STREPTOMYCIN IN THE BLOOD: CHEMICAL DETERMINATIONS AFTER SINGLE AND REPEATED INTRAMUSCULAR INJECTIONS

¹ The Research Laboratories of Merck & Co., Inc., Rahway, N.J.
² Department of Medicine, Cornell University, Medical College and the New York Hospital
³ The Merck Institute for Therapeutic Research, Rahway, N.J.

Chemical determinations of the concentrations of streptomycin in the blood have been made in dogs and humans, following intramuscular injections of the drug.

The concentrations of streptomycin in the blood were found to be proportional to the dose per kilogram of body weight, within a definite range of dosage. From the results obtained, it is possible to calculate with reasonable accuracy the serum concentrations of the drug in man after intramuscular injection of streptomycin in doses ranging from 4,000 to 20,000 / kg.

The rate of decrease of streptomycin concentration was found to be proportional to the concentration of the drug in the blood. The rate constants in man and in the dog were different, while the "apparent" volumes of distribution were similar in the two species.

A study was also made of the plasma concentrations of streptomycin in dogs after repeated injections of the drug at intervals of 2 hours and 3 hours.

A method is presented for the calculation of drug concentration in the blood after repeated injection, applicable to any drug in which the rate of decrease in concentration is proportional to its concentration in the blood. A close correlation was found between the theoretical values thus calculated and the actual values found in dogs after repeated injections of streptomycin at regular intervals.