Acyclovir Capsules

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

Acyclovir Capsules contain NLT 93.0% and NMT 107.0% of the labeled amount of acyclovir (C₈H₁₁N₅O₃).

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. Dissolve in 0.1 N sodium hydroxide, and dilute with water.

System suitability solution B: 2.0 μg/mL of guanine. Dissolve in 0.1 N sodium hydroxide, and dilute with water.

Standard solution: 0.1 mg/mL of USP Acyclovir RS. Dissolve in 0.1 N sodium hydroxide, and dilute with water.

Sample solution: Nominally 0.1 mg/mL of acyclovir prepared as follows. Transfer the contents of Capsules equivalent to 10 mg of acyclovir (NLT 10 Capsules) to a 100-mL volumetric flask. Dissolve in 10 mL of 0.1 N sodium hydroxide, dilute to volume with water, and filter.

3.2 Chromatographic system

Mode: LC

Detector: UV 254 nm

Column: 4.2-mm × 25-cm; packing L1

Flow rate: 1.5 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

Relative standard deviation: NMT 2.0%, System suitability solution B

Analysis: Standard solution and Sample solution

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

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of the Sample solution

r_s = peak response of the Standard solution

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

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

Acceptance criteria: 93.0%–107.0%

4 PERFORMANCE TESTS

4.1 Dissolution 〈711〉

Medium: 0.1 N hydrochloric acid; 900 mL

Apparatus 1: 100 rpm

Time: 45 min

Detector: UV 254 nm

Standard solution: USP Acyclovir RS in Medium

Sample solutions: Dilute with Medium to a concentration that is similar to the Standard solution.

Analysis: Determine the amount of acyclovir (C₈H₁₁N₅O₃) dissolved from UV absorption at the wavelength of maximum absorption on filtered portions of the solution under test.

Tolerances: NLT 75% (Q) of the labeled amount of acyclovir (C₈H₁₁N₅O₃) is dissolved.

4.2 Uniformity of Dosage Units 〈905〉

Meet the requirements for Content Uniformity

5 IMPURITIES

5.1 Procedure

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

Analysis: Sample solution

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

Result = (r_u/r_T) × 100

r_u = peak response for each impurity

r_T = sum of the responses for all of the peaks

Acceptance criteria

Guanine: NMT 2.0%

Any individual impurity: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. Store between 15° and 25°. Protect from light and moisture.

USP Reference Standards 〈11〉

USP Acyclovir RS