Assessment of biological potency of commercially available vancomycin products in Jordan using USP cylinder–plate assay

Background : Recent reports raising concerns regarding the clinical performance of vancomycin products in Jordan prompted a regulatory review focused on biological potency. Objective : To evaluate the biological potency of commercially available vancomycin products using the United States Pharmacopeia (USP) cylinder–plate assay method. Methods : Four different vancomycin hydrochloride products (designated as Product A, Product B, Product C, and Product D) from various batches were assessed using the USP cylinder–plate assay, with Bacillus subtilis ATCC 6633 as the indicator organism. Potency calculations were performed using standard curve analysis and expressed as a percentage of labeled potency. Results : Significant variability in biological potency was observed across the tested products. Several batches of Product A and comparative products failed to meet the USP acceptance criteria of 90–115% potency. A potential correlation between batch age and potency was observed, suggesting a possible association between increased batch age and lower potency. More recent batches in this sample set met the USP acceptance range, whereas at least one older batch showed reduced potency (78.3%); however, storage and thermal history were not documented, so causality cannot be inferred. Conclusion : The study identified potency-related concerns for some vancomycin products in Jordan. The findings suggest that enhanced post-market surveillance and adherence to proper storage protocols are important to help ensure that products meet potency specifications.