14 May, 2009

Experimental Mexican antivenom seems to be effective in treating critically ill children after Centruroides sting in USA

Many peoples get stung by scorpions in North America every year, especially in Mexico. Most cases cause mild symptoms, but moderate and serious symptoms are also observed, especially in children. In Arizona (USA), appr. 200 cases of severe scorpion envenomation are seen each year. The involved scorpion is the buthid Centruroides sculpturatus (previous in synonymy with C. excilicauda).

Between 1965 and and 1999, a goat derived antivenom was available in Arizona. The use of this product was controversial for many years and the drug was never FDA approved. Around 2005, there was no antivenom available in Arizona for serious sting cases.

In Mexico, a new antivenom has been commersically available. The antivenom has been produced using the venom of several Mexican species causing serious morbidity. Presently, this drug is not approved by the FDA.

Leslie Boyer and co-workers have now published a randomized, double-blind study showing a positive clinical effects of the antivenom compared to the use of plasebo medicine in children with severe neurotoxic symptoms after Centruroides envenomations. Also, no serious adverse effects of the use of antivenom were observed.

Background: Clinically significant scorpion envenomation by Centruroides sculpturatus produces a dramatic neuromotor syndrome and respiratory insufficiency that often necessitate intensive supportive care. We hypothesized that a scorpion-specific F(ab')2 antivenom would promptly resolve clinical symptoms in children with this syndrome.
Methods: In a randomized, double-blind study, the efficacy of scorpion-specific F(ab')2 antivenom, as compared with placebo, was assessed in 15 children 6 months to 18 years of age who were admitted to a pediatric intensive care unit with clinically significant signs of scorpion envenomation. The primary end point was the resolution of the clinical syndrome within 4 hours after administration of the study drug. Secondary end points included the total dose of concomitant midazolam for sedation and quantitative plasma venom levels, before and after treatment.
Results: The clinical syndrome resolved more rapidly among recipients of the antivenom than among recipients of placebo, with a resolution of symptoms in all eight antivenom recipients versus one of seven placebo recipients within 4 hours after treatment (P=0.001). More midazolam was administered in the placebo recipients than in the antivenom recipients (mean cumulative dose, 4.61 vs. 0.07 mg per kilogram of body weight; P=0.01). Plasma venom concentrations were undetectable in all eight antivenom recipients but in only one placebo recipient 1 hour after treatment (P=0.001).
Conclusions: Among critically ill children with neurotoxic effects of scorpion envenomation, intravenous administration of scorpion-specific F(ab')2 antivenom resolved the clinical syndrome within 4 hours, reduced the need for concomitant sedation with midazolam, and reduced the levels of circulating unbound venom. (ClinicalTrials.gov number, NCT00685230 .)

Boyer LV, Theodorou AA, Berg RA, Mallie J, the Arizona Envenomation Investigators, Chavez-Mendez A, et al. Antivenom for Critically Ill Children with Neurotoxicity from Scorpion Stings. N Engl J Med. 2009 May 14, 2009;360 (20):2090-8. [Free fulltext]

Family Buthidae

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