[Investigations in Bioavailability of resinates as peroral retard drug dosage forms. Part 1: Pharmaceutical availability of dihydrocodein-resinates (author's transl)].

The dissolution rate constants of dihydrocodein in two retard drug dosage forms based on synthetic ion exchange resin were determined with four dissolution methods. The usage of the flow cell, rotationsdisk method and half-change method with a new dissolution model gave comparable results. Using the paddle apparatus the dissolution is very quick. There is only a small influence on the dissolution rate by the pH. A higher ionic strength of the dissolution medium increases the dissolution rate.