Collaborative study for the establishment of the third international standard for nystatin.

Due to the depletion in stocks of the World Health Organization (WHO) 2nd International Standard (IS) for nystatin, an international collaborative study was organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM) to establish a replacement batch. Seventeen laboratories participated in the collaborative study, performing the microbiological diffusion assay to estimate the potency of the candidate 3rd International Standard for nystatin. The 2nd International Standard for nystatin was used as a standard to ensure the continuity of the unitage. Follow-up accelerated degradation studies demonstrated that the IS is stable when at the customary storage temperature of - 20 °C. The 3rd IS for nystatin was adopted by the WHO Expert Committee on Biological Standardization (ECBS) in 2006 with an assigned potency of 5710 International Units per mg (IU/mg). The 3rd IS for nystatin is available from the EDQM.