Ivermectin Paste

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

Ivermectin Paste contains NLT 90.0% and NMT 110.0% of the labeled amount of Ivermectin, calculated as the sum of component H₂B_1a (C₄₈H₇₄O₁₄) and component H₂B_1b (C₄₇H₇₂O₁₄). The ratio of the contents, H₂B_1a/(H₂B_1a + H₂B_1b), is NLT 90.0%.

2 IDENTIFICATION

A. Thin-Layer Chromatographic Identification Test 〈201〉

Sample solution: 0.5 mg/mL of ivermectin dispersed in methanol from a quantity of Paste. Sonicate if necessary until completely dispersed.

Application volume: 2 μL

Developing solvent system: Methylene chloride, methanol, and ammonium hydroxide (90:9:1)

Analysis: Develop the chromatogram in an unsaturated chamber. Remove the plate, allow to air dry, and examine under short- and long- wavelength UV light.

Acceptance criteria: Meets the requirements

B. The retention times of the two principal component peaks of ivermectin from the Sample solution correspond to those of the two principal component peaks of ivermectin from the Standard solution, as obtained in the Assay.

3 ASSAY

Procedure

Mobile phase: Acetonitrile, methanol, and water (106:55:39)

Standard solution: 0.4 mg/mL of USP Ivermectin RS in methanol

Sample solution: Disperse a quantity of Paste in methanol, using sonication if necessary, to obtain a solution containing 0.4 mg/mL of ivermectin.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 245 nm

Column: 4.6-mm × 25-cm; 5-μm packing L1

Flow rate: 1.5 mL/min

Injection size: 20 μL

System suitability

Sample: Standard solution

Suitability requirements

Resolution: NLT 3.0 between the

rst peak (component H₂B_1a) and the second peak (component H₂B_1b)

Relative standard deviation: NMT 2.0%, determined from the component H₂B_1a peak

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of ivermectin, component H₂B_1a (C₄₈H₇₄O₁₄) and component H₂B_1b (C₄₇H₇₂O₁₄), in the portion of Paste taken:

Result = (r_U/r_S)x(C_S/C_U) × 100

r_U = sum of the peak responses for component H₂B_1a and component H₂B_1b from the Sample solution

r_S = sum of the peak responses for component H₂B_1a and component H₂B_1b from the Standard solution

C_S = concentration of USP Ivermectin RS in the Standard solution (mg/mL)

C_U = nominal concentration of ivermectin in the Sample solution (mg/mL)

Calculate the ratio of the contents, in percentage, of the components, H₂B_1a/(H₂B_1a + H₂B_1b), in the portion of Paste taken:

Result = (r_U/r_T) × 100

r_U = peak response of H₂B_1a from the Sample solution

r_T = sum of the peak responses for component H₂B_1a and component H₂B_1b from the Sample solution

Acceptance criteria: 90.0%–110.0% of the labeled amount of ivermectin, calculated as the sum of component H₂B_1a (C₄₈H₇₄O₁₄) and component H₂B_1b (C₄₇H₇₂O₁₄). The ratio of the contents, H₂B_1a/(H₂B_1a + H₂B_1b), is NLT 90.0%.

4 IMPURITIES

Organic Impurities

Mobile phase, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay.

Standard solution: 0.004 mg/mL of USP Ivermectin RS in methanol

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each impurity in the portion of Paste taken, disregarding any peak below 0.05%:

Result = (r_U/r_S)x(C_S/C_U) × 100

r_U = peak response for each impurity from the Sample solution

r_S = peak response of the principal peak from the Standard solution

C_S = concentration of the Standard solution (mg/mL)

C_U = nominal concentration of ivermectin in the Sample solution (mg/mL)

Acceptance criteria: NMT 3.0% of any peak with a relative retention time of 1.3–1.5, relative to that of the principal peak

Any other impurity: NMT 1.0%

Total impurities: NMT 6.0%

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers. Store at a temperature not higher than 30°.

Labeling: Label it to indicate that it is for oral veterinary use only.

USP Reference Standards 〈11〉

USP Ivermectin RS