HPLC analysis of theophylline: bioequivalence study of two sustained-release formulations at steady state

Theophylline is at present one of the standard drugs used for asthma and obstructive respiratory diseases but still presents clinical problems due to its narrow therapeutic range. To provide additional studies in this important field, the in vivo bioavailability of Bronchoretard, a theophylline sustained-release preparation, not available at present in Italy, has been compared with that of Diffumal, formulation of large consumption. An isocratic reverse-phase HPLC method to assess the theophylline in plasma is described. The two formulations present good bioequivalence, though Bronchoretard seems to provide little therapeutic advantage.