What is the recommended dose of cephalexin (cephalexin) for a bacterial mouth sore?

Cephalexin Dosing for Bacterial Mouth Sores

For bacterial mouth sores in adults, use cephalexin 500 mg four times daily (every 6 hours) for 7-10 days, which is the standard dose recommended by the Infectious Diseases Society of America for soft tissue infections caused by susceptible bacteria. 1, 2

Standard Adult Dosing Regimen

• The recommended dose is 500 mg orally every 6 hours (four times daily) for soft tissue infections, including oral mucosal infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus species 1, 2
• For mild infections, the dose may be reduced to 250-500 mg every 6 hours, though the higher dose is preferred for adequate tissue penetration 1, 3
• Treatment duration should be 7-10 days depending on clinical response 1, 4

Microbiological Coverage and Critical Limitations

• Cephalexin provides excellent activity against MSSA and Streptococcus species, which are the most common pathogens in bacterial mouth sores 1, 2
• Cephalexin is completely ineffective against MRSA - if MRSA is suspected (risk factors include prior MRSA infection, recent hospitalization, or failure to respond to initial therapy), switch immediately to trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 1, 2
• Cephalexin has poor activity against anaerobes, making it unsuitable for deep oral abscesses that require metronidazole or clindamycin 1

When to Escalate Therapy

• If daily doses exceeding 4 grams are required for severe infections, switch to parenteral cephalosporins (e.g., cefazolin 1 g IV every 8 hours) 1, 3
• If no clinical improvement occurs within 5 days, extend treatment duration or consider alternative antibiotics 4
• If systemic signs develop (fever, lymphadenopathy, spreading cellulitis), broaden antimicrobial coverage 4

Allergy Considerations

• Patients with immediate hypersensitivity reactions to penicillin (anaphylaxis, angioedema, urticaria) should avoid cephalexin due to cross-reactivity risk 1, 4
• For non-immediate penicillin reactions, cephalexin remains an appropriate alternative 2

Pediatric Dosing (if applicable)

• For children, the recommended dose is 25-50 mg/kg/day divided into 4 doses for mild to moderate infections 1, 3
• For MSSA infections in children, increase to 75-100 mg/kg/day divided into 3-4 doses 1, 2