Increased incidence of mixed drug toxicity deaths involving tapentadol - A forensic study

Tapentadol is a relatively new synthetic opioid analgesic prescribed for the management of moderate to severe pain. While tapentadol has been shown to be more effective than traditional opioid analgesics, it still carries the risk of addiction, abuse, and misuse. In Australia, tapentadol has become one of the top five most commonly prescribed opioid drugs, with prescriptions increasing by approximately 150,000 each year since it first became available. The rapid increase in tapentadol prescriptions has occurred in parallel to an increasing number of post-mortem tapentadol detections in South Australia (SA). While the number of deaths in SA related to tapentadol use was low in the current study, findings suggest that an increasing trend of deaths involving tapentadol will continue in parallel to a rapidly increasing number of prescriptions, mirroring trends associated with traditional opioids in SA. As a comparatively new opioid analgesic, monitoring future trends will be important to determine if additional prescribing education, intervention, or restrictions are required.

Characteristics of fatal tapentadol-related toxicity in Australia

INTRODUCTION

Tapentadol is a centrally acting opioid analgesic prescribed for the treatment of moderate to severe pain. The study aimed to determine the characteristics of Australian toxicity deaths related to tapentadol.

METHODS

All cases in which tapentadol use was coded contributory to death (n = 159) were retrieved from the National Coronial Information System (1 July 2000-31 December 2020).

RESULTS

The mean age was 48.5 (18-81) and 56% were female. Documented histories of problems with chronic pain (66%), mental health (60.4%), substance use (44%) and injecting drug use (23.3%) were common. The majority of deaths were deemed unintentional (76.1%) and in 18.9% pre-existing disease was co-contributory. The median peripheral blood tapentadol concentration was 1.00 mg L^-1 (0.02-47.00), and the median aortic concentration was 2.05 mg L^-1 (0.10-30.00). In all cases, psychoactive drugs other than tapentadol were also detected, most commonly antidepressants (72.3%), opioids (66.7%), hypnosedatives (64.2%) and gabapentinoids (43.4%). Of cases where autopsies were conducted, 27.7% were diagnosed with cardiomegaly and 18.5% with severe coronary artery stenosis. Pulmonary oedema (68.1%), aspiration of vomitus (39.5%) and acute pneumonia (26.9%) were common.

DISCUSSION AND CONCLUSIONS

The typical tapentadol-related toxicity death involved unintentional death in the presence of multiple drugs, although a notable minority were intentional self-harm. Multiple morbidities were common. The identification and characteristics of these cases indicate that the adverse event profile of tapentadol needs to be considered in the setting of polypharmacy.

Evaluation of mitochondrial dysfunction due to oxidative stress in therapeutic, toxic and lethal concentrations of tramadol

Tramadol (TR) is a centrally acting analgesic drug that is used to relieve pain. The therapeutic (0.1-0.8 mg/l), toxic (1-2 mg/l) and lethal (>2 mg/l) ranges were reported for TR. The present study was designed to evaluate which doses of TR can induce liver mitochondrial toxicity. Mitochondria were isolated from the five rats' liver and were incubated with therapeutic to lethal concentrations (1.7-600 μM) of TR. Biomarkers of oxidative stress including: reactive oxygen species (ROS), lipid peroxidation (LPO), protein carbonyl content, glutathione (GSH) content, mitochondrial function, mitochondrial membrane potential (MMP) and mitochondrial swelling were assessed. Our results showed that ROS and LPO at 100 μM and protein carbonylation at 600 μM concentrations of TR were significantly increased. GSH was decreased specifically at 600 μM concentration. Mitochondrial function, MMP and mitochondrial swelling decreased in isolated rat liver mitochondria after exposure to 100 and 300 μM, respectively. This study suggested that TR at therapeutic and toxic levels by single exposure could not induce mitochondrial toxicity. But, in lethal concentration (≥100 μM), TR induced oxidative damage and mitochondria dysfunction. This study suggested that ROS overproduction by increasing of TR concentration induced mitochondrial dysfunction and caused mitochondrial damage via Complex II and membrane permeability transition pores disorders, MMP collapse and mitochondria swelling.

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.

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.

Toxicity of tapentadol: a systematic review

BACKGROUND

Tapentadol is a novel atypical opioid. Anecdotal evidence suggests that tapentadol has a lower toxicity than conventional opioids.

OBJECTIVES

To evaluate all single-drug mortality due to tapentadol and assess serious adverse events caused by tapentadol.

METHODS

The Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) reporting guidelines, an evidence-based minimum set of items for reporting in systematic reviews, were followed in this systematic review.

RESULTS

 24 peer-reviewed papers were identified. They indicate that tapentadol toxicity can cause mortality and serious adverse effects.

CONCLUSION(S)

At least four confirmed fatalities, and serious adverse effects have been documented for individuals abusing or using tapentadol as prescribed. Serious adverse effects of tapentadol use may include respiratory depression, confusion, coma, hallucination/delusion, seizures, tachycardia, hypertension, agitation, tremor, miosis, hypotension, dyspnea, electrolyte abnormality, atrial fibrillation or severe upper abdominal pain. Tapentadol is unlikely to cause serotonin syndrome. The toxicity of tapentadol is significantly less than pure mu opioids, such as oxycodone.

Comparative pharmacology and toxicology of tramadol and tapentadol

Moderate-to-severe pain represents a heavy burden in patients' quality of life, and ultimately in the society and in healthcare costs. The aim of this review was to summarize data on tramadol and tapentadol adverse effects, toxicity, potential advantages and limitations according to the context of clinical use. We compared data on the pharmacological and toxicological profiles of tramadol and tapentadol, after an extensive literature search in the US National Library of Medicine (PubMed). Tramadol is a prodrug that acts through noradrenaline and serotonin reuptake inhibition, with a weak opioid component added by its metabolite O-desmethyltramadol. Tapentadol does not require metabolic activation and acts mainly through noradrenaline reuptake inhibition and has a strong opioid activity. Such features confer tapentadol potential advantages, namely lower serotonergic, dependence and abuse potential, more linear pharmacokinetics, greater gastrointestinal tolerability and applicability in the treatment of chronic and neuropathic pain. Although more studies are needed to provide clear guidance on the opioid of choice, tapentadol shows some advantages, as it does not require CYP450 system activation and has minimal serotonergic effects. In addition, it leads to less side effects and lower abuse liability. However, in vivo and in vitro studies have shown that tramadol and tapentadol cause similar toxicological damage. In this context, it is important to underline that the choice of opioid should be individually balanced and a tailored decision, based on previous experience and on the patient's profile, type of pain and context of treatment.

SIGNIFICANCE

This review underlines the need for a careful prescription of tramadol and tapentadol. Although both are widely prescribed synthetic opioid analgesics, their toxic effects and potential dependence are not completely understood yet. In particular, concerning tapentadol, further research is needed to better assess its toxic effects.

Review of Post-Marketing Safety Data on Tapentadol, a Centrally Acting Analgesic

Introduction

Tapentadol is a centrally acting analgesic that has been available for the management of acute and chronic pain in routine clinical practice since 2009.

Methods

This is the first integrated descriptive analysis of post-marketing safety data following the use of tapentadol in a broad range of pain conditions relating to the topics overall safety, dose administration above approved dosages, administration during pregnancy, serotonin syndrome, respiratory depression, and convulsion. The data analyzed pertain to spontaneous reports from healthcare and non-healthcare professionals and were put in the context of safety information known from interventional and non-interventional trials.

Results

The first years of routine clinical practice experience with tapentadol have confirmed the tolerability profile that emerged from the clinical trials. Moreover, the reporting of expected side effects such as respiratory depression and convulsion was low and no major risks were identified. The evaluation of available post-marketing data did not confirm the theoretical risk of serotonin syndrome nor did it reveal unexpected side effects with administration of higher than recommended doses.

Conclusion

More than 8 years after its first introduction, the favorable overall safety profile of tapentadol in the treatment of various pain conditions is maintained in the general population.

Funding

Grünenthal GmbH.

Electronic supplementary material

The online version of this article (10.1007/s12325-017-0654-0) contains supplementary material, which is available to authorized users.

Acute administration of tramadol and tapentadol at effective analgesic and maximum tolerated doses causes hepato- and nephrotoxic effects in Wistar rats

Tramadol and tapentadol are two atypical synthetic opioid analgesics, with monoamine reuptake inhibition properties. Mainly aimed at the treatment of moderate to severe pain, these drugs are extensively prescribed for multiple clinical applications. Along with the increase in their use, there has been an increment in their abuse, and consequently in the reported number of adverse reactions and intoxications. However, little is known about their mechanisms of toxicity. In this study, we have analyzed the in vivo toxicological effects in liver and kidney resulting from an acute exposure of a rodent animal model to both opioids. Male Wistar rats were intraperitoneally administered with 10, 25 and 50mg/kg tramadol and tapentadol, corresponding to a low, effective analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively, for 24h. Toxicological effects were assessed in terms of oxidative stress, biochemical and metabolic parameters and histopathology, using serum and urine samples, liver and kidney homogenates and tissue specimens. The acute exposure to tapentadol caused a dose-dependent increase in protein oxidation in liver and kidney. Additionally, exposure to both opioids led to hepatic commitment, as shown by increased serum lipid levels, decreased urea concentration, increased alanine aminotransferase and decreased butyrylcholinesterase activities. It also led to renal impairment, as reflected by proteinuria and decreased glomerular filtration rate. Histopathological findings included sinusoidal dilatation, microsteatosis, vacuolization, cell infiltrates and cell degeneration, indicating metabolic changes, inflammation and cell damage. In conclusion, a single effective analgesic dose or the maximum recommended daily dose of both opioids leads to hepatotoxicity and nephrotoxicity, with tapentadol inducing comparatively more toxicity. Whether these effects reflect risks during the therapeutic use or human overdoses requires focused attention by the medical community.

Comparative study of the neurotoxicological effects of tramadol and tapentadol in SH-SY5Y cells

Opioid therapy and abuse are increasing, justifying the need to study their toxicity and underlying mechanisms. Given opioid pharmacodynamics at the central nervous system, the analysis of toxic effects in neuronal models gains particular relevance. The aim of this study was to compare the toxicological effects of acute exposure to tramadol and tapentadol in the undifferentiated human SH-SY5Y neuroblastoma cell line. Upon exposure to tramadol and tapentadol concentrations up to 600μM, cell toxicity was assessed through evaluation of oxidative stress, mitochondrial and metabolic alterations, as well as cell viability and death mechanisms through necrosis or apoptosis, and related signalling. Tapentadol was observed to trigger much more prominent toxic effects than tramadol, ultimately leading to energy deficit and cell death. Cell death was shown to predominantly occur through necrosis, with no alterations in membrane potential or in cytochrome c release. Both drugs were shown to stimulate glucose uptake and to cause ATP depletion, due to changes in the expression of energy metabolism enzymes. The toxicity mechanisms in such a neuronal model are relevant to understand adverse reactions to these opioids and to contribute to dose adjustment in order to avoid neurological damage.

Comparative Toxicity of Tapentadol and Tramadol Utilizing Data Reported to the National Poison Data System

Background: Tapentadol (TAP) and tramadol (TRA) provide pain relief through similar monoaminergic and opioid agonist properties. Objective: To compare clinical effects and medical outcomes between TAP and TRA exposures reported to the National Poison Data System of the American Association of Poison Control Centers. Methods: A retrospective cohort study was conducted analyzing national data for single medication TAP or TRA cases reported from June 2009 through December 2011. Case outcomes, dichotomized as severe versus mild; clinical effects; and use of naloxone were compared. Results: There were 217 TAP and 8566 TRA cases. Significantly more severe outcomes were associated with TAP exposures for an all-age comparison (relative risk [RR] = 1.24; 95% CI = 1.04-1.48), and for the <6-year-old age group (RR = 5.76; 95% CI = 2.20-15.11). Patients with TAP exposures had significantly greater risk of respiratory depression (RR = 5.56; 95% CI = 3.50-8.81), coma (RR = 4.16; 95% CI = 2.33-7.42), drowsiness/lethargy (RR = 1.38; 95% CI = 1.15-1.66), slurred speech (RR = 3.51; 95% CI = 1.98-6.23), hallucination/delusion (RR = 7.25; 95% CI = 3.61-14.57), confusion (RR = 2.54; 95% CI = 1.56-4.13) and use of naloxone (RR = 3.80; 95% CI = 2.96-4.88). TRA exposures had significantly greater risk of seizures (RR = 7.94; 95% CI = 2.99-20.91) and vomiting (RR = 1.96; 95% CI = 1.07-3.60). Conclusion: TAP was associated with significantly more toxic clinical effects and severe outcomes consistent with an opioid agonist. TRA was associated with significantly higher rates of seizures and vomiting.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).