First anti-venom for scorpion bites approved by FDA

By Dr. Ananya Mandal, MDAug 5 2011

The U.S. Food and Drug Administration (FDA) has approved a Mexican-made drug that is the first specific treatment for stings by the most common type of scorpion in the United States. The new preparation called Anascorp is found to have few allergic reactions and was approved after a series of clinical trials by the University of Arizona.

Karen Midthun, M.D., director of the FDA's Center for Biologics Evaluation and Research, said in a statement, “This product provides a new treatment for children and adults and is designed specifically for scorpion stings… Scorpion stings can be life-threatening, especially in infants and children.” The drug was approved because there was no specific treatment in the United States for these types of stings, which can cause loss of muscle control and shortness of breath and, in the worst-case scenario, require hospitalization, Midthun said. Around 11,000 people are stung each year in the south-western U.S. state of Arizona by scorpions, while there were 17,000 cases nationwide in 2009.

The preparation is made using the plasma of horses immunized with scorpion venom and vaccinated against human viruses. Thus Anascorp may cause early or delayed allergic reactions in people sensitive to horse proteins, the FDA said.

Dr. Leslie Boyer, director of UA's VIPER Institute, who oversaw the clinical trials said, “This is a historic event… This is the first-ever drug approved for this use by the FDA; the first-ever drug that we are aware of being developed fully in Latin America and subsequently approved by the FDA.”

Anascorp is a treatment for stings by the most common type of scorpion found in the U.S. - the Centruroides, or bark, scorpion. The effectiveness of Anascorp, manufactured by the Mexican firm Instituto Bioclon, S.A. de C.V., was determined through a study involving 15 children with neurological symptoms stemming from scorpion stings. The symptoms resolved in just four hours in all eight children who received Anascorp, but only in one of the children who were administered a placebo, the FDA said. Those results were published two years ago in the New England Journal of Medicine in 2009. In other studies, more than 1,500 people, ranging in age from under a month to 90, were treated the anti-venom, generally with good results. The most common side-effects of Anascorp were found to be vomiting, fever, rash, nausea, itchiness, runny nose, headache and muscle pain.

The drug, marketed by Rare Disease Therapeutics of Nashville, Tenn., isn't cheap. The wholesale price per vial of Anascorp will be $3,500 and the recommended dose is three vials per patient, so treatment will typically cost more than $10,000.