Edition: BP 2025 (Ph. Eur. 11.6 update)
Aciclovir Cream
Action and use
Purine nucleoside analogue; antiviral (herpesviruses).
DEFINITION
Aciclovir Cream contains Aciclovir in a suitable basis.
The cream complies with the requirements stated under Topical Semi-solid Preparations and with the following requirements.
Content of aciclovir, C8H11N5O3
95.0 to 105.0% of the stated amount.
IDENTIFICATION
A. Shake a quantity of the well-mixed cream containing about 7.5 mg of Aciclovir with 50 mL of 0.5M sulfuric acid. Shake well with 50 mL of ethyl acetate, allow to separate and collect the clear lower aqueous layer. Wash the organic layer with 20 mL of 0.5M sulfuric acid and dilute the combined washings and the aqueous layer to 100 mL with 0.5M sulfuric acid. Mix well and filter (Whatman GF/F is suitable). Discard the first few mL of the filtrate and to 10 mL of the filtrate add sufficient water to produce 50 mL. The light absorption, Appendix II B, in the range 230 to 350 nm of the solution exhibits a maximum at 255 nm and a broad shoulder at about 274 nm.
B. In the Assay, the retention time of the principal peak in the chromatogram obtained with solution (1) is similar to that of the principal peak due to aciclovir in the chromatogram obtained with solution (2).
TESTS
Acidity or alkalinity
pH, 6.5 to 7.5, Appendix V L.
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
Solution A: 1 volume of dimethyl sulfoxide and 4 volumes of water.
(1) Mix with the aid of ultrasound a quantity of the well-mixed cream containing 25 mg of Aciclovir in 10 mL of dimethyl sulfoxide, dilute to 25 mL with solution A and filter through a 0.2-µm nylon filter.
(2) Dilute 1 volume of solution (1) to 100 volumes with solution A and dilute 1 volume of this solution to 5 volumes with solution A.
(3) Dissolve 5 mg of aciclovir for system suitability A EPCRS in 1 mL of dimethyl sulfoxide and dilute to 5 mL with water.
(4) Dissolve the contents of a vial of aciclovir for impurity C identification EPCRS in 200 µL of dimethyl sulfoxide and dilute to 1 mL with water. Prepare the solution immediately before use.
(5) Dissolve the contents of a vial of aciclovir for impurity G identification EPCRS in 1 mL of solution (3).
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (5 µm) (Supelcosil LC-18-DB is suitable).
(b) Use gradient elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 254 nm.
(f) Inject 10 µL of each solution.
MOBILE PHASE
Phosphate buffer solution pH 3.1: Dissolve 3.48 g of dipotassium hydrogen orthophosphate in 1000 mL of water and adjust to pH 3.1 with orthophosphoric acid.
Phosphate buffer solution pH 2.5: Dissolve 3.48 g of dipotassium hydrogen orthophosphate in 1000 mL of water and adjust to pH 2.5 with orthophosphoric acid.
Mobile phase A: 1 volume of acetonitrile and 99 volumes of phosphate buffer solution pH 3.1.
Mobile phase B: 50 volumes of acetonitrile and 50 volumes of phosphate buffer solution pH 2.5.
| Time (Minutes) | Mobile phase A (% v/v) | Mobile phase B (% v/v) | Comment |
| 0-5 | 100 | 0 | isocratic |
| 5-27 | 100→80 | 0→20 | linear gradient |
| 27-40 | 80 | 20 | isocratic |
| 40-46 | 80→100 | 20→0 | linear gradient |
SYSTEM SUITABILITY
The test is not valid unless:
In the chromatogram obtained with solution (4), the resolution between the peaks due to impurity C and aciclovir is at least 1.5.
In the chromatogram obtained with solution (5), the resolution between the peaks due to impurity K and impurity G is at least 1.5.
LIMITS
Identify any peak in solution (1) corresponding to impurity C using the chromatogram obtained with solution (4) and multiply the area of this peak by a correction factor of 2.2.
In the chromatogram obtained with solution (1):
the area of any peak corresponding to impurity B is not greater than 5 times the area of the principal peak in the chromatogram obtained with solution (2) (1.0%);
the area of any other secondary peak is not greater than the area of the principal peak in the chromatogram obtained with solution (2) (0.2%);
the sum of the areas of any secondary peaks is not greater than 10 times the area of the principal peak in the chromatogram obtained with solution (2) (2.0%).
Disregard any peak with an area less than 0.5 times the area of the principal peak in the chromatogram obtained with solution (2) (0.1%).
ASSAY
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
Solution A: 1 volume of dimethyl sulfoxide and 4 volumes of water.
(1) Mix with the aid of ultrasound a quantity of the well-mixed cream containing 25 mg of Aciclovir in 10 mL of dimethyl sulfoxide, dilute to 25 mL with solution A and filter through a 0.2-µm nylon filter. Further dilute 1 volume to 10 volumes with solution A.
(2) Dissolve 25 mg of aciclovir BPCRS in 10 mL of dimethyl sulfoxide. Dilute 2 volumes to 5 volumes with solution A and dilute 1 volume of this solution to 10 volumes with solution A.
(3) Dissolve the contents of a vial of aciclovir for impurity C identification EPCRS in 200 µL of dimethyl sulfoxide and dilute to 1 mL with water. Prepare the solution immediately before use.
Chromatographic conditions: The chromatographic conditions described under Related substances may be used.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution factor between the peaks due to impurity C and aciclovir is at least 1.5.
DETERMINATION OF CONTENT
Calculate the content of C8H11N5O3 in the cream using the declared content of C8H11N5O3 in aciclovir BPCRS.
IMPURITIES
The impurities limited by the requirements of this monograph include those listed under Aciclovir.
