Influence of storage on in-vitro release of ibuprofen from sugar coated tablets

Studies performed on ibuprofen tablets (one brand of 400 mg, two brands of 200 mg sugar coated and one brand of film coated tablets) are reported. Tablets were subjected to conditions of 23 degrees C, 30 degrees C and 40 degrees C; at 75% RH and 96% RH for periods of up to 4 weeks. Tablets were stored in different ways--unpacked, packed in air-tight/moisture proof containers, packed in tablet vials and packed in two unit dose packs. Dissolution was carried out in pH 7.2 phosphate buffer using USP or FDA conditions for ibuprofen (Basket-150 rpm or Paddle-50 rpm) with sampling and UV analysis up to 90 or 120 min. Serious reduction in dissolution was noted for the 400 mg sugar coated tablets exposed to moisture. Mean % released at 30 mm (USP conditions) was as low as 1% and, for these tablets, dissolution continued to proceed extremely slowly for the full dissolution period. The film coated tablets were not affected. The tablet vials and unit dose packs showed some protection. Investigation showed not only a change in the subcoat properties (which did not break down easily) but also in the tablet core, which became hard and non-disintegrating.