The Mini Paddle Apparatus–a Useful Tool in the Early Developmental Stage? Experiences with Immediate-Release Dosage Forms

Introduction In recent years,there has been a strong push to identify bioavailability problems of a drug formulation based on the results of appropriately designed dissolution experiments. Particularly for immediate release (IR) dosage forms, the paddle apparatus has evolved as the method of choice for this purpose (1,2). However,standard paddle experiments require both large volumes of test media which, particularly when using biorelevant media,can be cost intensive and large sample sizes that are typically not available in the early stage development when the main objective is to characterize the physicochemical properties of the active ingredient and the final formulation has not been established. Therefore, it would be very helpful to use a test system that requires smaller sample sizes and smaller volumes of media but has the same reliability and predictivity as the standard test apparatus. The objective of the present series of tests was to determine if standard paddle experiments could be scaled down without losing the reliability and the predictivity of the standard method. Of particular concern are the hydrodynamic conditions, since these are known to influence in vivo dissolution of drugs after their oral administration (3, 4). However, provided suitable in vitro test conditions are chosen, it is often possible to predict dissolution limitations to oral absorption of drugs and to reflect variations in hydrodynamic conditions in the upper gastrointestinal (GI) tract (5). For this purpose, drug release profiles of four IR dosage forms containing drugs that belong to the BCS classes I, II, and III (6–8) were compared in the paddle and the mini paddle under different hydrodynamic conditions.