UA study of scorpion antivenom yields dramatic success

May 19, 2009

By hammersmith

For young children in Arizona, the sting of a bark scorpion no longer means a life-threatening emergency.

In a study published May 14 in the New England Journal of Medicine, a research team led by Leslie V. Boyer of the University of Arizona found that an experimental antivenom drug is tremendously effective in countering the neurotoxic effects of the bark scorpion’s sting. Among recipients of the antivenom in a small study group, only an hour after treatment, levels of plasma venom had diminished to undetectable levels, and within four hours, all symptoms in the patients had vanished.

“What was a life-threatening disease that would put kids in the pediatric ICU has become, for most of them, an outpatient disease,” said Andreas Theodorou, professor of pediatrics and chief medical officer of University Medical Center in Tucson, and one of the study’s co-authors.

The study, conducted in Tucson in 2004 and 2005, examined the efficacy of the drug Anascorp, which is widely available in Mexico but is considered an investigational drug in the United States. Patients in the study were children who had been stung by bark scorpions and had developed systemic neurotoxic symptoms–wildly flailing arms and legs, rapid, uncontrollable eye twitching, and/or trouble breathing.

Each year, some 8,000 Arizonans are stung by bark scorpions, the most dangerous kind of scorpion. Most adults recover without medical treatment, but around 200 cases, almost all of them children, require hospitalization.

“In effect, what happens with the venom, it locks every nerve in the ‘on’ position, so the nerves that go to muscles send signals that say ‘twitch,’ and the nerves that go to glands say ‘sweat,’ ‘drool,’ ‘pee,’ ‘cry,'” said Dr. Boyer in a Reuters news article. Dr. Boyer serves as director of the Venom Immunochemistry, Pharmacology and Emergency Response (VIPER) Institute at the UA College of Medicine.

“The biggest problem is that the nerves that make you breathe are all messed up,” she continued. “So the left side of the chest is saying inhale, while the right side of the chest is saying exhale. At the same time, you’re producing a lot of saliva and you don’t know how to swallow. You can kind of drown and you don’t exchange air as well.”

The seven members of the control group in the study received a placebo treatment coupled with the standard-of-care response for children stung by bark scorpions: heavy sedation and careful monitoring in a pediatric intensive care unit. In all but one case, their recovery was much longer and more painful than that of the patients who received Anascorp. The patients who received Anascorp also required much lower dosages of the intravenous sedative drug, midazolam.

“One-hundred percent of the children who received it (the antivenom) got better very quickly, meaning that using this antivenom in the emergency room will make intensive care treatment unnecessary for most patients,” Dr. Boyer said.

“This is particularly important in small Arizona towns without pediatric intensive care units. By avoiding helicopter trips and intensive care stays, we can save lives and keep treatment costs down at the same time,” she added.

Based on the study’s initial findings, Dr. Boyer’s team arranged for the manufacturer of Anascorp, Instituto Bioclon, which is based in Mexico City, to provide additional supplies of the drug for a Phase III clinical trial in Arizona. Anascorp, which is widely available in Mexico–where serious scorpion stings are far more common than in the United States–has now been administered to around 600 patients in Arizona since 2004. The drug is available in 22 hospitals around the state.

Expansion of the study is a vital step toward validating Anascorp’s safety for approval of the treatment by the U.S. Food and Drug Administration. The FDA is continuing to provide funding to support the study under its Office of Orphan Products Development.

David Moerdler-Green, a New York doctor whose 10 year-old son was stung by a bark scorpion on a visit to Phoenix and received Anascorp, was amazed by the antivenom’s effect.

“It was like a miracle,” said Dr. Moerdler-Green in the New York Times. “How many people go into the emergency room around the world and are able to get medication and be cured in the course of one hour?”

Dawn Bray of Dripping Springs, Ariz., a rural community 23 miles outside of Globe, lost her son Dally to a bark scorpion sting in 2002. Dally Bray died despite being treated with an earlier-generation antivenom that had not been approved by the FDA. Dawn Bray described in the Tucson Citizen the fear that overcame her when her son Morgan was stung in 2008.

“When Morgan got bit, I was thinking that it was happening again,” she said in the Citizen. “With another son, we would have the same outcome.”

Morgan Bray was airlifted from Globe to Tucson, where he was treated with Anascorp and rapidly recovered. “Dr. Boyer was our angel,” Dawn Bray said in the Citizen. “If she trusted it, we trusted it.”

For more information:

Antivenom for Critically Ill Children with Neurotoxicity from Scorpion Stings,” New England Journal of Medicine, 05/14/2009

UA research shows benefit of scorpion sting antivenin,” Tucson Citizen, 05/14/2009

An Experimental Drug Eases Poisonous Scorpion Stings in Children, a Study Finds,” New York Times, 05/13/2009

Antivenin saves children from scorpion’s sting,”, 05/13/2009

UA media release, 05/13/2009