From the Guidelines
The workup for a black widow spider bite should focus on clinical assessment, supportive care, and specific treatment when indicated, with an emphasis on monitoring for systemic symptoms and providing pain management as needed, as outlined in the 2024 American Heart Association and American Red Cross guidelines for first aid 1. The diagnosis of a black widow spider bite is primarily clinical, based on history and physical examination, looking for the characteristic symptoms of latrodectism, including severe abdominal pain, muscle cramping, hypertension, and diaphoresis.
Key Considerations
- Monitor vital signs and assess for systemic symptoms, as severe manifestations can compromise breathing or cause muscle injury and kidney failure, requiring treatment in a healthcare setting 1.
- Laboratory tests are generally not required but may include CBC, metabolic panel, and CPK if systemic toxicity is suspected.
- Treatment is primarily supportive with pain management using opioids if needed, and for severe cases, Antivenin Latrodectus mactans (black widow spider antivenin) at a dose of one vial IV is the definitive treatment, particularly for patients with severe pain, hypertension, or those who are very young, elderly, or pregnant.
- Over-the-counter acetaminophen and nonsteroidal anti-inflammatory agents can be used to alleviate local pain, and ice can be useful for local pain relief, as supported by studies on scorpion stings 1.
Management
- Most patients can be observed for 6-8 hours and discharged if symptoms are improving, though those receiving antivenin should be monitored for potential allergic reactions.
- Emergency services should be called if a person bitten by a spider or stung by a scorpion develops symptoms throughout the body such as difficulty breathing, muscle rigidity, dizziness, or confusion, as recommended by the 2024 American Heart Association and American Red Cross guidelines for first aid 1.
From the Research
Black Widow Spider Bite Workup
- The black widow spider bite is characterized by painful muscle rigidity and autonomic disturbances such as tachycardia, hypertension, and diaphoresis 2, 3, 4, 5, 6
- Symptoms typically last for 1-3 days 2
- Treatment options include:
- Symptomatic care with opioid analgesics and muscle relaxants, such as benzodiazepines 2, 5
- Antivenom (Antivenin Latrodectus mactans) which is effective in resolving symptoms, but its use is often limited due to fear of acute hypersensitivity reactions 2, 3, 4, 6
- Calcium gluconate and muscle relaxants may also be useful in treatment 6
- Antivenom is indicated for high-risk victims, such as those with hypertension and persons younger than 16 or older than 60 years of age 6
- A new purified F(ab)2 fragment Latrodectus mactans antivenom, Analatro®, is currently undergoing clinical trials and may offer similar efficacy with fewer adverse reactions compared to the currently available partially purified whole IgG Merck product 2
Clinical Manifestations
- Severe pain, muscle cramping, abdominal pain, and back pain are common symptoms of black widow spider envenomation 3, 5
- Autonomic disturbances such as tachycardia, hypertension, and diaphoresis may also occur 2, 5
- Respiratory failure and coma may result in severe envenomation 6
Treatment Outcomes
- Antivenom use is associated with shorter symptom duration in moderate and major outcome groups 4
- Adverse drug reactions are more common in patients receiving benzodiazepines and antivenom 4
- Most symptomatic Latrodectus spp. exposures reported to the National Poison Data System are minor, and few patients receive antivenom 4