Cocaethylene metabolism and interaction with cocaine and ethanol: role of carboxylesterases

Pharmacodynamic evaluation of the cardiovascular effects after the coadministration of cocaine and ethanol

One of the most common drug dependencies occurring with alcoholism is cocaine dependence. This combination is particularly worrisome because of the increased risk of cardiovascular events associated with their coabuse. Although it is well known that ethanol increases the cardiovascular effects of cocaine by inhibiting cocaine clearance and the formation of cocaethylene, it has also been postulated that ethanol enhances the cardiovascular effects of cocaine independent of the two latter mechanisms. In this study, we investigated the cardiovascular pharmacodynamics of the cocaine-ethanol interaction to determine whether ethanol directly enhanced the cardiovascular effects of cocaine. Dogs (n = 6) were administered cocaine alone (3 mg/kg i.v.) and in combination with ethanol (1 g/kg i.v.) on separate study days. Blood pressure, heart rate, and the electrocardiogram were monitored continuously, and blood samples were collected periodically after drug administration. Concentration-time data were fitted to a two-compartment model, and concentration-effect data were fitted to a simple E(max) model using WinNonlin software. Pharmacokinetic and pharmacodynamic parameters were compared between the two treatment phases by a paired t test. The administration of ethanol before cocaine resulted in a decrease in cocaine clearance, but there were no differences in any of the other pharmacokinetic or pharmacodynamic parameter values between the cocaine alone and cocaine plus ethanol phases. As has been demonstrated in previous animal and human studies, the clearance of cocaine was decreased by prior administration of ethanol. However, ethanol did not change the concentration-effect relationship of the cardiovascular response to cocaine administration. It is concluded from this study that ethanol does not directly enhance the cardiovascular effects of cocaine.

Two CES1 gene mutations lead to dysfunctional carboxylesterase 1 activity in man: clinical significance and molecular basis

The human carboxylesterase 1 (CES1) gene encodes for the enzyme carboxylesterase 1, a serine esterase governing both metabolic deactivation and activation of numerous therapeutic agents. During the course of a study of the pharmacokinetics of the methyl ester racemic psychostimulant methylphenidate, profoundly elevated methylphenidate plasma concentrations, unprecedented distortions in isomer disposition, and increases in hemodynamic measures were observed in a subject of European descent. These observations led to a focused study of the subject's CES1 gene. DNA sequencing detected two coding region single-nucleotide mutations located in exons 4 and 6. The mutation in exon 4 is located in codon 143 and leads to a nonconservative substitution, p.Gly143Glu. A deletion in exon 6 at codon 260 results in a frameshift mutation, p.Asp260fs, altering residues 260-299 before truncating at a premature stop codon. The minor allele frequency of p.Gly143Glu was determined to be 3.7%, 4.3%, 2.0%, and 0% in white, black, Hispanic, and Asian populations, respectively. Of 925 individual DNA samples examined, none carried the p.Asp260fs, indicating it is an extremely rare mutation. In vitro functional studies demonstrated the catalytic functions of both p.Gly143Glu and p.Asp260fs are substantially impaired, resulting in a complete loss of hydrolytic activity toward methylphenidate. When a more sensitive esterase substrate, p-nitrophenyl acetate was utilized, only 21.4% and 0.6% catalytic efficiency (V(max)/K(m)) were determined in p.Gly143Glu and p.Asp260fs, respectively, compared to the wild-type enzyme. These findings indicate that specific CES1 gene variants can lead to clinically significant alterations in pharmacokinetics and drug response of carboxylesterase 1 substrates.

Markers of chronic alcohol use in hair: Comparison of ethyl glucuronide and cocaethylene in cocaine users

Two direct ethanol metabolites, namely ethyl glucuronide (EtG) and cocaethylene (CE), in the hair of cocaine (COC) users were compared in this study. Hair samples (n=68) were submitted to the determination of EtG (by liquid chromatography-electrospray-tandem mass spectrometry) and of COC and metabolites, including CE (by gas chromatography-mass spectrometry). Quantitative and qualitative results were compared. No quantitative correlation was found between EtG and CE, as well as between EtG and the cocaethylene concentration divided by the concentration of COC and its metabolites (benzoylecgonine and ecgonine methylester, as COC equivalents). Nevertheless, many factors are supposed to affect the amount of the two substances incorporated in the hair matrix, such as the subject's habits in ethanol and COC use, genetic variability in the metabolism of both substances, and the different chemical and physical properties of EtG and CE. When establishing a cut-off of 4 pg/mg for EtG and of 200 pg/mg for CE, 47 samples tested positive for EtG and 41 samples tested positive for CE; 12 samples out of the 47 EtG-positives tested negative for CE (25%), whereas 6 samples out of the 41 CE-positives tested negative for EtG (15%). According to these data, EtG appears to be a more sensitive and specific marker of non-moderate alcohol users than CE.

Pharmacotherapy of dual substance abuse and dependence

The US FDA has approved a limited number of treatments for alcohol, nicotine and opioid dependence; however, no treatments for other abused drugs such as marijuana, cocaine or methamphetamine are approved. This review focuses on research into drug pharmacotherapies, particularly single-drug therapies, for substance abuse and dependence contributing to the most important dual substance use disorders (SUDs). Given the implications of poly-substance abuse, it is essential that clinicians and researchers be aware of potential pharmacotherapies for the treatment of dual SUDs.A substantial number of patients abuse more than one drug concurrently, complicating the treatment of SUD and leaving clinicians with few FDA-approved drug options for their patients. In this era of evidence-based medicine, such patients are typically treated with therapeutically proven medications, but in ways that are outside the scope of a drug's original indication by the FDA. Such 'off-label' prescribing has become an important therapeutic strategy for practitioners seeking treatments for other diseases in subpopulations such as paediatrics and gerontology or for medical conditions such as oncology or mental illness. Similarly, the information that most clinicians use to make their decisions for treating patients abusing multiple drugs stems from trials treating a single SUD, anecdotal experiences from their own practice or that of their colleagues, or single-case studies reported in the literature. The existing evidence suggests there are few treatments for SUDs that confer significant reductions in substance use across a broad patient population. Moreover, even fewer clinical efficacy trials have been conducted that provide evidence of therapeutic benefit for these drugs. Recognising the difficulty in making the proper drug choice for facilitating maximum treatment success, this review highlights the single drugs or drug combinations that show some potential for treating dual SUDs. This review finds strongest support for the use of disulfiram for treatment of alcohol and cocaine dependence (with or without concomitant methadone maintenance), baclofen for alcohol and cocaine dependence (but not opioid-dependent cocaine users), tiagabine for cocaine dependence in methadone-maintained patients, and topiramate for alcohol, nicotine and cocaine dependence. While ondansetron and olanzapine show some efficacy in treating alcohol and cocaine dependence, more research is needed to better delineate the subpopulation in which these drugs may provide their maximum effect.

Bioanalytical procedures for determination of drugs of abuse in blood

Determination of drugs of abuse in blood is of great importance in clinical and forensic toxicology. This review describes procedures for detection of the following drugs of abuse and their metabolites in whole blood, plasma or serum: Delta9-tetrahydrocannabinol, 11-hydroxy-Delta9-tetrahydrocannabinol, 11-nor-9-carboxy-Delta9-tetrahydrocannabinol, 11-nor-9-carboxy-Delta9-tetrahydrocannabinol glucuronide, heroin, 6-monoacetylmorphine, morphine, morphine-6-glucuronide, morphine-3-glucuronide, codeine, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, N-ethyl-3,4-methylenedioxyamphetamine, 3,4-methylenedioxyamphetamine, cocaine, benzoylecgonine, ecgonine methyl ester, cocaethylene, other cocaine metabolites or pyrolysis products (norcocaine, norcocaethylene, norbenzoylecgonine, m-hydroxycocaine, p-hydroxycocaine, m-hydroxybenzoylecgonine, p-hydroxybenzoylecgonine, ethyl ecgonine, ecgonine, anhydroecgonine methyl ester, anhydroecgonine ethyl ester, anhydroecgonine, noranhydroecgonine, N-hydroxynorcocaine, cocaine N-oxide, anhydroecgonine methyl ester N-oxide). Metabolites and degradation products which are recommended to be monitored for assessment in clinical or forensic toxicology are mentioned. Papers written in English between 2002 and the beginning of 2007 are reviewed. Analytical methods are assessed for their suitability in forensic toxicology, where special requirements have to be met. For many of the analytes sensitive immunological methods for screening are available. Screening and confirmation is mostly done by gas chromatography (GC)-mass spectrometry (MS) or liquid chromatography (LC)-MS(/MS) procedures. Basic information about the biosample assayed, internal standard, workup, GC or LC column and mobile phase, detection mode, and validation data for each procedure is summarized in two tables to facilitate the selection of a method suitable for a specific analytic problem.

Toxicokinetics of drugs of abuse: current knowledge of the isoenzymes involved in the human metabolism of tetrahydrocannabinol, cocaine, heroin, morphine, and codeine

This review summarizes the major metabolic pathways of the drugs of abuse, tetrahydrocannabinol, cocaine, heroin, morphine, and codeine, in humans including the involvement of isoenzymes. This knowledge may be important for predicting their possible interactions with other xenobiotics, understanding pharmaco-/toxicokinetic and pharmacogenetic variations, toxicological risk assessment, developing suitable toxicological analysis procedures, and finally for understanding certain pitfalls in drug testing. The detection times of these drugs and/or their metabolites in biological samples are summarized and the implications of the presented data on the possible interactions of drugs of abuse with other xenobiotics, ie, inhibition or induction of individual polymorphic and nonpolymorphic isoenzymes, discussed.

Pharmacogenetics and Human Molecular Genetics of Opiate and Cocaine Addictions and Their Treatments

Opiate and cocaine addictions are major social and medical problems that impose a significant burden on society. Despite the size and scope of these problems, there are few effective treatments for these addictions. Methadone maintenance is an effective and most widely used treatment for opiate addiction, allowing normalization of many physiological abnormalities caused by chronic use of short-acting opiates. There are no pharmacological treatments for cocaine addiction. Epidemiological, linkage, and association studies have demonstrated a significant contribution of genetic factors to the addictive diseases. This article reviews the molecular genetics and pharmacogenetics of opiate and cocaine addictions, focusing primarily on genes of the opioid and monoaminergic systems that have been associated with or have evidence for linkage to opiate or cocaine addiction. This evidence has been marshalled either through identification of variant alleles that lead to functional alterations of gene products, altered gene expression, or findings of linkage or association studies. Studies of polymorphisms in the mu opioid receptor gene, which encodes the receptor target of some endogenous opioids, heroin, morphine, and synthetic opioids, have contributed substantially to knowledge of genetic influences on opiate and cocaine addiction. Other genes of the endogenous opioid and monoaminergic systems, particularly genes encoding dopamine beta-hydroxylase, and the dopamine, serotonin, and norepinephrine transporters have also been implicated. Variants in genes encoding proteins involved in metabolism or biotransformation of drugs of abuse and also of treatment agents are reviewed.