Theophylline preparations are widely used in the treatment of asthma. Although most available oral preparations are well absorbed, and the dose of theophylline is often adjusted for the patients weight, the desired serum theophylline concentration is difficult to achieve. Reasons include: genetically-determined differences in individuals’ rates of hepatic metabolism; effects of disease states upon the distribution or elimination of theophylline; effects of other medications upon theophylline concentration; and, differences in the actual content of theophylline between the many marketed theophylline-containing preparations.
Since many available preparations require two, three, or even four daily doses, omission of one or more daily dose by patients may account for low serum theophylline levels in those patients. Although no available study has examined the compliance of asthma patients intake of daily prescribed medications, Kinsman et al showed an unsatisfactory compliance to PRN medications.
Therefore, the marketing of a theophylline preparation suitable for once daily oral administration may be of clinical use. Our study compares the bioavailability of a newer sustained release anhydrous theophylline suitable for once daily administration (od) to that of a currently available preparation taken twice a day (bid).