Biotransformation of amitriptyline in alcoholic depressive patients

Non-additivity of the functional properties of individual P450 species and its manifestation in the effects of alcohol consumption on the metabolism of ketamine and amitriptyline

To explore functional interconnections between multiple P450 enzymes and their manifestation in alcohol-induced changes in drug metabolism, we implemented a high-throughput study of correlations between the composition of the P450 pool and the substrate saturation profiles (SSP) of amitriptyline and ketamine demethylation in a series of 23 individual human liver microsomes preparations from donors with a known history of alcohol consumption. The SSPs were approximated with linear combinations of three Michaelis-Menten equations with globally optimized KM (substrate affinity) values. This analysis revealed a strong correlation between the rate of ketamine metabolism and alcohol exposure. For both substrates, alcohol consumption caused a significant increase in the role of the low-affinity enzymes. The amplitudes of the kinetic components and the total rate were further analyzed for correlations with the abundance of 11 major P450 enzymes assessed by global proteomics. The maximal rate of metabolism of both substrates correlated with the abundance of CYP3A4, their predicted principal metabolizer. However, except for CYP2D6 and CYP2E1, responsible for the low-affinity metabolism of ketamine and amitriptyline, respectively, none of the other potent metabolizers of the drugs revealed a positive correlation. Instead, in the case of ketamine, we observed negative correlations with the abundances of CYP1A2, CYP2C9, and CYP3A5. For amitriptyline, the data suggest inhibitory effects of CYP1A2 and CYP2A6. Our results demonstrate the importance of functional interactions between multiple P450 species and their decisive role in the effects of alcohol exposure on drug metabolism.

Toxicological interactions involving psychiatric drugs and alcohol: an update

This review focuses on the toxicological interactions between alcohol (ethanol) and psychiatric drugs (antidepressants and antipsychotics), including those leading to fatal poisoning. Acute or chronic ingestion of alcohol when combined with psychiatric drugs may lead to several clinically significant toxicological interactions. The metabolism of these drugs is generally but not always delayed by acute alcohol ingestion. Drugs undergoing metabolism may also show increased metabolic clearance with chronic alcohol ingestion. Therefore, the net effect may be influenced by internal (e.g. disease, age, gender), external (e.g. environment, diet) and pharmacokinetic (e.g. dose, timing of ingestion, gastrointestinal absorption, distribution and elimination) factors. Cases of fatal poisoning involving coadministration of psychiatric drugs, alcohol and other drugs prompted this review.

Dosing issues in the pharmacotherapy of alcoholism

Pharmacological treatments for alcohol dependence have focused increasingly on agents that reduce alcohol craving and consumption or that treat psychiatric disorders associated with drinking relapse. Clinicians who treat alcohol-dependent patients must find the optimal dose of these agents to maximize response. Determining the best dosing strategy has been the goal of recent treatment studies with alcohol-dependent patients. One study, for example, showed that an opiate antagonist medication had a dose-dependent relationship with patient outcome and retention in treatment. Another dosing consideration involves the effect of long-term alcohol abuse on drug metabolism (e.g., when treating alcohol-dependent patients for comorbid psychiatric disorders). This was demonstrated in a study of recently abstinent patients who were taking the antidepressant desipramine for major depression. Alcohol-dependent patients had higher hepatic enzyme activities and lower plasma levels of desipramine relative to oral dose than did a comparison group of depressed patients without an alcohol use disorder.

Gas chromatographic-mass spectrometric assessment of the pharmacokinetics of amineptine and its main metabolite in volunteers with liver impairment

A pharmacokinetic study of amineptine (Survector) and its C5 metabolite, resulting from a beta-oxidation of the heptanoic acid side-chain, was undertaken with ten human volunteers, who received a single 100-mg tablet of amineptine orally. They were affected with liver impairment in order to determine if this situation would alter greatly the pharmacokinetic parameters. The internal standard was the octanoic acid homologue. Analyses were carried out by gas chromatography (GC) and GC-mass spectrometry using TMS ester derivatives. Plasma samples were extracted using a C18 reversed-phase cartridge at pH 4.0. Mass fragmentographic measurements on the plasma samples were performed on the m/z ions (M + H)+ and (base peak)+ using ammonia chemical ionization. The global evaluation of precision was good and the coherence between the two modes of measurements, (base peak)+ and (M + H)+ ions, gave a regression factor r close to unity. For amineptine the total body clearance and mean residence time were accurate and precise with eight volunteers, but only four volunteers showed such coherent data for the slope of the elimination curve, beta, and half-life. However, the beta value, half-life and mean residence time of the C5 metabolite were accurate and precise with seven, eight and ten volunteers, respectively. It is concluded that the drug was still detoxified at normal levels.

Metabolism of amitriptyline in patients with chronic renal failure

The metabolism of amitriptyline (AMT) has been studied in two groups of depressed in-patients on long term AMT therapy: 11 patients with no other major disease and 8 patients with chronic renal failure, who were being dialysed. The patients with renal insufficiency had decreased concentrations of AMT, nortriptyline (NT) and their unconjugated hydroxymetabolites compared to patients with normal kidney function. The plasma levels of conjugated products were extremely high in the uraemics. The latter metabolites are probably inert. The reduced concentration of unconjugated hydroxymetabolites , which are active compounds, may decrease the clinical effectiveness of the drug.