Iopamidol Injection

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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lopamidol Injection is a sterile solution of lopamidol in Water for Injection. It contains not less than 95.0 percent and not more than 105.0 percent of the labeled amount of iopamidol (C₁₇H₂₂I₃N₃O₈). It may contain small amounts of suitable buffers and of Edetate Calcium Disodium as a stabilizer. lopamidol Injection intended for intravascular or intrathecal use contains no antimicrobial agents.

Packaging and storage-Preserve Injection intended for intravascular or intrathecal use in single-dose containers, preferably of Type I glass, and protected from light.

Labeling-Label containers of Injection to direct the user to discard any unused portion remaining in the container and to check for the

presence of particulate matter before using. Label it also to state its routes of administration.

1 USP REFERENCE STANDARDS (11)

USP lopamidol RS

USP loparnidol Related Compound A RS

N,N'-Bis-(1,3-dihydroxy-2-propyl)-5-amino-2,4,6-triiodoisophthalamide.

C₁₄H₁₈I₃N₃O₆  705.03

USP lopamidol Related Compound B RS

5-Glycolamido-N,N'-bis[2-hydroxy-1-(hydroxymeth yl)ethyl]-2,4,6-triiodoisophthalamide.

C₁₆H₂₀I₃N₃O₇  747.07

2 Identification

A: Evaporate a volume of Injection, equivalent to about 500 mg of iopamidol, to dryness, and heat the residue so obtained in a suitable crucible: violet vapors are evolved.

B: It responds to the Thin-Layer Chromatographic Identification Test (201), the test solution and the Standard solution being prepared at a concentration of 0.5 mg per mL in a mixture of methanol and water (9:1), the solvent mixture being chloroform, methanol, ammonium hydroxide, and water (60:30:9:1), and short-wavelength UV light being used to locate the spots.

BACTERIAL ENDOTOXINS TEST (85) -It contains not more than 0.6 USP Endotoxin Unit per mg of iodine.

pH (791): between 6.5 and 7.5.

PARTICULATE MATTER IN INJECTIONS (788) -The Injection labeled for intrathecal use meets the requirements for small-volume injections.

Free aromatic amine-Transfer an accurately measured volume of Injection, equivalent to about 500 mg of iopamidol, to a 25-mL volumetric flask, dilute with water to 20 mL, and mix. To a second 25-mL volumetric flask transfer 16 mL of water and 4.0 mL of Standard solution prepared by dissolving a suitable quantity of USP lopamidol Related Compound A RS in water and diluting with water to obtain a solution having a concentration of 62.5 µg per mL. Proceed as directed in the test for Free aromatic amine under lopamidol, beginning with "to the third 25-mL volumetric flask add 20 mL of water." The absorbance of the solution from the iopamidol is not greater than that of the Standard solution (0.05%).

Free iodine-Transfer a volume of Injection, equivalent to 2.0 g of iopamidol, to a glass-stoppered test tube. Add 2 mL of 2 N sulfuric acid and 1.0 mL of toluene, shake, and allow the layers to separate: the toluene layer shows no red color. Limit of free iodide-Transfer 10.0 mL of Injection to a beaker, add 40 mL of water, and mix. Proceed as directed in the Limit of free iodide test under lopamidol beginning with "add 2.0 mL of 0.001 M potassium iodide." Not more than 3.1 mL of 0.001 N silver nitrate is required (0.04 mg of iodide per mL).

Other requirements-It meets the requirements under Injections and Implanted Drug Products (1).

3 Assay

Solution A-Use water.

Solution B-Prepare a filtered and degassed mixture of water and methanol (3:1).

Mobile phase-Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary

(see System Suitability under Chromatography (621)).

Resolution solution-Transfer 10.0 mg of USP lopamidol Related Compound B RS and 10.0 mg of USP lopamidol RS to a 1000-mL volumetric flask. Dissolve in and dilute with water to volume, and mix.

Standard preparation-Dissolve about 20 mg of USP lopamidol RS, accurately weighed, in about 10 mL of water, and dilute quantitatively and

stepwise with water to obtain a solution having a known concentration of about 80 µg of USP lopamidol RS per mL.

Assay preparation-Dilute an accurately measured volume of Injection, equivalent to about 1000 mg of iopamidol, quantitatively and stepwise with water to obtain a solution having a concentration of about 80 µg of iopamidol per mL.

Chromatographic system (see CHROMATOGRAPHY (621).)-The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm x 25-cm stainless steel column that contains 5-µm packing L1. The column temperature is maintained at 35°, and the flow rate is about 1.5 mL per minute. The chromatograph is programmed to provide variable mixtures of Solution A and Solution B, the percentage of Solution B being 8.0% at the time of injection, and is held at that percentage for 6 minutes, then increased linearly to 35.0% at 18 minutes, after which it is changed to increase linearly to 92.0% at 30 minutes, maintained at that percentage for 4 minutes, and decreased linearly to 8.0% at 36 minutes, where it is held to the end of the run at 40 minutes. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between iopamidol related compound B and iopamidol is not less than 7.

Procedure-Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of iopamidol (C₁₇H₂₂I₃N₃O₈) in the portion of Injection taken by the formula:

12.5C(r_U/r_T)

in which C is the concentration, in µg per mL, of USP lopamidol RS in the Standard preparation, and r_U and r_T are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.