Effects of food on the bioavailability of theophylline from controlled-release products in adults.

A variety of formulation-dependent food-induced absorption changes ("food effect") occur with controlled-release formulations of theophylline. These changes are found in formulations with either pH-dependent or pH-independent in vitro dissolution characteristics. They include decreases in the rate or extent, increases in the rate and extent, and more erratic or variable theophylline absorption. In evaluating food effects from a test formulation, it is essential to standardize the meal composition (fat content) and dosing time relative to meal intake. For those formulations that exhibit pronounced food effect, drug dosing relative to meal intake should be made part of product labeling to assure consistent absorption.