Mechanisms for experimental buprenorphine hepatotoxicity: major role of mitochondrial dysfunction versus metabolic activation

Drug-Induced Fatty Liver Disease (DIFLD): A Comprehensive Analysis of Clinical, Biochemical, and Histopathological Data for Mechanisms Identification and Consistency with Current Adverse Outcome Pathways

Drug induced fatty liver disease (DIFLD) is a form of drug-induced liver injury (DILI), which can also be included in the more general metabolic dysfunction-associated steatotic liver disease (MASLD), which specifically refers to the accumulation of fat in the liver unrelated to alcohol intake. A bi-directional relationship between DILI and MASLD is likely to exist: while certain drugs can cause MASLD by acting as pro-steatogenic factors, MASLD may make hepatocytes more vulnerable to drugs. Having a pre-existing MASLD significantly heightens the likelihood of experiencing DILI from certain medications. Thus, the prevalence of steatosis within DILI may be biased by pre-existing MASLD, and it can be concluded that the genuine true incidence of DIFLD in the general population remains unknown. In certain individuals, drug-induced steatosis is often accompanied by concomitant injury mechanisms such as oxidative stress, cell death, and inflammation, which leads to the development of drug-induced steatohepatitis (DISH). DISH is much more severe from the clinical point of view, has worse prognosis and outcome, and resembles MASH (metabolic-associated steatohepatitis), as it is associated with inflammation and sometimes with fibrosis. A literature review of clinical case reports allowed us to examine and evaluate the clinical features of DIFLD and their association with specific drugs, enabling us to propose a classification of DIFLD drugs based on clinical outcomes and pathological severity: Group 1, drugs with low intrinsic toxicity (e.g., ibuprofen, naproxen, acetaminophen, irinotecan, methotrexate, and tamoxifen), but expected to promote/aggravate steatosis in patients with pre-existing MASLD; Group 2, drugs associated with steatosis and only occasionally with steatohepatitis (e.g., amiodarone, valproic acid, and tetracycline); and Group 3, drugs with a great tendency to transit to steatohepatitis and further to fibrosis. Different mechanisms may be in play when identifying drug mode of action: (1) inhibition of mitochondrial fatty acid β-oxidation; (2) inhibition of fatty acid transport across mitochondrial membranes; (3) increased de novo lipid synthesis; (4) reduction in lipid export by the inhibition of microsomal triglyceride transfer protein; (5) induction of mitochondrial permeability transition pore opening; (6) dissipation of the mitochondrial transmembrane potential; (7) impairment of the mitochondrial respiratory chain/oxidative phosphorylation; (8) mitochondrial DNA damage, degradation and depletion; and (9) nuclear receptors (NRs)/transcriptomic alterations. Currently, the majority of, if not all, adverse outcome pathways (AOPs) for steatosis in AOP-Wiki highlight the interaction with NRs or transcription factors as the key molecular initiating event (MIE). This perspective suggests that chemical-induced steatosis typically results from the interplay between a chemical and a NR or transcription factors, implying that this interaction represents the primary and pivotal MIE. However, upon conducting this exhaustive literature review, it became evident that the current AOPs tend to overly emphasize this interaction as the sole MIE. Some studies indeed support the involvement of NRs in steatosis, but others demonstrate that such NR interactions alone do not necessarily lead to steatosis. This view, ignoring other mitochondrial-related injury mechanisms, falls short in encapsulating the intricate biological mechanisms involved in chemically induced liver steatosis, necessitating their consideration as part of the AOP's map road as well.

Buprenorphine administration during gestation induces hepatotoxicity in the rat fetus

This study investigated the effect of buprenorphine (BUP) on the livers of pups exposed to this drug during the fetal stage. BUP decreased the activities of serum liver enzymes in exposed animals versus the controls. BUP (0.5 mg/kg) decreased malondialdehyde levels and increased the glutathione levels in the liver of animals versus other groups. The superoxide dismutase activity was elevated in the BUP 0.5 mg/kg group versus the control group. BUP (1 mg/kg) induced histopathological changes in the livers of pups. In conclusion, BUP may induce hepatotoxicity in pups exposed to this drug during the fetal stage.

Mitochondria as the Target of Hepatotoxicity and Drug-Induced Liver Injury: Molecular Mechanisms and Detection Methods

One of the major mechanisms of drug-induced liver injury includes mitochondrial perturbation and dysfunction. This is not a surprise, given that mitochondria are essential organelles in most cells, which are responsible for energy homeostasis and the regulation of cellular metabolism. Drug-induced mitochondrial dysfunction can be influenced by various factors and conditions, such as genetic predisposition, the presence of metabolic disorders and obesity, viral infections, as well as drugs. Despite the fact that many methods have been developed for studying mitochondrial function, there is still a need for advanced and integrative models and approaches more closely resembling liver physiology, which would take into account predisposing factors. This could reduce the costs of drug development by the early prediction of potential mitochondrial toxicity during pre-clinical tests and, especially, prevent serious complications observed in clinical settings.

Novel advances in biotransformation and bioactivation research-2019 year in review

Biotransformation is one of the main mechanisms used by the body to eliminate drugs. As drug molecules become more complicated, the involvement of drug metabolizing enzymes increases beyond those that are typically studied, such as the cytochrome P450 enzymes. In this review, we try to capture the many outstanding articles that were published in the past year in the field of biotransformation (see Table 1). We have divided the articles into two categories of (1) metabolites and drug metabolizing enzymes, and (2) bioactivation and safety.  This annual review is the fifth of its kind since 2016 (Baillie et al. 2016; Khojasteh et al. 2017, 2018, 2019). This effort in itself also continues to evolve. We have followed the same format we used in previous years in terms of the selection of articles and the authoring of each section. I am pleased of the continued support of Rietjens, Miller, Zhang, Driscoll and Mitra to this review. We would like to welcome Klarissa D. Jackson as a new author for this year's issue. We strive to maintain a balance of authors from academic and industry settings.  We would be pleased to hear your opinions of our commentary, and we extend an invitation to anyone who would like to contribute to a future edition of this review. Cyrus Khojasteh, on behalf of the authors.

Impact of Pharmacological Treatments for Opioid Use Disorder on Mortality

The use of pharmacological treatments for opioid use disorders, including methadone, buprenorphine and naltrexone has been associated with a reduction in mortality compared with illicit opioid use. However, these treatments can also contribute significantly to the risk of death. The opioid agonists methadone and buprenorphine achieve clinical efficacy in patients with an opioid use disorder through suppressing craving and diminishing the effectiveness of illicit opioid doses, while the antagonist naltrexone blocks the action of opioids. Pharmacological differences between opioid pharmacotherapies then create different temporal patterns of protection and mortality risk, different risks of relapse to illicit opioid use, and variations in direct and indirect toxicity, which are revealed in clinical and epidemiological studies. Induction onto methadone and the cessation of oral naltrexone treatment are associated with an elevated risk of opioid poisoning, which is not apparent in patients treated with buprenorphine or sustained-release naltrexone. Beyond drug-related mortality, these pharmacotherapies can impact a participant's risk of death. Buprenorphine may also have some advantages over methadone in patients with depressive disorders or cardiovascular abnormalities. Naltrexone, which is also commonly prescribed to manage problem alcohol use, may reduce deaths in chronic co-alcohol users. Understanding these pharmacologically driven patterns then guides the judicious choice of drug and dosing schedule and the proactive risk management that is crucial to minimising the risk of death in treatment.

Effects of N-acetyl cysteine, vitamin E and vitamin C on liver glutathione levels following amiodarone treatment in rats

Introduction

Amiodarone, a pharmaceutical extensively used to suppress atrial and ventricular tachyarrhythmias, is also known to cause many side effects on many tissues. N-acetyl-cysteine (NAC), vitamin E and vitamin C are known as antioxidants for their ability to minimize oxidative stress. In the peer-reviewed literature, there is no study reporting on the protective effects of these antioxidant agents against its hepatotoxicity.

Aim

We investigated the oxidative effects of NAC, vitamins E and C on liver tissue after amiodarone treatment.

Material and methods

Rats were randomly assigned to: control; amiodarone group; amiodarone + NAC treated group; amiodarone + Vit. E group and amiodarone + Vit. C group. Liver tissues were isolated from animals and total glutathione levels were measured.

Results

In all time intervals, the level of glutathione increased. When all time intervals were compared, the amiodarone group revealed the lowest levels. The antioxidant co-administered group was studied; the glutathione levels were statistically significantly higher than the sole amiodarone group. When vitamins E, C or N-acetyl cysteine were examined, there was no statistically significant difference among them.

Conclusions

In this study we found that hepatotoxicity capacity of amiodarone may be reduced by taking up antioxidants. In addition, the effect documented here may be reproducible and may be applied to clinical settings.

Drug-drug interactions and clinical considerations with co-administration of antiretrovirals and psychotropic drugs

Psychotropic medications are frequently co-prescribed with antiretroviral therapy (ART), owing to a high prevalence of psychiatric illness within the population living with HIV, as well as a 7-fold increased risk of HIV infection among patients with psychiatric illness. While ART has been notoriously associated with a multitude of pharmacokinetic drug interactions involving the cytochrome P450 enzyme system, the magnitude and clinical impact of these interactions with psychotropics may range from negligible effects on plasma concentrations to life-threatening torsades de pointes or respiratory depression. This comprehensive review summarizes the currently available information regarding drug-drug interactions between antiretrovirals and pharmacologic agents utilized in the treatment of psychiatric disorders-antidepressants, stimulants, antipsychotics, anxiolytics, mood stabilizers, and treatments for opioid use disorder and alcohol use disorder-and provides recommendations for their management. Additionally, overlapping toxicities between antiretrovirals and the psychotropic classes are highlighted. Knowledge of the interaction and adverse effect potential of specific antiretrovirals and psychotropics will allow clinicians to make informed prescribing decisions to better promote the health and wellness of this high-risk population.

A brief review of the genetics and pharmacogenetics of opioid use disorders

Increased physician prescribing of opioids to treat chronic nonprogressive pain has been accompanied by an increase in opioid addiction. Twin studies of opioid addiction are consistent with an inherited component of risk, approximately 50%. Several genome-wide association study (GWAS) reports indicate that genetic risk for opioid addiction is conveyed by many alleles of small effect (odds ratios <1.5). These reports have detected alleles in potassium-ion-channel genes (KCNC1 and KCNG2) and in a glutamate receptor auxiliary protein (CNIH3). Additionally, a variant at the µ-opioid receptor gene (OPRM1), which regulates OPRM1 expression appears promising. In pharmacogenetics of opioid addictions, methadone dose may be regulated by variants in cytochrome P450 2B6 (CYP2B6), a methadone-metabolizing enzyme, and by a locus 300 kb 5' to OPRM1. A δ-opioid-receptor gene single-nucleotide polymorphism may predict treatment response to methadone versus buprenorphine. To achieve better progress, larger sample sizes are needed for GWAS research, including controls with chronic opioid exposure, but no addiction. Large clinical trials comparing effective pharmacotherapies for opioid addiction (naltrexone, methadone, and buprenorphine) are needed for pharmacogenetic progress.

Assessment of Hepatic Impairment and Implications for Pharmacokinetics of Substance Use Treatment

Although the liver is the primary site of metabolism and biliary excretion for many medications, data are limited on the liver's pharmacokinetic abilities in cirrhosis. Cirrhosis develops through collagen deposition, eventually culminating in end-stage liver disease that compromises hepatic drug metabolism. Consequently, the US Food and Drug Administration (FDA) recommends evaluating the pharmacokinetics of medications in subjects with hepatic impairment if hepatic metabolism constitutes more than 20% of their elimination or if they have a narrow therapeutic range. A variety of noninvasive indices and radiologic procedures can be employed to assess hepatic drug metabolism and excretion. The Child-Pugh score is the most commonly used scale for assessing hepatic impairment among drugs submitted for US FDA approval. The score, originally developed to guide operative mortality in patients undergoing hepatic resection, has not been modified since its inception 5 decades ago. Furthermore, the score was not originally intended to be a guide for potential dose modification in patients with hepatic impairment. These reasons, in combination with the availability of a variety of new imaging modalities and an enhanced understanding of hepatic biology, should foster the development of novel methods to assess the effect of hepatic impairment on liver drug metabolism.

Friend or foe? Mitochondria as a pharmacological target in cancer treatment

Mitochondria have acquired numerous functions over the course of evolution, such as those involved in controlling energy production, cellular metabolism, cell survival, apoptosis and autophagy within host cells. Tumor cells can develop defects in mitochondrial function, presenting a potential strategy for designing selective anticancer therapies. Therefore, cancer has been the main focus of recent research to uncover possible mitochondrial targets for therapeutic benefit. This comprehensive review covers not only the recent discoveries of the roles of mitochondria in cancer development, progression and therapeutic implications but also the findings regarding emerging mitochondrial therapeutic targets and mitochondria-targeted agents. Current challenges and future directions for developments and applications of mitochondrial-targeted therapeutics are also discussed.

Mitochondrial impairments contribute to spatial learning and memory dysfunction induced by chronic tramadol administration in rat: Protective effect of physical exercise

Despite the worldwide use of tramadol, few studies have been conducted about its effects on memory and mitochondrial function, and controversial results have been reported. Recently, there has been an increasing interest in physical exercise as a protective approach to neuronal and cognitive impairments. Therefore, the aim of this study was to investigate the effects of physical exercise on spatial learning and memory and brain mitochondrial function in tramadol-treated rats. After completion of 2-week (short-term) and 4-week (long-term) treadmill exercise regimens, male Wistar rats received tramadol (20, 40, 80mg/kg/day) intraperitoneally for 30days. Then spatial learning and memory was assessed by Morris water maze test (MWM). Moreover, brain mitochondrial function was evaluated by determination of mitochondrial reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), mitochondrial swelling and cytochrome c release from mitochondria. Chronic administration of tramadol impaired spatial learning and memory as well as brain mitochondrial function as indicated by increased ROS level, MMP collapse, increased mitochondrial swelling and cytochrome c release from mitochondria. Conversely, treadmill exercise significantly attenuated the impairments of spatial learning and memory and brain mitochondrial dysfunction induced by tramadol. The results revealed that chronic tramadol treatment caused memory impairments through induction of brain mitochondrial dysfunction. Furthermore, pre-exposure to physical exercise markedly mitigated these impairments through its positive effects on brain mitochondrial function.

The Effects of Fentanyl on Hepatic Mitochondrial Function

BACKGROUND

Remifentanil interferes with hepatic mitochondrial function. The aim of the present study was to evaluate whether hepatic mitochondrial function is affected by fentanyl, a more widely used opioid than remifentanil.

METHODS

Human hepatoma HepG2 cells were exposed to fentanyl or pretreated with naloxone (an opioid receptor antagonist) or 5-hydroxydecanoate (5-HD, an inhibitor of mitochondrial adenosine triphosphate (ATP)-sensitive potassium [mitoKATP] channels), followed by incubation with fentanyl. Mitochondrial function and metabolism were then analyzed.

RESULTS

Fentanyl marginally reduced maximal mitochondrial complex-specific respiration rates using exogenous substrates (decrease in medians: 11%-18%; P = 0.003-0.001) but did not affect basal cellular respiration rates (P = 0.834). The effect on stimulated respiration was prevented by preincubation with naloxone or 5-HD. Fentanyl reduced cellular ATP content in a dose-dependent manner (P < 0.001), an effect that was not significantly prevented by 5-HD and not explained by increased total ATPase concentration. However, in vitro ATPase activity of recombinant human permeability glycoprotein (an ATP-dependent drug efflux transporter) was significantly stimulated by fentanyl (P = 0.004).

CONCLUSIONS

Our data suggest that fentanyl reduces stimulated mitochondrial respiration of cultured human hepatocytes by a mechanism that is blocked by a mitoKATP channel antagonist. Increased energy requirements for fentanyl efflux transport may offer an explanation for the substantial decrease in cellular ATP concentration.

Treatment of Opioid Dependence With Buprenorphine/Naloxone After Liver Transplantation: Report of Two Cases

Opioid dependence is an increasing public health problem. One of the complications of intravenous opioid use is hepatitis C virus infection, which, in turn, is one of the most common indications for liver transplantations throughout the world. Therefore, the treatment of opioid dependence in a liver transplant recipient requires special attention in terms of graft function, drug interactions, and patient compliance. Buprenorphine is a semi-synthetic opioid-derived agent with analgesic effects. To prevent buprenorphine abuse, it is combined with the opioid antagonist naloxone. This buprenorphine/naloxone combination is the only drug approved for the treatment of opioid dependence in Turkey. Although the literature includes data about the safe usage of buprenorphine in liver transplantation in animals, there is no such evidence in either case reports or clinical trials for the same in humans. In this article, we present a report of our treatment of 2 opioid-dependent patients with buprenorphine/naloxone after liver transplantation due to hepatitis C virus-induced liver cirrhosis.

The Importance of Patient-Specific Factors for Hepatic Drug Response and Toxicity

Responses to drugs and pharmacological treatments differ considerably between individuals. Importantly, only 50%-75% of patients have been shown to react adequately to pharmacological interventions, whereas the others experience either a lack of efficacy or suffer from adverse events. The liver is of central importance in the metabolism of most drugs. Because of this exposed status, hepatotoxicity is amongst the most common adverse drug reactions and hepatic liabilities are the most prevalent reason for the termination of development programs of novel drug candidates. In recent years, more and more factors were unveiled that shape hepatic drug responses and thus underlie the observed inter-individual variability. In this review, we provide a comprehensive overview of different principle mechanisms of drug hepatotoxicity and illustrate how patient-specific factors, such as genetic, physiological and environmental factors, can shape drug responses. Furthermore, we highlight other parameters, such as concomitantly prescribed medications or liver diseases and how they modulate drug toxicity, pharmacokinetics and dynamics. Finally, we discuss recent progress in the field of in vitro toxicity models and evaluate their utility in reflecting patient-specific factors to study inter-individual differences in drug response and toxicity, as this understanding is necessary to pave the way for a patient-adjusted medicine.

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.

Hepatic Safety of Buprenorphine in HIV-Infected and Uninfected Patients With Opioid Use Disorder: The Role of HCV-Infection

INTRODUCTION

Individuals with HIV and hepatitis C (HCV) infection, alcohol use disorder, or who are prescribed potentially hepatotoxic medications may be at increased risk for buprenorphine (BUP) associated hepatotoxicity.

MATERIALS AND METHODS

We examined a cohort of HIV-infected and uninfected patients receiving an initial BUP prescription between 2003 and 2012. We compared changes in alanine and aspartate aminotransferases (ALT and AST) and total bilirubin (TB) stratified by HIV status. We identified cases of liver enzyme elevation (LEE), TB elevation (TBE), and conducted chart review to assess for cases of drug induced liver injury (DILI) and death. We examined associations between age, sex, race, HIV-infection, HCV-infection, alcohol use disorder, and prescription of other potentially heptatotoxic medications with the composite endpoint of LEE, TBE, and DILI.

RESULTS

Of 666 patients prescribed BUP, 36% were HIV-infected, 98% were male, 60% had RNA-confirmed HCV infection, 50% had a recent diagnosis of alcohol use disorder, and 64% were prescribed other potentially hepatotoxic medications. No clinically significant changes were observed in median ALT, AST and TB and these changes did not differ between HIV-infected and uninfected patients. Compared with uninfected patients, HIV-infected (OR 7.3, 95% CI 2.1-26.1, p=0.002), HCV-infected (OR 4.9 95% CI 1.6-15.2, p=0.007) or HIV/HCV co-infected patients (OR 6.9, 95%CI 2.1-22.2, p=0.001) were more likely to have the composite endpoint of LEE, TB elevation or DILI, in analyses that excluded 60 patients with evidence of pre-existing liver injury. 31 patients had LEE, 14/187 HIV-infected and 17/340 uninfected (p=0.25); 11 had TBE, including 9/186 HIV-infected and 2/329 uninfected (p=0.002); 8 experienced DILI, 4/202 HIV-infected and 4/204 uninfected (p=0.45). There were no significant associations with alcohol use disorder or prescription of other potentially hepatotoxic medications after adjustment for HIV/HCV status.

CONCLUSIONS

Liver enzymes and TB are rarely elevated in HIV-infected and uninfected patients receiving BUP. Risk of hepatotoxicity was greater in individuals infected with HIV, HCV, or HIV/HCV co-infection, who may benefit from increased monitoring.

The Influence of Liver Resection on Intrahepatic Tumor Growth

The high incidence of tumor recurrence after resection of metastatic liver lesions remains an unsolved problem. Small tumor cell deposits, which are not detectable by routine clinical imaging, may be stimulated by hepatic regeneration factors after liver resection. It is not entirely clear, however, which factors are crucial for tumor recurrence. The presented mouse model may be useful to explore the mechanisms that play a role in the development of recurrent malignant lesions after liver resection. The model combines the easy-to-perform and reproducible techniques of defined amounts of liver tissue removal and tumor induction (by injection) in mice. The animals were treated with either a single laparotomy, a 30% liver resection, or a 70% liver resection. All animals subsequently received a tumor cell injection into the remaining liver tissue. After two weeks of observation, the livers and tumors were evaluated for size and weight and examined by immunohistochemistry. After a 70% liver resection, the tumor volume and weight were significantly increased compared to a laparotomy alone (p <0.05). In addition, immunohistochemistry (Ki67) showed an increased tumor proliferation rate in the resection group (p <0.05). These findings demonstrate the influence of hepatic regeneration mechanisms on intrahepatic tumor growth. Combined with methods like histological workup or RNA analysis, the described mouse model could serve as foundation for a close examination of different factors involved in tumor growth and metastatic disease recurrence within the liver. A considerable number of variables like the length of postoperative observation, the cell line used for injection or the timing of injection and liver resection offer multiple angles when exploring a specific question in the context of post-hepatectomy metastases. The limitations of this procedure are the authorization to perform the procedure on animals, access to an appropriate animal testing facility and acquisition of certain equipment.

LC-MS Analysis of Human Platelets as a Platform for Studying Mitochondrial Metabolism

Perturbed mitochondrial metabolism has received renewed interest as playing a causative role in a range of diseases. Probing alterations to metabolic pathways requires a model in which external factors can be well controlled, allowing for reproducible and meaningful results. Many studies employ transformed cellular models for these purposes; however, metabolic reprogramming that occurs in many cancer cell lines may introduce confounding variables. For this reason primary cells are desirable, though attaining adequate biomass for metabolic studies can be challenging. Here we show that human platelets can be utilized as a platform to carry out metabolic studies in combination with liquid chromatography-tandem mass spectrometry analysis. This approach is amenable to relative quantification and isotopic labeling to probe the activity of specific metabolic pathways. Availability of platelets from individual donors or from blood banks makes this model system applicable to clinical studies and feasible to scale up. Here we utilize isolated platelets to confirm previously identified compensatory metabolic shifts in response to the complex I inhibitor rotenone. More specifically, a decrease in glycolysis is accompanied by an increase in fatty acid oxidation to maintain acetyl-CoA levels. Our results show that platelets can be used as an easily accessible and medically relevant model to probe the effects of xenobiotics on cellular metabolism.

Partial hepatectomy in mice

The surgical procedure of two-thirds partial hepatectomy (PH) in rodents was first described more than 80 years ago by Higgins and Anderson. Nevertheless, this technique is still a state-of-the-art method for the community of liver researchers as it allows the in-depth analysis of signalling pathways involved in liver regeneration and hepatocarcinogenesis. The importance of PH as a key method in experimental hepatology has even increased in the last decade due to the increasing availability of genetically-modified mouse strains. Here, we propose a standard operating procedure (SOP) for the implementation of PH in mice, which is based on our experience of more than 10 years. In particular, the SOP offers all relevant background information on the PH model and provides comprehensive guidelines for planning and performing PH experiments. We provide established recommendations regarding optimal age and gender of animals, use of appropriate anaesthesia and biometric calculation of the experiments. We finally present an easy-to-follow step-by-step description of the complete surgical procedure including required materials, critical steps and postoperative management. This SOP especially takes into account the latest changes in animal welfare rules in the European Union but is still in agreement with current international regulations. In summary, this article provides comprehensive information for the legal application, design and implementation of PH experiments.

Drugs of abuse and addiction: A slippery slope toward liver injury

Substances of abuse induce alteration in neurobehavioral symptoms, which can lead to simultaneous exacerbation of liver injury. The biochemical changes of liver are significantly observed in the abused group of people using illicit drugs or drugs that are abused. A huge amount of work has been carried out by scientists for validation experiments using animal models to assess hepatotoxicity in cases of drugs of abuse. The risk of hepatotoxicity from these psychostimulants has been determined by different research groups. Hepatotoxicity of these drugs has been recently highlighted and isolated case reports always have been documented in relation to misuse of the drugs. These drugs induce liver toxicity on acute or chronic dose dependent process, which ultimately lead to liver damage, acute fatty infiltration, cholestatic jaundice, liver granulomas, hepatitis, liver cirrhosis etc. Considering the importance of drug-induced hepatotoxicity as a major cause of liver damage, this review emphasizes on various drugs of abuse and addiction which induce hepatotoxicity along with their mechanism of liver damage in clinical aspect as well as in vitro and in vivo approach. However, the mechanisms of drug-induced hepatotoxicity is dependent on reactive metabolite formation via metabolism, modification of covalent bonding between cellular components with drug and its metabolites, reactive oxygen species generation inside and outside of hepatocytes, activation of signal transduction pathways that alter cell death or survival mechanism, and cellular mitochondrial damage, which leads to alteration in ATP generation have been notified here. Moreover, how the cytokines are modulated by these drugs has been mentioned here.

Fulminant hepatic failure after intravenous injection of sublingual buprenorphine in a patient with hepatitis C

A 20-year-old indigenous Australian male was admitted to the intensive care unit with fulminant hepatic failure secondary to intravenous use of buprenorphine, which had been prescribed sublingually for opioid dependence. Intravenous buprenorphine-induced hepatitis is well recognized, however, life-threatening fulminant hepatic failure has not previously been reported.

Liver enzyme levels in adolescent patients treated with buprenorphine and additional psychotropic agents

BACKGROUND

There are limited efficacy and safety data for buprenorphine/naloxone treatment in adolescents, and little is known about the incidence and prevalence of liver function abnormalities in young patients using buprenorphine/naloxone.

OBJECTIVES

To assess the changes in liver enzyme levels associated with buprenorphine/naloxone treatment and co-medication with psychotropic agents among opioid dependent subjects aged 15-18 years.

METHODS

Liver enzyme levels (ALT and AST) were evaluated among 59 adolescent subjects before and following eight weeks of buprenorphine/naloxone treatment.

RESULTS

The frequency of additional psychotropic use was 60%. The patients' mean liver enzyme levels at weeks 2 and 4 were significantly higher than the baseline (ALT: p < 0.0001 and p = 0.003, and AST: p < 0.0001 and p = 0.016, respectively). However, there was no statistically significant difference in AST and ALT levels between the baseline and week 8. The majority of the abnormalities seen were clinically nonsignificant elevations (less than two times the upper limit of normal). It is plausible that the abnormalities in liver enzymes could have been mediated by the use of psychotropic medications.

CONCLUSIONS

Buprenorphine/naloxone was well tolerated in most adolescent patients, besides clinically nonsignificant liver enzyme elevations. Psychotropic medications may have been associated with the liver enzyme changes early in the course of treatment. Nevertheless, given the relatively small number of adolescents studied to date with buprenorphine/naloxone, additional studies evaluating liver enzymes in young patients receiving buprenorphine/naloxone (and no other psychotropics) are needed.

New developments in the management of opioid dependence: focus on sublingual buprenorphine-naloxone

Opioid maintenance therapy is a well-established first-line treatment approach in opioid dependence. Buprenorphine, a partial opioid agonist, has been found by numerous studies to be an effective and safe medication in the treatment of opioid dependence. At present, buprenorphine is available as a monodrug or in a fixed 4:1 ratio combination with naloxone. A diminished risk of diversion and abuse for the buprenorphine-naloxone combination is likely but not firmly established. Conventional formulations are given sublingually to avoid the hepatic first-pass effect. A novel film tablet is available only in the US and Australia. Other novel, sustained-release formulations (implant, depot) are currently being developed and tested. Recent studies, including a Cochrane meta-analysis, suggest that the retention with buprenorphine is lower than for methadone, but that buprenorphine may be associated with less drug use. Higher doses of buprenorphine are associated with better retention rates. Buprenorphine has a ceiling effect at the opioid receptor with regard to respiratory depression, and may cause fewer fatal intoxications than methadone. Possible antidepressant effects of buprenorphine and its use in comorbid psychiatric patients has not been studied in much detail. Clinical implications are discussed.

Alcohol use disorders in opioid maintenance therapy: prevalence, clinical correlates and treatment

Maintenance therapy with methadone or buprenorphine is an established and first-line treatment for opioid dependence. Clinical studies indicate that about a third of patients in opioid maintenance therapy show increased alcohol consumption and alcohol use disorders. Comorbid alcohol use disorders have been identified as a risk factor for clinical outcome and can cause poor physical and mental health, including liver disorders, noncompliance, social deterioration and increased mortality risk. The effects of opioid maintenance therapy on alcohol consumption are controversial and no clear pattern has emerged. Most studies have not found a change in alcohol use after initiation of maintenance therapy. Methadone and buprenorphine appear to carry little risk of liver toxicity, but further research on this topic is required. Recent data indicate that brief intervention strategies may help reduce alcohol intake, but the existing evidence is still limited. This review discusses further clinical implications of alcohol use disorders in opioid dependence.

Buprenorphine-naloxone treatment in opioid dependence and risk of liver enzyme elevation: results from a 12-month observational study

BACKGROUND

Some case series mention possible liver toxicity in opioid-dependent patients under buprenorphine treatment.

METHODS

This 12-month prospective observational follow-up study in opioid-dependent patients under buprenorphine-naloxone treatment assessed outcome and safety issues. At baseline, 337 eligible datasets were available; 181 patients completed the 12-month study. Liver enzymes were tested at baseline and after 12, 24, and 52 weeks' treatment.

RESULTS

One to two percent of patients showed mostly discrete elevations of liver enzymes, but no patient met the criteria for drug-induced liver injury. No serious liver-related adverse events occurred, but two non-serious cases of liver enzyme increase were recorded. No patient dropped out of treatment for liver-related disorders.

CONCLUSION

This study is in line with some recent studies and provides further evidence that buprenorphine-naloxone is relatively safe with respect to liver injury.

Hepatotoxicity in a 52-week randomized trial of short-term versus long-term treatment with buprenorphine/naloxone in HIV-negative injection opioid users in China and Thailand

BACKGROUND

Buprenorphine/naloxone (BUP/NX), an effective treatment for opioid dependence, has been implicated in hepatic toxicity. However, as persons taking BUP/NX have multiple hepatic risk factors, comparative data are needed to quantify the risk of hepatoxicity with BUP/NX.

METHODS

We compared rates of alanine aminotransferase (ALT) elevation≥grade 3 (ALT≥5.1 times the upper limit of normal) and graded bilirubin elevations in HIV-negative opioid injectors randomized to long-term (52 weeks) or short-term (18 days) medication assisted treatment (LT-MAT and ST-MAT, respectively) with BUP/NX in a multisite trial conducted in China and Thailand. ALT and bilirubin were measured at baseline, 12, 26, 40 and 52 weeks, times temporally remote from BUP/NX exposure in the ST-MAT participants.

RESULTS

Among1036 subjects with at least one laboratory follow-up measurement, 76 (7%) participants experienced ALT elevation≥grade 3. In an intent-to-treat analysis, the risk of ALT events was similar in participants randomized to LT-MAT compared with ST-MAT (adjusted hazard ratio 1.25, 95% confidence interval 0.79 to 1.98). This finding was supported by an as-treated analysis, in which actual exposure to BUP/NX was considered. Hepatitis C seroconversion during follow-up was strongly associated with ALT events. Bilirubin elevations≥grade 2 occurred in 2% of subjects, with no significant difference between arms.

CONCLUSIONS

Over 52-week follow-up, the risk of hepatotoxicity was similar in opioid injectors receiving brief and prolonged treatment with BUP/NX. These data suggest that most hepatotoxic events observed during treatment with BUP/NX are due to other factors.

Right upper-quadrant pain in a patient with drug abuse, secondary syphilis and occult hepatitis B virus

OBJECTIVE

To describe the etiology of hepatitis and identify occult hepatitis B virus (HBV) infection.

CLINICAL PRESENTATION AND INTERVENTION

A 40-year-old man presented with severe abdominal pain and jaundice, a history of acute HBV infection that had cleared as well as the use of acetaminophen, methamphetamine, buprenorphine and marijuana. He admitted to having had unprotected sex with multiple partners of both genders. A thorough skin examination revealed papulosquamous lesions on his penis, scrotum, upper and lower extremities and feet. Transaminases and bilirubin were elevated. His rapid plasma reagin was reactive, and hepatitis serologies showed occult HBV. Liver biopsy showed severe hepatitis, but the stains for hepatitis B surface antigen and hepatitis B core antigen were negative. The pathological findings were highly indicative of drug-induced hepatitis without evidence of chronic hepatitis, reactivation of HBV or syphilitic hepatitis. With supportive management and abstinence from drugs, his condition improved.

CONCLUSION

This case describes a patient with multiple potential causes for hepatitis and highlights the importance of obtaining a detailed social history. Further, one should consider the presence of occult HBV and recognize the serologic pattern.

Acute hepatitis and renal failure related to intranasal buprenorphine misuse: case report and analysis of cases reported to the French network for drug monitoring

BACKGROUND

Rare cases of acute hepatitis have been reported following injection, overdose, and even during the use of buprenorphine (BPN) at therapeutic doses, especially in carriers of hepatitis C virus (HCV).

OBJECTIVES

To report a case of acute hepatitis and renal failure related to intranasal BPN misuse in a HCV-negative patient and to analyze cases reported to the French postmarketing surveillance system (PMSS) of drugs and in the literature.

METHODS

All cases of hepatitis related to BPN reported to PMSS between January 1996 and December 2012 were analyzed.

RESULTS

A 42-year-old man with a history of intranasal BPN misuse (8 mg/d) for at least 10 years was admitted for flu-like symptoms and abdominal pain. At admission, the patient consumed alcohol, cannabis, and tobacco. Acute hepatitis and acute renal failure were diagnosed . Clinical signs and biological parameters resolved within 26 days. An objective causality assessment revealed that an adverse drug reaction (ADR) was possible. In the French PMSS database, 41 cases of suspected BPN-induced hepatitis are reported. In 36.6% of cases, BPN was misused by the intravenous route. In the literature, 16 cases of acute hepatitis related to BPN with or without renal failure are reported. In all cases, patients were HCV carriers. The primary mechanism of BPN-induced hepatitis is a mitochondrial dysfunction, exacerbated by cofactors (HCV, alcohol, and medications).

CONCLUSION

Intranasal misuse of BPN is increasingly frequent. We report here the first documented case of acute hepatitis and renal failure related to intranasal BPN misuse in a patient negative for HCV infection.

Safety and efficacy of buprenorphine for analgesia in laboratory mice and rats

Buprenorphine is a long-acting opiate with a high therapeutic index. The authors review the pharmacology, toxicity, analgesic effects and delivery of buprenorphine for use in laboratory mice and rats. Buprenorphine-based analgesic therapy has a substantial record of safety, and there is growing evidence of its effectiveness for treating post-operative pain. Nonetheless, more research is needed to determine optimal delivery systems and analgesic regimens for pain therapy in laboratory animals.

Buprenorphine/Naloxone and methadone effects on laboratory indices of liver health: a randomized trial

BACKGROUND

Buprenorphine/naloxone (BUP) and methadone (MET) are efficacious treatments for opioid dependence, although concerns about a link between BUP and drug-induced hepatitis have been raised. This study compares the effects of BUP and MET on liver health in opioid-dependent participants.

METHODS

This was a randomized controlled trial of 1269 opioid-dependent participants seeking treatment at 8 federally licensed opioid treatment programs and followed for up to 32 weeks between May 2006 and August 2010; 731 participants met "evaluable" criteria defined as completing 24 weeks of medication and providing at least 4 blood samples for transaminase testing. Participants were randomly assigned to receive BUP or MET for 24 weeks. Shift table analysis determined how many evaluable participants moved between categories of low and elevated transaminase levels. Predictors of moving from low to high transaminase levels were identified.

RESULTS

Changes in transaminase levels did not differ by medication condition. Baseline infection with hepatitis C or B was the only significant predictor of moving from low to elevated transaminase levels; 9 BUP and 15 MET participants showed extreme liver test elevations and were more likely than those without extreme elevations to have seroconverted to both hepatitis B and C during the study, or to use illicit drugs during the first 8 weeks of treatment. MET participants were retained longer in treatment than BUP participants.

CONCLUSIONS

This study demonstrated no evidence of liver damage during the initial 6 months of treatment in either condition. Physicians can prescribe either medication without major concern for liver injury.

Effect of hepatitis C virus status on liver enzymes in opioid-dependent pregnant women maintained on opioid-agonist medication

AIM

To examine hepatic enzyme test results throughout the course of pregnancy in women maintained on methadone or buprenorphine.

DESIGN

Participants were randomized to either methadone or buprenorphine maintenance. Blood chemistry tests, including liver transaminases and hepatitis C virus (HCV) status, were determined every 4 weeks and once postpartum. As part of a planned secondary analysis, generalized mixed linear models were conducted with aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) as the dependent variables.

SETTING

Six US sites and one European site that provided comprehensive treatment to pregnant opioid-dependent women.

PARTICIPANTS

A total of 175 opioid-dependent pregnant women enrolled in the Maternal Opioid Treatment: Human Experimental Research (MOTHER) study.

FINDINGS

ALT, AST and GGT levels decreased for all subjects across pregnancy trimesters, rising slightly postpartum. HCV-positive subjects exhibited higher transaminases at all time-points compared to HCV-negative subjects, regardless of medication (all Ps < 0.05) condition. Both HCV-positive and negative buprenorphine-maintained participants exhibited lower GGT levels than those who were methadone-maintained (P < 0.05).

CONCLUSIONS

Neither methadone nor buprenorphine appear to have adverse hepatic effects in the treatment of pregnant opioid-dependent women.

Short-term safety of buprenorphine/naloxone in HIV-seronegative opioid-dependent Chinese and Thai drug injectors enrolled in HIV Prevention Trials Network 058

BACKGROUND

Buprenorphine/naloxone (BUP/NX) is not licenced for use in China or Thailand and there was little clinical experience with this drug combination in these countries at the inception of HIV Prevention Trial Network (HPTN) 058, a randomized trial comparing risk reduction counselling combined with either short-term or long-term medication assisted treatment with BUP/NX to prevent HIV infection and death amongst opioid-dependent injectors.

METHODS

We conducted a safety phase that included the first 50 subjects enrolled at each of the three initial study sites (N=150). Clinical and laboratory assessments were conducted at baseline and weekly for the first 4 weeks. Changes in laboratory parameters were estimated with random effects models.

RESULTS

BUP/NX was well tolerated by study subjects and opioid withdrawal scores decreased substantially during the 3-day induction. Two participants experienced grade 3 clinical adverse events, which were categorized as probably not related to the study drug. Grade 2 or 3 increases in alanine aminotransferase (ALT) occurred in 25 (17%) subjects. The magnitude of ALT increase over 4-week follow-up was strongly associated with baseline ALT elevation.

CONCLUSIONS

In Chinese and Thai opioid-dependent injectors, we found BUP/NX to be effective in reducing opioid withdrawal symptoms and safe during short-term use. ALT increases were observed over 4-week-follow-up, which are consistent with reports from Western populations. Long-term safety and efficacy evaluations are indicated.

Central role of mitochondria in drug-induced liver injury

A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.

Structural alert/reactive metabolite concept as applied in medicinal chemistry to mitigate the risk of idiosyncratic drug toxicity: a perspective based on the critical examination of trends in the top 200 drugs marketed in the United States

Because of a preconceived notion that eliminating reactive metabolite (RM) formation with new drug candidates could mitigate the risk of idiosyncratic drug toxicity, the potential for RM formation is routinely examined as part of lead optimization efforts in drug discovery. Likewise, avoidance of "structural alerts" is almost a norm in drug design. However, there is a growing concern that the perceived safety hazards associated with structural alerts and/or RM screening tools as standalone predictors of toxicity risks may be over exaggerated. In addition, the multifactorial nature of idiosyncratic toxicity is now well recognized based upon observations that mechanisms other than RM formation (e.g., mitochondrial toxicity and inhibition of bile salt export pump (BSEP)) also can account for certain target organ toxicities. Hence, fundamental questions arise such as: When is a molecule that contains a structural alert (RM positive or negative) a cause for concern? Could the molecule in its parent form exert toxicity? Can a low dose drug candidate truly mitigate metabolism-dependent and -independent idiosyncratic toxicity risks? In an effort to address these questions, we have retrospectively examined 68 drugs (recalled or associated with a black box warning due to idiosyncratic toxicity) and the top 200 drugs (prescription and sales) in the United States in 2009 for trends in physiochemical characteristics, daily doses, presence of structural alerts, evidence for RM formation as well as toxicity mechanism(s) potentially mediated by parent drugs. Collectively, our analysis revealed that a significant proportion (∼78-86%) of drugs associated with toxicity contained structural alerts and evidence indicating that RM formation as a causative factor for toxicity has been presented in 62-69% of these molecules. In several cases, mitochondrial toxicity and BSEP inhibition mediated by parent drugs were also noted as potential causative factors. Most drugs were administered at daily doses exceeding several hundred milligrams. There was no obvious link between idiosyncratic toxicity and physicochemical properties such as molecular weight, lipophilicity, etc. Approximately half of the top 200 drugs for 2009 (prescription and sales) also contained one or more alerts in their chemical architecture, and many were found to be RM-positive. Several instances of BSEP and mitochondrial liabilities were also noted with agents in the top 200 category. However, with relatively few exceptions, the vast majority of these drugs are rarely associated with idiosyncratic toxicity, despite years of patient use. The major differentiating factor appeared to be the daily dose; most of the drugs in the top 200 list are administered at low daily doses. In addition, competing detoxication pathways and/or alternate nonmetabolic clearance routes provided suitable justifications for the safety records of RM-positive drugs in the top 200 category. Thus, while RM elimination may be a useful and pragmatic starting point in mitigating idiosyncratic toxicity risks, our analysis suggests a need for a more integrated screening paradigm for chemical hazard identification in drug discovery. Thus, in addition to a detailed assessment of RM formation potential (in relationship to the overall elimination mechanisms of the compound(s)) for lead compounds, effects on cellular health (e.g., cytotoxicity assays), BSEP inhibition, and mitochondrial toxicity are the recommended suite of assays to characterize compound liabilities. However, the prospective use of such data in compound selection will require further validation of the cellular assays using marketed agents. Until we gain a better understanding of the pathophysiological mechanisms associated with idiosyncratic toxicities, improving pharmacokinetics and intrinsic potency as means of decreasing the dose size and the associated "body burden" of the parent drug and its metabolites will remain an overarching goal in drug discovery.

Drug-induced toxicity on mitochondria and lipid metabolism: mechanistic diversity and deleterious consequences for the liver

Numerous investigations have shown that mitochondrial dysfunction is a major mechanism of drug-induced liver injury, which involves the parent drug or a reactive metabolite generated through cytochromes P450. Depending of their nature and their severity, the mitochondrial alterations are able to induce mild to fulminant hepatic cytolysis and steatosis (lipid accumulation), which can have different clinical and pathological features. Microvesicular steatosis, a potentially severe liver lesion usually associated with liver failure and profound hypoglycemia, is due to a major inhibition of mitochondrial fatty acid oxidation (FAO). Macrovacuolar steatosis, a relatively benign liver lesion in the short term, can be induced not only by a moderate reduction of mitochondrial FAO but also by an increased hepatic de novo lipid synthesis and a decreased secretion of VLDL-associated triglycerides. Moreover, recent investigations suggest that some drugs could favor lipid deposition in the liver through primary alterations of white adipose tissue (WAT) homeostasis. If the treatment is not interrupted, steatosis can evolve toward steatohepatitis, which is characterized not only by lipid accumulation but also by necroinflammation and fibrosis. Although the mechanisms involved in this aggravation are not fully characterized, it appears that overproduction of reactive oxygen species by the damaged mitochondria could play a salient role. Numerous factors could favor drug-induced mitochondrial and metabolic toxicity, such as the structure of the parent molecule, genetic predispositions (in particular those involving mitochondrial enzymes), alcohol intoxication, hepatitis virus C infection, and obesity. In obese and diabetic patients, some drugs may induce acute liver injury more frequently while others may worsen the pre-existent steatosis (or steatohepatitis).

Hepatic safety and lack of antiretroviral interactions with buprenorphine/naloxone in HIV-infected opioid-dependent patients

BACKGROUND

The safety of buprenorphine/naloxone (bup/nx) in HIV-infected patients has not been established. Prior reports raise concern about hepatotoxicity and interactions with atazanavir.

METHODS

We conducted a prospective cohort study of 303 opioid-dependent HIV-infected patients initiating bup/nx treatment. We assessed changes in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) over time. We compared bup/nx doses in patients receiving the antiretroviral atazanavir to those not receiving atazanavir. We conducted surveillance for pharmacodynamic interactions.

RESULTS

Median AST [37.0 vs. 37.0 units/liter (U/L) respective interquartile ranges (IQRs) 26-53 and 26-59] and ALT (33.0 vs. 33.0 U/L, respective IQRs 19-50 and 18-50) values did not change over time among 141 patients comparing pre-bup/nx exposure with post-bup/nx exposure measures. During bup/nx exposure, 207 subjects demonstrated no significant change in median AST (36.0 vs. 35.0 U/L, respective IQRs 25-57 and 25-61) and ALT (29.0 vs. 31.0 U/L, respective IQRs 19-50 and 18-50) values collected a median of 6 months apart. Analyses restricted to patients with hepatitis C and HIV co-infection yielded similar results, except a small but significant decrease in first to last AST, during treatment with bup/nx (P = 0.048). Mean bup/nx dose, ranging 16.0-17.8 mg, did not differ over time or with co-administration of atazanavir. No pharmacodynamic interactions were noted.

CONCLUSIONS

Buprenorphine/naloxone did not produce measurable hepatic toxicity or pharmacodynamic interaction with atazanavir in HIV-infected opioid-dependent patients.

Drug treatment outcomes among HIV-infected opioid-dependent patients receiving buprenorphine/naloxone

BACKGROUND

Buprenorphine/naloxone allows the integration of opioid dependence and HIV treatment.

METHODS

We conducted a prospective study in HIV-infected opioid-dependent patients to investigate the impact of buprenorphine/naloxone treatment on drug use. Self-report and chart review assessments were conducted every 3 months (quarters 1-4) for 1 year. Outcomes were buprenorphine/naloxone treatment retention, drug use, and addiction treatment processes.

RESULTS

Among 303 patients enrolled between July 2005 and December 2007, retention in buprenorphine/naloxone treatment was 74%, 67%, 59%, and 49% during Quarters 1, 2, 3, and 4, respectively. Past 30-day illicit opioid use decreased from 84% of patients at baseline to 42% in retained patients over the year. Patients were 52% less likely to use illicit opioids for each quarter in treatment (Odds ratio = 0.66; 95% CI: 0.61 to 0.72). Buprenorphine/naloxone doses and office visits approximated guidelines published by the United States Department of Health and Human Services. Urine toxicology monitoring was less frequent than recommended.

CONCLUSIONS

Buprenorphine/naloxone provided in HIV treatment settings can decrease opioid use. Strategies are needed to improve retention and address ongoing drug use in this treatment population.

FGF receptors 1 and 2 control chemically induced injury and compound detoxification in regenerating livers of mice

BACKGROUND & AIMS

Fibroblast growth factor receptor 4 (FGFR4) controls bile acid metabolism and protects the liver from fibrosis, but the roles of FGFR1 and FGFR2 in the adult liver are largely unknown. We investigated the functions and mechanisms of action of these receptors in liver homeostasis, regeneration, and fibrosis.

METHODS

We generated mice with hepatocytes that lack FGFR1 and FGFR2 and subjected them to acute and chronic carbon tetrachloride-induced liver injury and partial hepatectomy; mice were also injected with FGF7. We performed histology, histomorphometry, real-time reverse transcription polymerase chain reaction, and immunoblot analyses.

RESULTS

In hepatocytes, loss of FGFR1 and FGFR2 eliminated responsiveness to FGF7 and related FGF family members but did not affect toxin-induced liver injury and fibrosis. However, mortality after partial hepatectomy increased because of severe hepatocyte necrosis. These effects appeared to be mediated by a failure of hepatocytes to induce the expression of the transcriptional regulators Dbp and Tef upon liver surgery; this affected expression of their target genes, which encode detoxifying cytochrome P450 enzymes. We found that Dbp and Tef expression was directly controlled by FGFR signaling in hepatocytes. As a consequence of the reduced expression of genes that control detoxification, the liver tissue that remained after partial hepatectomy failed to efficiently metabolize endogenous compounds and the drugs applied for anesthesia/analgesia.

CONCLUSIONS

We identified a new, cytoprotective effect of FGFR1 and FGFR2 in the regenerating liver and suggest the use of recombinant FGF7 to increase survival of patients after surgical resection of large amounts of liver tissue.

Mitochondrial involvement in drug-induced liver injury

Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.

Acute liver and renal failure during treatment with buprenorphine at therapeutic dose

Buprenorphine is a semi-synthetic opioid derivative commonly used in the treatment of heroin addiction. Life-threatening complications have been described following overdoses while few cases of hepatotoxicity due to drug use at therapeutic doses have been recently described in hepatitis C virus carriers. In these cases, however, histological assessment was not exhaustive and no extra-hepatic organ failure was observed. We describe herein a case of acute liver and kidney failure in a patient with previously latent hepatitis C virus chronic infection following recommended doses of buprenorphine. Histology did not demonstrate any feature compatible with hepatitis C virus reactivation or liver cirrhosis and suspension of the treatment led to the resolution of both liver and kidney failure. Causality criteria fulfillment indicates a high probability of buprenorphine-induced liver toxicity. No signs of pre-existant kidney impairment or of pre- or post-renal causes were observed. Since buprenorphine is metabolized through cytochrome P450 3A4, we genotyped six genetic polymorphisms previously described in poor metabolizers but could not confirm these pharmacogenetic bases in this case. In conclusion, we surmise that buprenorphine at suggested doses can induce liver and kidney failure in susceptible individuals, possibly through direct mitochondrial toxicity.

Hepatitis After Intravenous Injection of Sublingual Buprenorphine in Acute Hepatitis C Carriers: Report of Two Cases of Disappearance of Viral Replication After Acute Hepatitis

Objective

To report 2 cases of acute hepatitis related to intravenous administration of buprenorphine in hepatitis C–infected patients.

Case Summary

Two patients, aged 33 and 50 years, respectively, who were hepatitis C virus (HCV) carriers were treated with sublingual buprenorphine 8 mg/day for addiction. Several years after initiation of buprenorphine, they were hospitalized because of clinical hepatitis with jaundice that developed after intravenous injection of buprenorphine. Serum alanine aminotransferase rose to 100 times the upper limit of normal (ULN) in the first patient and to 21 times the ULN in the second. As cofactors, the first patient had consumed alcohol, and the second patient took aspirin 600 mg in addition to the injection of buprenorphine 20 mg 4 days before the onset of jaundice. After stopping the intravenous injections, both patients continued sublingual buprenorphine therapy, with no relapse of hepatitis. Interestingly, in these 2 patients, buprenorphine-induced hepatitis was followed by the disappearance of HCV RNA.

Discussion

Most cases of hepatotoxicity related to buprenorphine have occurred in hepatitis C–infected patients. The main mechanism for buprenorphine-induced hepatitis is a mitochondrial defect, exacerbated by cofactors with additional potential to induce mitochondria dysfunction (eg, HCV, alcohol, concomitant medications). According to the Naranjo probability scale, buprenorphine was found to be the probable cause of acute hepatitis in both patients. In addition, we assessed the relationship between intravenous buprenorphine and acute hepatitis using 2 scales for causality assessment of hepatotoxicity (the Council for International Organizations of Medical Sciences scale and the Maria & Victorino scale). The diagnosis of intravenous buprenorphine-induced hepatitis was classified as probable in both cases. In addition, these 2 cases illustrate that acute hepatitis in a carrier of chronic HCV may occasionally facilitate the clearance of virus.

Conclusions

Although buprenorphine is well tolerated when used at recommended sublingual doses, patients should be informed about the risk of acute hepatitis with misuse of the drug by the intravenous route. These cases illustrate that, in carriers of chronic HCV, acute hepatitis may modify the host's immunotolerance and facilitate clearance of the virus.

A reproducible and well-tolerated method for 2/3 partial hepatectomy in mice

The ability of hepatocytes to enter the cell cycle and regenerate the liver after tissue loss provides an in vivo model to study the regulation of proliferation and organ regeneration. The extent of hepatocyte proliferation is directly proportional to the amount of resected liver tissue, and 2/3 partial hepatectomy (2/3 PH) leads to highly synchronized hepatocyte cell-cycle entry and progression. This surgical technique was first described in rats and requires modification for application in mice. Lack of standardization of 2/3 PH in mice has caused discrepancies in the results obtained in different laboratories. Here, we provide a protocol and a movie describing a straightforward surgical technique, which takes 15-20 min, to consistently remove two-thirds of the liver in mice. As this protocol is not associated with mortality and gives highly reproducible results, we hope that it will be widely used and serve to standardize 2/3 PH in mice.

Case series on the safe use of buprenorphine/naloxone in individuals with acute hepatitis C infection and abnormal hepatic liver transaminases

BACKGROUND

Hepatitis C virus (HCV) is the most prevalent chronic viral illness in the United States. Many individuals with virus HCV are opioid dependent requiring treatment with opiate substitution treatment such as buprenorphine. Previous reports in the literature have suggested hepatotoxicity with buprenorphine tempering initial enthusiasm of the safety of buprenorphine in HCV-infected patients.

METHODS

As part of an ongoing SAMHSA-funded grant to expand opiate substitution therapy with buprenorphine, all opioid-dependent patients seeking treatment with buprenorphine undergo a laboratory evaluation including transaminases (AST/ALT) as well as laboratory evaluation for acute and chronic hepatitis.

RESULTS

Of the 121 patients screened for entry into buprenorphine treatment, 4 patients had evidence of acute HCV infection.

CONCLUSIONS

Despite markedly elevated transaminases in the setting of acute hepatitis C infection, these patients tolerated buprenorphine treatment with improvement in their transaminases during the course of buprenorphine treatment.

Interactions between buprenorphine and antiretrovirals. I. The nonnucleoside reverse-transcriptase inhibitors efavirenz and delavirdine

This study examined drug interactions between buprenorphine, an opioid partial agonist medication used in the treatment of opioid dependence, and the nonnucleoside reverse-transcriptase inhibitors (NNRTIs) efavirenz (EFV) and delavirdine (DLV). Opioid-dependent, buprenorphine/naloxone-maintained, human immunodeficiency virus (HIV)-negative volunteers (n=10 per NNRTI) participated in 24-h sessions to determine pharmacokinetics of buprenorphine and of buprenorphine with either EFV or DLV after administration of standard doses of either antiretroviral for 15 or 7 days, respectively. Opiate withdrawal symptoms, cognitive effects, and adverse events were determined before and after antiretroviral administration in opioid-dependent participants. The pharmacokinetics of NNRTIs in healthy control participants were used to determine the effect of buprenorphine on NNRTIs. EFV decreased the buprenorphine area under the concentration-time curve (P<.001). DLV increased buprenorphine concentrations (P<.001). Clinically significant consequences of these interactions were not observed. Buprenorphine did not alter antiretroviral pharmacokinetics. Adjustments of doses of either buprenorphine or EFV or DLV are not likely to be necessary when these drugs are administered for the treatment of opiate dependence and HIV disease.

Buprenorphine Use: The International Experience

The confluence of the heroin injection epidemic and the human immunodeficiency virus (HIV) infection epidemic has increased the call for expanded access to effective treatments for both conditions. Buprenorphine and methadone are now listed on the World Health Organization's Model Essential Drugs List. In France, which has the most extensive experience, buprenorphine has been associated with a dramatic decrease in deaths due to overdose, and buprenorphine diversion appears to be associated with inadequate dosage, social vulnerability, and prescriptions from multiple providers. Other treatment models (in the United States, Australia, Germany, and Italy) and buprenorphine use in specific populations are also reviewed in the present article. In countries experiencing a dual epidemic of heroin use and HIV infection, such as former states of the Soviet Union and other eastern European and Asian countries, access to buprenorphine and methadone may be one potential tool for reducing the spread of HIV infection among injection drug users and for better engaging them in medical care.