Evaluation of Dissolution and Acid-resistance of L-Keflex Granule

L-Keflex granule is a sustained release preparation of cefalexin in rapid release granules (30%) and enteric coated granules (70%). The acid-resistance and the dissolution pattern of this preparation were measured with the U. S. P. dissolution tester in the following test solutions:(a) pH shift test solution in consideration of pH levels of gastrointestinal tract: pH of the medium was designed to rise gradually from 2.3 to 3.7 in the first 150 min, rapidly from 3.7 to 6.2 in the subsequent 30 min, and gradually up to 6.9 after 300 min.(b) Test solutions at pH 1. 2, 4. 5, 6.0 and 6.5. The following results were obtained: 1) In the pH shift test solution, the calculative dissolution rate rapidly increased to 30% in the first 20 min, unchanged in the subsequent 200 min, and again rapidly rose to 100% after 280 min. 2) At pH 1.2 and 4. 5, the calculative dissolution rapidly increased to 30% within 20 min, but the granules were not dissolved thereafter. At pH 6.0, the time required for 100% dissolution was about 140 min, and at pH 6.5, about 30 min. Thus, the dissolution of the rapid, release granules and the acidresistance and the dissolution of enteric coated granules were satisfactory, and the pH shift test method used above must be effective in a qualitative evaluation of granule preparations of such type.