Plasma levels of viomycin in man after single intramuscular injection.

Abstract

Twenty patients with pulmonary tuberculosis received single intramuscular injections of Viomycin sulfate, 10 receiving 1.0 Gm. and 10, 0.5 Gm. Blood samples were withdrawn immediately before the injection of the drug and at intervals of 1, 2, 4 and 8 hours thereafter. Specimens were collected in oxalate and centrifuged in the same tubes. Although sterile needles, tubes and syringes were used throughout, no other precaution to prevent contamination of the plasma was attempted. The agar diffusion assay procedure employed was essentially the same as that of Ehrlich, Iverson and Kohberger. Medium. Streptomycin assay-agar (beef extract, 1.5 Gm.; yeast extract, 3.0 Gm.; peptone, 6.0 Gm.; agar, 15 Gm.; and distilled water, 1000 ml.) adjusted to pH 7.4-7.6; autoclaved 15 minutes at 15-pounds pressure. Inoculum. Bacillus subtilis I strain, obtained from the Army Medical Department Research and Graduate School, Walter Reed Army Hospital, Washington, D. C., was used. A suspension was prepared by washing well-sporulated growth from nutrient agar slants, killing the vegetative cells by pasteurizing for 15 minutes at 80 C , and titrating the number of viable spores by plating serial dilutions in Streptomycin assay-agar. The growth of this organism is not appreciably affected by the presence of whole blood or serum. Preparation of the assay plates. Sufficient Bacillus subtilis spore suspension was added to the melted cooled agar (45 to 50 C.) to make a final concentration of 100,000 viable spores per milliliter of medium. Ten milliliters of this seeded agar was pipetted into sterile flat-bottom petri dishes and allowed to harden, and the plates were stored in the refrigerator (4 C.) until used. Stock solutions. Eight 2-fold serial dilutions of Viomycin sulfate in M/15 phosphate buffer pH 7.4 were prepared in concentrations ranging from 100 to 0.78 jug. per ml. Method of performing the assay. All determinations were made in triplicate. Using flamed forceps, filter paper disks (Schleicher and Schuell No. 740-E, 3^-inch diameter) were saturated in the stock solutions or in the supernatant