Interaction of ethanol with amylobarbitone, phenobarbitone and methaqualone.

The presence and mechanism of synergism of action between ethanol and amylobarbitone, phenobarbitone or methaqualone was determined by application of simple pharmacokinetic models to log dose-response curves and plasma concentration-time curves for the hypnotics alone or when ethanol was given concurrently. For all three hypnotics, ethanol was found to increase the duration of hypnosis, but the mechanism of action was different for each. A sub-hypnotic dose of ethanol increased the volume of distribution of amylobarbitone and the consequent reduction in fractional elimination prolonged the half-life of the hypnotic. The distribution and elimination of methaqualone were not affected by ethanol, but there was a sensitisation of the target organ, shown by a reduced minimum effective dose. The minimum effective dose of phenobarbitone was also reduced by ethanol, but in addition, the rate of elimination of phenobarbitone was increased after the period of hypnosis.