ABSORPTION Thiosulfate taken orally is not systemically absorbed. Most of the thiosulfate is oxidized to sulfate or is incorporated into endogenous sulphur compounds; a small proportion is excreted through the kidneys. ; After an intravenous injection of 1 g sodium thiosulfate in patients, the reported serum thiosulfate half-life was approximately 20 minutes. However, after an intravenous injection of a substantially higher dose of sodium thiosulfate (150 mg/kg, that is, 9 g for 60 kg body weight) in normal healthy men, the reported elimination half-life was 182 minutes.

MOA As antidote: Sodium thiosulfate acts as a sulfur donor for the endogenous sulfur transferase enzyme, rhodanese. It is used together with sodium nitrite for cyanide poisiong as antidote. Cyanide has a very high affinity for iron in the ferric state. It reacts with the trivalent (ferric) iron of mitochondrial cytochrome oxidase, thereby inhibiting cellular respiration, resulting in lactic acidosis and cytotoxic hypoxia. Sodium nitrite reacts with hemoglobin to form methemoglobin, which competes with cytochrome oxidase for the cyanide ion. Cyanide binds to methemoglobin to form cyanmethemoglobin and restore the activity of cytochrome oxidase. When cyanide dissociates from methemoglobin, sodium thiosulfate facilitates its conversion by rhodanese to thiocyanate, a less toxic ion. ; As antineoplastic adjunct: The mechanism of action of sodium thiosulfate is still not clear, but it is thought that it forms a complex with cisplastin via covalent bond, which renders cisplastin more readily eliminated from the kidneys. It was believed also that sodium thiosulfate plays a role in the protection from nephrotoxicity caused by cisplastin, through reducing delivery of cisplatin to the kidneys and by neutralizing cisplatin in the kidneys where sodium thiosulfate is highly concentrated.

INDICATION Indicated for sequential intravenous use with sodium nitrite for the treatment of acute cyanide poisoning that is judged to be life-threatening.

ROE Elimination is primarily renal, approximately 20-50% of exogenously administered thiosulfate is eliminated unchanged via the kidneys; Antidote (to cyanide poisoning): Primarily as thiocyanate.; Antineoplastic adjunct: As a nontoxic sodium thiosulfate/cisplatin complex.