Carbachol Intraocular Solution

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

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

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1 DEFINITION

Carbachol Intraocular Solution is a sterile solution of Carbachol in an aqueous medium. It contains NLT 90.0% and NMT 115.0% of the labeled amount of carbachol (C₆H₁₅CIN₂O₂). It contains no preservatives or antimicrobial agents.

2 IDENTIFICATION

A.

Solution A: A saturated (filtered) ammonium reineckate solution

Analysis: To 5 mL of Intraocular Solution add 4-5 drops of Solution A.

Acceptance criteria: A pink precipitate is formed that is soluble in acetone; the acetone solution is red.

3 ASSAY

PROCEDURE

Solution A: Dilute 1 volume of sodium hypochlorite TS with water to 15 volumes, and allow to stand for 30 min.

Solution B: Solution A and 1 N sodium hydroxide (50:50). Prepare fresh daily.

Solution C: Phenol in water (1 in 200)

Solution D: Potassium iodide in water (3 in 1000)

Standard solution: 100 µg/mL of USP Carbachol RS in water

Sample solution: Nominally 100 µg/mL of carbachol from a volume of Intraocular Solution in water

Instrumental conditions

Mode: UV-Vis

Analytical wavelength: Maximum absorbance at about 590 nm

Cell: 1 cm

Blank: Water

Analysis

Samples: Standard solution, Sample solution, and Blank

Transfer 2.0-mL portions each of the Standard solution, Sample solution, and Blank to separate 50-mL conical flasks. To each flask add 1.0 mL of 0.1 N hydrochloric acid. Treat each as follows. Add 4.0 mL of Solution B, rinsing the inner walls of the flask with small portions of water, mix, and allow to stand for 15 min, accurately timed. Add 2.0 mL of Solution C, rinsing the walls of the flask with Solution C and with additional small portions of water. Mix, and allow to stand for 5 min. Add 2.0 mL of 3.5 N hydrochloric acid, washing the sides of the flask upon addition. Rinse the flask sparingly with 0.1 N hydrochloric acid to ensure complete acidification of all content, then mix. Add 1.0 mL of Solution D, and allow to stand for 5 min. Add 3.0 mL of starch TS, mix, and transfer the solutions to 50-ml volumetric flasks with the aid of several small portions of water, and dilute each solution with water to volume. Concomitantly determine the absorbances of the solutions from the Sample solution and the Standard solution against the Blank. Calculate the percentage of the labeled amount of carbachol (C₆H₁₅CIN₂O₂) in the portion of Intraocular Solution taken:

Result = (A_u/A_s) × (C_s/C_u) × 100

A_u = absorbance of the Sample solution

A_s = absorbance of the Standard solution

C_s = concentration of USP Carbachol RS in the Standard solution (µg/mL)

C_u = nominal concentration of carbachol in the Sample solution (µg/mL)

Acceptance criteria: 90.0%-115.0%

4 SPECIFIC TESTS

STERILITY TESTS (71): Meets the requirements

PH (791): 5.0-7.5

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers, at controlled room temperature, and protect from freezing.

Labeling: Label it to indicate that it is for single-dose intraocular use only, and that the unused portion is to be discarded.

USP Reference Standards 〈11〉

USP Carbachol RS