Absorption of theophylline from enteric coated and sustained release formulations in fasted and non‐fasted subjects

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Abstract
The influence of prior food ingestion, and also of varying fluid volumes, on plasma theophylline levels was examined following single oral doses of two sustained‐release formulations, Theobid® (260 mg) and Theo‐Dur® (200 mg) and one partially enteric‐coated formulation, Choledyl® (128mg), to 9 healthy volunteers. Prior food ingestion tended to delay the absorption of theophylline from all formulations to a small extent. This effect was observed only at early sampling times, and plasma drug profiles were similar for all treatments within a particular formulation. Theobid® and Theo‐Dur® gave rise to plasma profiles that were characteristic of sustained‐release formulations, with mean Cmax values of 5·5−5·7 μgml−1 (Theobid®) and 2·8−3·2 μgmr−1 (Theo‐Dur®) occurring at 5·8−9·1 h after dosing. Choledyl® gave rise to a longer absorption lag time than the other formulations but was subsequently absorbed at a faster rate yielding mean Cmax values of 3·2−3·5μgml−1 at 2·8−4·1 h. The intersubject variability in theophylline plasma levels, and also in most pharmaco‐kinetic parameter values, was generally less following Theo‐Dur® compared to the other formulations.