Evaluation of biodegradable rifampicin-bearing microsphere formulations using a stability-indicating high-performance liquid chromatographic assay

The validation of a rapid and selective stability-indicating high-performan ce liquid chromatographic procedure for the determination of rifampicin (RI F) and its decomposition products in aqueous solution is described. Direct injection and column switching HPLC procedures have been compared and, owin g to the increased sensitivity and precision, the latter has been applied t o the study of RIF stability in the presence of isoascorbic acid at pH 7.4. The time-dependent hydrolytic decomposition of RIF to 3-formyl rifamycin S V (RSV) was found to be biexponential. Log concentration versus time plots of RIF and RSV decomposition were found to be parallel, indicating a pseudo equilibrium decomposition process. This feature allowed corrections for th e amounts lost to secondary reactions to be calculated when the assay was a pplied to the determination of release characteristics of RIF from biodegra dable poly-D,L-lactide-co-glycolide microspheres. (C) 1998 Elsevier Science B.V. All rights reserved.