THE INTERNATIONAL STANDARD FOR NYSTATIN.

At the request of a WHO Expert Committee on Biological Standardization, a batch of nystatin, comparable in purity to material used therapeutically, was submitted to an international collaborative study in nine laboratories in six countries. In this study the material was assayed by the plate diffusion method (and in one laboratory also by a turbidimetric method) against the United States Pharmacopeia Reference Preparation of Nystatin. On the basis of the results obtained the material has been established as the International Standard for Nystatin, and the International Unit of Nystatin is defined as the activity in 0.000333 mg of the International Standard.