Physicochemical pharmacokinetics as an optimization tool for generic development: A case study

In spite of the fact that dissolution time profiles of 250mg ursodeoxycholic acid (UCDA) capsules developed by Sponsor and 250mg hard capsules produced by Ursofalk®, Dr. Falk Pharma GmbH, indicated similarity (f₂=60.6), a bioavailability study indicated unexpected differences in the formulations. To find an explanation of the in vivo performance of the compared formulations, the dissolution profiles were analyzed using a novel dissolution theory considering: The dissolution model was applied to the measured data using SADAPT. Despite C_max and AUC values showing higher values after administration of the test product, a reduction of UDCA particle size for the test formulation was suggested for reformulation. The decision was based on the strongly pH-dependent UDCA solubility, formation of insoluble crystals at low pH condition and the known high pH fluctuations ranging from pH1 to 8 in empty stomach. The performed reformulation led to increased dissolution rate of the test product and to a positive bioequivalence study which compared the reformulated test generic formulation with two reference products purchased from two highly regulated markets.