title: A randomized, double-blind, placebo-controlled trial of a highly purified equine F(ab)2 antibody black widow spider antivenom.
abstract: OBJECTIVE
  Black widow spider antivenom has never been tested in a randomized clinical trial, to our knowledge. We explore various efficacy measures for a novel F(ab)2 antivenom in patients with moderate to severe pain caused by black widow spider envenomation.
  
  
  METHODS
  A randomized, placebo-controlled, double-blind, clinical trial was conducted in 12 academic emergency departments. We included patients at least 10 years old with moderate to severe latrodectism. Subjects received either a single intravenous infusion of antivenom or placebo. Pain was assessed with the visual analog scale. The primary efficacy outcome was the difference in pre- and posttreatment visual analog scale score. Prospectively defined secondary outcomes included treatment failures and time to clinically important decrease in pain.
  
  
  RESULTS
  Twenty-four subjects were enrolled between October 2005 and October 2006; 13 were randomized to antivenom and 11 to placebo. The median change in visual analog scale at 150 minutes posttreatment was -50.0 mm (Interquartile Range [IQR] -67, -41 mm) in the antivenom treatment group and -46.0 mm (IQR -51, 0 mm) in the placebo treatment group (P=.14). There were 7 treatment failures (64%; 95% confidence interval 35% to 92%) in the placebo group and 3 (23%; 95% confidence interval 0.2% to 46%) in the antivenom group (P=.06). The median time to a clinically important decrease in pain after treatment was shorter in the antivenom group compared with the placebo group (30 minutes [IQR 30, 60 minutes] versus 90 minutes [IQR 30, 90 minutes]; P=.03). No serious adverse events or deaths were reported.
  
  
  CONCLUSIONS
  Although the overall reduction in pain was similar for antivenom- and placebo-treated subjects, antivenom reduced pain more rapidly than placebo. No significant adverse events occurred in either group.
authors: Denver Health and Hospital Authority/Rocky Mountain Poison & Drug Center, Denver, CO, USA. richard.dart@rmpdc.org
authors: Richard C
authors: RC
authors: Dart
authors: Gregory
authors: G
authors: Bogdan
authors: Kennon
authors: K
authors: Heard
authors: Becki
authors: B
authors: Bucher Bartelson
authors: Walter
authors: W
authors: Garcia-Ubbelohde
authors: Sean
authors: S
authors: Bush
authors: Tom
authors: T
authors: Arnold
authors: Richard C
authors: RC
authors: Clark
authors: Gregory W
authors: GW
authors: Hendey
authors: Christopher
authors: C
authors: Holstege
authors: Elizabeth A
authors: EA
authors: Spradley
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000997:Antivenins / Q000627:therapeutic use*; D001740:Black Widow Spider; D002648:Child; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology; D010147:Pain Measurement; D001098:Spider Bites / Q000150:complications / Q000188:drug therapy*; D013111:Spider Venoms / Q000037:antagonists & inhibitors; D055815:Young Adult
chemical_list: D000997:Antivenins; D007140:Immunoglobulin Fab Fragments; D013111:Spider Venoms