Studies on Absorption and Excretion of Drug. VII. A New Estimation Method for the Release of Drugs from Dosage Forms and the Availability in vivo.

The convolution equation was introduced to estimate a drug release from various dosage forms in the gut. [numerical formula] From the application of the equation, the drug release in vivo F (t) was calculated from comparison of blood level or urinary excertion of drug and/or the metablites between the ingestions of a dosage form, X (t), and the dissolved solution, G (t). The evidence of merits of this method and the deviation of the results from the real value caused by the approximation for numerical calculation were investigated by means of a theoretical model. The actual sulfamethylthiadiazole release from the tablet in human gut was estimated from the urinary excretion by using this calculation method also.