Black widow: muscle rigidity/cramps. Brown recluse: necrotic ulcer
Black widow → opioids + benzodiazepines for cramps (IV calcium gluconate is NOT effective and no longer recommended); antivenom for severe envenomation
Brown recluse → supportive wound care ± delayed debridement
Order set
- Wound assessment
- Analgesia
- Opioids + benzos (widow) — NO IV calcium
- Tetanus status
Criteria
AdmitSystemic envenomation
ICUSevere systemic envenomation
DischargeSymptoms controlled, wound care, tetanus updated
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Systemic envenomation
- Necrotic spreading lesion
- Rhabdo/hemolysis
Differentials
- Cellulitis
- Other envenomation
- Abscess
Common mistakes
- Over-treating minor bites
- Missing systemic envenomation
- IV calcium for latrodectism (outdated, ineffective)
- Early excision of recluse lesions — NO; dapsone controversial (harm in G6PD deficiency)
- Forgetting tetanus prophylaxis (CDC wound guidance)
Disposition & follow-up
Mostly supportive; antivenom for severe widow envenomation.
Discharge package
MedicationsAnalgesia; wound care
Follow-upRecheck wound
Warning symptomsSpreading necrosis, systemic symptoms
💊 Treatment detail — doses & preparation
Analgesia + antivenomsupportive
DoseParacetamol/opioids for pain; antivenom only if systemic envenomation (per regional protocol)
Preparation—
MonitorLimb swelling progression, coagulation, tetanus status
📖 regional envenomation guidanceReviewed July 2026