Vigabatrin Tablets
Action and use
Antiepileptic.
Definition
Vigabatrin Tablets contain Vigabatrin.
Content of vigabatrin, C6H11NO2
95.0 to 105.0% of the stated amount.
Identification
To a quantity of the powdered tablets containing 0.5 g of Vigabatrin add 10 mL of water, shake and filter through a 0.7 µm filter (Whatman GF/F is suitable). To 0.2 mL of the filtrate add 5 mL of acetone and allow the solvent to evaporate in a current of nitrogen. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of vigabatrin (RS 360).
Tests
5-Vinyl-2-pyrrolidone
In the Assay, the area of any peak corresponding to 5-vinyl-2-pyrrolidone in the chromatogram obtained with solution (1) is not greater than the area of the peak in the chromatogram obtained with solution (3) (0.5%).
Assay
Carry out the method for liquid chromatography, Appendix III D, injecting 20 µL of each of the following solutions. For solution (1) add 800 mL of the mobile phase to 10 whole tablets, stir vigorously until all of the tablets are uniformLy dispersed into fine particles, add sufficient of the mobile phase to produce 1000 mL, mix well and filter through a 0.2 µm nylon-66 filter. Dilute 10 mL of the filtrate to 50 mL with the mobile phase. Solution (2) contains 0.10% w/v of vigabatrin BPCRS in the mobile phase. Solution (3) contains 0.0005% w/v of 5-vinyl-2-pyrrolidone BPCRS in the mobile phase. Solution (4) contains 0.0005% w/v of 5-vinyl-2-pyrrolidone BPCRS, 0.1% w/v of povidone and 0.1% w/v of vigabatrin BPCRS in the mobile phase.
The chromatographic procedure may be carried out using (a) a stainless steel column (25 cm × 4.6 mm) packed with cation exchange resin (10 µm) (Whatman Partisil SCX is suitable), (b) as the mobile phase with a flow rate of 1.5 mL per minute, a mixture of 4 volumes of acetonitrile, 40 volumes of methanol and 1000 volumes of a 0.34% w/v solution of potassium dihydrogen orthophosphate, adjusting the pH to 2.8 with orthophosphoric acid and (c) a detection wavelength of 210 nm.
In the chromatogram obtained with solution (4), the retention times are about 4 minutes for povidone, about 5 minutes for 5-vinyl-2-pyrrolidone and about 8 minutes for vigabatrin. The test is not valid unless the resolution factor between the peaks corresponding to 5-vinyl-2-pyrrolidone and vigabatrin in the chromatogram obtained with solution (4) is at least 1.5 and the resolution factor between the peaks corresponding to povidone and 5-vinyl-2-pyrrolidone is at least 1.5.
Calculate the percentage content of C6H11NO2 in the tablets from the areas of the peaks for vigabatrin in the chromatograms obtained with solutions (1) and (2) and from the declared content of C6H11NO2 in vigabatrin BPCRS.