Which medications in the drug class Antidotes are used in the treatment of Cyanide Toxicity?

Updated: May 30, 2020
  • Author: Inna Leybell, MD; Chief Editor: Michael A Miller, MD  more...
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Answer

Antidotes

Cyanide is a cellular toxin that binds to cytochrome oxidase, inhibiting cellular respiration. Antidotes either directly counteract cyanide's toxicity on the electron transport chain or help the body eliminate the cyanide molecule. Administration of antidotes is critical for life-threatening intoxication.

Gastrointestinal (GI) decontamination with oral activated charcoal is selectively used in the emergency treatment of poisoning caused by some drugs and chemicals. The network of pores present in activated charcoal adsorbs 100-1000 mg of drug per gram of charcoal. Consider decontamination with activated charcoal in any patient who presents within 4 hours after the ingestion.

Alkalinizing agents are used in severe poisoning, which causes marked lactic acidosis.

Hydroxocobalamin (Cyanokit)

Hydroxocobalamin contains cobalt ion, which is able to bind to cyanide with greater affinity than cytochrome oxidase to form nontoxic cyanocobalamin (vitamin B-12), which is excreted in urine. Hydroxocobalamin has few adverse effects and is tolerated by critically ill patients. It is well tolerated by patients with concomitant carbon monoxide poisoning, because unlike sodium nitrite it has no effect on the oxygen-carrying capacity of hemoglobin.

Hydroxocobalamin may be used in combination with sodium thiosulfate for treatment of acute cyanide toxicity. Low-dose hydroxocobalamin in combination with sodium thiosulfate has been used successfully to prevent cyanide toxicity in patients receiving prolonged sodium nitroprusside infusions.

The disadvantages of hydroxocobalamin are that a large dose is required for antidotal efficacy and that it is available in the United States only in very dilute solutions. It can cause transient hypertension, allergic reactions (rarely including anaphylaxis and angioedema), and a reddish discoloration of body fluids and urine.

Sodium thiosulfate & sodium nitrite (Nithiodote)

Sodium nitrite induces methemoglobin formation and vasodilation. Sodium thiosulfate has a slower mechanism of action. It donates sulfur, which is used as a substrate by rhodanese and other sulfur transferases for detoxification of cyanide to thiocyanate. In patients with concomitant carbon monoxide poisoning, for whom sodium nitrite is contraindicated, sodium thiosulfate can be used alone; sodium thiosulfate can also be administered with hydroxocobalamin in severe cases.

The recommended dose assumes a patient hemoglobin level of 12 mg/dL; dosage adjustment may be necessary in patients with anemia. Half the original dose may be repeated in 1 hour if the patient continues to exhibit signs of cyanide toxicity.

Amyl nitrite

The nitrite ions in amyl nitrite react with hemoglobin to form methemoglobin, which unites with cyanide to form cyanomethemoglobin. Amyl nitrite rushed and contents poured onto a gauze and placed in front of patient's mouth pearls can be crushed and inhaled by a spontaneously breathing patient or ventilated into an apneic patient using a bag-valve-mask device; this is a temporizing measure until IV access can be established.

The effect of an ampule lasts approximately 3 minutes; separate administration by at least 30 seconds to allow patient to oxygenate. Due to the volatile nature of this compound, rescuers should ensure that they themselves have an adequate fresh air supply and can maintain a sufficient distance from the amyl nitrite source.

Activated charcoal (Actidose-Aqua, EZ-Char, Kerr Insta-Char)

Activated charcoal binds cyanide poorly; 1 g of charcoal adsorbs only 35 mg of cyanide. Nonetheless, a 1-g/kg dose of charcoal could potentially bind a lethal dose of cyanide and has a low risk profile. Consequently, charcoal should be administered as soon as possible following oral ingestion of cyanide salts or organic cyanides.

Sodium bicarbonate (Neut)

Sodium bicarbonate may be required in large doses for alkalization.


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