FDA approves first drug for scorpion stings

The FDA says it has approved Anascorp as the first specific treatment to counteract the sometimes dangerous or even fatal effects of stings by venomous centruroides scorpions.

The federal agency says in a news release that in the United States, venomous scorpions are mostly found in Arizona, and that stings can cause serious reactions, including shortness of breath, fluid in the lungs, breathing problems, excess saliva, and blurred vision.

Severe stings occur most often in infants and children, the FDA says.

Other reactions to stings from venomous scorpions include slurred speech, trouble swallowing, abnormal eye movements, muscle twitching, trouble walking, and uncoordinated muscle movements. Stings that are not treated can be fatal.

Scorpion stings especially dangerous for children

Anascorp is made from the plasma of horses that have been immunized with scorpion venom. The medication may cause early or delayed allergic reactions in people who are sensitive to horse proteins, FDA says.

Anascorp's manufacturing process includes steps to decrease the chance allergic reactions will occur and reduces the risk of transmission of viruses that may be present in plasma, FDA says.

Anascorp's effectiveness

Anascorp received a priority review by the FDA and is licensed to Rare Disease Therapeutics Inc. in Franklin, Tenn.

The drug is distributed by Accredo Health Group Inc. in Memphis, Tenn., and manufactured by an institute in Tlalpan, Mexico.

FDA says the effectiveness of Anascorp was based on results of a trial of 15 children who had neurological signs of scorpion stings.

The signs went away within four hours of treatment for the eight children who received Anascorp, but in only one of the seven children who received a placebo.

Side effects of Anascorp

The most common side effects of the drug were vomiting, fever, rash, nausea, itchiness, headache, runny nose, and muscle pain, the FDA says.

Safety and efficacy data were collected from 1,534 patients. Anascorp was designated as an "orphan" drug by the FDA, thus receiving priority review. An orphan drug is a pharmaceutical agent developed specifically to treat a rare medical condition.

According to a consumer health information statement on the FDA's web site, the centruroides scorpion is the most common type in the U.S. It says about 11,000 people are stung annually in Arizona alone.

Keith Boesen, managing director of the Arizona Poison and Drug Information Center, says in the statement that 17,000 scorpion stings were reported to U.S. poison centers nationwide in 2009.

By Bill Hendrick

Reviewed by Laura J. Martin, MD