Collaborative study for the establishment of the second international standard for gramicidin.

An international collaborative study was organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM) to establish the WHO second International Standard (IS) for gramicidin as the stocks of the 1st IS, established in 1964, were close to depletion. The candidate material did not show any sign of potency loss when kept at elevated temperatures of + 4 °C, + 20 °C, + 37 °C and + 45 °C for 3 months. Six laboratories from 5 countries as well as the EDQM laboratory participated in the collaborative study. Potencies of the candidate material were estimated by microbiological assays with sensitive micro-organisms. To ensure continuity between consecutive batches, the 1st IS for gramicidin was used as standard. Based on the results of the study, the 2nd IS for gramicidin was adopted at the meeting of the WHO Expert Committee on Biological Standardization (ECBS) in 2008 with an assigned potency of 1070 International Units per mg (IU/mg). The 2nd IS for gramicidin is available from the EDQM.