[Gastrointestinal absorption of theophylline, especially with reference to retard preparations]

Little is known about the absorption of theophylline from definite parts of the intestine, though there are many depot or slow-release formulations of theophylline on the market and this topic should be of relevant importance. Most of these formulations are releasing the drug for up to 24 hours while passing the bowels. In this prospective, open, randomised, study with an interchange trial design the absorption of theophylline from the colon was studied in eight healthy male volunteers: 400 mg theophylline was given intravenously and in two different forms into the colon transversum by application with an endoscope. Under these conditions, theophylline was absorbed in an amount of 54% on the average with some variation due to the applied formulation. Therefore, it could be concluded that theophylline is absorbed to a clinically relevant extent from the large intestine. These results are remarkable with regard to the development and pharmaceutical profiles of retard or slow-release formulations of theophylline and the undesired effects of this therapy.