Antivenom Targets Nerve Toxins in Scorpion Sting

Developed by researchers at Instituto Bioclon (Mexico City, Mexico), the injectable antivenom, Centruroides (Scorpion) Immune F(ab)2 (Equine) Injection, is made from the plasma of horses immunized with scorpion venom. Since the antivenom, commercially known as Anascorp, may cause early or delayed allergic reactions in people sensitive to horse proteins, the manufacturing process includes steps to decrease the chance of allergic reactions and to reduce the risk of transmission of viruses that may be present in the plasma.

The effectiveness of Anascorp was based on the results of a randomized, double blind, placebo-controlled trial of 15 children with neurological signs of scorpion stings. The signs resolved within four hours of treatment in the eight subjects who received Anascorp, but in only one of the seven participants who received the placebo. The most common side effects were vomiting, fever, rash, nausea, itchiness, headache, runny nose, and muscle pain. In addition, safety and efficacy data for approval by the US Food and Drug Administration (FDA) were collected from 1,534 patients in open-label and blinded studies conducted over 12 years at a consortium of 27 hospitals in Arizona and Nevada (USA).

“Ninety-eight percent of children treated with this drug have their symptoms from scorpion stings resolved in less than 4 hours,” said Leslie Boyer, MD, director of the Venom Immunochemistry, Pharmacology, and Emergency Response (VIPER) Institute at the University of Arizona College of Medicine (Tucson, USA), and lead investigator in the antivenom's clinical study. “Historically, chart records of the same types of patients showed that 98% of children were still sick and still needing intensive care if they were admitted before the antivenom was available; a record like that is just about as strong as a new drug can have.”

Venomous scorpions occupy a vast geographic area in North America, thriving in Mexico, Arizona, and a narrow slice of Nevada, affecting 250,000 people annually in Mexico and a further 8,000 in the United States. Severe stings occur most frequently in infants and children, and can cause shortness of breath, fluid in the lungs, breathing problems, excess saliva, blurred vision, slurred speech, trouble swallowing, abnormal eye movements, muscle twitching, trouble walking, and other uncoordinated muscle movements; untreated cases can be fatal.

Related Links:
Instituto Bioclon
VIPER Institute