In spite of the fact that dissolution time profiles of 250 mg ursodeoxycholic acid (UCDA) capsules developed by Sponsor and 250 mg 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 Cmax 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 pH 1 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.