Packaging and storage— Preserve in tight containers.

USP Reference standards 11— USP Gramicidin RS.

Identification— Add about 5 mg to 5 mL of p-dimethylaminobenzaldehyde TS, and shake for 2 minutes. Add 2 drops of sodium nitrite solution (1 in 150) and 5 mL of water, and mix: a blue color is produced.

Loss on drying 731— Dry about 100 mg, accurately weighed, in a capillary-stoppered bottle in vacuum at a pressure not exceeding 5 mm of mercury at 60 for 3 hours: it loses not more than 5.0% of its weight.

Residual solvents 467: meets the requirements.

Assay— Proceed as directed for gramicidin under Antibiotics—Microbial Assays 81 , using a suitable, accurately weighed portion of Tyrothricin dissolved quantitatively in alcohol to yield a stock solution of convenient concentration. Dilute an accurately measured volume of this solution quantitatively and stepwise with alcohol to obtain a Test Dilution having a concentration of tyrothricin assumed to be 5.0 times the median dose level of the gramicidin Standard. Multiply the result of the gramicidin assay by 5.0 to obtain the amount of tyrothricin, in µg, in each mL of the Test Dilution.

Expert Committee : (MDANT05) Monograph Development-Antibiotics

USP29–NF24 Page 2229

Phone Number : 1-301-816-8223