Rapid turbidimetric assay for quantification of fusidic acid in a dermatological cream

• Simple turbidimetric method for the quantification of fusidic acid in cream was developed.
• Method development was based on pharmacopeial principles.
• Validation of turbidimetric assay was carried out according of the ICH guidelines.
• Results obtained by RP-LC and turbidimetric methods showed no significant difference.
• An alternative method for the routine quality control of the fusidic acid is proposed.

Fusidic acid is an antibiotic steroid widely used for the treatment of serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains. Microbiological methods are indispensable to determine the mean percentage of antimicrobial in medicaments during manufacturing and quality control processes. The aim of this study was to develop and validate a microbiological method for the quantification of fusidic acid in dermatological cream by turbidimetry, using Staphylococcus epidermidis (ATCC 12228) and casoy broth as the culture medium. The validation parameters were in accordance with ICH specifications and demonstrated accuracy, precision, selectivity, and robustness, with linear ranges from 0.25 to 2.25 μg mL−1. This method is an alternative to the diffusion agar assay currently employed to quantify fusidic acid in dermatological cream, since it is sensitive, fast, and more economical.

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