Acyclovir Ointment

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

https://trungtamthuoc.com/pdf/acyclovir-ointment-usp-ttt.pdf

1 DEFINITION

Acyclovir Ointment contains NLT 90.0% and NMT 110.0% of the labeled amount of acyclovir (C₈H₁₁N₅O₃), in a suitable ointment base.

2 IDENTIFICATION

A. 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

Mobile phase: 0.02 M acetic acid

System suitability solution A: 0.1 mg/mL each of USP Acyclovir RS and guanine in 0.1 N sodium hydroxide

System suitability solution B: 2.0 μg/mL of guanine in 0.1 N sodium hydroxide

Standard solution: 0.1 mg/mL of USP Acyclovir RS in 0.1 N sodium hydroxide

Sample solution: Nominally 0.1 mg/mL of acyclovir prepared as follows. Transfer an amount of Ointment, equivalent to 10 mg of acyclovir, to a 100-mL volumetric flask. Dissolve in and dilute with 0.1 N sodium hydroxide to volume.

3.2 Chromatographic system

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 3 mL/min

Injection volume: 20 μL

3.3 System suitability

Samples: System suitability solution A and System suitability solution B

[Note - The relative retention times for guanine and acyclovir are about 0.6 and 1.0, respectively, in System suitability solution A.]

3.4 Suitability requirements

Resolution: NLT 2.0 between guanine and acyclovir, System suitability solution A

Relative standard deviation: NMT 2.0% for the acyclovir peak, System suitability solution A; NMT 2.0%, System suitability solution B

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of acyclovir (C₈H₁₁N₅O₃) in the portion of Ointment taken:

Result = (r_u/r_s ) × (C_S/C_u) × 100

r_u = peak response from the Sample solution

r_s = peak response from the Standard solution

C_u = concentration of USP Acyclovir RS in the Standard solution (mg/mL)

C_s = nominal concentration of acyclovir in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Minimum Fill 〈755〉: Meets the requirements

5 IMPURITIES

Limit of Guanine

Mobile phase, Sample solution, and Chromatographic system: Proceed as directed in the Assay.

Standard solution: 2.0 μg/mL of guanine in 0.1 M sodium hydroxide

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of guanine in the portion of Ointment taken:

Result = (r_u/r_s ) × (C_S/C_u) × 100

r_u = peak response of guanine from the Sample solution

r_s  = peak response of guanine from the Standard solution

C_S = concentration of guanine in the Standard solution (mg/mL)

C_u = nominal concentration of acyclovir in the Sample solution (mg/mL)

Acceptance criteria: NMT 2.0%

6 SPECIFIC TESTS

Microbial Enumeration Tests 〈61〉andTests for Specified Microorganisms 〈62〉: It meets the requirements of the tests for the absence of Staphylococcus aureus and Pseudomonas aeruginosa.

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. Store between 15° and 25° in a dry place.

SP Reference Standards 〈11〉

USP Acyclovir RS