Source: Health Products and Food Branch (CA) Revision Year: 2014
Seacalphyx (Sodium thiosulfate pentahydrate injection BP), is indicated for sequential use with sodium nitrite for the treatment of acute cyanide poisoning that is judged to be life-threatening. When the diagnosis of cyanide poisoning is uncertain, the potential risks associated with Seacalphyx, should be carefully weighed against the potential benefits, especially if the patient is not in extremis.
Cyanide poisoning may result from inhalation, ingestion, or dermal exposure to various cyanide containing compounds, including smoke from closed-space fires. Sources of cyanide poisoning include hydrogen cyanide and its salts, cyanogenic plants, aliphatic nitriles, and prolonged exposure to sodium nitroprusside.
The presence and extent of cyanide poisoning are often initially unknown. There is no widely available, rapid, confirmatory cyanide blood test. Treatment decisions must be made on the basis of clinical history and signs and symptoms of cyanide intoxication. If clinical suspicion of cyanide poisoning is high, sodium thiosulfate pentahydrate injection and Sodium Nitrite Injection should be administered without delay.
Common Signs and Symptoms of Cyanide Poisoning:
Symptoms:
Signs:
In some settings, panic symptoms including tachypnea and vomiting may mimic early cyanide poisoning signs. The presence of altered mental status (e.g., confusion and disorientation) and/or mydriasis is suggestive of true cyanide poisoning although these signs can occur with other toxic exposures as well.
The expert advice of a provincial poison control center may be obtained. Details can be found at this website: http://www.safetyxchange.org/health-safety/canadian-poison-control-centres-contact-information
Not all smoke inhalation victims will have cyanide poisoning and may present with burns, trauma, and exposure to other toxic substances making a diagnosis of cyanide poisoning particularly difficult. Prior to administration of sodium thiosulfate pentahydrate injection, smoke-inhalation victims should be assessed for the following:
Although hypotension is highly suggestive of cyanide poisoning, it is only present in a small percentage of cyanide-poisoned smoke inhalation victims. Also indicative of cyanide poisoning is a plasma lactate concentration greater than or equal to 10 mmol/L (a value higher than that typically listed in the table of signs and symptoms of isolated cyanide poisoning because carbon monoxide associated with smoke inhalation also contributes to lactic acidemia). If cyanide poisoning is suspected, treatment should not be delayed to obtain a plasma lactate concentration.
Comprehensive treatment of acute cyanide intoxication requires support of vital functions. Administration of sodium nitrite and sodium thiosulfate should be considered adjunctive to appropriate supportive therapies. Airway, ventilatory and circulatory support, and oxygen administration should not be delayed to administer sodium nitrite and sodium thiosulfate.
| Population | Intravenous Dose of Sodium thiosulfate and Sodium Nitrite |
|---|---|
| Adults (>18 years of age) | 1.) Sodium Nitrite -10 mL of sodium nitrite at the rate of 2.5 to 5 mL/minute. 2.) Sodium thiosulfate, -50 mL of sodium thiosulfate immediately following administration of sodium nitrite. |
| Children (<18 years of age) | 1.) Sodium Nitrite -0.2 mL/kg (6 mg/kg or 6-8 mL/m² BSA) of sodium nitrite at the rate of 2.5 to 5 mL/minute not to exceed 10 mL 2.) Sodium thiosulfate -1 mL/kg of body weight (250 mg/kg or approximately 30-40 mL/m² of BSA) not to exceed 50 mL total dose immediately following administration of sodium nitrite. |
NOTE: If signs of poisoning reappear, repeat treatment using one-half the original dose of both sodium nitrite and sodium thiosulfate.
In adult and pediatric patients with known anemia, it is recommended that the dosage of sodium nitrite should be reduced proportionately to the hemoglobin concentration.
Sodium nitrite injection and sodium thiosulfate pentahydrate injection are administered by slow intravenous injection. They should be given as early as possible after a diagnosis of acute life-threatening cyanide poisoning has been established. Sodium nitrite should be administered first, followed immediately by sodium thiosulfate. Blood pressure must be monitored during infusion in both adults and children. The rate of infusion should be decreased if significant hypotension is noted.
All parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
Chemical incompatibility has been reported between sodium thiosulfate pentahydrate injection and hydroxocobalamin and these drugs should not be administered simultaneously through the same IV line. No chemical incompatibility has been reported between sodium thiosulfate and sodium nitrite, when administered sequentially through the same IV line as described in Dosage and Administration.
There is limited information about the effects of large doses of sodium thiosulfate in humans. Oral administration of 3 g sodium thiosulfate per day for 1-2 weeks in humans resulted in reductions in room air arterial oxygen saturation to as low as 75%, which was due to a rightward shift in the oxygen hemoglobin dissociation curve. The subjects returned to baseline oxygen saturations 1 week after discontinuation of sodium thiosulfate. A single intravenous administration of 20 mL of 10% sodium thiosulfate reportedly did not change oxygen saturations.
For management of a suspected overdose, contact your regional Poison Control Centre.
Store at room (15⁰C to 30⁰C). Protect from direct light. Do not freeze.
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