SODIUM NITRITE- sodium nitrite injection, solution
Hope Pharmaceuticals
WARNING: LIFE THREATENING HYPOTENSION AND METHEMOGLOBIN FORMATION
Sodium nitrite can cause serious adverse reactions and death in humans, even at doses less than twice the recommended therapeutic dose. Sodium nitrite causes hypotension and methemoglobin formation, which diminishes oxygen carrying capacity. Hypotension and methemoglobin formation can occur concurrently or separately. Because of these risks, sodium nitrite should be used to treat acute life-threatening cyanide poisoning and be used with caution in patients where the diagnosis of cyanide poisoning is uncertain.
Patients should be closely monitored to ensure adequate perfusion and oxygenation during treatment with sodium nitrite.
Alternative therapeutic approaches should be considered in patients known to have diminished oxygen or cardiovascular reserve (e.g., smoke inhalation victims, pre-existing anemia, cardiac or respiratory compromise), and those at higher risk of developing methemoglobinemia (e.g., congenital methemoglobin reductase deficiency) as they are at greater risk for potentially life-threatening adverse events related to the use of sodium nitrite. [see Warnings and Precautions (5.1 and 5.2)]
1 INDICATIONS AND USAGE
1.1 Indication
Sodium Nitrite Injection is indicated for sequential use with sodium thiosulfate for the treatment of acute cyanide poisoning that is judged to be life-threatening. When the diagnosis of cyanide poisoning is uncertain, the potentially life-threatening risks associated with Sodium Nitrite Injection should be carefully weighed against the potential benefits, especially if the patient is not in extremis.
1.2 Identifying Patients with Cyanide Poisoning
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 Nitrite Injection and Sodium Thiosulfate Injection should be administered without delay.
Table 1. Common Signs and Symptoms of Cyanide Poisoning Symptoms Signs
Headache
Confusion
Dyspnea
Chest Tightness
Nausea
Altered Mental Status
(e.g., confusion, disorientation)
Seizures or Coma
Mydriasis
Tachypnea/Hyperpnea (early)
Bradypnea/Apnea (late)
Hypertension (early)/ Hypotension (late)
Cardiovascular Collapse
Vomiting
Plasma Lactate Concentration ≥ 8 mmol/L
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 regional poison control center may be obtained by calling 1-800-222-1222.
Smoke Inhalation
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 Nitrite Injection, smoke-inhalation victims should be assessed for the following:
Exposure to fire or smoke in an enclosed area
Presence of soot around the mouth, nose, or oropharynx
Altered mental status
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.
1.3 Use with Other Cyanide Antidotes
Caution should be exercised when administering cyanide antidotes, other than sodium thiosulfate, simultaneously with Sodium Nitrite Injection, as the safety of co-administration has not been established. If a decision is made to administer another cyanide antidote, other than sodium thiosulfate, with Sodium Nitrite Injection, these drugs should not be administered concurrently in the same IV line. [see Dosage and Administration (2.2)]
2 DOSAGE AND ADMINISTRATION
2.1 Administration Recommendation
Comprehensive treatment of acute cyanide intoxication requires support of vital functions. Administration of sodium nitrite, followed by 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.
Sodium nitrite injection and sodium thiosulfate 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.
Age Intravenous Dose of Sodium Nitrite and Sodium Thiosulfate
Adults
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
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. [see Warnings and Precautions (5.2)]
All parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
2.2 Recommended Monitoring
Patients should be monitored for at least 24-48 hours after Sodium Nitrite Injection administration for adequacy of oxygenation and perfusion and for recurrent signs and symptoms of cyanide toxicity. When possible, hemoglobin/hematocrit should be obtained when treatment is initiated. Measurements of oxygen saturation using standard pulse oximetry and calculated oxygen saturation values based on measured PO2 are unreliable in the presence of methemoglobinemia.
Methemoglobin level: Administrations of sodium nitrite solely to achieve an arbitrary level of methemoglobinemia may be unnecessary and potentially hazardous. The therapeutic effects of sodium nitrite do not appear to be mediated by methemoglobin formation alone [see Clinical Pharmacology (12)] and clinical responses to sodium nitrite administration have been reported in association with methemoglobin levels of less than 10%. Administration of sodium nitrite beyond the initial dose should be guided primarily by clinical response to treatment (i.e., a second dose should be considered only if there is inadequate clinical response to the first dose). It is generally recommended that methemoglobin concentrations be closely monitored and kept below 30%. Serum methemoglobin levels should be monitored during treatment using co-oximetry, and administration of sodium nitrite should generally be discontinued when methemoglobin levels exceed 30%. Intravenous methylene blue and exchange transfusion have been reported in the literature as treatments for life-threatening methemoglobinemia.
2.3 Incompatibility Information
Chemical incompatibility has been reported between sodium nitrite 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.
3 DOSAGE FORMS AND STRENGTHS
Sodium Nitrite Injection consists of:
One vial of sodium nitrite injection, USP 300 mg/10mL (30 mg/mL)
Administration of the contents of one vial constitutes a single dose.
10 OVERDOSAGE
Large doses of sodium nitrite result in severe hypotension and toxic levels of methemoglobin which may lead to cardiovascular collapse.
Sodium nitrite administration has been reported to cause or significantly contribute to mortality in adults at oral doses as low as 1 g and intravenous doses as low as 600 mg. A death attributed to sodium nitrite has been reported following administration of an adult dose (300 mg IV followed by a second dose of 150 mg) to a 17-month old child.
Cyanosis may become apparent at a methemoglobin level of 10-20%. Other clinical signs and symptoms of sodium nitrite toxicity (anxiety, dyspnea, nausea, and tachycardia) can be apparent at methemoglobin levels as low as 15%. More serious signs and symptoms, including cardiac dysrhythmias, circulatory failure, and central nervous system depression are seen as methemoglobin levels increase, and levels above 70% are usually fatal.
Treatment of overdose involves supplemental oxygen and supportive measures such as exchange transfusion. Treatment of severe methemoglobinemia with intravenous methylene blue has been described in the medical literature; however, this may also cause release of cyanide bound to methemoglobin. Because hypotension appears to be mediated primarily by an increase in venous capacitance, measures to increase venous return may be most appropriate to treat hypotension.
11 DESCRIPTION
Sodium nitrite has the chemical name nitrous acid sodium salt. The chemical formula is NaNO2 and the molecular weight is 69.0.
Sodium Nitrite Injection is a cyanide antidote which contains one 10 mL glass vial of a 3% solution of sodium nitrite injection.
Sodium nitrite injection is a sterile aqueous solution and is intended for intravenous injection. Each vial contains 300 mg of sodium nitrite in 10 mL solution (30 mg/mL). Sodium nitrite injection is a clear solution with a pH between 7.0 and 9.0.
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
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.
