Probenecid

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

Probenecid contains NLT 98.0% and NMT 101.0% of probenecid (C₁₃H₁₉NO₄S), calculated on the dried basis.

2 IDENTIFICATION

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

B. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U

Sample solution: 20 µg/mL in alcohol

Analytical wavelength: 248 nm

Acceptance criteria: Absorptivities, calculated on the dried basis, differ by NMT 3.0%.

3 ASSAY

Change to read:

Procedure

Solution A: 1% glacial acetic acid in water

Solution B: 1% glacial acetic acid in acetonitrile

Buffer: 0.05 M monobasic sodium phosphate in Solution A. Adjust with phosphoric acid to a pH of 3.0.

Mobile phase: Solution B and Buffer (50:50)

Standard solution: 0.50 mg/mL of USP Probenecid RS in Mobile phase

Sample solution: 0.50 mg/mL of Probenecid in Mobile phase

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 3.9-mm × 30-cm; ▲5-µm▲ (USP 1-Aug-2022) packing L11

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.3

Relative standard deviation: NMT 1.5%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of probenecid (C₁₃H₁₉NO₄S) in the portion of Probenecid taken:

Result = (rᵤ / rₛ) × (Cₛ / Cᵤ) × 100

rᵤ = peak response ▲of probenecid▲ (USP 1-Aug-2022) from the Sample solution

rₛ = peak response ▲of probenecid▲ (USP 1-Aug-2022) from the Standard solution

Cₛ = concentration of USP Probenecid RS in the Standard solution (mg/mL)

Cᵤ = concentration of Probenecid in the Sample solution (mg/mL)

Acceptance criteria: 98.0%–101.0% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Delete the following:

▲Selenium 〈291〉

Sample: Mix 100 mg of Probenecid with 100 mg of magnesium oxide

Acceptance criteria: NMT 30 ppm▲ (USP 1-Aug-2022)

Organic Impurities

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

Analysis

Sample: Sample solution

Calculate the percentage of each impurity in the portion of Probenecid taken:

Result = (rᵢ / rₜ) × 100

rᵢ = peak response of each impurity from the Sample solution

rₜ = sum of the responses of all of the peaks from the Sample solution

Acceptance criteria

Individual impurities: NMT 0.5%

Total impurities: NMT 2.0%

5 SPECIFIC TESTS

Delete the following:

▲Melting Range or Temperature 〈741〉: 198°–200°▲ (USP 1-Aug-2022)

Acidity

Sample solution: 20 mg/mL of Probenecid in water prepared as follows. Transfer 2 g of Probenecid to a suitable container and add 100 mL of water. Heat on a steam bath for 30 min, cool, filter, and dilute with water to 100 mL.

Titrimetric system

Mode: Direct titration

Titrant: 0.10 N sodium hydroxide

Endpoint detection: Visual

Analysis: To 25.0 mL of the Sample solution, add 1 drop of phenolphthalein TS. Titrate with Titrant.

Acceptance criteria: NMT 0.50 mL is required to produce a pink color.

Loss on Drying 〈731〉

Analysis: Dry at 105° for 4 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Probenecid RS