What is the effectiveness of antivenom for scorpion envenomation?

Updated: Nov 09, 2018
  • Author: David Cheng, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Answer

In a prospective, randomized, double-blind study, Boyer et al compared scorpion-specific F(ab')2 antivenom (Anascorp, Centruroides [scorpion] immune F(ab)2 intravenous [equine], Instituto Bioclon) (n=8) with placebo (n=7) in children who developed neurotoxic symptoms following scorpion envenomation. [36] Neuromotor abnormalities were present in all patients at baseline, and respiratory distress was present in 20%. Beginning 2 hours after treatment, symptom resolution differed significantly in the antivenom group compared with the placebo group. Plasma venom concentrations were undetectable and cessation of the neurologic syndrome occurred within 4 hours in 100% of antivenom recipients compared with 1 placebo recipient (p=0.001).

Thus, the Boyer et al study suggests that scorpion-specific F(ab')2 antivenom successfully treated the clinical syndrome, reducing the need for concomitant sedation and reducing circulating unbound venom levels for Centruroides envenomation. [36]

For Mesobuthus tamulu envenomations, horse-derived antivenom has been developed. Natu et al compared the newer antivenom treatment versus the traditional prazosin treatment in their open label study of 81 envenomated patients and found that antivenom decreased clinical recovery time to 4.14 hours +/- 1.6 hours compared to prazosin’s clinical recovery time of 19.28 hours +/- 5.03 hours. [37]

Natu et al also found that the antivenom plus prazosin combination group had a recovery time of 3.46 hours +/- 1.1 hours but felt it was comparable to the antivenom group recovery time and recommended that the combination therapy be reserved for patients presenting with pulmonary edema with hypertension.

Bawaskar et al compared antivenom plus prazosin versus prazosin in their open label trial of 70 patients with only grade 2 envenomations (beginning of systemic involvement) and found that 91.4% of the combination treatment group had resolution of their clinical symptoms within the 10-hour mark compared to 22.9% in the prazosin treatment group. [38] Both the Natu and the Bawaskar studies suggest the utility of the new Mesobuthus tamulus antivenom for systemic symptoms envenomations.

Kumar et al found that early (39</ref> [40]


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