Treating Cyanide Poisoning

If a smoke inhalation victim is suspected to be suffering from cyanide poisoning, it is important to quickly treat them as you would any smoke inhalation victim:

The Food and Drug Administration (FDA) on Dec. 15, 2006, approved Cyanokit® (containing the drug hydroxocobalamin, intravenous tubing and a sterile spike for reconstituting the drug product with saline) for the treatment of known or suspected cyanide poisoning. The approval, which is based on evidence of the drug's effectiveness when tested in animals, improves the nation's ability to respond to emergencies, including a potential attack by terrorists. "Cyanide is a potent poison and one of the substances that could be used in a chemical attack," said Dr. Steven Galson, Director of FDA's Center for Drug Evaluation and Research.  "Today's approval is yet another measure to counter the threat of terrorism, which is a critical component of FDA's public health mission." Cyanokit® received a priority review and was approved under the Animal Efficacy Rule, which allows use of animal data for evidence of a drug's effectiveness for certain conditions when the drug cannot be ethically or feasibly tested in humans.

FDA Press Release About Approval of Cyanokit®

Dey LP Press Release About Development and Availability of Cyanokit®

Read more about cyanide antidotes

There are, however, certain limitations associated with these medications, especially when considering using them on the scene of a fire. These limitations include:

• The methemoglobin formed by the administration of the nitrites does not transport oxygen, as the unconverted hemoglobin does. This condition is called methemoglobinemia, which can be especially toxic when combined with carbon monoxide poisoning.
• Sodium nitrite can cause life-threatening low blood pressure when administered too rapidly, and should generally be avoided in patients with smoke inhalation.
• Sodium thiosulfate can cause vomiting, psychosis and arthralgias and myalgia, and acts too slowly on its own.
• Use of the Cyanide Antidote Kit is limited primarily to hospital settings because of the demands of managing potential antidote-associated toxicities.

Medical Interventions Approved in the United States

Medical professionals in the United States have access to an antidote called the Cyanide Antidote Kit, (also called the Taylor, Lilly or Pasadena Kit). This kit contains three different medicines - amyl nitrite, sodium nitrite and sodium thiosulfate - to be used in a specific sequence: the amyl nitrite is administered as an inhalant, followed by the sodium nitrite and sodium thiosulfate, which are given intravenously.

The nitrites are given to convert hemoglobin in the red blood cell to methemoglobin, which attracts the cyanide away from the cytochrome oxidase and allows the cell to continue the process of aerobic metabolism. Sodium thiosulfate is given to facilitate detoxification of cyanide by the body's own cyanide clearance system.

Learn more about aerobic metabolism

Medical Interventions in Other Parts of the World

In countries throughout the world, other antidotes have been developed and are currently used by emergency medical personnel in various situations.

Hydroxocobalamin, a precursor of vitamin B12, has been used safely and effectively in France (with the trade name Cyanokit, made by Merck Sant s.a.s.) since 1996 to treat smoke inhalation victims for known or suspected cyanide exposure. While not currently available in the United States, hydroxocobalamin is being investigated for possible use in the U.S. The mechanism of action of hydroxocobalamin is straightforward. The hydroxocobalamin chelates the cyanide directly, creating cyanocobalamin, a natural form of vitamin B12, which is excreted in the urine. The advantage of this approach is that methemoglobin is not produced and the oxygen-carrying capacity of the victim's blood is not lowered. Therefore, it is suitable for use in smoke inhalation victims. The most common side effect of hydroxocobalamin is temporary pink discoloration of the skin, urine and mucous membranes.

Dicobalt Ededate, is used in the UK to treat cyanide poisoning. Cobalt compounds fixate to the cyanide ion. One 300mg ampoule is administered intravenously at a regular rate over one minute followed by 50ml glucose intravenous infusion. The most common side effects include vomiting, hypotension or hypertension, and tachycardia. Dicobalt edetate can be extremely toxic in the absence of cyanide ions and can only be given when the presence of severe cyanide poisoning is detected.

4-dimethylaminophenol (DMAP) is used in Germany as an antiodote for severe cyanide poisoning in patients who are in a deep coma and who have dilated non-reactive pupils and detoriating cardio-respitaroy function. DMAP converts part of the hemoglobin in the blood from ferrous hemoglobin to ferric hemoglobin. This creates a pool of binding potential that can divert cyanide from the cytochromes it poisons. Patients are given an intravenous dose of 3.25 mg/kg body weight. There are differences in individual susceptibility, which may result in an unacceptably high level of methemoglobin after normal therapeutic doses. Adverse side effects include: hemolyisis, mild headache, dizziness, hyperventilation, cyanosis, and discoloration of the urine.