What antibiotics (abx) are used to treat lower extremity cellulitis?

From the Guidelines

For lower extremity cellulitis, the first-line antibiotic treatment should include a 5- to 6-day course of antibiotics active against streptococci, such as cephalexin (500 mg orally four times daily) or clindamycin (300-450 mg orally four times daily). This recommendation is based on the most recent and highest quality study, which suggests that a shorter course of antibiotics is effective for nonpurulent cellulitis, particularly for patients who can self-monitor and have close follow-up with primary care 1. The choice of antibiotic should target the most common causative organisms, Streptococcus and Staphylococcus species.

• Key considerations for antibiotic selection include:
  • Patient allergies and local resistance patterns
  • Presence of systemic signs of infection or suspected MRSA, which may require broader coverage with antibiotics such as trimethoprim-sulfamethoxazole or doxycycline
  • Severity of infection, with more severe cases potentially requiring hospitalization and intravenous antibiotics such as cefazolin, vancomycin, or piperacillin-tazobactam
• Additional management strategies for lower extremity cellulitis include:
  • Elevation of the affected limb to reduce swelling
  • Monitoring for spreading redness or fever
  • Follow-up within 48-72 hours to ensure improvement
  • Adjustment of antibiotic selection based on culture results when available The 2014 IDSA guideline also recommends considering extension of treatment if the infection has not improved after 5 days 1. However, the more recent 2021 guideline from the American College of Physicians suggests that a 5- to 6-day course of antibiotics is sufficient for nonpurulent cellulitis 1.

From the FDA Drug Label

Prescribing dicloxacillin sodium capsules in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria

Prescribing cephalexin capsules, cephalexin for oral suspension, or cephalexin tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria

The antibiotics (abx) that can be used to treat lower extremity cellulitis are:

• Dicloxacillin
• Cephalexin 2 3

From the Research

Antibiotics for Lower Extremity Cellulitis

• The choice of antibiotics for lower extremity cellulitis depends on the suspected causative pathogens and local resistance patterns 4, 5, 6.
• Commonly used antibiotics for cellulitis include:
  • Cephalexin
  • Trimethoprim-sulfamethoxazole
  • Clindamycin
  • Cefdinir
• A study found that trimethoprim-sulfamethoxazole had a higher treatment success rate than cephalexin for outpatient cellulitis, especially in areas with high prevalence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections 4.
• Another study found that the addition of trimethoprim-sulfamethoxazole to cephalexin did not improve outcomes for patients with uncomplicated cellulitis, but the results were not conclusive and further research may be needed 5, 6.
• Cefdinir has been shown to be effective in treating mild to moderate uncomplicated skin and skin structure infections, including cellulitis, with a clinical cure rate similar to that of cephalexin 7.

Considerations for Antibiotic Choice

• The presence of MRSA should be considered when choosing an antibiotic, as some antibiotics such as trimethoprim-sulfamethoxazole and clindamycin have activity against MRSA 4, 5, 6.
• The severity of the cellulitis and the presence of underlying conditions such as diabetes or immunosuppression should also be considered when choosing an antibiotic 4, 5, 6.
• The use of anti-inflammatory therapy in addition to antibiotics may help to hasten the resolution of inflammation and improve outcomes 8.