A Randomized, Double-Blind, Placebo-Controlled Trial of a Highly Purified Equine F(ab)2 Antibody Black Widow Spider Antivenom
Black widow spider bites can cause a variety of symptoms collectively known as latrodectism. Common symptoms include pain, agitation, anxiety, and autonomic dysfunction such as tachycardia and diaphoresis. The equine-derived black widow spider antivenom was initially licensed in the United States in 1936, but no formal clinical trials have been conducted. The investigators performed a randomized, double-blind, placebo-controlled clinical trial to compare the effects of placebo and black widow spider antivenom. The primary outcome was the difference in pretreatment and post-treatment pain, assessed by the visual analog scale; secondary outcomes were treatment failure and clinically relevant decrease in pain.
Among the 24 subjects, the antivenom group had a shorter median time to clinically significant pain reduction compared with placebo (30 vs 90 minutes). Although the antivenom group had a greater overall decrease in pain, this difference was not statistically significant. Additionally, there were 7 treatment failures in the placebo group and only 3 in the antivenom group. No serious adverse advents or deaths were observed in either group. The authors of this report conclude that although overall pain reduction between placebo and antivenom was similar, the antivenom reduced pain more rapidly than placebo did. Limitations of the study include small sample size and difficulty identifying true black widow bite. The investigators recognize the need for further studies analyzing the costs, risks, and long-term outcomes of black widow antivenom administration.
(Ann Emerg Med. 2013 Feb 1 [Epub ahead of print]) RC Dart, G Bogdan, K Heard, et al.