The International Standard for sisomicin.

An International Standard for Sisomicin has been established on the basis of a collaborative assay. There were seven participating laboratories in seven countries. The activity of the contents of each ampoule of the International Standard of Sisomicin is defined as 35,200 International Units of Sisomicin.

The International Standard for Amikacin.

An International Standard for Amikacin has been established on the basis of a collaborative assay. Seven laboratories, in seven countries, took part. Each ampoule of the International Standard of Amikacin is defined as containing the activity of 50 600 International Units of Amikacin.

Control of the composition of gentamicin sulphate by proton magnetic resonance spectrometry.

The proportions of the main components present in gentamicin sulphate complex, gentamicins C1, C1a and C2, can be monitored by 1H nuclear magnetic resonance (nmr) spectrometry. The method depends on measurement of the peak heights of signals for N-methyl and C-methyl groups present in all three components and of those present in C1 and C2 only, followed by calculation of peak height ratios to control composition within acceptable limits. The precision and reproducibility of the method have been established through two collaborative studies each involving seven laboratories. In the second study, with an improved procedure, the mean variance between laboratories with 10 samples was 3.4 X 10(-4) for the N-methyl ratio of the peak at delta 2.75 to that at delta 2.95, and 1.25 X 10(-3) for the C-methyl ratio of the peak at delta 1.25 to that at delta 1.35. Within laboratories the mean variance for triplicate determinations was 7.4 X 10(-5) and 8.9 X 10(-5) respectively. The data presented here form the experimental basis for the test controlling the composition of gentamicin sulphate in the British Pharmacopoeia 1973: Addendum 1975, and for the introduction into the British Pharmacopoeia of nmr spectrometry as an analytical technique. The reference standards and all batches of gentamicin sulphate intended for therapeutic use in the United Kingdom examined by this procedure comply with the limits laid down.

The second international reference preparation of viomycin.

The first International Reference Preparation of Viomycin was replaced by the second international reference preparation, consisting of material from the batch that provided the second Working Standard of the US Food and Drug Administration. The International Unit of viomycin was redefined as the activity contained in 0.0012285 mg of the second international reference preparation. Examination of batches of viomycin sulfate from the various sources of production showed that the second international reference preparation was suitable for their assay, whereas a sample previously proposed as the international standard of viomycin was unsatisfactory.

The international standard for colistin.

An International Standard for Colistin has been established and the International Unit defined as the activity contained in 0.00004878 mg of this preparation. The unit was defined on the basis of a collaborative assay in which nine laboratories from six different countries participated. The material used to prepare the international standard had been manufactured in Japan; it was shown to have a composition similar to that of material produced in Europe and to be suitable for the assay of colistin from the existing sources of manufacture.