EFFECT OF COATING ON THE FLOW, WETTING AND DISSOLUTION FOR DIMENHYDRINATE CRYSTALS

Abstract

Crystals of dimenhydrinate were coated with a gastric-soluble polymer (hydroxypropyl-methylcellulose) in a fluidized bed apparatus in order to increase the poor flowabilty of crystals. The amount of coating polymer can influence the wetting, the dissolution rate of the active ingredient and the sensitivity to heat. There was an increase in particle size due to the coating, but the increase is less than that during conventional granulation. The flow properties was increased by the film coating. The different wetting behaviour of the crystals is explained in terms of the contact angle of distilled water on the surface of tablets. Here different quantities of film forming polymer were examined. The characteristic water uptake reflects the wetting of the crystals. The thermal sensitivity, determined by a differential scanning calorimetry, was improved by the coating. The quantity of the polymer in the film plays an important part in the thermal sensitivity.