Colistimethate for Injection

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

Colistimethate for Injection contains an amount of Colistimethate Sodium equivalent to not less than 90.0 percent and not more than 120.0 percent of the labeled amount of colistin.

1 Packaging and storage

Preserve as described in Packaging and Storage Requirements (659), Injection Packaging, Packaging for constitution.

2 USP REFERENCE STANDARDS (11)

USP Colistimethate Sodium RS

3 Constituted solution

At the time of use, it meets the requirements for Injections and Implanted Drug Products (1), Specific Tests, Completeness and clarity of solutions.

4 BACTERIAL ENDOTOXINS TEST (85)

It contains not more than 2.0 USP Endotoxin Units per mg of colistin.

5 STERILITY TESTS (71)

It meets the requirements when tested as directed for Membrane Filtration under Test for Sterility of the Product to be Examined.

6 Other requirements

It responds to the Identification test and meets the requirements for pH, Loss on drying, and Free colistin under Colistimethate Sodium. It meets also the requirements for Uniformity of Dosage Units (905) and for Injections and Implanted Drug Products (1), Specific Tests. Completeness and clarity of solutions and for Labeling (7), Labels and Labeling for Injectable Products.

7 Assay

Assay preparation 1 (where it is represented as being in a single-dose container)-Constitute Colistimethate for Injection in a volume of water, accurately measured, corresponding to the volume of diluent specified in the labeling. Withdraw all of the withdrawable contents, using a suitable hypodermic needle and syringe, and quantitatively dilute with Buffer B.6 to obtain a solution having a convenient concentration.

Assay preparation 2 (where the label states the quantity of colistin equivalent in a given volume of constituted solution)-Constitute Colistimethate for Injection in a volume of water, accurately measured, corresponding to the volume of diluent specified in the labeling.

Quantitatively dilute an accurately measured volume of the constituted solution with Buffer B.6 to obtain a solution having a convenient concentration.

Procedure-Proceed as directed for Colistimethate Sodium under Antibiotics-Microbial Assays (81), using an accurately measured volume of Assay preparation diluted quantitatively with Buffer B.6 to yield a Test Dilution having a concentration assumed to be equal to the median dose level of the Standard.