Bioavailability of two Soviet sustained-release theophylline formulations in comparison with TheoDur

The pharmacokinetic parameters of two theophylline preparations of Soviet origin (Theobiolongas and Theopaek) were compared with the reference preparation TheoDur. The three sustained-release preparations were administered in a single oral dose (400 mg) to healthy volunteers. Blood samples were drawn over 36 hr and plasma concentrations of theophylline were measured by HPLC. Significant differences in the pharmacokinetic parameters were observed between the drugs. Compared to TheoDur, the two Soviet drugs, Theobiolongas and Theopaek, had lower bioavailability (86% and 82%, respectively), and higher rate of absorption. An 8-hr dosing interval should be preferred for Theobiolongas and Theopaek while twice-daily administration appears to be appropriate for these preparations only in exceptional cases.