International standard for erythromycin.

A batch of highly purified erythromycin A has been examined by 9 laboratories in 6 different countries, and has been assayed against the erythromycin standard of the Food and Drug Administration of the US Department of Health, Education, and Welfare. The material examined has been established as the International Standard for Erythromycin, and the International Unit of Erythromycin is defined as the activity contained in 0.001053 mg of the International Standard. The International Unit is, for practical purposes, equivalent to one mug of pure erythromycin base.