From the Guidelines
For most spider bites, antibiotics are not routinely needed, but if an infection occurs, cephalexin 500 mg orally four times daily for 7-10 days is a recommended first-line treatment, as seen in the 2014 update by the Infectious Diseases Society of America 1. When considering the management of spider bites, it's crucial to prioritize the prevention of infection through proper wound care, including cleaning with soap and water, applying antibiotic ointment, and using a clean bandage. However, if signs of infection such as increasing redness, warmth, swelling, pus, or red streaks extending from the bite appear, antibiotic therapy may be necessary.
- The choice of antibiotic should target the common skin bacteria (Staphylococcus and Streptococcus species) that typically cause secondary infections.
- Cephalexin, dicloxacillin, and clindamycin are among the options for treating such infections, with cephalexin being a preferred choice due to its efficacy against a broad range of bacteria, including Staphylococcus and Streptococcus species, as indicated in the guidelines 1.
- For patients with penicillin allergies, alternatives like clindamycin 300-450 mg orally three times daily can be considered.
- It's also important to note that for severe infections or those caused by specific spiders like the brown recluse, which can lead to tissue necrosis, medical evaluation is crucial, and treatments may include intravenous antibiotics or surgical debridement.
- The guidelines from the Infectious Diseases Society of America provide a comprehensive approach to managing skin and soft tissue infections, including those resulting from spider bites, emphasizing the importance of appropriate antibiotic selection based on the suspected or confirmed causative pathogens 1.
From the Research
Spider Bite Management
- Most spider bites cause minimal or no effects, but some can lead to significant morbidity and rarely, mortality 2
- The management of spider bites depends on the type of spider and the severity of the bite
Antibiotic Treatment
- There is no specific antibiotic recommended for spider bites in the provided studies
- However, for skin and skin structure infections, cephalexin and dicloxacillin have been shown to be effective in treating staphylococcal infections 3
- Cephalexin, in particular, has been recommended for twice-daily therapy with confidence for staphylococcal skin and skin structure infections 3
Important Considerations
- Lay identification of the spider is not reliable, and clinicians must consider spider bite in the differential diagnosis of unexplained autonomic and neurological dysfunction 2
- In Australia, skin ulceration is more likely to be an infective, inflammatory, or traumatic cause than a case of necrotising arachnidism 2