Carbamazepine-provoked hepatotoxicity and possible aetiopathological role of glutathione in the events. Retrospective review of old data and call for new investigation

Update and Application of a Deep Learning Model for the Prediction of Interactions between Drugs Used by Patients with Multiple Sclerosis

Patients with multiple sclerosis (MS) often take multiple drugs at the same time to modify the course of disease, alleviate neurological symptoms and manage co-existing conditions. A major consequence for a patient taking different medications is a higher risk of treatment failure and side effects. This is because a drug may alter the pharmacokinetic and/or pharmacodynamic properties of another drug, which is referred to as drug-drug interaction (DDI). We aimed to predict interactions of drugs that are used by patients with MS based on a deep neural network (DNN) using structural information as input. We further aimed to identify potential drug-food interactions (DFIs), which can affect drug efficacy and patient safety as well. We used DeepDDI, a multi-label classification model of specific DDI types, to predict changes in pharmacological effects and/or the risk of adverse drug events when two or more drugs are taken together. The original model with ~34 million trainable parameters was updated using >1 million DDIs recorded in the DrugBank database. Structure data of food components were obtained from the FooDB database. The medication plans of patients with MS (n = 627) were then searched for pairwise interactions between drug and food compounds. The updated DeepDDI model achieved accuracies of 92.2% and 92.1% on the validation and testing sets, respectively. The patients with MS used 312 different small molecule drugs as prescription or over-the-counter medications. In the medication plans, we identified 3748 DDIs in DrugBank and 13,365 DDIs using DeepDDI. At least one DDI was found for most patients (n = 509 or 81.2% based on the DNN model). The predictions revealed that many patients would be at increased risk of bleeding and bradycardic complications due to a potential DDI if they were to start a disease-modifying therapy with cladribine (n = 242 or 38.6%) and fingolimod (n = 279 or 44.5%), respectively. We also obtained numerous potential interactions for Bruton's tyrosine kinase inhibitors that are in clinical development for MS, such as evobrutinib (n = 434 DDIs). Food sources most often related to DFIs were corn (n = 5456 DFIs) and cow's milk (n = 4243 DFIs). We demonstrate that deep learning techniques can exploit chemical structure similarity to accurately predict DDIs and DFIs in patients with MS. Our study specifies drug pairs that potentially interact, suggests mechanisms causing adverse drug effects, informs about whether interacting drugs can be replaced with alternative drugs to avoid critical DDIs and provides dietary recommendations for MS patients who are taking certain drugs.

MD Investigation on the Interaction between Carbamazepine and Two CYP Isoforms, CYP3A4 and CYP3A5

Carbamazepine (CBZ), a commonly prescribed antiepileptic drug, in human liver, is mainly metabolized by two isoforms of cytochrome P450 (CYP), CYP3A4 and CYP3A5. Therefore, the binding of CBZ with these two enzymes plays crucial role in the biotransformation of the drug into its active metabolite. In the present work, classical molecular dynamics (MD) simulation was used to investigate the detailed interaction mechanism between CBZ and these two CYP isoforms at the atomic level. The results revealed that although CBZ can bind with the two proteins, all kinds of the interactions, including hydrogen bonds, salt bridges, hydrophobic interaction, and π-π interaction, are isoform specific. The specificity directly leads to a binding environment difference at the active sites of the two isoforms, as represented by the electrostatic surface potential maps, which further results in the varied dynamic behavior of CBZ in the two isoforms. Our research will help to deepen the understanding of the physiological functions of CYP isoforms and opens the door for the rational design and development of isoform-specific inhibitors.

Influence of nanoparticle size on blood-brain barrier penetration and the accumulation of anti-seizure medicines in the brain

Anti-seizure medicines constitute a common yet important modality to treat epilepsy. However, some of them are associated with serious side effects including hepatotoxicity and hypersensitivity. Furthermore, the blood-brain barrier (BBB) is an insurmountable obstacle for brain drug delivery. Fortunately, the introduction of the nanoparticles for drug delivery is a feasible approach to overcome these obstacles. Encapsulating drugs into nanoparticles and delivering them to specific sites shows great potential for improving the efficiency of drug delivery and reducing systemic toxicity. Several in vivo studies have investigated the effect of nanoparticle size on biodistribution in mice, but very few have investigated its effects on efficient drug delivery while crossing the BBB. Therefore, we designed a methoxy poly(lactide-co-glycolide)-b-poly(ethylene glycol) methyl ether (mPEG-PLGA) nanoparticle delivery system and explored the cell uptake efficiency of nanoparticles with different sizes and their ability to penetrate the BBB while carrying carbamazepine (CBZ). CBZ-loaded nanoparticles could significantly reduce the cytotoxicity of CBZ to L929 cells at high concentrations. Results from the endocytosis experiment involving human cerebral microvessel endothelial cell/D3 showed that the DiR-loaded mPEG_5K-PLGA_10K nanoparticles possessed the highest cell uptake efficiency. The endocytosis efficiency was 90% at 30 min, which far exceeded that of the other groups. Moreover, similar results were obtained from subsequent experiments where fluorescence images of the isolated organs of the mice were acquired. To summarize, our study demonstrated that drug delivery to the brain using nanocarriers is size dependent. Nanoparticles with the smallest particle size can be internalized more effectively, and easily penetrate the BBB, and accumulate in the brain.

Nanostructured lipid carriers (NLCs) as drug delivery platform: Advances in formulation and delivery strategies

NLCs have provoked the incessant impulsion for the development of safe and valuable drug delivery systems owing to their exceptional physicochemical and then biocompatible characteristics. Throughout the earlier period, a lot of studies recounting NLCs based formulations have been noticeably increased. They are binary system which contains both solid and liquid lipids aiming to produce less ordered lipidic core. Their constituents particularly influence the physicochemical properties and effectiveness of the final product. NLCs can be fabricated by different techniques which are classified according to consumed energy. More utilization NLCs is essential due to overcome barriers surrounded by the technological procedure of lipid-based nanocarriers' formulation and increased information of the core mechanisms of their transport via various routes of administration. They can be used in different applications and by different routes such as oral, cutaneous, ocular and pulmonary. This review article seeks to present an overview on the existing situation of the art of NLCs for future clinics through exposition of their applications which shall foster their lucid use. The reported records evidently demonstrate the promise of NLCs for innovate therapeutic applications in the future.

Something Old, Something New: Ion Channel Blockers as Potential Anti-Tuberculosis Agents

Tuberculosis (TB) remains a challenging global health concern and claims more than a million lives every year. We lack an effective vaccine and understanding of what constitutes protective immunity against TB to inform rational vaccine design. Moreover, treatment of TB requires prolonged use of multi-drug regimens and is complicated by problems of compliance and drug resistance. While most Mycobacterium tuberculosis (Mtb) bacilli are quickly killed by the drugs, the prolonged course of treatment is required to clear persistent drug-tolerant subpopulations. Mtb’s differential sensitivity to drugs is, at least in part, determined by the interaction between the bacilli and different host macrophage populations. Therefore, to design better treatment regimens for TB, we need to understand and modulate the heterogeneity and divergent responses that Mtb bacilli exhibit within macrophages. However, developing drugs de-novo is a long and expensive process. An alternative approach to expedite the development of new TB treatments is to repurpose existing drugs that were developed for other therapeutic purposes if they also possess anti-tuberculosis activity. There is growing interest in the use of immune modulators to supplement current anti-TB drugs by enhancing the host’s antimycobacterial responses. Ion channel blocking agents are among the most promising of the host-directed therapeutics. Some ion channel blockers also interfere with the activity of mycobacterial efflux pumps. In this review, we discuss some of the ion channel blockers that have shown promise as potential anti-TB agents.

Non-Dose-Dependent Changes in Liver Enzyme Levels of Children With Epilepsy on Treatment With Sodium Valproate

Background:

Sodium valproate (VPA) is considered as the drug of choice for the treatment of generalized epilepsy in children. Sodium Valproate may be hepatotoxic.

Aim:

To assess the level of derangement of liver enzymes in children with epilepsy on treatment with sodium valproate.

Methods:

A cohort study. One hundred fifty-three children, comprising 51 with epilepsy on treatment with VPA (group I), 51 with epilepsy on treatment with other antiepileptic drugs (AEDs) but not VPA (group II), and 51 with nonconvulsive disorders (group III) had liver function tests performed for them. Data were analyzed by SPSS version 23.0.

Results:

There were 85 males and 68 females, aged 6 months to 14 years (median = 7.0 years). There was no significant difference in the mean plasma levels of alanine transaminase (ALT), alkaline phosphatase, and gamma glutamyl transferase across the three groups of children. The mean aspartate transaminase level was significantly higher in children in group III. There was a statistically significant negative correlation between the duration of AED therapy and the mean serum level of AST (r = −0.266, P = 0.016). The serum ALT level showed a statistically significant positive correlation with the duration of AED therapy (r = 0.268, P = 0.015).

Conclusion:

Sodium valproate monotherapy does not appear to be associated with significant hepatotoxicity in children in our cohort.

Evaluation of Anticonvulsant Activity and Toxicity Screening of Semicarbazones Derived from Quinazolinone Scaffold

Background:

Epilepsy is one of the most prevalent noncommunicable neurological conditions. More than 10 million people in India are afflicted with epilepsy. Treatment available has many detrimental side effects. Up to one-third of epilepsy patients remain resistance to optimum drug treatment. These facts triggered the further scope and search for newer more effective and less toxic anticonvulsants.

Methods:

Quinazolinone semicarbazone derivatives showing protection in chemoconvulsant induced seizure models (as reported in our previous study) were further screened in MES and scPTZ induced seizure models. Neurotoxicity was determined; quantification of anticonvulsant activity and toxicity was also done. Finally compounds were screened by liver functional test to ascertain the possible hepatotoxicity in the active compounds.

Results:

Compounds N-1- (menthone) -N- [3-(4-(substituted)-phenyl) -4-oxo- 3,4-dihydroquinazolin- 2-yl] methyl semicarbazone (3A-d-4, 3B-d-4 and 3C-d-4) showed significant protection in both MES and scPTZ induced seizure model with no neurotoxicity at the given dose. In MES test, compounds showed an ED50 close to that of phenytoin and carbamazepine. They also showed Protective Index (PI) higher as compared to phenytoin and carbamazepine. A high safety profile (HD50/ED50 values) was noted and hypnosis, analgesia, and anesthesia were only observed at higher doses.

Conclusion:

Compounds showed no significant increase or decrease in the concentration of alkaline phosphatase, Serum Glutamate Oxaloacetate Transaminase (SGOT), Serum Glutamate Pyruvate Transaminase (SGPT), albumin and bilirubin.

Carbamazepine adverse drug reactions

INTRODUCTION

Carbamazepine (CBZ) is used for the treatment of epilepsy and other neurological and psychiatric disorders. The occurrence of adverse reactions (ADRs) to CBZ can negatively impact the quality of life of patients, as well as increase health-care costs. Thus, knowledge of CBZ-induced ADRs is important to achieve safer treatment outcomes. Areas covered: This review describes the clinical features, known mechanisms, and clinical management of the main CBZ-induced ADRs. In addition, pharmacogenetic studies focused on ADRs induced by CBZ are cited. Expert commentary: CBZ-induced ADRs are well known in the literature. The metabolite CBZ-10,11-epoxide plays an important role in the mechanism that underlies the ADRs induced by CBZ. Several factors should be considered for a safer use of CBZ, such as monotherapy prescription when possible, an adequate dose titration, knowledge of previous ADRs in the patient, and routine monitoring of CBZ plasma concentrations in symptomatic patients. Pharmacogenetics is a potential tool for CBZ therapy improvement, and the design of multicenter studies focused on the identification of biomarkers for CBZ-induced ADRs could provide useful information for a safer CBZ therapy.

Glutathione S-transferase M1 and T1 polymorphisms and the risk of mild hepatotoxicity induced by carbamazepine in a tunisian population study

BACKGROUND

The aim of this study was to evaluate whether the glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) null alleles may contribute to carbamazepine-induced hepatotoxicity.

METHODS

A cross-sectional prospective study was conducted to identify the frequency distribution of GSTM1 and GSTT1 alleles in 129 Tunisian epileptic patients treated with carbamazepine. Null alleles were determined using a Polymerase Chain Reaction. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured by standard methods.

RESULTS

Our results showed that the frequencies of GSTM1 (-) null allele and GSTT1 null (-) allele were 74.4 and 17.8% respectively. The ALT and AST levels were elevated in 46 (35.7%) and 33 (25.6%) cases. The mean values of ALT and AST were approximately 1.32 and 3.61 times higher than the upper limit of normal levels, respectively. The values of ALT and AST were significantly higher in GSTM1 (-) allele than in GSTM1 (+) (p = 10^-3.and 0.004, respectively). The level of ALT was significantly higher in combination of GSTM1 (-)/T1(-) than in combined GSTM1(-)/T1(+) and combined GSTM1(+)/T1(+) (p = 0.2 and 0.03, respectively), and that of AST was significantly higher in combination of GSTM1(-)/T1(-) and in combination of GSTM1(+)/T1(-) than in combination of GSTM1(+)/T1(+) (p = 10^-3 and 10^-3, respectively).

CONCLUSIONS

Our findings suggest that the GSTM1 (-) allele may be considered as a key factor for the development of carbamazepine-induced hepatotoxicity. Results related to GSTT (-) allele and elevation in AST levels should be considered with caution as AST may be elevated in other pathophysiological conditions.

Antiepileptic Drugs and Liver Disease

Acute, symptomatic seizures or epilepsy may complicate the course of hepatic disease. Choosing the most appropriate antiepileptic drug in this setting represents a difficult challenge, as most medications are metabolized by the liver. This article focuses on the acute and chronic treatment of seizures in patients with advanced liver disease and reviews the hepatotoxic potential of specific antiepileptic drugs. Newer antiepileptic drugs without, or with minimal, hepatic metabolism, such as levetiracetam, lacosamide, topiramate, gabapentin, and pregabalin should be used as first-line therapy. Medications undergoing extensive hepatic metabolism, such as valproic acid, phenytoin, and felbamate should be used as drugs of last resort. In special circumstances, as in patients affected by acute intermittent porphyria, exposure to most antiepileptic drugs could precipitate attacks. In this clinical scenario, bromides, levetiracetam, gabapentin, and vigabatrin constitute safe choices. For the treatment of status epilepticus, levetiracetam and lacosamide, available in intravenous preparations, are good second-line therapies after benzodiazepines fail to control seizures. Hepatotoxicity is also a rare and unexpected side effect of some antiepileptic drugs. Drugs such as valproic acid, phenytoin, and felbamate, have a well-recognized association with liver toxicity. Other antiepileptic drugs, including phenobarbital, benzodiazepines, ethosuximide, and the newer generations of antiepileptic drugs, have only rarely been linked to hepatotoxicity. Thus physicians should be mindful of the pharmacokinetic profile and the hepatotoxic potential of the different antiepileptic drugs available to treat patients affected by liver disease.

A rare case of methimazole-induced cholestatic jaundice in an elderly man of Asian ethnicity with hyperthyroidism: A case report

BACKGROUND

Methimazole is an antithyroid drug that is widely used for the treatment of hyperthyroidism. As an inhibitor of the enzyme thyroperoxidase, methimazole is generally well-tolerated. However, there have been increasing reports of methimazole-induced liver damage, although this effect of methimazole has been limited by the absence of objective diagnosis of the liver condition or the inappropriate use of the Naranjo scale. We present the case of an elderly man with hyperthyroidism, gastritis, and epilepsy who developed liver damage after administration of multiple drugs.

KEY POINTS FROM THE CASE

Considering the low sensitivity of the Naranjo scale in detecting rare reactions associated with liver damage, we used the Roussel-Uclaf Causality Assessment Method scale, with a finding of cholestatic jaundice hepatitis induced by methimazole. The patient's liver enzyme levels improved after discontinuation of methimazole.

MAIN LESSONS LEARNED

Our case underlines the possible hepatoxicity associated with the use of methimazole. A review of the literature confirmed a selective hepatoxicity risk in individuals of Asian ethnicity, which has not been identified in Caucasian or Black populations. Physicians should be aware of the risk of hepatoxicity when prescribing oral methimazole to patients of Asian ethnicity.

Bioaccumulation and bioconcentration of carbamazepine and other pharmaceuticals in fish under field and controlled laboratory experiments. Evidences of carbamazepine metabolization by fish

There is a growing interest in evaluating the presence of pharmaceutical residues and their metabolites in aquatic biota. In this study, twenty pharmaceuticals, including carbamazepine (CBZ) and two metabolites, were analyzed in homogenates of two fish species (Gambusia affinis and Jenynsia multidentata) captured in polluted areas of the Suquía River (Córdoba, Argentina). The twenty target pharmaceuticals were found in G. affinis, while only fifteen were detected in J. multidentata. We observed a noticeable difference in the accumulation pattern of both fish species, suggesting different pathways for the bioaccumulation of polar pharmaceuticals in each fish. In order to investigate uptake and tissue distribution of pharmaceuticals, a detailed study was performed under controlled laboratory conditions in J. multidentata, exposed to CBZ. CBZ and two of its metabolites (carbamazepine-10,11-epoxide - CBZ-EP and 2-hydroxycarbamazepine - 2-OH-CBZ) were monitored in five organs of fish under laboratory exposure. To our knowledge, this is the first report on the presence of CBZ and its metabolite 2-OH-CBZ in gills, intestine, liver, brain and muscle of fish, while the metabolite carbamazepine-10,11-epoxide (CBZ-EP) was detected in gills and muscle. A ratio CBZ-EP/CBZ close to 0.1 suggests that gills and muscle of J. multidentata could metabolize CBZ through the CBZ-EP pathway. Our results reinforce the need of analyzing multiple species to account for the environmental impact of pollutants, negating the simplification of a single, "representative model" during ecotoxicological biomonitoring. To our knowledge, the biotransformation of CBZ to its metabolites (CBZ-EP, 2-OH-CBZ) in fish, under controlled laboratory in vivo exposures, is reported for the first time.

Pharmacogenetics of adverse reactions to antiepileptic drugs

INTRODUCTION

Adverse drug reactions (ADRs) are a major public health concern and a leading cause of morbidity and mortality in the world. In the case of antiepileptic drugs (AEDs), ADRs constitute a barrier to successful treatment since they decrease treatment adherence and impact patients' quality of life of patients. Pharmacogenetics aims to identify genetic polymorphisms associated with drug safety. This article presents a review of genes coding for drug metabolising enzymes and drug transporters, and HLA system genes that have been linked to AED-induced ADRs.

DEVELOPMENT

To date, several genetic variations associated with drug safety have been reported: CYP2C9*2 and *3 alleles, which code for enzymes with decreased activity, have been linked to phenytoin (PHT)-induced neurotoxicity; GSTM1 null alleles with hepatotoxicity induced by carbamazepine (CBZ) and valproic acid (VPA); EPHX1 polymorphisms with teratogenesis; ABCC2 genetic variations with CBZ- and VPA-induced neurological ADRs; and HLA alleles (e.g. HLA-B*15:02, -A*31:01, -B*15:11, -C*08:01) with cutaneous ADRs.

CONCLUSIONS

Published findings show that there are ADRs with a pharmacogenetic basis and a high interethnic variability, which indicates a need for future studies in different populations to gather more useful results for larger number of patients. The search for biomarkers that would allow predicting ADRs to AEDs could improve pharmacotherapy for epilepsy.

Preliminary anticonvulsant and toxicity screening of substituted benzylidenehydrazinyl-N-(6-substituted benzo[d]thiazol-2-yl)propanamides

Keeping in view the structural requirements suggested in the pharmacophore model for anticonvulsant activity, a new series of 3-(2-(substitutedbenzylidene)hydrazinyl)-N-(substituted benzo[d]thiazol-2-yl)-propanamides were synthesized with aromatic hydrophobic aryl ring (A), NH-C=O as hydrogen bonding domain (HBD), nitrogen atom as electron donor (D), and phenyl as distal aryl ring (C). Synthesized compounds were characterized by FTIR, (1)H NMR, (13)C NMR, mass spectroscopy, and elemental analysis. Preliminary in vivo anticonvulsant screening (phase I) was performed by two most adopted seizure models, maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ). Based on anticonvulsant screening results, two compounds, 5h and 5p, were found to be most active; they exhibited activity comparable to standard drugs phenytoin (PHY) and carbamazepine (CBZ). These active compounds were subjected to phase II and phase III screening, where they displayed much higher protective index (PI) in comparison to the standard drugs. In phase IV screening, the bioavailability of active compounds was assessed on oral administration. Further, preliminary safety profiles of 5h and 5p were evaluated by the neurotoxicity testing and liver enzyme estimation.

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.

The new psychoactive substances regime in New Zealand: a different approach to regulation

The New Zealand government has proposed a new psychoactive substances regime, which will place the onus onto manufacturers to prove that their products pose a low risk of harm, prior to receiving approval which allows the products to be legally manufactured and sold. This is an innovative and unique development in the regulation of emerging psychoactive substances, and offers an alternative response to prohibition. The details of the new regime and how it will operate are now emerging, and this offers an opportunity to critically explore some of the issues related to the proposed new regime and to speculate on some of the outcomes. This paper brings together a group of New Zealand based researchers from a range of disciplines with experience of 'legal high' research to discuss this innovative new regime.

Perturbation of bile acid homeostasis is an early pathogenesis event of drug induced liver injury in rats

Drug-induced liver injury (DILI) is a significant consideration for drug development. Current preclinical DILI assessment relying on histopathology and clinical chemistry has limitations in sensitivity and discordance with human. To gain insights on DILI pathogenesis and identify potential biomarkers for improved DILI detection, we performed untargeted metabolomic analyses on rats treated with thirteen known hepatotoxins causing various types of DILI: necrosis (acetaminophen, bendazac, cyclosporine A, carbon tetrachloride, ethionine), cholestasis (methapyrilene and naphthylisothiocyanate), steatosis (tetracycline and ticlopidine), and idiosyncratic (carbamazepine, chlorzoxasone, flutamide, and nimesulide) at two doses and two time points. Statistical analysis and pathway mapping of the nearly 1900 metabolites profiled in the plasma, urine, and liver revealed diverse time and dose dependent metabolic cascades leading to DILI by the hepatotoxins. The most consistent change induced by the hepatotoxins, detectable even at the early time point/low dose, was the significant elevations of a panel of bile acids in the plasma and urine, suggesting that DILI impaired hepatic bile acid uptake from the circulation. Furthermore, bile acid amidation in the hepatocytes was altered depending on the severity of the hepatotoxin-induced oxidative stress. The alteration of the bile acids was most evident by the necrosis and cholestasis hepatotoxins, with more subtle effects by the steatosis and idiosyncratic hepatotoxins. Taking together, our data suggest that the perturbation of bile acid homeostasis is an early event of DILI. Upon further validation, selected bile acids in the circulation could be potentially used as sensitive and early DILI preclinical biomarkers.

Autophagy in nonalcoholic steatohepatitis

Autophagy is a critical pathway for the degradation of intracellular components by lysosomes. Established functions for both macroautophagy and chaperone-mediated autophagy in hepatic lipid metabolism, insulin sensitivity and cellular injury suggest a number of potential mechanistic roles for autophagy in nonalcoholic steatohepatitis (NASH). Decreased autophagic function in particular may promote the initial development of hepatic steatosis and progression of steatosis to liver injury. Additional functions of autophagy in immune responses and carcinogenesis may also contribute to the development of NASH and its complications. The impairment in autophagy that occurs with cellular lipid accumulation, obesity and aging may therefore have an important impact on this disease, and agents to augment hepatic autophagy have therapeutic potential in NASH.

Hepatotoxicity associated with antiepileptic drugs

BACKGROUND

Drug-induced liver injury associated with antiepileptic drugs (AED) is well recognized. The frequency of the most common AED is rare but the consequences can be very serious leading to death or liver transplantation due to acute liver failure induced by these drugs.

CLINICAL FEATURES

Hypersensitivity features are found in more than 70% of patients with phenytoin-induced liver injury, whereas this is only observed in 30% of carbamazepine-associated hepatotoxicity and very rarely with valproate (VPA)-induced liver injury.

PATHOPHYSIOLOGY

The underlying mechanisms behind hepatotoxicity induced by AED are not clear. Reactive metabolites from AED can, in some cases, lead to direct cytotoxicity and liver cell necrosis, whereas in other cases this may lead to neoantigen formation inducing immunoallergic mechanisms.

TREATMENT

No specific therapy is of proved value in severe hepatotoxicity due to AED. However, N-acetylcystein is an appropriate treatment in patients with clinically significant liver injury due to phenytoin and carbamazepine. In patients with VPA-associated liver injury, carnitine that is an important co-factor in the mitochondrial beta-oxidation of fatty acids is the recommended treatment. Early referral of patients with severe liver reactions and coagulopathy to liver transplant centers before encephalopathy can be the difference between liver transplantation and death.

Dual negative precursor ion scan approach for rapid detection of glutathione conjugates using liquid chromatography/tandem mass spectrometry

Screening for conjugates formed by the tripeptide glutathione with new chemical entities is an essential step during the drug discovery process, as the formation of these conjugates serves as an indicator for the presence of reactive electrophilic intermediates. To increase the selectivity and throughput of this analysis, various mass spectral scan types have evolved over time. Historically, samples were analyzed under positive ionization conditions for the neutral loss of m/z 129 (loss of the pyroglutamic acid moiety from glutathione); however, more recently, negative precursor ion scanning for the loss of m/z 272 (deprotonated gamma-glutamyl-dehydroalanyl-glycine from glutathione) has emerged as a more selective tool. Further increasing the selectivity, we report on an extension of this methodology by incorporating a simultaneous dual negative precursor ion scan for two commonly observed ion fragments from glutathione conjugates, m/z 272 and 254 (the dehydrated form of m/z 272). This negative dual precursor ion scan methodology was first validated using substrates known to undergo metabolic bioactivation (diclofenac, carbamazepine, and 3-methyl indole) and has then been applied to the routine analysis of proprietary compounds undergoing active lead optimization. In comparison to alternative scan methodologies, the increased selectivity offered by this simultaneous dual precursor method results in a reduction in the generation of false positive results as well as reduced data interpretation time.

Aromatic antiepileptic drugs and mitochondrial toxicity: effects on mitochondria isolated from rat liver

Idiosyncratic hepatotoxicity is a well-known complication associated with aromatic antiepileptic drugs (AAED), and it has been suggested to occur due to the accumulation of toxic arene oxide metabolites. Although there is clear evidence of the participation of an immune process, a direct toxic effect involving mitochondria dysfunction is also possible. The effects of AAED on mitochondrial function have not been studied yet. Therefore, we investigated, in vitro, the cytotoxic mechanism of carbamazepine (CB), phenytoin (PT) and phenobarbital (PB), unaltered and bioactivated, in the hepatic mitochondrial function. The murine hepatic microsomal system was used to produce the anticonvulsant metabolites. All the bioactivated drugs (CB-B, PB-B, PT-B) affected mitochondrial function causing decrease in state three respiration, RCR, ATP synthesis and membrane potential, increase in state four respiration as well as impairment of Ca2+ uptake/release and inhibition of calcium-induced swelling. As an unaltered drug, only PB, was able to affect mitochondrial respiration (except state four respiration) ATP synthesis and membrane potential; however, Ca2+ uptake/release as well as swelling induction were not affected. The potential to induce mitochondrial dysfunction was PT-B>PB-B>CB-B>PB. Results suggest the involvement of mitochondrial toxicity in the pathogenesis of AAED-induced hepatotoxicity.

[Management of comorbid bipolar disorder and alcohol dependence]

Recent studies confirm the clear association between bipolar disorders and alcohol abuse and dependence. Lifetime prevalence of disorders associated with alcohol abuse or dependence appears to be 3 to 4 times higher in patients with bipolar disorders than in the general population. Lifetime prevalence of mood disorders in alcohol-dependent subjects is approximately 10 times higher than in the general population. Despite the strength of this association, there is little information about specific management that takes into account both disorders and their interaction. One study shows that valproate may reduce excessive alcohol consumption in bipolar alcohol-dependent patients, especially because of its stabilizing and anticonvulsant effects. Based on this study, the American Psychiatry Association (APA) recently suggested the use of valproate in the treatment of patients with comorbid bipolar disorder and alcohol dependence.

Carbamazepine induces mitotic arrest in mammalian Vero cells

We reported recently that the anticonvulsant drug carbamazepine, at supratherapeutic concentrations, exerts antiproliferative effects in mammalian Vero cells, but the underlying mechanism has not been elucidated. This motivates us to examine rigorously whether growth arrest was associated with structural changes in cellular organization during mitosis. In the present work, we found that exposure of the cells to carbamazepine led to an increase in mitotic index, mainly due to the sustained block at the metaphase/anaphase boundary, with the consequent inhibition of cell proliferation. Indirect immunofluorescence, using antibodies directed against spindle apparatus proteins, revealed that mitotic arrest was associated with formation of monopolar spindles, caused by impairment of centrosome separation. The final consequence of the spindle defects induced by carbamazepine, depended on the duration of cell cycle arrest. Following the time course of accumulation of metaphase and apoptotic cells during carbamazepine treatments, we observed a causative relationship between mitotic arrest and induction of cell death. Conversely, cells released from the block of metaphase by removal of the drug, continued to progress through mitosis and resume normal proliferation. Our results show that carbamazepine shares a common antiproliferative mechanism with spindle-targeted drugs and contribute to a better understanding of the cytostatic activity previously described in Vero cells. Additional studies are in progress to extend these initial findings that define a novel mode of action of carbamazepine in cultured mammalian cells.

CYP3A4-Mediated carbamazepine (CBZ) metabolism: formation of a covalent CBZ-CYP3A4 adduct and alteration of the enzyme kinetic profile

Carbamazepine (CBZ) is a widely prescribed anticonvulsant whose use is often associated with idiosyncratic hypersensitivity. Sera of CBZ-hypersensitive patients often contain anti-CYP3A antibodies, including those to a CYP3A23 K-helix peptide that is also modified during peroxidative CYP3A4 heme-fragmentation. We explored the possibility that cytochromes P450 (P450s) such as CYP3A4 bioactivate CBZ to reactive metabolite(s) that irreversibly modify the P450 protein. Such CBZ-P450 adducts, if stable in vivo, could engender corresponding serum P450 autoantibodies. Incubation with CBZ not only failed to inactivate functionally reconstituted, purified recombinant CYP3A4 or CYP3A4 Supersomes in a time-dependent manner, but the inclusion of CBZ (0-1 mM) also afforded a concentration-dependent protection to CYP3A4 from inactivation by NADPH-induced oxidative uncoupling. Incubation of CYP3A4 Supersomes with (3)H-CBZ resulted in its irreversible binding to CYP3A4 protein with a stoichiometry of 1.58 +/- 0.15 pmol (3)H-CBZ bound/pmol CYP3A4. Inclusion of glutathione (1.5 mM) in the incubation reduced this level to 1.09. Similar binding (1.0 +/- 0.4 pmol (3)H-CBZ bound/pmol CYP3A4) was observed after (3)H-CBZ incubation with functionally reconstituted, purified recombinant CYP3A4(His)(6). The CBZ-modified CYP3A4 retained its functional activity albeit at a reduced level, but its testosterone 6beta-hydroxylase kinetics were altered from sigmoidal (a characteristic profile of substrate cooperativity) to near-hyperbolic (Michaelis-Menten) type, suggesting that CBZ may have modified CYP3A4 within its active site.

Antiepileptic drugs in the treatment of neuropathic pain

Antiepileptic drugs are an effective treatment for various forms of neuropathic pain of peripheral origin, although they rarely provide complete pain relief. Multiple multicentre randomised controlled trials have shown clear efficacy of gabapentin and pregabalin for postherpetic neuralgia and painful diabetic neuropathy. Theses drugs can be rapidly titrated and are well tolerated. Topiramate, lamotrigine, carbamazepine and oxcarbazepine are alternatives for the treatment of painful diabetic neuropathy, but should be titrated slowly. Carbamazepine remains the drug of choice for trigeminal neuralgia; however, oxcarbazepine and lamotrigine are potential alternatives. There is an apparent need for large-scale randomised controlled trials on the efficacy of antiepileptic drugs in neuropathic pain in general, and in cancer-related neuropathic pain and neuropathic pain of central origin in particular. Trials with long-term follow-up are required to establish the long-term efficacy of antiepileptic drugs in neuropathic pain. There is only limited scientific evidence to support the idea that drug combinations are likely to be more efficacious and safer than each drug alone; further studies are warranted in this area.

Glutathione S-transferase M1 null genotype as a risk factor for carbamazepine-induced mild hepatotoxicity

The aim of this study is to verify whether the combination of glutathione S-transferase (GST) M1 null and GSTT1 null genotypes, which is a candidate genetic risk factor for troglitazone-induced liver failure, is common to that for the carbamazepine-induced mild hepatotoxicity. Patients & methods: The genotypes of GSTM1 and GSTT1, and microsomal epoxide hydrolase-3 and -4, were determined in 192 Japanese epileptics treated with carbamazepine. Results: The GSTM1 null (GSTM1-) and GSTT1 null (GSTT1-) genotypes in the subjects were 55.7 and 39.6%, respectively. The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were elevated in 46 (24.0%) and 62 (32.3%) cases, and the mean values were approximately 2.3- and 1.8-times higher than the upper limit of normal levels, respectively. The levels of ALT and AST were significantly higher in GSTM1- than in GSTM1 present (GSTM1+) genotypes (p = 0.007 and 0.004, respectively). The level of ALT was significantly higher in GSTM1-/T1- than in GSTM1+/T1- and GSTM1+/T1+ (p = 0.01 and 0.01, respectively), and that of AST was significantly higher in GSTM1-/T1- and GSTM1-/T1+ than in GSTM1+/T1+ (p = 0.02 and 0.003, respectively). The microsomal epoxide hydrolase genotype did not influence the hepatotoxicity. Conclusion: These findings suggested that GSTM1- rather than GSTM1-/T1- was a risk factor for carbamazepine-induced mild hepatotoxicity.

Anticonvulsant hypersensitivity syndrome: cross-reactivity with tricyclic antidepressant agents

BACKGROUND

Aromatic anticonvulsant agents such as carbamazepine and phenytoin can induce anticonvulsant hypersensitivity syndrome (AHS) at a frequency of 1 in 10,000 to 1 in 1,000 treated patients. The hypersensitivity syndrome is a potentially life-threatening adverse drug reaction with multiorgan involvement, and incidental reexposure must be strictly avoided. Patients and treating physicians must be informed and educated about the causal drug and its potential immunologic or toxicologic cross-reactivity with other compounds. It has been well established that for future antiepileptic drug therapy, carboxamides (carbamazepine and oxcarbazepine), phenytoin, and barbiturates (phenobarbital and primidone) have to be avoided owing to their high degree of cross-reactivity. Other anticonvulsant agents, such as valproic acid, benzodiazepines, and gabapentin, may be prescribed.

OBJECTIVES

To present the clinical data for and to describe the potential cross-reactivity between aromatic anticonvulsant and tricyclic antidepressant agents in patients with carbamazepine- and phenytoin-induced AHS.

METHODS

The knowledge of cross-reactivity among aromatic anticonvulsant agents mainly emerged from clinical experience and observations because diagnostic challenge tests are not advisable. Thirty-six patients with the diagnosis of AHS were instructed to contact our unit if the symptoms relapsed.

RESULTS

Despite better knowledge of AHS, one third of the patients had avoidable recurrences after exposure to cross-reactive drugs. Besides the known cross-reactivity among aromatic anticonvulsant agents, we observed a recurrence of the hypersensitivity syndrome in 5 patients after the administration of tricyclic antidepressant agents.

CONCLUSION

The important potential cross-reactivity between aromatic anticonvulsant and tricyclic antidepressant drugs should be brought to the attention of treating physicians.

Identification of primary and sequential bioactivation pathways of carbamazepine in human liver microsomes using liquid chromatography/tandem mass spectrometry

Carbamazepine (CBZ)-induced idiosyncratic toxicities are commonly believed to be related to the formation of reactive metabolites. CBZ is metabolized primarily into carbamazepine-10,11-epoxide (CBZE), 2-hydroxycarbamazepine (2-OHCBZ) and 3-hydroxycarbamazepine (3-OHCBZ), in human liver microsomes (HLM). Over the past two decades, the 2,3-arene oxidation has been commonly assumed to be the major bioactivation pathway of CBZ. Recently, CBZE has been also confirmed to be chemically reactive. In order to identify other possible primary and sequential CBZ bioactivation pathways, individual HLM incubations of CBZ, CBZE, 2-OHCBZ and 3-OHCBZ were conducted in the presence of glutathione (GSH). In the CBZ incubation, a variety of GSH adducts were formed via individual or combined pathways of 10,11-epoxidation, arene oxidation and iminoquinone formation. In the CBZE incubation, the only detected GSH adducts were CBZE-SG1 and CBZE-SG2, which represented the two most abundant conjugates observed in the CBZ incubation. In the incubation of either 2-OHCBZ or 3-OHCBZ, a number of sequential GSH adducts were observed. However, none of the 2-OHCBZ-derived GSH adducts were detected in the CBZ incubation. Meanwhile, several GSH adducts were only observed in the CBZ incubation. In conclusion, CBZ can be bioactivated in HLM via 10,11-epoxidation, 2,3-arene oxidation, and several other pathways. In addition, the sequential bioactivation of 3-OHCBZ appeared to play a more important role than that of either CBZE or 2-OHCBZ in the overall bioactivation of CBZ in HLM. The identification of several new bioactivation pathways of CBZ in HLM demonstrates that possible CBZ bioactivation can be more complex than previously thought.

Effects of the antiepileptic drug carbamazepine on human erythrocytes

The structural effects of the antiepileptic drug carbamazepine (CBZ) on the human erythrocyte membrane and molecular models have been investigated in the present work. This report presents the following evidence that CBZ interacts with red cell membranes: (a) X-ray diffraction and fluorescence spectroscopy of phospholipid bilayers showed that CBZ perturbed a class of lipids found in the outer moiety of the erythrocyte membrane; (b) in isolated unsealed human erythrocytes (IUM) the drug induced a disordering effect on the polar head groups and acyl chains of the membrane lipid bilayer; (c) in scanning electron microscopy (SEM) studies on human erythrocytes the formation of echinocytes was observed, due to the preferential insertion of CBZ in the outer monolayer of the red cell membrane. The effects of the drug detected in the present work were observed at concentrations of the order of those currently appearing in serum when it is therapeutically administered. This is the first time that toxic effects of carbamazepine on the human erythrocyte membrane have been described.

Drug Interactions with Paracetamol

Paracetamol (acetaminophen) is one of the most commonly used analgesic antipyretic drugs worldwide, and it is widely available by prescription and over the counter (OTC). Fortunately, few clinically significant drug interactions have been documented. There is probable potentiation of hepatotoxicity following an overdose from the paracetamol metabolite NAPQI by enzyme-inducing drugs. There is considerable controversy regarding the possible interaction with warfarin in its potential to increase its anticoagulant effects because of discrepancies between observational studies and those in healthy volunteers. Otherwise, no serious adverse drug interactions with therapeutic doses of paracetamol have been confirmed in humans. Because the absorption of paracetamol is so dependent on gastric emptying, other drugs that alter gastric emptying can change its pharmacokinetics; but this would not cause serious adverse effects. Although animal experiments have demonstrated that many compounds can modify paracetamol hepatotoxicity, these are unlikely to be important at therapeutic doses.

Drug-induced liver disease

The year 2002 saw a warning from the US Food and Drug Administration not to use the diet agent, Lipokinetix, and brought to light a few new agents as potential hepatotoxins. Numerous other reports confirmed the hepatotoxicity of several previously described agents. Refinements in causality assessment remain an important aspect in defining drug-induced liver disease and proposed new upper limits of normal for alanine aminotransferase that are lower than most laboratories currently report may require rethinking our definition of "normal liver function tests." Chronic viral hepatitis B and C remain important risk factors for antiretroviral-induced liver injury in patients co-infected with the human immunodeficiency virus and in patients receiving antituberculosis therapy. Acetaminophen retains its status as the most common cause of acute drug-induced liver failure in the United States and in many other countries. Several papers addressed the issue of accidental versus intentional overdoses, the role of alcohol consumption as a risk factor, and newer aspects of treating and preventing acetaminophen injury to the liver. Finally, the use of potentially hepatotoxic medications in patients with underlying liver disease continues to be a controversial topic and a rational approach to the use of such drugs in this setting is provided.