Roxithromycin potency quantification in pharmaceutical preparation by applying a validated bioassay method and...

Roxithromycin (RXM) is used to treat bacterial infections. An alternative bioassay for the assessment of the potency of this drug in pharmaceutical formulations has not been reported earlier. This study reports the development and validation of cost-effective, simple, sensitive, precise, accurate and reproducible one-level agar diffusion (5+1) bioassay for estimation of potency and bioactivity of RXM in tablet. Among six tested microbial strains, Streptococcus pneumoniae (MTCC-1935) was used as the most susceptible strain against RXM. Bioassay was optimized by investigating buffer pH, inoculums and reference standard concentration. The results of proposed bioassay displayed high linearity, precision, accuracy, robustness and specificity. All potency results were statistically analyzed and found to be linear (R(2)=0.9957) in between 2.0 and 6.0μg/mL, precise with relative standard deviation (RSD) of repeatability intra-assay below 1.5%, and intermediate precision between day RSD 0.39% and accurate (100.68%). The bioassay and previously validated HPLC methods were compared, which indicated that there was no significant difference between these two methods. The results demonstrated the validity of the proposed microbial assay, which allows reliable quantitation of RXM in pharmaceutical samples and therefore can be used as a substitute alternative methodology for the routine quality control of this medicine, in situation when HPLC is not affordable in the laboratory.