Serum profile and bioavailability of a controlled-release theophylline formulation for once-daily use: comparison with a 12-hr preparation.

Two controlled-release theophylline drugs, T-D (Theo-Dur tablets) administered 12-hourly, and preparation U (Uniphyl tablets) once daily, given in 7-day sequences in daily 800-mg doses, produced comparable steady-state serum profiles in nonsmoking adults with asthma, chronic bronchitis, or both, showing acceptable theophylline clearances. With either regimen, mean serum levels were within the 10-20 mcg/ml range at most time points, never falling below 9 mcg/ml or exceeding 20 mcg/ml. Analyses of variance for troughs, peaks, trough-peak fluctuations and AUCs (0,24) could not differentiate between drugs. The theophylline in each was fully bioavailable relative to immediate-release theophylline. Side effects, least prevalent with Drug U, were of the "minor nuisance" variety. These data indicate the suitability of Drug U for once-daily prescription.