Action and use
Nucleoside reverse transcriptase inhibitor; antiviral (HIV).
Preparations
Zidovudine Capsules
Zidovudine Tablets
Zidovudine and Lamivudine Tablets
Ph Eur
DEFINITION
1-(3-Azido-2,3-dideoxy-b-D-erythro-pentofuranosyl)-5-methylpyrimidine-2,4(1H,3H)- dione.
Content
97.0 per cent to 102.0 per cent (dried substance).
CHARACTERS
Appearance
White or brownish powder.
Solubility
Sparingly soluble in water, soluble in anhydrous ethanol.
mp
About 124 °C.
It shows polymorphism (5.9).
IDENTIFICATION
Infrared absorption spectrophotometry (2.2.24).
Comparison zidovudine CRS.
If the spectra obtained in the solid state show differences, dissolve the substance to be examined and the reference substance separately in the minimum volume of water R, evaporate to dryness in a desiccator, under high vacuum over diphosphorus pentoxide R and record new spectra using the residues.
TESTS
Appearance of solution
The solution is not more intensely coloured than reference solution BY5 (2.2.2, Method II).
Dissolve 0.5 g in 50 mL of water R, heating if necessary.
Specific optical rotation (2.2.7)
+ 60.5 to + 63.0 (dried substance).
Dissolve 0.50 g in anhydrous ethanol R and dilute to 50.0 mL with the same solvent. Carry out the determination at 25 °C.
Related substances
A. Thin-layer chromatography (2.2.27).
Test solution Dissolve 0.20 g of the substance to be examined in methanol R and dilute to 10 mL with the same solvent.
Reference solution (a) Dissolve 5 mg of thymine R (impurity C), 5 mg of zidovudine impurity A CRS and 5 mg of triphenylmethanol R (impurity D) in methanol R, add 0.25 mL of the test solution and dilute to 25 mL with methanol R.
Reference solution (b) Dilute 5.0 mL of reference solution (a) to 10 mL with methanol R.
Plate TLC silica gel F254 plate R.
Mobile phase methanol R, methylene chloride R (10:90 V/V).
Application 10 µL.
Development Over a path of 12 cm.
Drying In air.
Detection A Examine in ultraviolet light at 254 nm.
Limits:
— impurity A: any spot due to impurity A is not more intense than the corresponding spot in the chromatogram obtained with reference solution (b) (0.5 per cent);
— any other impurity: any other spot apart from the principal spot and any spot due to impurity C (which is limited by liquid chromatography) is not more intense than the spot due to zidovudine in the chromatogram obtained with reference solution (b) (0.5 per cent).
Detection B Spray with a 10 g/L solution of vanillin R in sulfuric acid R.
Limit:
— impurity D: any spot due to impurity D is not more intense than the corresponding spot in the chromatogram obtained with reference solution (b) (0.5 per cent).
System suitability Reference solution (a):
— the chromatogram shows 4 clearly separated spots, due to impurity C, impurity A, zidovudine and impurity D, in order of increasing RF value.
B. Liquid chromatography (2.2.29).
Test solution (a) Dissolve 50.0 mg of the substance to be examined in the mobile phase and dilute to 50.0 mL with the mobile phase.
Test solution (b) Dilute 10.0 mL of test solution (a) to 50.0 mL with the mobile phase.
Reference solution (a) Dissolve 10.0 mg of zidovudine CRS in the mobile phase and dilute to 50.0 mL with the mobile phase.
Reference solution (b) Dissolve 10.0 mg of thymine R (impurity C) in methanol R and dilute to 50.0 mL with the same solvent. Dilute 5.0 mL of this solution to 50.0 mL with the mobile phase.
Reference solution (c) Dissolve 5 mg of zidovudine impurity B CRS in 25.0 mL of reference solution (a) and dilute to 50.0 mL with the mobile phase.
Reference solution (d) Dilute 5.0 mL of reference solution (c) to 50.0 mL with the mobile phase.
Reference solution (e) Dilute 0.25 mL of test solution (a) to 50.0 mL with the mobile phase.
Column:
— size: l = 0.25 m, Ø = 4.6 mm;
— stationary phase: octadecylsilyl silica gel for chromatography R (5 µm).
Mobile phase methanol R, water R (20:80 V/V).
Flow rate 1.2 mL/min.
Detection Spectrophotometer at 265 nm.
Equilibration With the mobile phase for about 45 min.
Injection 10 µL of test solution (a) and reference solutions (b), (c), (d) and (e).
Run time 1.5 times the retention time of zidovudine.
Elution order Impurity C, zidovudine, impurity B.
System suitability Reference solution (c):
— resolution: minimum 1.5 between the peaks due to zidovudine and impurity B.
Limits:
— impurity C: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (b) (2 per cent);
— impurity B: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (d) (1 per cent);
— any other impurity: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (e) (0.5 per cent);
— total: not more than 6 times the area of the principal peak in the chromatogram obtained with reference solution (e) (3.0 per cent);
— disregard limit: 0.1 times the area of the principal peak in the chromatogram obtained with reference solution (e) (0.05 per cent).
Heavy metals (2.4.8)
Maximum 20 ppm.
1.00 g complies with test D. Prepare the reference solution using 2 mL of lead standard solution (10 ppm Pb) R.
Loss on drying (2.2.32)
Maximum 1.0 per cent, determined on 1.000 g by drying in an oven at 105 °C.
Sulfated ash (2.4.14)
Maximum 0.25 per cent, determined on 1.00 g.
ASSAY
Liquid chromatography (2.2.29) as described in the test for related substances with the following modification.
Injection Test solution (b) and reference solution (a).
Calculate the content of C10H13N5O4 from the declared content of zidovudine CRS.
STORAGE
Protected from light.