title: Interference of isonicotinyl hydrazone in the microbiological analysis of rifampicin from anti-tuberculosis FDC products containing isoniazid.
abstract: Microbiological assay is a sensitive method for the estimation of rifampicin (R). In the present study, interference due to isonicotinyl hydrazone (HYD), an interaction product of R and isoniazid (H), was checked during microbiological analysis of R, employing Bacillus subtilis and Sarcina lutea. The assays were done by disc diffusion method. Both R and HYD showed linear log response curves in the range of 0.01-10microg. In the presence of HYD, R was overestimated when tested against S. lutea and underestimated in case of B. subtilis. The same extent and type of interference was observed on assay of a marketed anti-tuberculosis fixed-dose combination product, subjected to accelerated stability testing (40 degrees C/75% RH) for 1 month. This means that response of organisms used in microbiological assay of R might vary in the presence of HYD, with possibility of incorrect conclusions. Therefore, the study suggests that before a microbiological method involving a particular organism is extended to the determination of R in FDC formulations containing H, it should be tested for the influence of HYD and used only if non-interfering.
authors.affiliation: Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar, Punjab, India.
authors.forename: T T
authors.initials: TT
authors.lastname: Mariappan
authors.forename: Thiraviam
authors.initials: T
authors.lastname: Geetha
authors.forename: Rajesh
authors.initials: R
authors.lastname: Pandey
authors.forename: K C
authors.initials: KC
authors.lastname: Jindal
authors.forename: Saranjit
authors.initials: S
authors.lastname: Singh
mesh_terms: D000995:Antitubercular Agents / Q000378:metabolism* / Q000494:pharmacology; D001412:Bacillus subtilis / Q000187:drug effects; D002626:Chemistry, Pharmaceutical; D004347:Drug Interactions / Q000502:physiology; D006835:Hydrazones / Q000378:metabolism* / Q000494:pharmacology; D007538:Isoniazid / Q000378:metabolism* / Q000494:pharmacology; D007539:Isonicotinic Acids / Q000378:metabolism* / Q000494:pharmacology; D008828:Microbiological Techniques / Q000379:methods; D012293:Rifampin / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000995:Antitubercular Agents; D006835:Hydrazones; D007539:Isonicotinic Acids; D007538:Isoniazid; D012293:Rifampin