Propylthiouracil Tablets

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

Propylthiouracil Tablets contain NLT 93.0% and NMT 107.0% of the labeled amount of propylthiouracil (C₇H₁₀N₂OS).

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

Sample: Boil a quantity of finely powdered Tablets equivalent to 100 mg of propylthiouracil with 10 mL of alcohol under a reflux condenser for 20 min. Filter while hot, and evaporate the filtrate on a steam bath to dryness. Use the residue.

Acceptance criteria: Meet the requirements

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 Procedure

Buffer: Transfer 3.40 g of monobasic potassium phosphate to a 1000-mL beaker. Add 500 mL of water, and stir until dissolved. Adjust with phosphoric acid or 0.1 N sodium hydroxide to a pH of 4.6, and add 500 mL of water. Adjust the resulting solution with phosphoric acid or 0.1 N sodium hydroxide to a pH of 4.6.

Mobile phase: Acetonitrile and Buffer (20:80)

Standard stock solution: 0.5 mg/mL of USP Propylthiouracil RS prepared as follows. Transfer 25 mg of USP Propylthiouracil RS to a 50-mL volumetric flask, add 5 mL of methanol, and sonicate for 5 min. Add 25 mL of water, and shake by mechanical means for 15 min. Dilute with water to volume.

Standard solution: 50 µg/mL of USP Propylthiouracil RS from the Standard stock solution in water

Sample stock solution: Nominally 0.5 mg/mL of propylthiouracil from Tablets prepared as follows. Finely powder NLT 20 Tablets. Transfer a portion of the powder, equivalent to 50 mg of propylthiouracil to a 100-mL volumetric flask, add 10 mL of methanol, and sonicate for 5 min. Add 50 mL of water, and shake by mechanical means for 20 min. Dilute with water to volume and pass through a suitable filter. Use the filtrate.

Sample solution: Nominally 50.0 µg/mL of propylthiouracil from the Sample stock solution in water

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 272 nm

Column: 4.6-mm × 10-cm; 5-µm packing L1

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

Suitability requirements

Column efficiency: NLT 3500 theoretical plates

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of propylthiouracil (C₇H₁₀N₂OS) in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of propylthiouracil from the Sample solution

r_S = peak response of propylthiouracil from the Standard solution

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

C_U = nominal concentration of propylthiouracil in the Sample solution (µg/mL)

Acceptance criteria: 93.0%–107.0%

4 PERFORMANCE TESTS

4.1 Dissolution 〈711〉

Medium: Water; 900 mL

Apparatus 1: 100 rpm

Time: 30 min

Standard solution: USP Propylthiouracil RS at a known concentration in Medium

Sample solution: Pass a portion of the solution under test through a suitable filter and dilute with Medium to a concentration that is similar to the Standard solution.

Instrumental conditions

Mode: UV

Analytical wavelength: Maximum absorbance at about 274 nm

Analysis

Samples: Standard solution and Sample solution

Determine the amount of propylthiouracil (C₇H₈N₂OS) dissolved from the UV absorbances.

Tolerances: NLT 85% (Q) of the labeled amount of propylthiouracil (C₇H₈N₂OS) is dissolved.

4.2 Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Propylthiouracil RS