Ondansetron Compounded Topical Gel

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

Ondansetron Compounded Topical Gel contains NLT 90.0% and NMT 110.0% of the labeled amount of ondansetron (C₁₈H₁₉N₃O).

Prepare Ondansetron Compounded Topical Gel, 20 mg/mL, as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

Ondansetron (as Ondansetron Hydrochloride) 200 mg (249.4 mg)

Propylene Glycol ▲3▲ (RB 1-Jun-2018) mL

Lipoderm,a a sufficient quantity to make 10 mL

a PCCA, Houston, TX.

Wet the Ondansetron Hydrochloride with the Propylene Glycol in a suitable container. Add the Lipoderm stepwise and quantitatively. Bring to final volume and mix well.

2 ASSAY

Procedure

Mobile phase: Dissolve 2.72 g of monobasic potassium phosphate in 750 mL of water and adjust to a pH of 6.0. Mix with 250 mL of acetonitrile.

Diluent: Methanol and water (50:50)

Standard solution: 0.1 mg/mL of ondansetron (free base) prepared from USP Ondansetron Hydrochloride RS in Diluent (approximately equal to 0.1247 mg/mL of ondansetron hydrochloride)

Sample solution: Fill a 1-mL syringe with Topical Gel and weigh. Transfer the sample to a 200-mL volumetric flask, add about 150 mL of Diluent, and sonicate until the gel has broken down. Dilute with Diluent to final volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 15-cm; 5-µm packing L1

Column temperature: 30°

Flow rate: 1.8 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

[Note—The retention time for ondansetron is about 5.3 min.]

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0% for replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of ondansetron (C₁₈H₁₉N₃O) in the portion of Topical Gel taken:

Result = (rᵤ / rₛ) × (Cₛ / Cᵤ) × 100

rᵤ = peak response of ondansetron from the Sample solution

rₛ = peak response of ondansetron from the Standard solution

Cₛ = concentration of ondansetron in the Standard solution (mg/mL)

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

Acceptance criteria: 90.0%–110.0%

3 ADDITIONAL REQUIREMENTS

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

Beyond-Use Date: NMT 90 days after the date on which it was compounded when stored at controlled room temperature.

Labeling: Label it to indicate that it is for external use only and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Ondansetron Hydrochloride RS