The international standard for dihydrostreptomycin.

In 1950, the Department of Biological Standards, National Institute for Medical Research, London, was authorized by the WHO Expert Committee on Biological Standardization to proceed with the establishment of an International Standard for Dihydrostreptomycin. A 50-g batch of dihydrostreptomycin was obtained and was compared with the Standard Preparation of Dihydrostreptomycin of the Food and Drug Administration (FDA), United States Department of Health, Education and Welfare, in a collaborative assay in which seven laboratories in five countries participated.In all, 76 assays were carried out; 62 of these were done by biological methods, using Staphylococcus aureus, Bacillus subtilis, or Klebsiella pneumoniae, and the remaining 14 by physicochemical methods. The results were subjected to standard methods of analysis, and the overall weighted mean potency (calculated from the results of biological assays only) was 0.958, with limits of error of 99.6% to 100.4%.Since the FDA Standard Preparation is considered to be substantially pure dihydrostreptomycin sulfate, the content of dihydrostreptomycin base (after allowing for known moisture content) is assumed to be 79.2%. The potency of the International Standard has been established as 760 International Units per mg, so that, on the foregoing assumption, one International Unit may be regarded as equivalent to the activity of one microgram of dihydrostreptomycin base.