Estriol Compounded Vaginal Cream

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

Estriol Compounded Vaginal Cream contains NLT 90.0% and NMT 110.0% of the labeled amount of estriol (C₁₈H₂₄O₃). Prepare Estriol Compounded Vaginal Cream, 0.5 mg/g (0.05%), as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

^a PCCA, Houston, TX.

Wet the Estriol with the Propylene Glycol in a suitable container and mix until smooth and homogenous. Add the Emollient Cream Base by geometric dilution until final weight is achieved. Mix after each addition of the Emollient Cream Base.

2 ASSAY

Procedure

Solution A: 25 mM monobasic potassium phosphate

Solution B: Acetonitrile and methanol (50:50)

Mobile phase: See Table 1.

Table 1

Diluent: Methanol and water (80:20)

Standard stock solution: Transfer about 20 mg of USP Estriol RS to a 250-mL volumetric flask and dilute with Diluent to final volume.

Standard solution: 0.005 mg/mL of estriol prepared from Standard stock solution and Diluent

Sample solution: Weigh about 3 mL of Vaginal Cream and transfer into a 100-mL volumetric flask, add about 5 mL of chloroform, and sonicate until the cream is broken down. Dilute with Diluent to final volume and pass through a filter of 0.45-μm pore size.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 230 nm

Column: 4.6-mm × 15-cm; 3-μm packing L11

Column temperature: 60°

Flow rate: 1.0 mL/min

Injection volume: 20 μL

System suitability

Sample: Standard solution

[Note—The retention time for estriol is about 17.2 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 estriol (C₁₈H₂₄O₃) in the portion of Vaginal Cream taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of estriol from the Sample solution

r_S = peak response of estriol from the Standard solution

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

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

Acceptance criteria: 90.0%–110.0%

3 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in a tight, light-resistant suitable calibrated 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 vaginal use only, and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Estriol RS (USP 1-Aug-2019)