Methanol elimination in non-alcoholics: inter- and intraindividual variation

Abstract

Five male subjects aged between 25 and 40 years were given methanol at a dose of 10 mg/kg, once orally and once intravenously, while the enzyme systems responsible for methanol oxidation were blocked by ethanol. The study assessed the duration of inhibition of methanol oxidation in relation to the blood ethanol concentration, and the elimination of methanol not influenced by ethanol. Methanol elimination was found to begin at a blood ethanol concentration of 0.04–0.13 g/kg. Elimination constants of 0.406–0.267 h −1 with corresponding half-lives of 1.71–2.60 h were established for methanol not influenced by ethanol. When data from a previous study using an identical protocol for parenteral administration were included, making the total number of subjects nine, the mean elimination constant was found to be 0.298±0.470 h −1 and the mean half-life 2.37±0.357 h, distribution being normal. No evidence of any differences in methanol elimination kinetics between alcoholics and non-alcoholics or of a significant influence of the route of administration was found. The extent of intraindividual variation in methanol elimination, as indicated by the difference in each subject between the values established, expressed as a percentage of the corresponding mean values, was found to be 3–25%, which is comparable to the magnitude of intraindividual variation in the rate of ethanol elimination.