Food additives Europe numbers;E539
Functional Category
Antioxidant.
Applications in Pharmaceutical Formulation
Sodium thiosulfate is used as an antioxidant in pharmaceuticals (ophthalmic, intravenous, and oral preparations). It has also been used for its antifungal properties(1) and as a reagent in analytical chemistry.
Description
Sodium thiosulfate occurs as odorless and colorless crystals, a crystalline powder or granules. It is efflorescent in dry air and deliquescent in moist air.
Stability and Storage Conditions
Sodium thiosulfate decomposes on heating. The bulk powder should be stored in a cool place, and the container should be kept tightly closed in a dry and well-ventilated place. It should not be stored near acids.
Incompatibilities
Sodium thiosulfate is incompatible with iodine, with acids, and with lead, mercury, and silver salts. It may reduce the activity of some preservatives, including bronopol, phenylmercuric salts, and thimerosal.
Safety
Sodium thiosulfate is used in ophthalmic, intravenous, and oral pharmaceutical preparations. Apart from osmotic disturbances, sodium thiosulfate is relatively nontoxic. It is moderately toxic by SEM 1: Excipient: sodium thiosulfate; magnification: 100; voltage: 10 kV. Table I: Pharmacopeial specifications for sodium thiosulfate. Test JP XV PhEur 6.0 USP32–NF27 Identification þþþ Characters — þ — pH 6.0–8.0 6.0–8.4 — Appearance of solution þ þ — Water — — 32.0–37% Calcium þ — þ Heavy metals 420 ppm 410 ppm 40.002% Arsenic 45 ppm — — Loss on drying þ — — Sulfides — þ — Sulfates and sulfites — 40.2% — Assay (dried basis) 99.0–101.0% 99.0–101.0% 99.0–100.5% S 671 the subcutaneous route and mildly irritating to respiratory tract and skin. Large oral doses have a cathartic action.(1) LD50 (IP, mouse) 5.6 g/kg(4) LD50 (IV, mouse) 2.4 g/kg