Sodium Thiosulfate

Sodium Thiosulfate Injection is indicated for sequential use with sodium nitrite for the treatment of acute cyanide poisoning that is judged to be serious or life-threatening. When the diagnosis of cyanide poisoning is uncertain, the potential risks associated with Sodium Thiosulfate Injection should be carefully weighed against the potential benefits, especially if the patient is not in extremis. Sodium Thiosulfate Injection, an antidote, is indicated for sequential use with sodium nitrite for treatment of acute cyanide poisoning that is judged to be serious or life-threatening. ( 1 ) Use with caution if the diagnosis of cyanide poisoning is uncertain. ( 1 )

Sodium Thiosulfate Injection consists of: One vial of sodium thiosulfate injection USP 12.5 grams/50 mL (250 mg/mL) Administration of one vial constitutes a single dose. Sodium Thiosulfate Injection consists of: One vial of sodium thiosulfate injection USP 12.5 grams/50 mL (250 mg/mL) ( 3 )

None None. ( 4 )

Sulfites: Sodium thiosulfate may contain trace impurities of sodium sulfite ( 5.1 )

5.1 Sulfites Sodium thiosulfate drug product may contain trace impurities of sodium sulfite. The presence of a trace amount of sulfites in this product should not deter administration of the drug for treatment of emergency situations, even if the patient is sulfite-sensitive.

There have been no controlled clinical trials conducted to systematically assess the adverse events profile of sodium thiosulfate. The medical literature has reported the following adverse events in association with sodium thiosulfate administration. These adverse events were not reported in the context of controlled trials or with consistent monitoring and reporting methodologies for adverse events. Therefore, frequency of occurrence of these adverse events cannot be assessed. Cardiovascular system: hypotension Central nervous system: headache, disorientation Gastrointestinal system: nausea, vomiting Hematological : prolonged bleeding time Body as a Whole: salty taste in mouth, warm sensation over body In humans, rapid administration of concentrated solutions or solutions not freshly prepared, and administration of large doses of sodium thiosulfate have been associated with a higher incidence of nausea and vomiting. However, administration of 0.1 g sodium thiosulfate per pound up to a maximum of 15 g in a 10-15% solution over 10-15 minutes was associated with nausea and vomiting in 7 of 26 patients without concomitant cyanide intoxication. In a series of 11 human subjects, a single intravenous infusion of 50 mL of 50% sodium thiosulfate was associated with increases in clotting time 1-3 days after administration. However, no significant changes were observed in other hematological parameters. Most common adverse reactions are: Hypotension, headache, disorientation ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Hope Pharmaceuticals at 1-800-755-9595 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

Formal drug interaction studies have not been conducted with Sodium Thiosulfate Injection.

Lactation : Breastfeeding not recommended. ( 8.2 ) Renal impairment : Sodium thiosulfate is substantially excreted by the kidney. The risk of toxic reactions to this drug may be greater in patients with impaired renal function. ( 8.6 ).

8.1 Pregnancy Risk Summary There are no available data on Sodium Thiosulfate Injection use in pregnant women to establish a drug-associated risk for major birth defects, miscarriage, or adverse maternal or fetal outcomes. There are risks to the pregnant woman and fetus associated with untreated cyanide poisoning (see Clinical Considerations ). Therefore, if a pregnant woman has known or suspected cyanide poisoning, Sodium Thiosulfate Injection for sequential use with sodium nitrite is recommended [see Indications and Usage (1) ] . In published animal studies, no evidence of embryotoxicity or malformations was reported when sodium thiosulfate was administered during organogenesis to pregnant mice, rats, hamsters, or rats at 0.2 to 0.9 times the human daily dose of 12.5 g for cyanide poisoning. The studies did not test doses that were comparable to the human dose for cyanide poisoning (see Data ). The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the US general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Clinical Considerations Disease-associated maternal and/or embryo/fetal risk Cyanide readily crosses the placenta. Cyanide poisoning is a medical emergency in pregnancy, which can be fatal for the pregnant woman and fetus if left untreated. Life-sustaining therapy should not be withheld due to pregnancy. Data Animal Data: No malformations or evidence of embryo-fetal toxicity were noted when pregnant mice, rats, hamsters, or rabbits were administered oral doses of sodium thiosulfate of up to 550, 400, 400, or 580 mg/kg, respectively during organogenesis (0.2, 0.3, 0.26, and 0.9 times the human dose of 12.5 g/60 kg person for cyanide poisoning based on body surface area). Published studies suggest that treatment with sodium thiosulfate ameliorates the teratogenic effects of maternal cyanide poisoning in hamsters.

8.2 Lactation Risk Summary There are no data on the presence of sodium thiosulfate in human or animal milk, the effects on the breastfed infant, or the effects on milk production. Cyanide and thiocyanate (which is formed when sodium thiosulfate combines with cyanide) are present in human milk. Because of the potential for serious adverse reactions in the breastfed infant, breastfeeding is not recommended during treatment with Sodium Thiosulfate Injection. There are no data to determine when breastfeeding may be safely restarted following the administration of Sodium Thiosulfate Injection.

8.4 Pediatric Use There are case reports in the medical literature of sodium nitrite in conjunction with sodium thiosulfate being administered to pediatric patients with cyanide poisoning; however, there have been no clinical studies to evaluate the safety or efficacy of sodium thiosulfate in the pediatric population. As for adult patients, dosing recommendations for pediatric patients have been based on theoretical calculations of antidote detoxifying potential, extrapolation from animal experiments, and a small number of human case reports.

8.5 Geriatric Use Sodium thiosulfate is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

8.6 Renal Disease Sodium thiosulfate is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

Exposure to a high dose of cyanide can result in death within minutes due to the inhibition of cytochrome oxidase resulting in arrest of cellular respiration. Specifically, cyanide binds rapidly with cytochrome a3, a component of the cytochrome c oxidase complex in mitochondria. Inhibition of cytochrome a3 prevents the cell from using oxygen and forces anaerobic metabolism, resulting in lactate production, cellular hypoxia and metabolic acidosis. In massive acute cyanide poisoning, the mechanism of toxicity may involve other enzyme systems as well. The synergy resulting from treatment of cyanide poisoning with the combination of sodium nitrite and sodium thiosulfate is the result of differences in their primary mechanisms of action as antidotes for cyanide poisoning. Sodium Nitrite Sodium nitrite is thought to exert its therapeutic effect by reacting with hemoglobin to form methemoglobin, an oxidized form of hemoglobin incapable of oxygen transport but with high affinity for cyanide. Cyanide preferentially binds to methemoglobin over cytochrome a 3 , forming the nontoxic cyanomethemoglobin. Methemoglobin displaces cyanide from cytochrome oxidase, allowing resumption of aerobic metabolism. The chemical reaction is as follows: NaNO 2 + Hemoglobin → Methemoglobin HCN + Methemoglobin → Cyanomethemoglobin Vasodilation has also been cited to account for at least part of the therapeutic effect of sodium nitrite. It has been suggested that sodium nitrite-induced methemoglobinemia may be more efficacious against cyanide poisoning than comparable levels of methemoglobinemia induced by other oxidants. Also, sodium nitrite appears to retain some efficacy even when the formation of methemoglobin is inhibited by methylene blue. Sodium Thiosulfate The primary route of endogenous cyanide detoxification is by enzymatic transulfuration to thiocyanate (SCN – ), which is relatively nontoxic and readily excreted in the urine. Sodium thiosulfate is thought to serve as a sulfur donor in the reaction catalyzed by the enzyme rhodanese, thus enhancing the endogenous detoxification of cyanide in the following chemical reaction: Rhodanese Na 2 S 2 O 3 + CN – → SCN – + Na 2 SO 3 .