Monographs: Pharmaceutical substances: Sodium stibogluconate (Natrii stibogluconas)
Chemical name. D-Gluconic acid cyclic ester with antimonic acid (H8Sb2O9) (2:1), trisodium salt, nonahydrate; 2,4:2',4'-O-(oxydistibylidyne)bis-D-gluconic acid, Sb,Sb'-dioxide, trisodium salt, nonahydrate; CAS Reg. No. 16037-91-5.
Description. A colourless, mostly amorphous powder; odourless.
Solubility. Very soluble in water; practically insoluble in ethanol (~750 g/l) TS and ether R.
Category. Antileishmaniasis drug.
Storage. Sodium stibogluconate should be kept in a well-closed container.
Definition. Sodium stibogluconate is a pentavalent antimony compound of indefinite composition. It has been represented by the formula C6H9Na2O9Sb, but it usually contains less than 2 atoms of sodium for each atom of antimony.
Sodium stibogluconate contains not less than 30.0% and not more than 34.0% of total antimony, calculated with reference to the dried substance.
C. A 10 mg/mL solution is dextrorotatory.
Chlorides. Dissolve 2.5 g in a mixture of 50 mL of water, 2 mL of nitric acid (~130 g/l) TS, and 75 mL of acetate buffer, pH 5.0, TS. Titrate with silver nitrate (0.1 mol/l) VS, determining the end-point potentiometrically; not more than 3.0 mL of silver nitrate (0.1 mol/l) VS are required.
Loss on drying. Dry to constant weight at 130°C under reduced pressure (not exceeding 0.6 kPa or about 5 mm of mercury); it loses not more than 150 mg/g.
Colour and pH value. Dissolve 0.3 g in 10 mL of water and heat the solution in an autoclave under reduced pressure (about 70 kPa) for 30 minutes; the solution is colourless or almost colourless and has a pH between 5.0 and 5.6.
Trivalent antimony. Dissolve 2.0 g in 30 mL of water, add 15 mL of hydrochloric acid (~250 g/l) TS, and titrate with potassium bromate (0.00833 mol/l) VS using methyl/orange TS as indicator; not more than 1.3 mL of potassium bromate (0.00833 mol/l) VS are required.
Assay. Place about 0.25 g, accurately weighed, in a 300-mL long-necked flask, add 10 mL of nitric acid (~1000 g/l) TS and 5 mL of sulfuric acid (~1760 g/l) TS, and heat cautiously over a small flame, keeping the liquid in motion by rotating the flask; remove the flask from the flame at the onset of the first vigorous reaction until this subsides. Continue to heat until white fumes are evolved and allow the liquid to cool. Add 1 mL of nitric acid (~1000 g/l) TS and again heat until white fumes are evolved. Add 1 g of ammonium sulfate R, again heat to the point of fuming, cool thoroughly, and add 1 g of tartaric acid R and 60 mL of water. To the clear, almost colourless solution add 1 g of potassium iodide R and boil the solution gently for about 5 minutes or until free iodine is expelled, the liquid becoming pure yellow in colour. Cool, add sodium hydroxide (~400 g/l) TS until just alkaline (about 15 mL), cool again, acidify with sulfuric acid (~100 g/l) TS until just acid, add an excess of sodium hydrogen carbonate R, and titrate with iodine (0.02 mol/l) VS, using starch TS as indicator if necessary. Each mL of iodine (0.02 mol/l) VS is equivalent to 2.435 mg of total antimony.