Dissolution Methods to Increasing Discriminatory Power of In Vitro Dissolution Testing for Ibuprofen Free Acid and Its Salts

The predictive capacity of in vitro dissolution tests using the Biopharmaceutics Classification System (BCS)-based experimental setup to anticipate in vivo bioequivalence outcomes for BCS class 2 weak acids has been questioned. In this work, the effect of buffer concentration media was investigated as a possible approach to ensuring the discriminative capacity of the in vitro dissolution methods. The case example used to test this approach was ibuprofen, formulated as either the free acid or in various salt forms. By matching the concentration of buffers commonly used to prepare media which aim to simulate the intestinal conditions with that of bicarbonate buffer, which is the predominant buffer species in vivo, to arrive at the same surface pH (pH0), the discriminative power of the in vitro dissolution tests was improved. To simulate the in vivo results even better, a pretreatment at acidic pH was added to the dissolution test simulating the gastric conditions to create a 2-stage test. With the 2-stage test, it was possible to account for differences in disintegration in a more physiologically relevant way and thus to better reflect the in vivo performance of the various formulations.