Intravenous diazepam and oral ethanol interaction

Area of Science:

• Pharmacology
• Toxicology
• Drug Metabolism

Background:

• The interaction mechanism between ethanol and diazepam remains unclear.
• Ethanol is frequently co-administered with benzodiazepines like diazepam.
• Understanding this interaction is critical for patient safety and effective treatment.

Purpose of the Study:

• To elucidate the pharmacokinetic interaction between ethanol and diazepam.
• To investigate the effect of ethanol on diazepam's metabolism and clearance.
• To evaluate the role of N-desmethylation inhibition in this interaction.

Main Methods:

• A balanced crossover study involving six healthy male subjects.
• Two treatment conditions: diazepam alone and diazepam with ethanol administration.
• Ethanol administration involved oral intake and continuous infusion to maintain specific blood alcohol concentrations (800-1,000 mg/l).

Main Results:

• Ethanol significantly increased the area under the curve (AUC) for total diazepam (30.1%) and free diazepam (26.5%).
• Ethanol markedly reduced the AUC of the metabolite N-desmethyldiazepam (50.5%), indicating inhibited hepatic clearance.
• Individual susceptibility to N-desmethylation inhibition by ethanol correlates with total drug concentrations.

Conclusions:

• Ethanol inhibits the hepatic intrinsic clearance of free diazepam, primarily by inhibiting N-desmethylation.
• Measuring free diazepam concentrations and its metabolite provides a comprehensive evaluation of the ethanol-diazepam interaction.
• This interaction highlights the importance of considering ethanol co-ingestion when prescribing diazepam.