Background: Black widow spider (Latrodectus spp.) envenomation remains the most clinically significant spider envenomation in the US. The syndrome is characterized by painful muscle rigidity and autonomic disturbances. Treatment has ranged from symptomatic care to administration of specific antivenom. Declining antivenom availability and, possibly, the fear of hypersensitivity allergic reactions, has limited antivenom use in the US.

Objective: To describe Latrodectus spp. exposures and the subsequent treatment reported to US poison centers; the secondary objective was to Identify factors associated with shorter duration of symptoms (<24 hours).

Methods: All Latrodectus spp. exposures reported to the National Poison Data System (NPDS) between January 1, 2000, and December 31, 2008, were reviewed. Cases with at least minor clinical effects due to Latrodectus spp. exposure were extracted. Descriptive statistics were generated. The probability that symptom duration was less than 24 hours was modeled, using logistic regression.

Results: From 2000 through 2006, a total of 23,409 Latrodectus spp. exposures were reported in 47 states; 9872 cases had at least minor clinical effects and were included in the subsequent analysis. Exposures peaked in September and fell to a nadir in January and February. Fifty-eight percent of the cases involved males, and the mean (SD) age was 31.5 (17.4) years. Sixty-five percent of the patients had minor clinical effects, 33.5% had moderate effects, 1.4% had major effects, and there were no deaths. Antivenom use was associated with symptom duration of less than 24 hours in moderate and major outcome groups. There was no evidence of shorter symptom duration in patients who received benzodiazepines or calcium. Adverse drug reactions were more common in patients receiving benzodiazepines and antivenom.