cent of C5H4N4O, calculated with reference to the dried substance. Identification Test A may be omitted if tests

Assay. Weigh accurately about 0.25 g. add 25 ml of water and 25.0 ml of O I M sodium hydroxide and titrate O.1 M hydrochloric acid using 0.2 ml of dilute phenolphthaiein solution as indicator Each ml of 0.1 M sodium hydroxide is equivalent to 0.004502 g of carbxolic acid groups [COOH) ALLOPURlNOL AIlopurinol is a tautomeric mature of 1H-pyrazolo[3,4-d] poyrimidin-4-ol and 1.5-dihydro-4H-pyrazolo [3.4.d) pyrimdin -4-one Category Gout therapy Dose. Initially. 1.00 mg daily as a single dose gradually increased to 300 mg daily Usual maintenance dose, 200 to 400 mg daily, in divided doses in moderate and severe gout. Description White or almost white, crystalline powder Solubility Very slightly soluble in water and in ethanol (95%), practrically insoluble in chloroform and in ether it Is soluble in dilute solutions of alkali hydroxides Storage Store in well-closed containers STANDARDSAIlopurinoI contains not less than 98.0 per cent and not more than 101.0 per. cent of C5H4N4O, calculated with reference to the dried substance. Identification Test A may be omitted if tests B, C and D are earned out Tests B, C and D may be omitted if test A is earned out A The infra-red absorption spettnjm, Appendix 54, is concordant with the reference spectrum of allopurinol or with the spectrum obtained from allopurinol RS.B Dissolve 0.10 g in 10 ml of 0.1 M sodium hydroxide and add sufficient 0.1 M hydrochloric acid to produce 100 ml, dilute 10 ml to 100 ml with 0 IM hydrochloric acid and dilute 10 ml of this solution to 100 ml with 0.1 M hydrochloric acid The light absorption in me range 220 to 330 run of the resulting solution exhibits a maximum only at about 250 nm and a minimum at about 231 nm. ratio of the absorbance at the minimum at about 231 nm to that at the maximum at about 250 nm, 0.52 to 0.62, Appendix 5.5 C. Dissolve 50 mg in 5 ml of dilute sodium hydroxide solution, add 1 ml of alkaline potassium mercuriodide solution, heat to boiling and allow to stand, a flocculent yellow precipitate is produced. D :Shake about 1 g with 5 ml of dilute sodium hydroxide solution, add 3 ml of lithium and sodium moiybdophos photungstate solution and 5 ml of a 20% w/v solution of sodium carbonate, a grey-blue colour is produced Clarity, and colour of solution A 5.0% w/v solution In 2 M sodium hydroxide is -Clear. Appendix 6.1. and not more intensely coloured than reference solution YS6 or GYS4, Appendix 6.2 Heavy metals: Not more than 20 ppm. Appendix 3.12, determined by Method D on a solution prepared in me following manner. Take 1.0 g in a silica crucible. mix carefully with 4 ml of a 25% w/v solution of magnesium sulphate in IM sulphuric acid and heat cautiously to dryness Ignite the residue at a temperature not exceeding 800* and continue heating unit a white or greyish reside is obtained Allow to cool, moisten with 0.2 ml of IM sulphuric and, evaporate, ignite again and allow to cool The total ignition period should be less than 2 hours Dissolve the residue with two quantities, each of 5 ml, of 2M hydrochloric acid Add 2 drops of dilute phenolphthalein solution and strong ammonia solution dropwise until a pink colour is produced Cool, add glacial acetic acid until the solution gets decolorized and add a further 0.5 ml. Filter, if necessary, and dilute the solution to 20 ml with water Related substances Carry out the method for thin-layer chromatography. Appendix 4.6. using silica gel GF254 as the coating substance and a mixture of 60 volumes of 2-butanone. 20 volumes of 2-methoxyethanol and 20 volumes of strong ammonia solution as the mobile phase Apply separately to the plate 10 u of each of the following solutions in strong ammonia solution. Solution (1)is a 2.5% w/v solution of the substance being examined and solution (2) is a 0.0050% w/v solution of 5-aminopyrazole-4-carboxamide herosulphate RS. After removal of the plate, allow it to dry in a current of air and examine under ultra-violet light (254 nm). Any secondary spot in me chromatograrn obtained with solution (1) is not more Intense than the spot in the chromatogram obtained with solution (2)Sulphated ash: Not more than 0.1%, Appendix 3.22.Loss on drying Not more than 0.5%. determined on 1 g by drying in an oven at 105°, Appendix 8.6 Assay: Weigh accurately about 0.2 g, dissolve with gentle heating, if necessary, in 50 ml of dimethylformamide and carry out the Method A for non-aqueous nutrition. Appendix 345, using 0.1 M tetrabuty Iammonium hydroxide as the titrant and determining the end-point potentiometrically Each ml of 0.1 M tetrabutylammonium hydroxide is equivalent to 0.01361 g of C5H4N4OALLOPURINOL TABLETS Usual strengths 100 mg, 300 mg Storage Store in well-closed containers. STANDARDS Allopurinol Tablets contain not less than 92.5 percent and not more than 107.5 per cent of the stated amount of allopurinol, C5H4N4O Identification