In vitro release of felodipine from original brand and generic products

Eight different felodipine (CAS 72509-76-3) products (nominal content: 5 mg) were tested for their in vitro release profile: The generic drugs A-G and the reference product Modip. During an incubation period of 7 h in dissolution vessels (paddle method in accordance with USP XXII) samples were taken to be assayed for the active ingredient concentration within 24 h by means of UV spectroscopy. All products examined released at least the content declared. While the 6 tablets of the reference differed only slightly in their release kinetics, the other products showed considerable variability with the exception of Drug D (uniform rapid release) and Drug C. The reference offered the linear controlled-release profile expected from an extended-release product. Three different time profiles could be distinguished in the generics: a) Drugs A, B, F, and D practically showed immediate release of the active ingredient, b) Drugs E and G showed some extent of controlled release (however, more than 50% of the total content was released within 60 min); c) Drug C displayed controlled-release properties but a more rapid release than the reference at all sampling times.