary outcome was the incidence of opioid-related adverse events. Patients receiving tapentadol or oxycodone were matched using nearest-neighbour propensity score matching. In the matched cohorts (n = 1,530 vs n = 2,775; mean [standard deviation] age 62.3 [17.0] years vs 61.9 [standard deviation 17.9] years; 43% vs 45% male for the tapentadol vs oxycodone groups, respectively), patients given tapentadol experienced a similar incidence of adverse events overall (14.4%, 220/1,530 vs 12.6%, 349/2,775; P = .100; 95% CI -.35% to 3.95%). Secondary outcomes included an increased risk of delirium (2.7%, 41/1,530 vs 1.3%, 37/2,775), arrhythmias (3.4%, 52/1,530 vs 2.2%, 62/2,775), and length of hospital stay (5 [range 1-201] vs 4 [range 1-226] days) compared with oxycodone use. Further real-world studies are warranted to determine the impact of tapentadol use on a broad range of patient outcomes. PERSPECTIVE: This study provides an early signal that tapentadol use may be associated with an increased risk of some adverse events and a longer length of stay. Further research is needed to examine the impact of tapentadol use on a broad range of patient outcomes in clinical practice settings.

Pharmacokinetics of oral tapentadol in cats

To evaluate pharmacokinetics of one dose of tapentadol hydrochloride orally administered to cats. Prospective experimental study. Five healthy adult mixed-breed cats. Each cat received 18.8 ± 1.0 mg/kg tapentadol orally. Venous blood samples were collected at time 0 (immediately prior to administration of tapentadol) 1, 2, 5, 10, 15, 30, 45, 60, 90 min, and 2, 4, 8, 12 to 24 h after drug administration. Plasma tapentadol concentrations and its metabolites were determined using ultra-performance liquid chromatography-tandem mass spectrometry. Geometric mean Tmax of tapentadol, desmethyltapentadol, tapentadol-O-glucuronide, and tapentadol-O-sulfate was 2.3, 7.0, 6.0, and 4.6 h, respectively. Mean Cmax of tapentadol, desmethyltapentadol, tapentadol-O-glucuronide, and tapentadol-O-sulfate was 637, 66, 1134, and 15,757 ng/mL, respectively, after administration. Mean half-life of tapentadol, desmethyltapentadol, tapentadol-O-glucuronide, and tapentadol-O-sulfate was 2.4, 4.7, 2.9, and 10.8 h. The relative exposure of tapentadol and its metabolites were tapentadol 2.65%, desmethyltapentadol 0.54%, tapentadol-O-glucuronide 6.22%, and tapentadol-O-sulfate 90.6%. Tapentadol-O-sulfate was the predominant metabolite following the administration of oral tapentadol in cats. Further studies are warranted to evaluate the association of analgesia with plasma concentrations of tapentadol.

Novel Opioids in the Setting of Acute Postoperative Pain: A Narrative Review

Although traditional opioids such as morphine and oxycodone are commonly used in the management of acute postoperative pain, novel opioids may play a role as alternatives that provide potent pain relief while minimizing adverse effects. In this review, we discuss the mechanisms of action, findings from preclinical studies and clinical trials, and potential advantages of several novel opioids. The more established include oliceridine (biased ligand activity to activate analgesia and downregulate opioid-related adverse events), tapentadol (mu-opioid agonist and norepinephrine reuptake inhibitor), and cebranopadol (mu-opioid agonist with nociceptin opioid peptide activity)-all of which have demonstrated success in the clinical setting when compared to traditional opioids. On the other hand, dinalbuphine sebacate (DNS; semi-synthetic mu partial antagonist and kappa agonist), dual enkephalinase inhibitors (STR-324, PL37, and PL265), and endomorphin-1 analog (CYT-1010) have shown good efficacy in preclinical studies with future plans for clinical trials. Rather than relying solely on mu-opioid receptor agonism to relieve pain and risk opioid-related adverse events (ORAEs), novel opioids make use of alternative mechanisms of action to treat pain while maintaining a safer side-effect profile, such as lower incidence of nausea, vomiting, sedation, and respiratory depression as well as reduced abuse potential.

Tapentadol Immediate Release (IR) versus Morphine Hydrochloride for Postoperative Analgesia of Patients Undergoing Total Abdominal Hysterectomy-A Prospective Cohort Study

Background and Objectives: This study aimed to examine the efficacy of tapentadol immediate release (IR) and morphine hydrochloride in the treatment of acute postoperative pain after total abdominal hysterectomy, as well as to examine the frequency of opioid-related side effects in observed patients. Materials and Methods: The prospective observational study was conducted over five months, and it included a total number of 100 patients. The two cohorts had different types of postoperative analgesia, and the effects were observed for 24 h postoperatively, by following the pain scores on NRS (Numerical Pain Scale), contentment with analgesia, and opioid-related side effects. Results: Statistical significance was found when assessing pain 24 h after surgery while coughing, where patients in the tapentadol IR group had significantly higher mean pain scores (p < 0.01). The subjective feeling of satisfaction with postoperative analgesia was statistically significant in the tapentadol IR group (p = 0.005). Vertigo appeared significantly more in patients from the morphine group (p = 0.03). Conclusions: Tapentadol IR (immediate release) and morphine hydrochloride are both effective analgesics used in the first 24 h after total transabdominal hysterectomy. Overall satisfaction of patients with analgesia was good. The frequency of side effects was higher in the morphine group, with statistical significance regarding the vertigo.

Differences in the Analgesic Effect of Opioids on Pain in Cancer Patients With Spinal Metastases

Background

Spinal metastasis pain includes both inflammatory and neuropathic pain, and opioids, which have only a μ-opioid receptor-stimulating effect, are generally less effective in neuropathic pain. However, no previous study has been conducted for the comparisons of the efficacy of opioids in treating spinal metastasis pain.

Objective

To compare the efficacy of tapentadol and methadone with other opioids for back pain caused by a metastatic spinal tumor.

Design

Retrospective cohort study.

Setting/Subjects

A total of 274 patients were enrolled, who started a tapentadol extended-release tablet, methadone tablet, hydromorphone extended-release tablet, oxycodone extended-release tablet, or transdermal fentanyl patch for cancer pain due to spinal metastasis in Japan from January 1, 2013 to October 31, 2021.

Measurements

The primary endpoint, the difference in the numerical rating scale (NRS) scores before and seven days after each opioid administration, was compared among the five groups.

Results

In patients with numbness, a decrease of the NRS score on day seven compared with before starting each opioid was significantly higher in the tapentadol group than those in the hydromorphone, oxycodone, and fentanyl groups and comparable to that in the methadone group. In patients without numbness, no significant differences were observed in decreases of the NRS scores on day seven among the five groups.

Conclusions

Tapentadol and methadone may be more effective than hydromorphone, oxycodone, and fentanyl for cancer pain due to spinal metastasis with numbness.

Tapentadol: A Review of Experimental Pharmacology Studies, Clinical Trials, and Recent Findings

Tapentadol is an analgesic compound that acts centrally to attenuate pain. Previous studies have shown that tapentadol has dual mechanisms of action as a mu-opioid receptor agonist and noradrenaline re-uptake inhibition. Therefore, tapentadol provides a great advantage over classic opioids in pain management from nociceptive to neuropathic. Cumulative evidence from in vitro data suggests that tapentadol effect of norepinephrine re-uptake could be a new target that overcomes other classic opioids in chronic neuropathic pain. Compared to tramadol and other opioids, tapentadol is associated with fewer adverse effects than tramadol. Tapentadol is a new alternative to treat acute, chronic, and neuropathic pain. Thus, this review article was focused on understanding the studies that led to the development of tapentadol as a novel analgesic drug and its advantages over conventional opioids. Thus, tapentadol is a good alternative with fewer adverse effects and is available for human use.

Influence of tapentadol and oxycodone on the spinal cord and brain using electrophysiology: a randomized, placebo-controlled trial

AIMS

The aim of this study was to investigate the effects of tapentadol and oxycodone using the nociceptive withdrawal reflex and sensory evoked potentials.

METHODS

Twenty-one healthy volunteers completed a cross-over trial with oxycodone (10 mg), tapentadol (50 mg) extended-release tablets, or placebo treatment administered orally BID for 14 days. Electrical stimulations were delivered on the plantar side of the foot to evoke a nociceptive withdrawal reflex at baseline and post-interventions. Electromyography, recorded at tibialis anterior, and electroencephalography were recorded for analysis of: number of reflexes, latencies, and area under the curve of the nociceptive withdrawal reflex as well as latencies, amplitudes and dipole sources of the sensory-evoked potential.

RESULTS

Tapentadol decreased the odds ratio of eliciting nociceptive withdrawal reflex by -0.89 (P = .001, 95% confidence interval [CI] -1.46, -0.32), whereas oxycodone increased the latency of the N1 component of the sensory-evoked potential at the vertex by 12.5 ms (P = .003, 95% CI 3.35, 21.69). Dipole sources revealed that the anterior cingulate component moved caudally for all three interventions (all P < .02), and the insula components moved caudally in both the oxycodone and tapentadol arms (all P < .03).

CONCLUSION

A decrease in the number of nociceptive withdrawal reflex was observed during tapentadol treatment, possibly relating to the noradrenaline reuptake inhibition effects on the spinal cord. Both oxycodone and tapentadol affected cortical measures possible due to μ-opioid receptor agonistic effects evident in the dipole sources, with the strongest effect being mediated by oxycodone. These findings could support the dual effect analgesic mechanisms of tapentadol in humans as previously shown in preclinical studies.

Prescribing trend of tapentadol in a Sydney local health district

AIMS

Tapentadol, an opioid with mu-opioid receptor agonism and noradrenaline reuptake inhibition, has been increasingly used in Australia since 2011. However, data on hospital prescribing trends and indications are scarce. This study aimed to investigate hospital prescribing trends of tapentadol, oxycodone and tramadol in a Sydney local health district (LHD) and the indications for tapentadol hospital prescriptions in an Australian tertiary hospital.

METHODS

We analysed 5-year patient dispensing for tapentadol, oxycodone and tramadol from four hospitals in a Sydney LHD with data expressed as oral morphine equivalents (OME). We also conducted a retrospective review of 140 and 54 patients prescribed tapentadol at a tertiary hospital's surgical and spinal units in 2020.

RESULTS

Over 5 years in the Sydney LHD, there was a 19.5% reduction in total dispensing of these opioids from 1 225 210 to 986 477.5 OME milligrams. Decreases were specifically for oxycodone (-37.8% immediate-release, -65.2% sustained-release) and tramadol (-74.6% immediate-release, -70.1% sustained-release). Contrastingly, hospital prescriptions of tapentadol immediate-release increased by 223.2% between 2018-19 and 2020-21 while sustained-release increased by 17.9% from 2016-17 to 2020-21. By 2020-21, tapentadol overtook oxycodone to become the most prescribed opioid in the Sydney LHD (51.4%). At the hospital's surgical units, 137 (97.9%) patients were prescribed tapentadol for acute post-operative pain with the majority (54.0%) prescribed both immediate-release and sustained-release tapentadol, while 71.1% were prescribed for neuropathic pain in the spinal units.

CONCLUSION

In a Sydney LHD, tapentadol prescriptions increased significantly to become the preferred opioid analgesic. At the hospital's surgical units, off-label prescriptions of tapentadol sustained-release for acute post-operative pain were observed.

Pharmacological Probes to Validate Biomarkers for Analgesic Drug Development

There is an urgent need for analgesics with improved efficacy, especially in neuropathic and other chronic pain conditions. Unfortunately, in recent decades, many candidate analgesics have failed in clinical phase II or III trials despite promising preclinical results. Translational assessment tools to verify engagement of pharmacological targets and actions on compartments of the nociceptive system are missing in both rodents and humans. Through the Innovative Medicines Initiative of the European Union and EFPIA, a consortium of researchers from academia and the pharmaceutical industry was established to identify and validate a set of functional biomarkers to assess drug-induced effects on nociceptive processing at peripheral, spinal and supraspinal levels using electrophysiological and functional neuroimaging techniques. Here, we report the results of a systematic literature search for pharmacological probes that allow for validation of these biomarkers. Of 26 candidate substances, only 7 met the inclusion criteria: evidence for nociceptive system modulation, tolerability, availability in oral form for human use and absence of active metabolites. Based on pharmacokinetic characteristics, three were selected for a set of crossover studies in rodents and healthy humans. All currently available probes act on more than one compartment of the nociceptive system. Once validated, biomarkers of nociceptive signal processing, combined with a pharmacometric modelling, will enable a more rational approach to selecting dose ranges and verifying target engagement. Combined with advances in classification of chronic pain conditions, these biomarkers are expected to accelerate analgesic drug development.

Causal Effect of Chronic Pain on Mortality Through Opioid Prescriptions: Application of the Front-Door Formula

BACKGROUND

Chronic pain is the leading cause of disability worldwide and is strongly associated with the epidemic of opioid overdosing events. However, the causal links between chronic pain, opioid prescriptions, and mortality remain unclear.

METHODS

This study included 13,884 US adults aged ≥20 years who provided data on chronic pain in the National Health and Nutrition Examination Survey 1999-2004 with linkage to mortality databases through 2015. We employed the generalized form of the front-door formula within the structural causal model framework to investigate the causal effect of chronic pain on all-cause mortality mediated by opioid prescriptions.

RESULTS

We identified a total of 718 participants at 3 years of follow-up and 1260 participants at 5 years as having died from all causes. Opioid prescriptions increased the risk of all-cause mortality with an estimated odds ratio (OR) (95% confidence interval) = 1.5 (1.1, 1.9) at 3 years and 1.3 (1.1, 1.6) at 5 years. The front-door formula revealed that chronic pain increased the risk of all-cause mortality through opioid prescriptions; OR = 1.06 (1.01, 1.11) at 3 years and 1.03 (1.01, 1.06) at 5 years. Our bias analysis showed that our findings based on the front-door formula were likely robust to plausible sources of bias from uncontrolled exposure-mediator or mediator-outcome confounding.

CONCLUSIONS

Chronic pain increased the risk of all-cause mortality through opioid prescriptions. Our findings highlight the importance of careful guideline-based chronic pain management to prevent death from possibly inappropriate opioid prescriptions driven by chronic pain.

An overview of painful diabetic peripheral neuropathy: Diagnosis and treatment advancements

Diabetes mellitus remains a public health problem, affecting 422 million people worldwide. Currently, there is no consensus around treating painful diabetic peripheral neuropathy in a step-wise manner. Among the non-pharmacological interventions, neuromodulation has become a promising alternative. Over the past decade, significant clinical trials have paved the way for prompt inclusion of high-frequency spinal cord stimulation within the painful diabetic peripheral neuropathy treatment algorithm. This article aims to provide an updated evidence-based approach for the management of painful diabetic peripheral neuropathy.

A prospective, multicenter, open-label study of the clinical efficacy of tapentadol extended-release in the treatment of cancer-related pain and improvement in the quality of life of opioid-naïve or opioid-resistant patients

Purpose

This study aimed to investigate the clinical efficacy of tapentadol extended-release (ER) on pain control and the quality of life (QoL) of patients with moderate to severe chronic cancer pain in clinical practice in Korea.

Methods

In this prospective, open-label, multicenter trial, patients with sustained cancer pain as well as chronic pain, who were or were not using other analgesics were enrolled. Thirteen centers recorded a total of 752 patients during the 6-month observation period, based on the tapentadol ER dose and tolerability, prior and concomitant analgesic treatment, pain intensity, type of pain, adverse effects, and clinical global impression change (CGI-C). Of those 752 patients, 688 were enrolled, and 650 completed the study for efficacy and adverse drug reactions; among them, 349 were cancer patients.

Results

Tapentadol ER significantly reduced the mean pain intensity including neuropathic pain during the observation period by 2.9 points (from a mean 7 ± 0.87 to 4.1 ± 2.02). Furthermore, QoL was observed to be significantly improved based on the CGI-C, an objective measure.

Conclusion

This study showed that tapentadol ER was effective for treating patients with moderate to severe cancer pain and neuropathic pain, and therefore it significantly improved the patients’ QoL.

Targeting Chemokines and Chemokine GPCRs to Enhance Strong Opioid Efficacy in Neuropathic Pain

Neuropathic pain (NP) originates from an injury or disease of the somatosensory nervous system. This heterogeneous origin and the possible association with other pathologies make the management of NP a real challenge. To date, there are no satisfactory treatments for this type of chronic pain. Even strong opioids, the gold-standard analgesics for nociceptive and cancer pain, display low efficacy and the paradoxical ability to exacerbate pain sensitivity in NP patients. Mounting evidence suggests that chemokine upregulation may be a common mechanism driving NP pathophysiology and chronic opioid use-related consequences (analgesic tolerance and hyperalgesia). Here, we first review preclinical studies on the role of chemokines and chemokine receptors in the development and maintenance of NP. Second, we examine the change in chemokine expression following chronic opioid use and the crosstalk between chemokine and opioid receptors. Then, we examine the effects of inhibiting specific chemokines or chemokine receptors as a strategy to increase opioid efficacy in NP. We conclude that strong opioids, along with drugs that block specific chemokine/chemokine receptor axis, might be the right compromise for a favorable risk/benefit ratio in NP management.

Tapentadol shows lower intrinsic efficacy at µ receptor than morphine and oxycodone

Tapentadol is a centrally acting analgesic with a dual mechanism of action. It acts as an agonist at the µ receptor and inhibitor of noradrenaline reuptake. Clinical trials suggest similar analgesic efficacy of tapentadol, oxycodone, and morphine in acute and chronic pain. Given the limited information about the molecular actions of tapentadol at the µ receptor, we investigated the intrinsic efficacy of tapentadol and compared it with other opioids. β-chlornaltrexamine (β-CNA, 100 nM, 20 min) was used to deplete spare receptors in AtT20 cells stably transfected with human µ receptor wild-type (WT). Opioid-mediated changes in membrane potential were measured in real-time using a membrane potential-sensitive fluorescent dye. Using Black and Leff's operational model, intrinsic efficacy relative to DAMGO was calculated for each opioid. Tapentadol (0.05 ± 0.01) activated the GIRK channel with lesser intrinsic efficacy than morphine (0.17 ± 0.02) and oxycodone (0.16 ± 0.02). We further assessed the signaling of tapentadol in the common µ receptor variants (N40D and A6V) which are associated with altered receptor signaling. We found no difference in the response of tapentadol between these receptor variants.

Incidence of Delirium With Different Oral Opioids in Previously Opioid-Naive Patients

Background: Opioids are known to induce delirium, but few studies have closely investigated differences in incidence of delirium among different opioids. Objectives: To determine whether there is a clinically significant difference in the incidence of delirium between oral opioids in previously opioid-naive patients. Methods: Subjects were 259 opioid-naive in-patients with cancer who were started on morphine sulfate, oxycodone hydrochloride, or tapentadol hydrochloride extended-release tablets at our hospital between August 1, 2014, and September 30, 2018. The incidence of delirium during the first week of treatment was compared between the drugs. Results: The incidence of delirium was 4.8% (n = 83) for morphine sulfate, 6.9% (n = 131) for oxycodone hydrochloride, and 6.7% (n = 45) for tapentadol hydrochloride. The incidence did not significantly differ between oxycodone hydrochloride (OR = .69, 95% CI = .20–2.30, P [Fisher’s exact test] = .77) or tapentadol hydrochloride (OR = .71, 95% CI = .15–3.32, P [Fisher’s exact test] = .70) and morphine sulfate (reference group). Moreover, the incidence did not significantly differ between tapentadol hydrochloride (OR = 1.03, 95% CI = .27–3.00, P [Fisher’s exact test] = 1.00) and oxycodone hydrochloride (reference group). Conclusion: The incidence of delirium in previously opioid-naive patients did not differ significantly among morphine sulfate, oxycodone hydrochloride, and tapentadol hydrochloride extended-release tablets, suggesting similar risk of delirium in opioid-naive patients among these oral opioids.

Polypharmacology: The science of multi-targeting molecules

Polypharmacology is a concept where a molecule can interact with two or more targets simultaneously. It offers many advantages as compared to the conventional single-targeting molecules. A multi-targeting drug is much more efficacious due to its cumulative efficacy at all of its individual targets making it much more effective in complex and multifactorial diseases like cancer, where multiple proteins and pathways are involved in the onset and development of the disease. For a molecule to be polypharmacologic in nature, it needs to possess promiscuity which is the ability to interact with multiple targets; and at the same time avoid binding to antitargets which would otherwise result in off-target adverse effects. There are certain structural features and physicochemical properties which when present would help researchers to predict if the designed molecule would possess promiscuity or not. Promiscuity can also be identified via advanced state-of-the-art computational methods. In this review, we also elaborate on the methods by which one can intentionally incorporate promiscuity in their molecules and make them polypharmacologic. The polypharmacology paradigm of "one drug-multiple targets" has numerous applications especially in drug repurposing where an already established drug is redeveloped for a new indication. Though designing a polypharmacological drug is much more difficult than designing a single-targeting drug, with the current technologies and information regarding different diseases and chemical functional groups, it is plausible for researchers to intentionally design a polypharmacological drug and unlock its advantages.

Cost-effectiveness of tapentadol immediate release versus oxycodone immediate release for acute post-operative pain after major hip surgeries

OBJECTIVE

To evaluate the cost-effectiveness of tapentadol immediate-release (IR) versus oxycodone IR for post-operative pain after a major hip surgery.

METHODS

This study has been conducted using an Australian societal perspective, focusing on adult patients after a major hip surgery. A cost-effectiveness analysis was conducted using a decision-analytic model. The model incorporated drug and other resource costs, the probability of opioid-related adverse events, and quality-adjusted life months (QALM) in each treatment arm. A willingness to pay (WTP) threshold of AU$2500 was used per QALM gained. A probabilistic sensitivity analysis was conducted to examine the uncertainty of the assumptions. The primary outcome was the incremental cost-effectiveness ratio (ICER) of tapentadol IR versus oxycodone IR, expressed as Australian dollars (AU$) per QALM gained.

RESULTS

Tapentadol IR dominated oxycodone IR, with a cost savings of AU$201 and an increase in QALM by 0.014. The ICER was -13,946 AU$/QALM (negative value attributed to numerator). In the probabilistic sensitivity analysis, 84.2% of the simulations were in favour of tapentadol IR at the WTP threshold.

CONCLUSIONS

Tapentadol IR may be more cost-effective than oxycodone IR for the treatment of acute postoperative pain after major hip surgeries.

Web-Based Discussion and Illicit Street Sales of Tapentadol and Oxycodone in Australia: Epidemiological Surveillance Study

Background

Opioid use disorder and its consequences are a persistent public health concern for Australians. Web activity has been used to understand the perception of drug safety and diversion of drugs in contexts outside of Australia. The anonymity of the internet offers several advantages for surveilling and inquiring about specific covert behaviors, such as diversion or discussion of sensitive subjects where traditional surveillance approaches might be limited.

Objective

This study aims to characterize the content of web posts and compare reports of illicit sales of tapentadol and oxycodone from sources originating in Australia. First, post content is evaluated to determine whether internet discussion encourages or discourages proper therapeutic use of the drugs. Second, we hypothesize that tapentadol would have lower street price and fewer illicit sales than oxycodone.

Methods

Web posts originating in Australia between 2017 and 2019 were collected using the Researched Abuse, Diversion, and Addiction-Related Surveillance System Web Monitoring Program. Using a manual coding process, unstructured post content from social media, blogs, and forums was categorized into topics of discussion related to the harms and behaviors that could lead to harm. Illicit sales data in a structured format were collected through a crowdsourcing website between 2016 and 2019 using the Researched Abuse, Diversion, and Addiction-Related Surveillance System StreetRx Program. In total, 2 multivariable regression models assessed the differences in illicit price and number of sales.

Results

A total of 4.7% (28/600) of tapentadol posts discussed an adverse event, whereas 10.27% (95% CI 9.32-11.21) of oxycodone posts discussed this topic. A total of 10% (60/600) of tapentadol posts discussed unsafe use or side effects, whereas 20.17% (95% CI 18.92-21.41) of oxycodone posts discussed unsafe use or side effects. There were 31 illicit sales reports for tapentadol (geometric mean price per milligram: Aus $0.12 [US $0.09]) and 756 illicit sales reports for oxycodone (Aus $1.28 [US $0.91]). Models detected no differences in the street price or number of sales between the drugs when covariates were included, although the potency of the pill significantly predicted the street price (P<.001) and availability predicted the number of sales (P=.03).

Conclusions

Australians searching the web for opinions could judge tapentadol as safer than oxycodone because of the web post content. The illicit sales market for tapentadol was smaller than that of oxycodone, and drug potency and licit availability are likely important factors influencing the illicit market.

Comparative study of dezocine, pentazocine and tapentadol on antinociception and physical dependence

AIMS

Dezocine and pentazocine, widely prescribed in China for postoperative pain, were initially considered as mixed agonist/antagonist targeting μ-opioid receptors (MORs) and κ-opioid receptors (KORs). However, dezocine has been revealed to alleviate chronic neuropathic pain through MOR activation and norepinephrine reuptake inhibition (NRI). This study investigated dezocine- and pentazocine-induced antinociception and physical dependence development, compared to the typical MOR-NRI opioid tapentadol.

MAIN METHODS

Calcium mobilization assay was conducted to assess the potency of the drugs while hot-plate test was performed to compare the antinociception. Physical dependence development was compared with morphine.

KEY FINDINGS

Treatment with dezocine, pentazocine and tapentadol stimulated calcium mobilization in HEK293 cells stably expressed MORs but not KORs, whereas dezocine and pentazocine inhibited KOR activities. Subcutaneously injected dezocine-, tapentadol- and pentazocine-induced antinociception dose-dependently, in hot-plate test. Intrathecally injected MOR antagonist CTAP, norepinephrine depletor 6-OHDA and α₂-adrenoceptor (α₂-AR) antagonist yohimbine partially antagonized dezocine, pentazocine and tapentadol antinociception. Whereas specific KOR antagonist GNTI did not alter their antinociception, the putative inverse KOR agonist nor-BNI reduced dezocine and pentazocine antinociception. Moreover, combined CTAP and 6-OHDA or yohimbine blocked dezocine and tapentadol antinociception but displayed the same partial inhibition on pentazocine antinociception as CTAP alone. Furthermore, compared to morphine and pentazocine, long-term treatment with dezocine and tapentadol produced much less physical dependence-related withdrawal signs, which were restored by spinal 6-OHDA or yohimbine treatment.

SIGNIFICANCE

Our findings illustrated that dezocine and tapentadol, but not pentazocine, exert remarkable antinociception in nociceptive pain with less abuse liability via dual mechanisms of MOR activation and NRI.

Nitric oxide modulates tapentadol antinociceptive tolerance and physical dependence

Tapentadol, an analgesic with a dual mechanism of action, involving both μ-opioid receptor agonism and noradrenaline reuptake inhibition (MOP-NRI), was designed for the treatment of moderate to severe pain. However, the widely acknowledged risk of analgesic tolerance and development of physical dependence following sustained opioid use may hinder their effectiveness. One of the possible mechanisms behind these phenomena are alterations in nitric oxide synthase (NOS) system activity. The aim of the study was to investigate the tolerance and dependence potential of tapentadol in rodent models and to evaluate the possible role of nitric oxide (NO) in these processes. Our study showed that chronic tapentadol treatment resulted in tolerance to its antinociceptive effects to an extent similar to tramadol, but much less than morphine. A single injection of a non-selective NOS inhibitor, NG-nitro-L-arginine (L-NOArg), reversed the tapentadol tolerance. In dependence studies, repeated administration of L-NOArg attenuated naloxone-precipitated withdrawal in tapentadol-treated mice, whereas a single injection of L-NOArg was ineffective. Biochemical analysis revealed that tapentadol decreased nNOS protein levels in the dorsal root ganglia of rats following 31 days of treatment, while no significant changes were found in iNOS and eNOS protein expression. Moreover, pre-treatment with L-NOArg augmented tapentadol antinociception in an opioid- and α2-adrenoceptor-dependent manner. In conclusion, our data suggest that the NOS system plays an important role in the attenuation of tapentadol-induced tolerance and withdrawal. Thus, inhibition of NOS activity can serve as a promising treatment option for long-term tapentadol use by extending its effectiveness and improving the side-effects profile.

Tapentadol versus oxycodone analgesia and side effects after laparoscopic hysterectomy: A randomised controlled trial

BACKGROUND

Tapentadol is an opioid, which acts as a μ-opioid receptor agonist and inhibits noradrenaline reuptake in the central nervous system. This dual mechanism of action results in synergistic analgesic effects and potentially less side effects. This has been shown in treatment of chronic pain but postoperative studies are sparse.

OBJECTIVES

The main aim was to compare the analgesic effect of tapentadol with oxycodone after laparoscopic hysterectomy. Opioid side effects were recorded as secondary outcomes.

DESIGN

Randomised, blinded trial.

SETTING

Single-centre, Oslo University Hospital, Norway, December 2017 to February 2019.

PATIENTS

Eighty-six opioid-naïve American Society of Anesthesiologists physical status 1 to 3 women undergoing laparoscopic hysterectomy for nonmalignant conditions.

INTERVENTION

The patients received either oral tapentadol (group T) or oxycodone (group O) as part of multimodal pain treatment. Extended-release study medicine was administered 1 h preoperatively and after 12 h. Immediate-release study medicine was used as rescue analgesia.

MAIN OUTCOME MEASURES

Pain scores, opioid consumption and opioid-induced side effects were evaluated during the first 24 h after surgery.

RESULTS

The groups scored similarly for pain at rest using a numerical rating scale (NRS) 1 h postoperatively (group T 4.4, 95% CI, 3.8 to 5.0, group O 4.6, 95% CI, 3.8 to 5.3). No statistically significant differences were found between the groups for NRS at rest or while coughing during the 24-h follow-up period (P = 0.857 and P = 0.973). Mean dose of oral rescue medicine was similar for the groups (P = 0.914). Group T had significantly lower odds for nausea at 2 and 3 h postoperatively (P = 0.040, P = 0.020) and less need for antiemetics than group O. No differences were found for respiratory depression, vomiting, dizziness, pruritus, headache or sedation.

CONCLUSION

We found tapentadol to be similar in analgesic efficacy to oxycodone during the first 24 h after hysterectomy, but with significantly less nausea.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03314792.

Toxicities of opioid analgesics: respiratory depression, histamine release, hemodynamic changes, hypersensitivity, serotonin toxicity

Opioid-induced respiratory depression is potentially life-threatening and often regarded as the main hazard of opioid use. Main cause of death is cardiorespiratory arrest with hypoxia and hypercapnia. Respiratory depression is mediated by opioid μ receptors expressed on respiratory neurons in the CNS. Studies on the major sites in the brainstem mediating respiratory rate suppression, the pre-Bӧtzinger complex and parabrachial complex (including the Kӧlliker Fuse nucleus), have yielded conflicting findings and interpretations but recent investigations involving deletion of μ receptors from neurons have led to greater consensus. Some opioid analgesic drugs are histamine releasers. The range of clinical effects of released histamine include increased cardiac output due to an increase in heart rate, increased force of myocardial contraction, and a dilatatory effect on small blood vessels leading to flushing, decreased vascular resistance and hypotension. Resultant hemodynamic changes do not necessarily relate directly to the concentration of histamine in plasma due to a range of variables including functional differences between mast cells and histamine-induced anaphylactoid reactions may occur less often than commonly believed. Opioid-induced histamine release rarely if ever provokes bronchospasm and histamine released by opioids in normal doses does not lead to anaphylactoid reactions or result in IgE-mediated reactions in normal patients. Hypersensitivities to opioids, mainly some skin reactions and occasional type I hypersensitivities, chiefly anaphylaxis and urticaria, are uncommon. Hypersensitivities to morphine, codeine, heroin, methadone, meperidine, fentanyl, remifentanil, buprenorphine, tramadol, and dextromethorphan are summarized. In 2016, the FDA issued a Drug Safety Communication concerning the association of opioids with serotonin syndrome, a toxicity associated with raised intra-synaptic concentrations of serotonin in the CNS, inhibition of serotonin reuptake, and activation of 5-HT receptors. Opioids may provoke serotonin toxicity especially if administered in conjunction with other serotonergic medications. The increasing use of opioid analgesics and widespread prescribing of antidepressants and psychiatric medicines, indicates the likelihood of an increased incidence of serotonin toxicity in opioid-treated patients.

Tapentadol Versus Tramadol: A Narrative and Comparative Review of Their Pharmacological, Efficacy and Safety Profiles in Adult Patients

We conducted a narrative review of the literature to compare the pharmacological, efficacy and safety profiles of tapentadol and tramadol, and to assess the clinical interest of tapentadol in adult patients. Tapentadol and tramadol share a mixed mechanism of action, including both mu-agonist and monoaminergic properties. Tapentadol is approximately two to three times more potent than tramadol and two to three times less potent than morphine. It has no identified analgesically active metabolite and is not significantly metabolised by cytochrome P450 enzymes, thus overcoming some limitations of tramadol, including the potential for pharmacokinetic drug-drug interactions and interindividual variability due to genetic polymorphisms of cytochrome P450 enzymes. The toxicity profiles of tramadol and tapentadol are similar; however tapentadol is likely to result in less exposure to serotoninergic adverse effects (nausea, vomiting, hypoglycaemia) but cause more opioid adverse effects (constipation, respiratory depression, abuse) than tramadol. The safety of tapentadol in real-world conditions remains poorly documented, particularly in at-risk patient subgroups and also in the ability to assess the risk associated with its residual serotonergic activity (serotonin syndrome, seizures). Because of an earlier market introduction, more real-world safety data are available for tramadol, including data from at-risk patient subgroups. The level of evidence on the efficacy of both tramadol and tapentadol for the treatment of chronic pain is globally low. The trials published to date show overall that tapentadol does not provide a clinically significant analgesic improvement compared to existing treatments, for which the safety profile is much better known. In conclusion, tapentadol is not a first-line opioid but represents an additional analgesic in the therapeutic choices, which some patients may benefit from after careful examination of their clinical situation, co-morbidities and co-medications.

Comparison of opioid prescribing upon hospital discharge in patients receiving tapentadol versus oxycodone following orthopaedic surgery

Background The changing of opioids during the transition of care from hospital to home may be associated with harm. Objective To compare patients receiving tapentadol IR versus oxycodone IR following orthopaedic surgery during hospitalisation with regard to the changing of opioids at hospital discharge. Setting A major metropolitan tertiary referral hospital in Australia. Methods This is a retrospective cohort study. Participants included adult orthopaedic surgery patients receiving postoperative tapentadol IR or oxycodone IR during hospitalisation between 1 January 2018 and 30 June 2019. Main outcome measure The proportion of patients for whom the opioid prescribed was changed at hospital discharge. Results The study cohort included 199 patients. Of these, 100 patients received oxycodone and 99 patients received tapentadol post-operatively during hospitalisation. The mean age was 66 years (SD, 12 years) and 111 (56%) were female. The most common surgeries were total knee arthroplasty (91, 46%), total hip arthroplasty (63, 32%) and shoulder surgery (26, 13%). Patients in the tapentadol group were more likely to be changed to a different opioid upon hospital discharge than the oxycodone group (57% versus 9%, difference 48% [95% CI 36-59%, p < 0.01). After adjusting for confounders, post-operative tapentadol use was more likely to be associated with opioid changing upon discharge (OR 16.5, 95% CI 6.7 to 40.8, p < 0.01). Conclusions The post-operative use of tapentadol IR during hospitalisation was associated with an increased likelihood of opioid changing at hospital discharge. This practice could have patient safety implications.

Evaluation of Abuse and Route of Administration of Extended-Release Tapentadol Among Treatment-Seeking Individuals, as Captured by the Addiction Severity Index-Multimedia Version (ASI-MV)

Background

Tapentadol is a molecule incorporating mu opioid receptor agonism and norepinephrine reuptake inhibition to provide analgesia, with the potential for a lower incidence of gastrointestinal side effects than full mu opioid agonists. Postmarketing surveillance of tapentadol as an active pharmaceutical ingredient has consistently revealed low levels of abuse and diversion.

Objective

The purpose of the present study was to further characterize the abuse liability of tapentadol extended-release (ER) by evaluating the prevalence of past 30-day tapentadol ER abuse and reported routes of administration as compared with ER opioids with Food and Drug Administration (FDA) abuse-deterrent labeling (“ADF opioids”) and ER opioids without FDA abuse-deterrent labeling (“non-ADF opioids”).

Methods

Data were collected from January 2014 through December 2017 from 776 centers located in 43 states throughout the United States using the Addiction Severity Index–Multimedia Version (ASI-MV), an instrument that is integral to the National Addictions Vigilance Intervention and Prevention Program (NAVIPPRO, Inflexxion, an IBH Company, Costa Mesa, CA, USA).

Results

Tapentadol ER had lower rates of past 30-day abuse than ADF ER and non-ADF ER opioid comparators, both at a population level and when adjusted for drug utilization. Tapentadol ER was primarily abused orally, although it was also abused through alternate routes of administration. Cumulative rates of tapentadol ER abuse by alternative routes of administration were lower than both ADF and non-ADF ER opioid comparators, although large confidence intervals resulting from the small sample size of reported tapentadol ER use limit firm conclusions.

Conclusions

In summary, tapentadol ER was found to have lower rates of both past 30-day abuse and use via alternate routes of administration, specifically snorting and smoking, than ADF and non-ADF ER comparators.

Pilot Study of a Single Dose of Orally Administered Tapentadol Suspension in Hispaniolan Amazon Parrots (Amazona ventralis)

Tapentadol is an analgesic agent that acts as both a µ-opioid receptor agonist and a norepinephrine reuptake inhibitor. It is a common therapeutic agent in human medicine for management of acute and chronic pain, and it is currently being investigated for use in veterinary medicine. Tapentadol was evaluated in Hispaniolan Amazon parrots (Amazona ventralis) because there is only 1 other oral opioid-like analgesic agent, tramadol, which has been evaluated in an avian species. The effectiveness of tramadol after administration to a patient involves a complex physiologic metabolism and has been found to have variable pharmacokinetics between species. Because of the lack of active metabolites from tapentadol, less interspecific variation was expected. Seven Hispaniolan Amazon parrots were used to evaluate the pharmacokinetics of tapentadol after a single 30 mg/kg PO administration of a compounded 5 mg/mL tapentadol suspension. Blood samples were collected before (time 0) and 0.25, 0.5, 0.75, 1, 1.5, 3, and 6 hours after administration, following a balanced, incomplete-block design. Plasma tapentadol concentrations were measured by high-pressure liquid chromatography with mass spectrometry. Results revealed detectable plasma concentrations in only 2 of 7 birds (29%), and the bird with the highest plasma levels had a peak concentration (C_max) of 143 ng/mL and a half-life (T _1/2) of 24.8 minutes. The variable plasma concentrations and short half-life of this drug in Hispaniolan Amazon parrots suggests that this drug would be of limited clinical use in this species; however, it is possible that this drug will be more bioavailable in other avian species.

Opioids for chronic low back pain management: a Bayesian network meta-analysis

Introduction: Chronic low back pain (LBP) is common, and some patients require opiates therapy. This Bayesian network meta-analysis (NMA) analyzed available randomized clinical trials (RCTs) on the use of opioids for LBP.Methods: All RCTs comparing two or more opioids for chronic LBP and reporting results under the Numeric Rating Scale were included. The following drugs were analyzed: fentanyl, morphine, tapentadol, oxycodone, buprenorphine, oxymorphone, tramadol. The NMA was performed through the STATA routine for Bayesian hierarchical random-effects model analysis, with standardized mean difference (SMD) effect measure. Data regarding the rate of adverse events and different drug formulations were also reported.Results: Data from 2933 patients were obtained, with a mean age of 53.30 ± 6.95 years. The mean duration of symptoms prior to beginning the trial was 95.16 ± 47.29 months. The mean follow-up was 3.29 ± 1.72 months. Among the analyzed compounds, oxymorphone, tapentadol and fentanyl showed the highest efficacy in terms of pain reduction.Conclusion: According to published level I evidence, oxymorphone, tapentadol and fentanyl were the most effective drugs in the treatment of chronic LBP. However, different formulation and pharmacokinetic characteristics need to be taken into consideration when choosing the ideal compound for a given patient.

Design, synthesis and molecular docking of new pyrazole-thiazolidinones as potent anti-inflammatory and analgesic agents with TNF-α inhibitory activity

A new set of derivatives bearing pyrazole-methylenehydrazono-thiazolidinone scaffold 4-23 was designed, synthesized and confirmed by different spectroscopic means and elemental analyses. In-vivo anti-inflammatory and ulcerogenic evaluation was performed for all the newly synthesized derivatives using indomethacin, celecoxib and diclofenac as standard drugs. The compounds 5, 10, 15, 17, 21, 22 appeared to be the most promising candidates producing rapid onset and long duration of anti-inflammatory activity as well as promising GIT safety profile. Furthermore, analgesic evaluation revealed that the compounds 5, 10, 15 and 22 produced potent and long acting analgesia accompanied with significant inhibition of the inflammatory cytokine TNF-α level in comparison with the standard drugs. Molecular docking study of the latter derivatives was also carried out to rationalize their binding affinities and their modes of interactions with the active site of TNF-α.

Tapentadol and Sleepwalking: A Case Report

OBJECTIVE

This is a case report of a patient with sleepwalking likely caused by tapentadol ER secondary to higher than the recommended dose for the treatment of pain.

METHODS

This report presents the relevant patient history, laboratory data and literature review on possible causes of this patient's sleepwalking.

RESULTS

A 39-year-old female reported sleepwalking as the dose of tapentadol increased above the recommended maximum provided in the package insert. The mechanism of action of tapentadol involving norepinephrine reuptake inhibition affecting the central nervous system, higher dosage and drug interactions with other home medications likely contributed to her sleepwalking.

CONCLUSION

This case highlights the importance of adhering to the recommended dosage of a medication and if it is clinically warranted to exceed the maximum recommended dose, the importance of diligent monitoring for any adverse effects.

Tapentadol vs oxycodone for postoperative pain treatment the first 7 days after total knee arthroplasty: a randomized clinical trial

ABSTRACT

Pain after total knee arthroplasty is a prevalent condition. This study compared the effectiveness of tapentadol extended-release (ER) 50 mg × 2, oxycodone controlled-release (CR) 10 mg × 2, and placebo, as added to a multimodal analgesic regime both in-hospital and at home the first week after total knee arthroplasty. The study was randomized and blinded for investigators, staff, outcome assessors, and patients. Follow-up included pain intensity on mobilization, pain at rest, worst pain in the previous 24 hours, and adverse effects measured on 0 to 10 numerical rating scales. A total of 134 patients in 3 study groups received their allocated intervention and were included in the analysis. The primary outcome pain on mobilization the 7 first postoperative days reported as area under the curve was 528.1 (SD 267.5, interquartile range (IQR) 356.6-665.4) for placebo, 427.2 (SD 203.9, IQR 303.6-544.3) for tapentadol ER, and 507.9 (SD 243.7, IQR 292.4-686.8) for oxycodone CR (P = 0.12). With the exception of constipation being less prevalent in the tapentadol ER group (P = 0.02), we found no significant differences between treatment groups for the secondary outcomes. Tapentadol ER as an add-on to multimodal analgesia did not significantly improve pain relief when compared to oxycodone CR or placebo. Constipation was lowest in the tapentadol ER group.

Repeated Administration of Clinically Relevant Doses of the Prescription Opioids Tramadol and Tapentadol Causes Lung, Cardiac, and Brain Toxicity in Wistar Rats

Tramadol and tapentadol, two structurally related synthetic opioid analgesics, are widely prescribed due to the enhanced therapeutic profiles resulting from the synergistic combination between μ-opioid receptor (MOR) activation and monoamine reuptake inhibition. However, the number of adverse reactions has been growing along with their increasing use and misuse. The potential toxicological mechanisms for these drugs are not completely understood, especially for tapentadol, owing to its shorter market history. Therefore, in the present study, we aimed to comparatively assess the putative lung, cardiac, and brain cortex toxicological damage elicited by the repeated exposure to therapeutic doses of both prescription opioids. To this purpose, male Wistar rats were intraperitoneally injected with single daily doses of 10, 25, and 50 mg/kg tramadol or tapentadol, corresponding to a standard analgesic dose, an intermediate dose, and the maximum recommended daily dose, respectively, for 14 consecutive days. Such treatment was found to lead mainly to lipid peroxidation and inflammation in lung and brain cortex tissues, as shown through augmented thiobarbituric acid reactive substances (TBARS), as well as to increased serum inflammation biomarkers, such as C reactive protein (CRP) and tumor necrosis factor-α (TNF-α). Cardiomyocyte integrity was also shown to be affected, since both opioids incremented serum lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) activities, while tapentadol was associated with increased serum creatine kinase muscle brain (CK-MB) isoform activity. In turn, the analysis of metabolic parameters in brain cortex tissue revealed increased lactate concentration upon exposure to both drugs, as well as augmented LDH and creatine kinase (CK) activities following tapentadol treatment. In addition, pneumo- and cardiotoxicity biomarkers were quantified at the gene level, while neurotoxicity biomarkers were quantified both at the gene and protein levels; changes in their expression correlate with the oxidative stress, inflammatory, metabolic, and histopathological changes that were detected. Hematoxylin and eosin (H & E) staining revealed several histopathological alterations, including alveolar collapse and destruction in lung sections, inflammatory infiltrates, altered cardiomyocytes and loss of striation in heart sections, degenerated neurons, and accumulation of glial and microglial cells in brain cortex sections. In turn, Masson's trichrome staining confirmed fibrous tissue deposition in cardiac tissue. Taken as a whole, these results show that the repeated administration of both prescription opioids extends the dose range for which toxicological injury is observed to lower therapeutic doses. They also reinforce previous assumptions that tramadol and tapentadol are not devoid of toxicological risk even at clinical doses.

Effect of tapentadol on experimental model of orofacial pain - a pilot study

Acute orofacial pain is associated with significant disability and has a detrimental impact on quality of life. Although various origins of the pain in trigeminal territory can be identified an odontogenic pathology is the most common cause of acute orofacial pain in patients. Due to complex pathophysiology drugs with multitarget action might provide beneficial effect in pain management. The aim of the present study was to experimentally examine the anti-nociceptive effects of tapentadol, an opioid agonist and a norepinephrine reuptake inhibitor (MOR/NRI), in our animal model of orofacial pain. We tested the effect of tapentadol at gradual doses of 1, 2 and 5 mg/kg during thermal and mechanical stimulation in the trigeminal area of adult rats. We observed that tapentadol exhibits antinociceptive effect at dosages of 2 mg/kg and 5 mg/kg and only in association with mechanical stimulation.

Antinociception and less gastric injury with the dexketoprofen-tapentadol combination in mice

The purpose of this study was to evaluate the antinociceptive interaction between dexketoprofen and tapentadol in three different dose ratios, as well as the ulcerogenic activity of this combination. Dose-response curves were carried out for dexketoprofen, tapentadol, and dexketoprofen-tapentadol combinations in the acetic acid-induced writhing test in mice. On the other hand, the gastric damage of all treatments was assessed after the surgical extraction of the stomachs. Intraperitoneal administration of dexketoprofen and tapentadol induced a dose-dependent antinociceptive effect, reaching a maximal effect of about 58% and 99%, respectively. Isobolographic analysis and the interaction index showed that the three proportions produced an analgesic potentiation (synergistic interaction). Interestingly, the 1:1 and 1:3 ratios of the drugs combination produced minor gastric injury in comparison with the 3:1 proportion. Our data suggest that all proportions of the dexketoprofen-tapentadol combination produced a synergistic interaction in the acetic acid-induced visceral pain model in mice with a low incidence of gastric injury.

Opioid-Induced Reductions in Gait Variability in Healthy Volunteers and Individuals with Knee Osteoarthritis

OBJECTIVE

To investigate differences in gait variability induced by two different single-dose opioid formulations and an inert placebo in healthy volunteers and knee osteoarthritis patients.

DESIGN

Experimental, randomized, double-blinded, crossover study of inert placebo (calcium tablets), 50 mg of tapentadol, and 100 mg of tramadol.

SETTING

Laboratory setting.

SUBJECTS

Healthy volunteers and knee osteoarthritis patients.

METHODS

At three visits, separated by seven days, one tablet was administered per visit according to the randomization code. At each visit, a baseline measurement was done before tablet administration, after which hourly measurements were performed for six hours, yielding a total of seven measurements per visit. Gait variability was measured by three-dimensional gait analysis, recorded during six minutes of continuous treadmill walking at self-selected speed. One hundred seventy gait cycles were identified from detection of clear events of the knee joint angle trajectories. Gait variability was assessed as average standard deviations over a gait cycle of the sacrum displacements and accelerations; sagittal plane ankle, knee, and hip joint angles; step widths; and stride times.

RESULTS

Twenty-four opioid-naïve and neurologically intact participants (12 healthy volunteers and 12 knee osteoarthritis patients) were included and completed the experiment. Tapentadol reduced the variability of sacrum displacements and accelerations compared with placebo and tramadol. There were no differences between experimental conditions regarding the variability in lower-extremity joint angle variability, step widths, or stride times.

CONCLUSIONS

In opioid-naïve and neurologically intact individuals, tapentadol seems to reduce movement variability during treadmill walking, compared with placebo and tramadol. This can be interpreted as a loss of adaptability that might increase the risk of falling if the system is perturbed.

Anti-Nociceptive and Anti-Inflammatory Effects of Stem Bark Extract of Ficus Capensis Thunb (Moraceae) by Bioactivity Fractionation

OBJECTIVE

This study investigated the antinociceptive and anti-inflammatory activities of the aqueous extract of Ficus capensis (AEFC) by bio-guided fractionation.

METHODS

The anti-nociceptive and anti-inflammatory effects of AEFC (250, 500, 1000 mg/kg, i.p) were assessed using acetic acid-induced writhing, hot plate, tail-flick, formalin tests, and carrageenan- induced paw edema, respectively. The AEFC was fractionated base on polarity difference into butanol, ethyl acetate, and n-hexane fractions. The fractions (500 mg/kg) obtained were subjected to the same experimental procedures mentioned above. The EAF, which exerted the most productive activities, was further subjected to fractionation procedures that yielded six fractions (labeled CF1-CF6). These fractions (200 mg/kg) were tested for potential antinociceptive and anti-inflammatory activities. Notable antagonists (Naloxone and atropine) of the nociceptive pathway were used to evaluate the mechanism of the antinociceptive action of F. capensis.

RESULTS AND DISCUSSION

The AEFC, BF, EAF, and CF4 caused a significant (p<0.05) reduction in the number of abdominal writhes, an increase in reaction time against the hot plate, tail-flick tests, and a significant (p<0.05) inhibition in both phases of formalin test. The AEFC, BF, EAF, CF4, and CF6 caused a significant (p<0.05) inhibition of paw edema development due to carrageenan. Atropine significantly reversed the antinociceptive effect of CF4 in both phases of the formalin test. The results obtained revealed that CF4 produced central and peripheral antinociceptive effects, while CF6 is peripherally mediated.

CONCLUSION

The results support the traditional uses of F. capensis in the treatment of various diseases associated with pain and inflammation. The column fraction CF4 exhibited muscarinic receptor- mediated antinociceptive activity.

Central IRAK-4 kinase inhibition for the treatment of pain following nerve injury in rats

There is ample evidence for the role of the immune system in developing chronic pain following peripheral nerve injury. Especially Toll-like receptors (TLRs) and their associated signaling components and pro-inflammatory cytokines such as IL-1β, induced after injury, are involved in nociceptive processes and believed to contribute to the manifestation of chronic neuropathic pain states. Whereas the inhibition of the kinase function of IRAK-4, a central kinase downstream of TLRs and IL-1 receptors (IL-1Rs), seems efficacious in various chronic inflammatory and autoimmune models, it's role in regulating chronic neuropathic pain remained elusive to date. Here, we examined whether pharmacological inhibition of IRAK-4 kinase activity using PF-06650833 and BMS-986147, two clinical-stage kinase inhibitors, is effective for controlling persistent pain following nerve injury. Both inhibitors potently inhibited TLR-triggered cytokine release in human peripheral blood mononuclear cell (PBMC) as well as human and rat whole blood cultures. BMS-986147 showing favorable pharmacokinetic (PK) properties, significantly inhibited R848-triggered plasma TNF levels in a rat in vivo cytokine release model after single oral dosing. However, BMS-986147 dose dependently reversed cold allodynia in a rat chronic constriction injury (CCI) model following intrathecal administration only, supporting the notion that central neuro-immune modulation is beneficial for treating chronic neuropathic pain. Although both inhibitors were efficacious in inhibiting IL-1β- or TLR-triggered cytokine release in rat dorsal root ganglion cultures, only partial efficacy was reached in IL-1β-stimulated human glial cultures indicating that inhibiting IRAK-4́'s kinase function might be partially dispensable for human IL-1β driven neuroinflammation. Overall, our data demonstrate that IRAK-4 inhibitors could provide therapeutic benefit in chronic pain following nerve injury, and the central driver for efficacy in the neuropathic pain model as well as potential side effects of centrally available IRAK-4 inhibitors warrant further investigation to develop effective analgesia for patients in high unmet medical need.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

A unified approach for divergent synthesis of contiguous stereodiads employing a small boronyl group

Acyclic contiguous stereocenters are frequently seen in biologically active natural and synthetic molecules. Although various synthetic methods have been reported, predictable and unified approaches to all possible stereoisomers are rare, particularly for those containing non-reactive hydrocarbon substituents. Herein, a β-boronyl group is employed as a readily accessible handle for predictable α-functionalization of enolates with either syn or anti selectivity depending on reaction conditions. Contiguous tertiary-tertiary and tertiary-quaternary stereocenters are thus accessed in generally good yields and diastereoselectivity. Based on experimental and computational studies, mechanism for syn selective alkylation is proposed, and Bpin (pinacolatoboronyl) behaves as a smaller group than most carbon-centered groups. The synthetic utility of this methodology is demonstrated by preparation of several key intermediates for bioactive molecules.

Predictable and unified approaches to all possible stereoisomers of acyclic compounds with contiguous stereocentres are rare. Here, the authors disclose a divergent α-functionalization of enolates with either syn or anti selectivity employing a β-boronyl group as a small, directing handle.

Tapentadol Prevents Motor Impairments in a Mouse Model of Dyskinesia

The motor features in Parkinson's disease (PD) are associated with the degeneration of dopaminergic cells in the substantia nigra in the brain. Thus, the gold-standard in PD therapeutics still consists of dopamine replacement with levodopa. However, as the disease progresses, this therapeutic option becomes less effective and can be accompanied by levodopa-induced complications. On the other hand, several other neuronal pathways have been implicated in the pathological mechanisms of PD. In this context, the development of alternative therapeutic options that modulate non-dopaminergic targets is emerging as a major goal in the field. In a phenotypic-based screen in a zebrafish model of PD, we identified tapentadol as a candidate molecule for PD. The therapeutic potential of an agent that modulates the opioid and noradrenergic systems has not been explored, despite the implication of both neuronal pathways in parkinsonism. Therefore, we assessed the therapeutic properties of this µ-opioid receptor agonist and norepinephrine reuptake inhibitor in the 6-hydroxydopamine mouse model of parkinsonism. We further submitted 6-hydroxydopamine-lesioned mice to chronic treatment with levodopa and evaluated the effects of tapentadol during levodopa OFF states and on levodopa-induced dyskinesia. Importantly, we found that tapentadol halted the aggravation of dyskinesia and improved the motor impairments during levodopa OFF states. Altogether, our findings raise the hypothesis that concomitant modulation of µ-opioid receptor and norepinephrine transporter might constitute relevant intervention strategies in PD and that tapentadol holds therapeutic potential that may be translated into the clinical practice.

Identification of antiparkinsonian drugs in the 6-hydroxydopamine zebrafish model

Parkinson's disease (PD) is known as a movement disorder due to characteristic motor features. Existing therapies for PD are only symptomatic, and their efficacy decreases as disease progresses. Zebrafish, a vertebrate in which parkinsonism has been modelled, offers unique features for the identification of molecules with antiparkinsonian properties. Here, we developed a screening assay for the selection of neuroactive agents with antiparkinsonian potential. First, we performed a pharmacological validation of the phenotypes exhibited by the 6-hydroxydopamine zebrafish model, by testing the effects of known antiparkinsonian agents. These drugs were also tested for disease-modifying properties by whole mount immunohistochemistry to TH⁺ neurons and confocal microscopy in the dopaminergic diencephalic cluster of zebrafish. Next, we optimized a phenotypic screening using the 6-hydroxydopamine zebrafish model and tested 1600 FDA-approved bioactive drugs. We found that 6-hydroxydopamine-lesioned zebrafish larvae exhibit bradykinetic and dyskinetic-like behaviours that are rescued by the administration of levodopa, rasagiline, isradipine or amantadine. The rescue of dopaminergic cell loss by isradipine was also verified, through the observation of a higher number of TH⁺ neurons in 6-OHDA-lesioned zebrafish larvae treated with this compound as compared to untreated lesioned larvae. The phenotypic screening enabled us to identify several compounds previously positioned for PD, as well as, new molecules with potential antiparkinsonian properties. Among these, we selected stavudine, tapentadol and nabumetone as the most promising candidates. Our results demonstrate the functional similarities of the motor impairments exhibited by 6-hydroxydopamine-lesioned zebrafish with mammalian models of PD and with PD patients, and highlights novel molecules with antiparkinsonian potential.