Pyrantel Pamoate

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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C₁₁H₁₄N₂S.C₂₃H₁₆O₆ 594.68 

Pyrimidine, 1,4,5,6-tetrahydro-1-methyl-2-[2-(2-thienyl) ethenyl]-, (E)-, compd. with 4,4'-methylenebis[3-hydroxy-2-naphthalenecarboxylic acid] (1:1); 

(E)-1,4,5,6-Tetrahydro-1-methyl-2-[2-(2-thienyl)vinyl]pyrimidine 4,4'-methylenebis[3-hydroxy-2-naphthoate] (1:1) CAS RN®: 22204-24-6; UNII:  81BK194Z5M.

1 DEFINITION 

Pyrantel Pamoate contains NLT 97.0% and NMT 103.0% of pyrantel pamoate (C₃₄H₃₀N₂O₆S), calculated on the dried basis.

2 IDENTIFICATION 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K or 197A 

B. The retention time of the major peaks due to pyrantel base and pamoic acid of the Sample solution correspond to those of the Standard solution, as obtained in the Assay. 

3 ASSAY 

Procedure 

[Note—Use low-actinic glassware in preparing solutions of pyrantel pamoate, or otherwise protect the solutions from unnecessary exposure to bright light. Complete the Assay without prolonged interruption.] 

Mobile phase: Acetonitrile, glacial acetic acid, diethylamine, and water (92.8: 3: 1.2: 3) 

[Note—Increasing the amount of acetonitrile in the Mobile phase increases retention times. Increasing the amount of acetic acid, water, and diethylamine decreases retention times. Should the Mobile phase need to be adjusted, maintain the ratios among acetic acid, diethylamine, and water (1: 0.4: 1).] 

Standard solution: 80 µg/mL of USP Pyrantel Pamoate RS in Mobile phase 

Sample solution: 80 µg/mL of Pyrantel Pamoate in Mobile phase 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 288 nm 

Column: 4.6-mm × 25-cm; 5-μm packing L3 

Flow rate: 1 mL/min 

Injection volume: 20 µL 

Run time: NLT 2.5 times the retention times of pyrantel 

System suitability 

Sample: Standard solution 

[Note—The relative retention times for pamoic acid and pyrantel are 0.6 and 1.0, respectively.] 

Suitability requirements 

Resolution: NLT 10.0 between pyrantel and pamoic acid 

Tailing factor: NMT 1.3 for the pyrantel peak 

Relative standard deviation: NMT 1.0% for the pyrantel peak 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of pyrantel pamoate (C₃₄H₃₀N₂O₆S) in the portion of Pyrantel Pamoate taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response of pyrantel from the Sample solution 

r_S = peak response of pyrantel from the Standard solution 

C_S = concentration of USP Pyrantel Pamoate RS in the Standard solution (µg/mL) 

C_U = concentration of Pyrantel Pamoate in the Sample solution (µg/mL)

Acceptance criteria: 97.0%–103.0% on the dried basis 

4 OTHER COMPONENTS 

Content of Pamoic Acid 

Mobile phase: Acetonitrile, glacial acetic acid, diethylamine, and water (92.8: 3: 1.2: 3) 

[Note—Increasing the amount of acetonitrile in the Mobile phase increases retention times. Increasing the amount of acetic acid, water, and diethylamine decreases retention times. Should the Mobile phase need to be adjusted, maintain the ratios among acetic acid, diethylamine, and water (1: 0.4: 1).] 

Standard solution: 52 µg/mL of USP Pamoic Acid RS in Mobile phase 

Sample solution: 80 µg/mL of Pyrantel Pamoate in Mobile phase 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 288 nm 

Column: 4.6-mm × 25-cm; 5-μm packing L3 

Flow rate: 1 mL/min 

Injection volume: 20 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Relative standard deviation: NMT 1.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of pamoic acid (C₂₃H₁₆O₆) in the portion of Pyrantel Pamoate taken:

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response of pamoic acid from the Sample solution 

r_S = peak response of pamoic acid from the Standard solution 

C_S = concentration of USP Pamoic Acid RS in the Standard solution (µg/mL)  

C_U = concentration of Pyrantel Pamoate in the Sample solution (µg/mL) 

Acceptance criteria: 63.4%–67.3% of pamoic acid, calculated on the dried basis 

5 IMPURITIES 

Residue on Ignition 〈281〉 

Sample: 1.33 g 

Acceptance criteria: NMT 0.5% 

Change to read: 

Limit of Iron 

(See Iron 〈241〉, Procedures, Procedure 1 .) 

Analysis: To the residue obtained in the test for Residue on Ignition, add hydrochloric acid and nitric acid (3:2) and evaporate on a steam bath to dryness. Dissolve the residue in 2 mL of hydrochloric acid with the aid of gentle heat. Add 18 mL of hydrochloric acid, dilute with water to 50 mL, and mix. Dilute 5 mL of this solution with water to 47 mL. 

Acceptance criteria: NMT 0.0075% 

Organic Impurities 

Diluent: Glacial acetic acid, diethylamine, and water (5:2:5) 

Mobile phase: Acetonitrile and Diluent (92.8: 7.2). [Note—Prepare the solutions immediately before use, and protect from light at all stages.] Standard stock solution: 0.8 mg/mL of USP Pyrantel Pamoate RS prepared as follows. Dissolve using 7% of the nal volume of Diluent, and dilute with acetonitrile to volume. 

Standard solution: 4 µg/mL of USP Pyrantel Pamoate RS in Mobile phase from the Standard stock solution 

System suitability stock solution: 0.2 mg/mL of USP Pyrantel Related Compound A RS and 40 µg/mL of USP Pyrantel Pamoate RS prepared as follows. Dissolve a quantity of USP Pyrantel Related Compound A RS first in the Standard stock solution, using 5% of the nal volume, and dilute with Diluent to volume. 

System suitability solution: 4 µg/mL of USP Pyrantel Related Compound A RS and 0.8 µg/mL of USP Pyrantel Pamoate RS in Mobile phase from the System suitability stock solution 

Sensitivity solution: 0.2 µg/mL of USP Pyrantel Pamoate RS in Mobile phase from the Standard solution 

Sample solution: 0.8 mg/mL of Pyrantel Pamoate prepared as follows. Dissolve the sample in 7% of the nal volume of Diluent. Dilute with acetonitrile to volume. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 288 nm 

Column: 4.6-mm × 25-cm; 5-μm packing L3 

Flow rate: 1.0 mL/min Injection volume: 20 µL System suitability 

Samples: System suitability solution and Sensitivity solution 

Suitability requirements 

Resolution: NLT 4.0 between pyrantel and pyrantel related compound A, System suitability solution 

Tailing factor: NMT 1.5 for the pyrantel peak, System suitability solution 

Relative standard deviation: NMT 10.0% for the pyrantel peak, System suitability solution 

Signal-to-noise ratio: NLT 10.0, Sensitivity solution 

Analysis 

Samples: Standard solution, System suitability solution, and Sample solution 

[Note—Record the chromatograms for about 4 times the retention time of pyrantel. Disregard any peak in the Sample solution having an area less than one-tenth the principal peak in the Standard solution.] 

Calculate the percentage of pyrantel related compound A in the portion of Pyrantel Pamoate taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response of pyrantel related compound A from the Sample solution 

r_S = peak response of pyrantel related compound A from the System suitability solution 

C_S = concentration of USP Pyrantel Related Compound A RS in the System suitability solution (µg/mL) 

C_U = concentration of Pyrantel Pamoate in the Sample solution (µg/mL) 

Calculate the percentage of impurity B or any unspecified impurity in the portion of Pyrantel Pamoate taken: 

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × 100 

r_U = peak response of impurity B or any unspecified impurity from the Sample solution 

r_S = peak response of pyrantel from the Standard solution 

C_S = concentration of USP Pyrantel Pamoate RS in the Standard solution (µg/mL) 

C_U = concentration of Pyrantel Pamoate in the Sample solution (µg/mL) 

F = relative response factor (see Table 1)

Acceptance criteria: See Table 1. The reporting threshold is 0.05%. 

Table 1 

a For identification purposes only. 

b 1-Methyl-2-[(Z)-2-(thiophen-2-yl)ethenyl]-1,4,5,6-tetrahydropyrimidine. 

c (E)-N-[3-(Methylamino)propyl]-3-(thiophen-2-yl)prop-2-enamide. 

6 SPECIFIC TESTS 

Loss on Drying 〈731〉 

Analysis: Dry under vacuum at 60° for 3 h. 

Acceptance criteria: NMT 2.0% 

7 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in well-closed, light-resistant containers. 

USP Reference Standards 〈11〉 

USP Pamoic Acid RS C₂₃H₁₆O₆ 388.38 

USP Pyrantel 

USP Pyrantel Related Compound A RS 

(Z)-1-Methyl-2-[2-(2-thiophenyl)vinyl]-1,4,5,6-tetrahydropyrimidine 4,4’-methylenebis[3-hydroxy-2-naphthoate] (1:1). C₁₁H₁₄N₂S.C₂₃H₁₆O₆ 594.68