In normal male subjects, the half-lives of antipyrine, aminopyrine, or phenacetin were not significantly different from the half-lives of each drug in saliva. Apparent volumes of distribution (aVd) in plasma and saliva differed by the extent to which each drug has been reported to bind to plasma proteins. Thus, the aVd of antipyrine in plasma and saliva was similar; there were significant differences in aVd for aminopyrine; even greater differences were observed for penacetin. The expression (see article) equals the fraction of the drug bound to plasma proteins. Rates of appearance in the urine of metabolites of antipyrine and aminopyrine were measured. General equations were used to show the relationship between half-life for elimination of the parent drug from the body and rate of excretion of metabolites. There were significant correlations between the half-life for elimination of antipyrine from the body and the half-life for production of 4-OH antipyrine (r equal 0.90), as well as between the plasma half-life of aminopyrine and the half-life of 4-aminoantipyrine (r equal 0.95). No significant correlation was observed in the same individual between the plasma half-lives of antipyrine and phenacetin (r equal 0.05, p greater than 0.05), of aminopyrine and phenacetin (r equal 0.11, p greater than 0.05), or of antipyrine and aminopyrine (r equal 0.50, p greater than 0.05).

The relative contribution of genetic and environmental factors to maintaining twofold differences in rates of ethanol elimination from plasma was examined in 14 sets of nonmedicated, nonhospitalized healthy twins. After a single oral dose of 1 ml. per kilogram of 95 per cent ethanol, intrapair differences in rates of elimination were less in identical than in fraternal twins. Thew results indicate that individual differences in rates of ethanol elimination among the 28 twins were genetically controlled and that environmental factors played a negligible role. In 6 prisoners in solitary confinement, rates of ethanol metabolism increased in 3 but declined in the remaining 3 after 21 days of ethanol administration. Rates of antipyrine elimination from pla~ma were accelerated by ethanol administration in each of the 6 volunteers. Considerable individual variation occurred in the degree to which ethanol shortened plasma antipyrine half-lifes; reduction ranged from 4 to 37 per cent of the initial antipyrine half-life. These results suggest that ethanol administration for 21 days at this dosage fails to alter consistently the rate of its own metabolism but increases antipyrine metabolism in all subjects to vary:ng extents.