Microwave-assisted drying of pharmaceutical granules and its impact on drug stability.

The advent of microwave technology has intensified the search for pharmaceuticals amenable to microwave processing. This study investigated the influences of powder load, diluent particle size and amount of granulating liquid employed on the microwave-assisted drying and stability of acetylsalicylic acid (ASA)-loaded granules in a single pot high shear processor. Powder load affected the profiles, rate and extent of drying. Drying was more dependent on the size and structural properties of granules rather than their surface areas as heat was generated volumetrically. Increased granule size brought about by increasing the size of diluent particles and amount of granulating liquid resulted in higher drying rates. Drug stability was negatively correlated to the drying time of granules.