INFLUENCE OF AGE AND SEX ON THE PHARMACOKINETICS OF THIOPENTONE

Thiopentone was given to eight women and eight men (60–79yr). The disappearance of thiopentone from the venous bloodwas described by a three-compartment open model. The only significantdifference between the sexes was a higher initial venous concentrationin males. The dose (mg kg ^–1) for induction was 70% ofthe value (P<0.05) previously reported for a comparable groupof younger men and women (20–40 yr). The volumes of distributionV₂ and V₃ were larger in the elderly (P<0.05). The terminalhalf-lives were increased with advancing age (from 75% to 100%on average) (P0.01). The clearance value was 50% greater inthe older women than in a group of young women. For all groupsa significant correlation between initial drug concentrationand k₁₂ supported the hypothesis that the redistribution rateconstant k₁₂ is the predominant factor in the pharmacokineticprofile of a dose of thiopentone sufficient to obtund the eyelashreflex.