title: Theophylline kinetics in relation to age: the importance of smoking.
abstract: 1 Single dose studies of theophylline kinetics were compared in groups of young and elderly smokers and non-smokers to assess the effect of age on theophylline absorption and the effect of smoking on drug metabolising enzyme activity in old age. 2 The rate and extent of absorption was not affected by age. Distribution and elimination kinetics were similar in young and elderly non-smokers. 3 In young subjects the elimination half-life of theophylline was shorter and clearance was significantly greater in smokers than in non-smokers. 4 In the elderly mean elimination half-life was significantly shorter in smokers and their plasma clearance was 40% higher than in non-smokers. The statistical difference for clearance was at the 7% level of significance. 5 These data indicate that ageing per se does not affect theophylline elimination and also that induction of theophylline metabolism due to smoking occurs in old age. Smoking is a variable that should be taken account of when assessing drug metabolism in elderly patients.
mesh_terms: D000042:Absorption; D000328:Adult; D000367:Age Factors; D000368:Aged; D006801:Humans; D007700:Kinetics; D008657:Metabolic Clearance Rate; D013806:Theophylline / Q000378:metabolism*; D014029:Tobacco Use Disorder / Q000378:metabolism*
chemical_list: D013806:Theophylline