Alcohol does not enhance diazepam absorption

A single 5-mg oral dose of diazepam was administered to 6 healthy volunteers on 3 occasions in a randomized 3-way crossover study. Modes of administration were: (A) (control): diazepam with 120 ml of water, preceded 30 min before with 120 ml of water; (B) diazepam with 120 ml water, preceded by 120 ml of a 50:50 vodka:water mixture, and (C) diazepam with 120 ml of the vodka mixture, preceded by 120 ml of water. Peak plasma diazepam levels averaged 166, 140 and 145 ng/ml in trials A, B and C, respectively; the time of peak concentration was 0.71, 2.1 and 1.5 h after the dose, respectively. Differences were not significant. Total areas under the plasma concentration curve were nearly identical (2.7, 2.8 and 2.9 micrograms/ml X h) among the 3 trials, as were values of diazepam elimination half-life (29, 36 and 35 h). The rate and extent of desmethyldiazepam formation also did not differ among trials. Thus, coadministration of diazepam with or shortly after a typical social cocktail tends to slow the rate of diazepam absorption, but does not influence the completeness of absorption or the rate of elimination.