Bites, Spider & Scorpion

Clinical Findings

• 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

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

• No specific treatment other than analgesics is required for envenomations by most scorpions found in the United States

• An FDA-approved specific antivenom is now available for Centruroides stings