Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 38-56: Spider Bites & Scorpion Stings + Clinical Findings Download Section PDF Listen +++ ++ Envenomation from most species of spiders in the United States causes only Local pain Redness, swelling Venomous black widow spiders (Latrodectus mactans) cause Generalized muscular pains Muscle spasms Rigidity Brown recluse spider (Loxosceles reclusa) causes Progressive local necrosis Hemolytic reactions (rare) Stings by most scorpions in United States cause only local pain Stings by the more toxic Centruroides species (found in southwestern United States) may cause Muscle cramps Twitching and jerking Hypertension, convulsions, and pulmonary edema (occasionally) + Treatment Download Section PDF Listen +++ +++ Black widow spider bites ++ Relieve pain with parenteral opioids or muscle relaxants (eg, methocarbamol, 15 mg/kg) Calcium gluconate 10%, 0.1–0.2 mL/kg intravenously, may relieve muscle rigidity Antivenom is available; because of concerns about acute hypersensitivity reactions, it is often reserved for very young or elderly patients and those who do not respond to the above measures Horse serum sensitivity testing required (instruction and testing materials are in the antivenin kit) +++ Brown recluse spider bites ++ No universally accepted management Some authorities recommend early excision of the bite site Other experts recommend oral corticosteroids Anecdotal reports claim success with dapsone and colchicine +++ Scorpion stings ++ An FDA-approved specific antivenom is now available for Centruroides stings