Treatment—The treatment of local and systemic brown recluse spider bites also has been a source of controversy over the years. Several treatment regimens, including early and late surgical excision and debridement, systemic steroids, hyperbaric oxygen therapy, cryproheptadine, electric shock therapy, and dapsone, have been anecdotally described in the literature; however, none of these treatments have prospective human trials to back up this anecdotal evidence. With conservative wound management, ice, elevation, and analgesics, almost all patients exhibit a full recovery with minimal scarring that rarely needs surgical revision.19
Dapsone has been the most controversial of the treatments for brown recluse bites. Dapsone makes theoretical sense in the treatment of these lesions because of its ability to inhibit polymorphonuclear leukocytes from entering the wound area and causing local destruction. There are many anecdotal reports supporting the use of dapsone for more severe bites, the most famous being the King and Rees20 case report of a patient with a brown recluse bite of the leg that was seen 24 hours after the bite had occurred. They reported that 2 days after prescribing dapsone 100 mg twice daily along with ice and local wound care, the bite site was pain free with marked reduction in induration and erythema. Their argument was based on an assumption that the lesion "probably would have developed an indolent ulcer." They supported their use of dapsone with an animal model of guinea pigs that were pretreated with dapsone before being injected with Loxosceles venom. The authors reported that pretreated guinea pigs showed a reduction in lesion size at 24 hours compared with those without treatment.20 The methods of this study have come into question primarily due to the rarity of patients with brown recluse bites pretreated with dapsone. Also, follow-up animal studies have conflicted with the benefit of dapsone for this indication.21,22
Although the benefit of dapsone is controversial, the side effects of this medicine are protean and well known. The development of hemolytic anemia has long been attributed to this medication and will occur to some degree in all patients.23 This predictable hemolysis can sometimes become confused with the direct effects of the brown recluse venom, which can delay definitive diagnosis of the etiology of the hemolysis and expose patients to an unproven drug with multiple toxicities. Severe hemolysis can be expected in patients with glucose-6-phosphate dehydrogenase deficiency; therefore, dapsone is absolutely contraindicated in this patient population.
Methemoglobinemia is another feared side effect of dapsone. Although mostly asymptomatic and usually undetectable, sometimes elevated levels of methemoglobin can cause severe systemic symptoms requiring hospitalization.24 Unfortunately, it is impossible to predict who will experience this complication because of a lack of simple blood testing such as that available for patients with subclinical glucose-6-phosphate dehydrogenase deficiency. Because of these serious and sometimes common adverse events attributed to dapsone, and the lack of solid evidence to support its effectiveness, there is no place for dapsone in the treatment of loxoscelism at this time.
The role of early surgical excision has changed over the past few decades. Reports prior to 1975 often suggested early surgical excision of bites with grafting as the treatment of choice.25,26 Since then, multiple reports have shown that early surgical excision often does more harm than good in the treatment of brown recluse bites.5,6 Early surgical excision is contraindicated because of the rapid spread of the toxin through the wound in the first weeks following a bite. The toxin may continue to spread for at least 4 weeks, which makes demarcation between envenomed and healthy tissue difficult.27 DeLozier et al6 suggested that the added surgical trauma from early excision may potentiate the inflammatory response to the brown recluse venom, prolonging healing time.
Conservative debridement may be performed to prevent secondary infection, but surgery should generally be withheld for 4 to 6 weeks. Early local wound care during this time followed by late surgical excision and grafting are more successful than early surgical excision. However, most wounds, if treated with supportive therapy alone, will ultimately heal with minimal scarring.28 A retrospective study of 149 patients with brown recluse bites showed that nearly half of all bites healed within 2 weeks and only 13% of bites left a visible scar. None of these patients were treated with surgery.29
Corticosteroids also have been used extensively for more serious reactions after envenomation from a brown recluse spider, but documentation in the literature is sparse. In a white rabbit model, Jansen et al30 did not find any treatment value for either intramuscular or intralesional methylprednisolone in the prevention of dermonecrosis after a brown recluse spider bite. Berger et al31 also concluded that large doses of steroids had no effect on the progression or development of necrotic arachnidism. Despite this evidence, there are many who still advocate the use of steroids for more serious bites and for those associated with systemic symptoms.32 Given the extensive use of corticosteroids in patients with autoimmune hemolytic anemia, this treatment may be of use in patients with Coombs-positive hemolytic anemia secondary to brown recluse envenomation.33,34 For this reason, direct Coombs testing in patients with hemolytic anemia due to brown recluse bites could provide useful information in the inpatient management of these patients.