A double-blind crossover study was conducted to compare the acute and steady-state response of enteric coated oxytriphylline (Choledyl) 400-mg tablets and uncoated micropulverized theophylline (Theolair) 250-mg tablets in terms of theophylline levels and maximum expiratory flow volume curves (MEFVC). Acute administra- tion of oxytriphylline was followed by a mean peak theophylline level of 5 µg/ml at 4 hours, with minimal improvement in MEFVC. In contrast, the highest mean theophylline level during the acute administration of Theolair was within 60 minutes, with significant improvement in MEFVC. Highest mean theophylline level during chronic administration of oxytriphylline was 15.8 µg/ml 4 hours following an oral dose on the 7th day of the study, while Theolair had its highest theophylline level of 14.9 µg/ml 1 hour following oral administration on the 7th day. During chronic administration there was no significant difference in MEFVC between the two drugs. These data indicated that while uncoated micropulverized theophylline has a more rapid onset of action than oxytriphylline, chronic administration of the two preparations at 6-hour intervals achieves similar effects after one week.
Thompson et al. (Tue,) studied this question.