[In vivo testing of a peroral theophylline depot preparation with zero-order release].

A theophylline depot preparation on the basis of microcapsules (multiple-units principle) with an initial dose Di = 133 mg and a maintenance dose Dm = 217 mg (kof = 22.8 mg/h) is examined after single application to 7 volunteers in comparison with the aqueous solution. The relative bioavailability of the depot preparation is about 92%. Curve fitting shows that the liberation in vivo is clearly slower (kof = 15.6 mg/h) than in vitro. This could be of general importance for the development of peroral depot preparations. Furthermore the data suggest considerable absorption from the large intestine (colon). This is of interest for the conception of peroral preparations with exceptionally long action.