Rifampin Compounded Oral Suspension

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

Rifampin Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of rifampin (C₄₃H₅₈N₄O₁₂).

Prepare Rifampin Compounded Oral Suspension 10 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

Empty the required number of capsules into a suitable mortar, or use Rifampin powder. If necessary, gently crush the capsule contents with a pestle to produce a fine powder. Add 2 mL of Syrup to the mortar, and triturate until a smooth paste is formed. Add 10 mL of Syrup, and triturate to form a suspension. Continue to add Syrup until 80 mL has been added. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add Syrup in portions to rinse the mortar, and add the rinses to the bottle. If necessary, add Citric Acid or Sodium Citrate to adjust to a pH of 5.0. Add a suitable flavor if desired. Add sufficient Syrup to bring the preparation to final volume. Shake vigorously.

2 ASSAY

2.1 Procedure

Solution A: 1.0 M monobasic potassium phosphate containing 6.3 mL/L of phosphoric acid

Solution B: Acetonitrile, 1.0 M dibasic potassium phosphate, 1.0 M monobasic potassium phosphate, 1.0 M citric acid, and water (25:7.7:2.3:1:64)

Mobile phase: Acetonitrile, Solution A, 1.0 M citric acid, 0.5 M sodium perchlorate, and water (36:10:2:2:50). Pass through a suitable filter of 0.7-µm or finer pore size, and degas.

Diluent: Acetonitrile and water (50:50)

System suitability solution: 0.1 mg/mL of USP Rifampin RS and 0.1 mg/mL of USP Rifampin Quinone RS in acetonitrile. Transfer 1.0 mL of the solution into a 10-mL volumetric flask, and dilute with Solution B to volume.

Standard solution: 0.5 mg/mL of USP Rifampin RS in Diluent. If necessary, sonicate for 30 s to dissolve. Transfer 5.0 mL of the solution to a 50-mL, low-actinic volumetric flask, and dilute with Diluent to volume. Use the solution within 1 h.

Sample solution: Transfer 5.0 mL of Oral Suspension, freshly mixed and free of air bubbles, to a 100-mL, low-actinic volumetric flask, and dissolve in and dilute with Diluent to volume. Transfer 5.0 mL of the resulting solution to a 50-mL, low-actinic volumetric flask, and dilute with Diluent to volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 10-cm; 5-µm packing L7

Injection volume: 20 µL

System suitability

Samples: System suitability solution and Standard solution

[Note—The relative retention times for rifampin quinone and rifampin are about 0.6 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 4.0 between rifampin quinone and rifampin, System suitability solution

Relative standard deviation: NMT 1.0% for replicate injections, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of rifampin (C₄₃H₅₈N₄O₁₂) in the portion of Oral Suspension taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak area from the Sample solution

r_S = peak area from the Standard solution

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

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

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

pH 〈791〉: 4.5–5.5

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in a tight, light-resistant container. Store at controlled room temperature.

Beyond-Use Date: NMT 30 days after the date on which it was compounded when stored at controlled room temperature

Labeling: Label it to state that it is to be well shaken and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Rifampin RS

USP Rifampin Quinone RS