[Microbiological method of determining cyanocobalamin in tissues and finished drugs made from animal raw materials].

An assay for cyanocobalamin with the use of the test microorganism E. coli, mutant ATCC 9637, is offered. The measurement of the content of cyanocobalamin in the blood serum and liver of intact rats after intraperitoneal drug injection demonstrated its content to reach a maximum 30 minutes after injection and to depend on the dose. When given in doses 100 and 400 micrograms/kg, the drug dose in the serum amounted to 82 and 261 ng/g, respectively, and in the liver to 80 and 259 ng/g. The method is readily reproducible, does not require the observance of strict aseptics, it is economical and time-saving.