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Spiders: Controversies - Loxosceles

Brown recluse spider bites are characterized by polymorphonuclear leukocyte infiltration at the site of the lesion. The optimal treatment is controversial. Diverse treatments have been advocated, including steroids, antibiotics, surgical excision, antihistamines, colchicine, hyperbaric oxygen therapy, antivenom, electroshock therapy, and observation.34


Dapsone is the therapy most frequently recommended by authorities secondary to its leukocyte-inhibiting properties, but scientific evidence supporting the efficacy of dapsone for the treatment of brown recluse bites is scarce.34,68,69 In one study involving guinea pig models, there was some evidence that the lesions healed better with dapsone. However, in these studies, the dapsone was either given prior to or at the same time as the injection of the venom.68 This approach is clearly not possible from a clinical standpoint.34,70 To date, no double blind, randomized trial has been conducted to compare dapsone and placebo in human beings for the treatment of brown recluse spider envenomations.34

Furthermore, dapsone has many potential side effects. Reported complications from the treatment of brown recluse bites and other medical conditions with dapsone include hemolysis, agranulocytosis, aplastic anemia, methemoglobinemia, hypersensitivity reactions, rashes, and toxic epidermal necrolysis. Dapsone-related fatal reactions have also been reported.34,69-73

Local Treatment

Aggressive Excision

Aggressive early surgical excision has been anecdotally advocated to limit the extent of dermatonecrosis caused by brown recluse spider envenomation, but controlled trials have found that early surgical intervention should be avoided. Surgery appears to increase local inflammation resulting in chronicity of the wound, repeated graft rejection, and pyoderma granuloma. Sharp debridement or excision of spider bite lesions should be discouraged.55,74-80


Steroids are commonly recommended for the treatment of brown recluse bites. However, systemic and intralesional steroids have not been observed to alter lesion size or progression in animal models or human studies and should not be routinely used. Likewise, the use of corticosteroids for severe systemic complications has been recommended without strong evidence-based support.55,58,81-83

Anti-Loxosceles Fab Fragments

Intradermal injection of rabbit-derived anti-Loxosceles Fab fragments has only been studied in animal models. Although early injection (less than four hours) was shown to attenuate dermatonecrotic lesion size, the following two factors make this therapy impractical: 1) the anti-Loxosceles Fab fragments are not available commercially, and 2) the typical delay in presentation of dermatonecrosis makes early treatment virtually impossible.58,84

Hyperbaric Oxygen

The use of hyperbaric oxygen therapy to treat brown recluse bites has been proposed. Two studies of this modality have been conducted in small animals and both found no benefit of hyperbaric oxygen therapy in the treatment of brown recluse spider bites.34,72,85,86

Electroshock Therapy

Though electroshock therapy has been reported in case reports as a possible therapy for the treatment of brown recluse bites, it is not accepted as standard treatment of these envenomations and may be harmful.87

Prophylactic Antibiotics

As with the other envenomations discussed in this article, prophylactic antibiotics are not of proven benefit and should be used only if secondary bacterial infection occurs.55

Cyproheptadine And Colchicine

Cyproheptadine (a serotonin antagonist) and colchicine (a leukocyte inhibitor) are of unproven utility in the treatment of dermatonecrosis and are not recommended due to the potential for serious side-effects.55

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