Hydrogen cyanide

CAS RN: 74-90-8

Treatment in the Hot Zone



Victims exposed to hydrogen cyanide require supportive care (including administration of 100 % oxygen) and rapid administration of specific antidotes. Cyanide agent specific antidotes and supportive treatment may have to be initiated prior to decontamination.

Antidote Dosing and Sequencing:

When possible, treatment with cyanide antidotes should be given under medical supervision to unconscious victims who have known or strongly suspected cyanide poisoning. Amyl nitrite has the advantage of being able to be given quickly without IV access. AMYL and SODIUM NITRITE have the potential to put the fetus of a pregnant woman at serious risk. In addition, there is increased vulnerability of infants and young children, those with active respiratory disease or diminished pulmonary reserve as well as those who have cardiovascular disease, particularly the elderly or frail, to increased methemoglobin levels (especially if combined with carbon monoxide exposure). If you are concerned that a patient is not oxygenating well such as in smoke exposure consider going directly to hydroxocobalamin or sodium thiosulfate.

Therefore, initial treatment with hydroxocobalamin is recommended vs. amyl and sodium nitrite in pregnant women, infants, young children (especially with co-morbidities such as smoke inhalation). An IO needle can be placed in the hot zone while wearing level A PPEs to facilitate treatment.

  • Cyanide antidotes - amyl nitrite* perles and intravenous infusions of sodium nitrite§ and sodium thiosulfate* - are packaged in the cyanide antidote kit.
    • Amyl nitrite perle should be broken onto a gauze pad and held under the nose, placed under the lip of a facemask, or over the Ambu-valve intake. The patient should inhale for 30 seconds of each minute and a new perle should be utilized every three minutes if sodium nitrite infusions will be delayed. CAUTION AMYL NITRITE MAY CAUSE SIGNIFICANT HYPOTENSION AND IF TAKEN WITH DRUGS LIKE VIAGRA, CIALIS, OR LEVITRA (OTHER NITRITE-CONTAINING DRUGS), THIS EFFECT IS MAGNIFIED, POTENTIALLY CAUSING FAINTING AND EVEN DEATH.
    • As soon as IV access has been achieved in a symptomatic patient DC the perles and initiate IV sodium nitrite (ASAP).
    • The usual adult dose is 10 ml of a 3 % solution (300 mg).
    • The pediatric dose is 0.12 to 0.33 ml/kg.
    • It should be infused over no less than 5 minutes (monitor BP frequently).
    • If hypotension develops, slow rate down consider giving crystalloids and vasopressors.
    • In patients who initially improve with nitrite therapy, but then exhibit signs or symptoms of hypoxia/cyanosis, a diagnosis of methemoglobinemia should be considered in the differential diagnosis along with continued cyanide toxicity. See methylene blue treatment in Hospital Management.
    • Follow-up immediately with IV sodium thiosulfate. (12.5 grams infused over 10 - 20 minutes).
    • The adult dose is 50 ml of a 25 % solution.
    • The pediatric dose is 1.65 mL/kg of a 25 % solution.
    • Repeat one-half of the initial dose in 30 minutes if there is an inadequate clinical response or at 2 hours for prophylaxis.
  • Hydroxocobalamin
    • A dose of 70 mg/kg (not to exceed 5 grams initially) administered over 15 minutes is recommended. This dose can be given IV push in situations of cyanide induced cardiac arrest. (Adult Pediatric Pregnancy§)
    • Depending upon the severity of the poisoning and the clinical response, a second dose of 70 mg/kg (not to exceed 5 g) may be administered by intravenous infusion for a total dose of 10 g. The rate of infusion for the second dose may range from 15 minutes (for patients in extremis) to two hours, as clinically indicated
    • Many patients with cyanide poisoning will be hypotensive; however, elevations in blood pressure have also been observed in known or suspected cyanide poisoning victims. Elevations in blood pressure (≥180 mmHg systolic or ≥110 mmHg diastolic) were observed in approximately 18% of healthy subjects (not exposed to cyanide) receiving hydroxocobalamin 5 g and 28% of subjects receiving 10 g. Increases in blood pressure were noted shortly after the infusions were started; the maximal increase in blood pressure was observed toward the end of the infusion. These elevations were generally transient and returned to baseline levels within 4 hours of dosing.
    • While a safe drug, animal and anecdotal human studies have demonstrated limited or no additional therapeutic benefit by administering sodium thiosulfate in addition to treatment with hydroxocobalamin.
    • Physical incompatibility (particle formation) and chemical incompatibility were observed with the mixture of hydroxocobalamin in solution with selected drugs that are frequently used in resuscitation efforts. Hydroxocobalamin is chemically incompatible with sodium thiosulfate or sodium nitrite. Therefore, these and other drugs should not be administered simultaneously through the same intravenous line as hydroxocobalamin. If a second line is unavailable thoroughly flush the single line prior to administering sodium thiosulfate or sodium nitrite.

Ingestion Exposure

Do not induce emesis. If the victim is symptomatic, immediately institute emergency life support measures including the use of a cyanide antidote kit. If the victim is alert, asymptomatic, has a gag reflex, and it has not been done previously, give activated charcoal as soon as possible. Because cyanide absorption from the gut is rapid, the usefulness of activated charcoal will depend on how quickly after ingestion it can be administered.

  • Administer slurry of activated charcoal at 1 gm/kg (usual adult dose 60-90 g, child dose 25-50 g). A soda can and a straw may be of assistance when offering charcoal to a child.
  • Toxic vomitus or gastric washings should be isolated (e.g., by attaching the lavage tube to isolated wall suction or another closed container).
  • Because of potential toxicity of vomitus/aspiration, recommend consultation with Emergency Physician prior to administration of charcoal (if possible).

FDA approved for this indication

Not FDA approved for this indication/Off-label use

* Fetal risk cannot be ruled out, see DailyMed for additional details

§ Category C, see DailyMed for additional details

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