FDA Gives Green Light to Cyanide Treatment

Drug safety officials in the USA have approved an emergency treatment used in France for cyanide poisoning.

Beginning next month, a kit called Cyanokit can be used by U.S. paramedics to treat cyanide poisoning, which poses a terrorist threat and could play a role in thousands of deaths each year from smoke inhalation.

The Food and Drug Administration approved Cyanokit based on the French experience and on animal studies because of the danger that studying therapy for cyanide poisoning in humans poses to test subjects.

Cyanide kills quickly. But current cyanide treatment -- which involves the use of amyl nitrite, sodium nitrite and sodium thiosulfate -- is tricky, doctors say, because the fix can also kill. For that reason, doctors must be sure the culprit is cyanide. And the new Cyanokit allows medics to make an educated guess. "If you were wrong, you would likely make them worse and you may actually kill them with the old treatment," says Marc Eckstein, medical director for the Los Angeles Fire Department and associate professor of emergency medicine at the University of Southern California School of Medicine. He has worked as a consultant to EMD Pharmaceuticals of Durham, N.C., which won FDA approval for Cyanokit. "The Cyanokit offers a safe and pure treatment that a paramedic can administer in the field."

Cyanide kills by binding to an enzyme that helps cells use oxygen. When cyanide is present, the body is starved of oxygen. Heart and brain cells die fast. The FDA says that Cyanokit's active drug, hydroxocobalamin, binds to cyanide, which keeps it off the enzymes. This bond forms vitamin B12, which is expelled in urine.

Stephen Borron, an American toxicology expert who participated in the French studies, says, "The patient's effects from the cyanide are very rapidly diminished."

French scientists discovered the drug after Charles de Gaulle, who was head of the French provisional government in the 1940s, worried he was going to be poisoned. Cyanide is considered a terrorist threat because it is not hard to get, says Donald Walsh, Chicago's assistant fire chief for Emergency Medical Services. Mine and metal workers have access to cyanide.

Today, rescuers in Paris routinely use hydroxocobalamin to treat smoke inhalation. They report fire survival rates increasing 30% to 70%. And, according to the National Fire Protection Association, about 4,000 people die each year from fires across the USA.

The key to survival is speed.

"You really need to treat these patients at the scene of the fire for maximum benefit," says Borron, of the University of Texas Health Science Center in San Antonio, who has worked as an EMD consultant.

He says Cyanokit 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.

By focusing on cyanide's role in smoke inhalation, doctors have found that firefighters are also more susceptible to cyanide poisoning than was previously known. Modern combustibles spew toxins when burned. Cyanide is produced when common household materials, such as fiberglass insulation, burn.

Firefighters have been poisoned by cyanide even after the bulk of a fire has been extinguished, Walsh says. While working amid smoldering debris without their breathing gear, firefighters have been sickened by cyanide, he says.

"We're really starting to wake up the American fire service on this," says Walsh, an EMD consultant who traveled to Paris to see how the drug is used by the fire brigade.

"I think this will affect the numbers of morbidity and mortality for smoke inhalation," he says. French firefighters "were pulling people out of buildings in cardiac arrest who were burned, and they revived them."

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