Comparison of colchicine, dapsone, triamcinolone, and diphenhydramine therapy for the treatment of brown recluse spider envenomation - A double-blind, controlled study in a rabbit model

Objective: To compare the efficacy of dapsone, diphenhydramine, colchicine, and intralesional triamcinolone in the treatment of brown spider bites. We used a purified venom that reproducibly produces a large eschar. To mimic real-life circumstances, all agents were administered following a 2-hour delay after envenomation. The animals were evaluated for the presence of coagulopathy to determine if the incidence of systemic findings correlated with the type of treatment. Design and Setting: In a research laboratory, 60 New Zealand white rabbits each received an intradermal injection of 20 μ g of purified Loxosceles reclusa venom. The rabbits were divided into 5 groups of 12; a control group and 4 groups treated with a drug (either colchicine, triamcinolone, diphenhydramine, or dapsone). Measured end points included maximum eschar size as well as histologic grading of depth, inflammation, and thrombosis. Interventions: Treatment with colchicine, triamcinolone, diphenhydramine, or dapsone. Main Outcome Measures: Maximum eschar size as well as histologic grading of depth, inflammation, and thrombosis. Results: There was no significant difference with respect to eschar size (1-way analysis of variance, P = .003). There was no significant difference between any treatment with respect to presence or absence of ulcer, necrosis, large vessel vasculitis, or small vessel vasculitis. The only outcome of significance was that triamcinolone offered protection from thrombosis (X(2)Iikelihood ratio, P = .04). We also noted evidence of coagulopathy in all of the envenomated animals. The rabbits had grossly elevated activated partial thromboplastin time results, which were corrected with 1: 1 mixing with normal rabbit plasma, suggesting an acquired factor deficiency. We did not detect an individual factor deficiency or a lupus anticoagulant. Conclusions: In a rabbit model, none of the agents tested (dapsone, diphenhydramine, colchicine, and intralesional triamcinolone) had an effect on eschar size. Triamcinolone appeared to offer some protection against histologic evidence of thrombosis, but this protection did not translate into a difference in clinical outcome. All animals developed evidence of coagulopathy, regardless of treatment. The coagulopathy could be corrected by fresh rabbit plasma, suggesting an acquired factor deficiency.