Antivenom for scorpion stings works but lacks FDA approval

A study of Tucson children who were stung by bark scorpions and treated with the Mexican-made Anascorp is the subject of an article that will come out in the New England Journal of Medicine today.

The small, slender bark scorpion is the most common house visitor of all Arizona scorpions. It's also the most dangerous.

Dr. Leslie Boyer's research team concluded that the antivenom cures youngsters suffering from severe nerve poisoning following a bark scorpion sting. The catch is that Anascorp has not yet been approved by the U.S. Food and Drug Administration.

Boyer — the medical director of the Arizona Poison and Drug Information Center at the University of Arizona's College of Pharmacy — is the article's lead author.

Her research team hopes their work will help move along the drug approval process, as well as draw attention to a global shortage of antivenom that the World Health Organization has deemed as public health crisis.

The article is titled, "Antivenom for Critically Ill Children With Neurotoxicity from Scorpion Stings," and focuses on a Tucson study of 15 children who ended up in pediatric intensive care in 2004 and 2005 following a scorpion sting. The FDA's Office of Orphan Products Development funded the research.

All the children were experiencing classic symptoms of poisoning caused by the bark scorpion — abnormal eye movements, uncontrollable thrashing of limbs and respiratory distress.

Eight of the children were treated with Anascorp and their symptoms resolved in less than four hours, usually in less than two. The seven children who received a placebo continued to experience nerve poisoning for four hours or more and required large doses of sedative medication and extended hospitalization.

"What was a life-threatening disease that would put kids in the pediatric intensive care unit has become, for most of them, an outpatient disease," said Dr. Andreas Theodorou, chief medical officer of University Medical Center, and a member of the research team.

The Mexico City-based pharmaceutical company Instituto Bioclon, which makes the antivenom, supplied it to the UA study at no charge.

Arizona children who suffer from a life-threatening scorpion sting are still able to be treated with Anascorp, since additional funding from the state has made it available to 22 Arizona emergency rooms. But without the Tucson-based study, which laid the groundwork for that funding, there would likely be no antivenom available in Arizona at all.

About 200 people — almost all children — require treatment for bark scorpion stings every year in Arizona, the article says.

Dally Michael Bray was one of the unlucky ones. Dally died shortly after his second birthday in 2002, after being stung by a bark scorpion in the backyard of his home. Dally's family lives in the rural community of Dripping Springs, which is about 27 miles outside of Globe, and the nearest hospital is 45 minutes away.

Dally had a history of serious allergies, which may have compounded his reaction to the sting, his mother said, though no one knows for sure. He was treated with an Arizona-made predecessor to Anascorp, but it wasn't enough to save his life.

Until the late 1940s, bark scorpion stings caused more deaths in Arizona than rattlesnake bites. Around that time, Arizona researchers developed a scorpion antivenom using antibodies developed in goat serum.

But after supplies of that drug ran out several years ago, no company would agree to make it because it failed to meet modern FDA standards, and caused significant side effects. Anascorp is made with horse serum and doctors say it has caused no serious side effects.

"He was just one in a million," said Dally's mother, Dawn Bray . "The new drug (Anascorp) may have saved him, but I try not to speculate. I do have time to help get Anascorp approved in the U.S. It's something Dally can still do for all of us."

Dally was the third of four boys in his family and his parents had a second scorpion scare last year when Dally's younger brother Morgan was stung by a scorpion at school. He was 6 years old and Bray didn't waste any time telling workers in the Globe hospital that she wasn't going to lose another son. Morgan was airlifted to University Medical Center, treated with Anascorp, and completely recovered.

Boyer hopes that by getting the antivenom into emergency rooms in small Arizona towns without pediatric intensive care units, it will eliminate the need for helicopter trips and intensive care stays.

A bigger issue that she hopes today's article will accomplish is drawing attention to a worldwide shortage of antivenom. Drug companies no longer see antivenom as profitable, and the repercussions are serious, she said.

There's currently a shortage of antivenom for coral snake bites, which occur mostly in Florida. The only facility making FDA-approved antivenom for North American coral snakes shut down in 2002 .

The World Health Organization in 2007 called management of scorpion stings, snakebites and potentially rabid mammal bites a global public health emergency. Among other things, the WHO has called for action by manufacturers and regulatory bodies to ensure safe and effective antivenoms are available, particularly in developing countries.

Scorpion Stings

Small children are at highest risk of severe reactions. They can show jerky body and wild eye movements. The majority of stings occurring in older children and adults may be managed at home with basic first aid measures and follow-up.

First aid should include cleaning the site with soap and water; cool compress; elevating the affected limb to approximately heart level; and aspirin or Tylenol as needed for minor discomfort.

Call the Arizona Poison and Drug Information Center at 1-800-222-1222 if a child under 5 has been bitten or if an older patient is experiencing more than minor discomfort. Stings occurring in children or any patient experiencing severe symptoms should be seen at a medical facility immediately.

Scorpions are relatively inactive during the daylight hours. The majority of stings reported to the poison center occur at night during the warm summer months.

SOURCE: Arizona Poison and Drug Information Center