Different effects of different nutrients on theophylline absorption in man

The influence of concomitant intake of a standardized breakfast (1,840 kJ) and of carbohydrate (830 kJ), fat (645 kJ), and protein (365 kJ) on the absorption of theophylline (400 mg) from a modern formulation of choline theophylline (4 X 135 mg) was examined in 18 healthy volunteers. After fasting overnight, they ingested the drug both immediately after the meal/nutrient and on an empty stomach, fasting being continued for another 4 h. Theophylline concentrations in serum were analyzed by high-pressure liquid chromatography. The results indicate that carbohydrate and the complete breakfast, but not fat or protein, delayed the absorption of theophylline. This is of particular interest as previous animal studies suggest that theophylline may be partially absorbed by an active transport mechanism operating in glucose uptake, and as carbohydrate has been found to increase the absorption rate of phenytoin, another acidic drug with a pKa similar to that of theophylline. This emphasizes the complexity of factors regulating the absorption of drugs and their interactions with food and dietary components.