Scorpion

VIPER scientists are developing better ways to treat nerve poisoning from scorpion sting.

We are in a unique situation.

The sting of the bark scorpion (Centruroides sculpturatus) can cause severe nerve poisoning, especially when the victim is a small child. In the United States, severe cases are very rare, affecting perhaps 250 people per year. But just to the south of Arizona, and extending all the way through the western half of Mexico, an additional quarter of a million people need treatment for scorpion sting annually. A history of the efforts by US and Mexican scientists, doctors, priests and manufacturers dealing with this issue was published in the journal Toxicon (Boyer: History of scorpion antivenom: one Arizonan's view, Toxicon 2013;69:14-20).

So we did a unique study.

In Tucson's pediatric intensive care units, VIPER doctors and nurses conducted a one-of-a-kind study of scorpion sting. Over the course of two years, children with severe scorpion sting symptoms were given the opportunity to participate in the most rigidly controlled type of study of an investigational new drug: a double-blind, placebo-controlled trial. Results of this study, funded by the United States FDA's Office of Orphan Products Development, showed that children who are treated with antivenom recover faster and need less sedative medication than children who receive intensive care alone. After receiving antivenom, children also had lower levels of scorpion venom detectable in their bloodstream, a finding that may lead to better drug development in the future. Results of this study were published and can be found in the New England Journal of Medicine (Boyer et al.: Antivenom for critically ill children with neurotoxicity from scorpion stings, N Engl J Med 2009;360:2090-8). 

But we needed to do more, to prove our case.

At hospitals that do not have pediatric intensive care units, it is not possible to give a placebo treatment during this kind of scorpion study, because there would be a risk of suffering from lack of oxygen among patients who received high doses of sedative medication during nerve poisoning. But doctors at even a small rural hospital can give a quick dose of antivenom in the emergency department. VIPER doctors expanded the small intensive care study to include more patients by including children far from intensive care units. To learn how these children might have done without antivenom, VIPER nurses combed through the charts of patients who, in the past, had been treated without antivenom. These two studies, funded by the US FDA's Office of Orphan Products Development, have been published in the journal Toxicon (Boyer et al.: Effectiveness of Centruroides scorpion antivenom compared to historical controls, Toxicon 01/2013; DOI:ISSN 0041-0101, http://dx.doi.org/10.1016/j.toxicon.2013.07.014).

We have an obligation to the people of Arizona.

During the course of VIPER's scorpion antivenom studies, the State of Arizona ran out of its supplies of an older antivenom that once was made by Arizona State University. Because the results of the studies looked very promising, the Arizona legislature, governor and health department asked VIPER in 2003 to expand its research network to include any hospital in the state that wanted to try the new antivenom. Using funds from the State of Arizona, plus the generous support of Instituto Bioclon (the antivenom manufacturer) and Rare Disease Therapeutics (Bioclon's US business partner), VIPER opened our study enrollment to enable 27 hospitals and clinics around Arizona (plus one in Las Vegas) to participate, and we documented selected cases on videotape to create teaching materials for students and healthcare professionals. By August of 2011, approximately 2000 Americans stung by scorpions had participated in this special program, which ensured the availability of antivenom while collecting safety information that will benefit future victims of scorpion sting. On August 2, 2011, we celebrated the approval of the antivenom by the US FDA, for marketing under the name Anascorp. In 2013, we expect to publish the results of the extended network's research, which we believe was the biggest prospective study ever to include so much information on antivenom safety.

And a University program must stay alert to new discoveries.

Many important questions have come up because the people who were treated in these studies came from all kinds of different circumstances. What should a doctor do when a critically ill patient is only one month old, too tiny for standard medication dosing? What does it mean if someone has an asthma attack at the same time as a scorpion sting? Should a pregnant woman receive antivenom? Is a patient with a heart condition at greater risk from a scorpion sting? Can scorpion venom poisoning be diagnosed by a blood test? Is it possible that a child who was exposed to drugs of abuse could be mistaken for a scorpion sting case? If a family is tent camping in a place that supposedly has no dangerous scorpions, but a child has a dangerous reaction, does that mean they carried the scorpion with them, or does it mean the scorpions there are a newly discovered risk to others? These and other questions have come up during the course of VIPER's studies, and our faculty and students have worked individually, case by case, to make sure that we learn everything possible from this unique study situation, for the benefit of future patients in the U.S., Mexico, and around the world.