title: Effects of dietary protein on theophylline pharmacokinetics and caffeine and aminopyrine breath tests.
abstract: The effects of low- and high-protein diets on theophylline kinetics and the time course of changes in 13C-labeled caffeine and aminopyrine CO2 breath tests were examined in six young men. With a low-protein diet, mean theophylline clearance fell 21% (P less than 0.04) and the t1/2 rose from 8.0 to 10.6 hours (P less than 0.02). With a high-protein diet, mean theophylline clearance rose 26% (P less than 0.004) and the t1/2 shortened to 7.4 hours (P less than 0.03). Theophylline volume of distribution and protein binding did not change. Renal clearance of theophylline was lowered during the low-protein diet. Theophylline clearance correlated with caffeine breath test values during the low- (r = 0.73) and high- (r = 0.70) protein diets. Theophylline clearance correlated less well with the aminopyrine breath test values during the low- (r = 0.47) and high- (r = 0.55) protein diets. Thus dietary protein significantly influenced theophylline clearance, but the caffeine and aminopyrine breath tests showed a differential response to this important environmental factor.
mesh_terms: D000328:Adult; D000632:Aminopyrine / Q000032:analysis*; D000633:Aminopyrine N-Demethylase / Q000378:metabolism; D001944:Breath Tests; D002110:Caffeine / Q000378:metabolism*; D004044:Dietary Proteins / Q000494:pharmacology*; D006801:Humans; D007263:Infusions, Parenteral; D007700:Kinetics; D008297:Male; D013806:Theophylline / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D000632:Aminopyrine; D002110:Caffeine; D013806:Theophylline; D000633:Aminopyrine N-Demethylase