Effect of dietary protein and carbohydrate on theophylline metabolism in children.

Theophylline metabolism can be altered by a variety of abnormal physiologic states as well as by exogenous factors. Adult studies demonstrate a significant influence of dietary composition on theophylline biotransformation. To examine this effect of diet, 14 children with bronchial asthma were studied during long-term theophylline administration. Each patient was maintained for 12 days on three separate diets with varying proportions of protein and carbohydrate and with constant calories and fat. Results showed significant differences in drug half-life and metabolic clearance rate parameters. Compared to the normal diet, high protein diet markedly decreased the half-life, and high carbohydrate diet greatly prolonged it (P < .001). Multiple regression analysis demonstrated these differences to correlate only with the dietary alterations. Adverse reactions and blood chemistry abnormalities were not detected during any test period. These findings firmly establish that nutritional factors exert a significant influence on theophylline pharmacokinetics in children.