Cephalexin Dosing for Paronychia
For paronychia in adults, use cephalexin 500 mg orally four times daily (every 6 hours) for 7-10 days, which is the standard dose for skin and soft tissue infections caused by methicillin-susceptible Staphylococcus aureus. 1, 2
Dosing Regimen
- Adults: Cephalexin 500 mg orally every 6 hours (four times daily) is the recommended dose for skin and soft tissue infections 1, 2
- Pediatric patients: Use 25-50 mg/kg/day divided into 4 doses for mild to moderate infections, or 75-100 mg/kg/day divided into 3-4 doses for MSSA infections 1
- Duration: Continue therapy for 7-10 days depending on clinical response 1
Important Clinical Considerations
When Cephalexin May Not Be Appropriate
- Consider alternative antibiotics if MRSA is suspected or confirmed, as cephalexin is completely ineffective against methicillin-resistant organisms 1
- Bacterial cultures should be obtained before starting antibiotics, especially in severe cases or treatment failures 3
- Up to 25% of paronychia cases may have secondary fungal infections (particularly Candida), which will not respond to cephalexin and require antifungal therapy 3
Fungal Paronychia Considerations
- If the paronychia is associated with Candida onychomycosis, itraconazole should be considered first-line treatment at 200 mg per day or as pulse therapy (400 mg per day for 1 week each month) for a minimum of 4 weeks for fingernails 4
- Fluconazole 50 mg per day or 300 mg per week is an alternative for Candida infections if itraconazole is contraindicated 4
Common Pitfalls to Avoid
- Do not use cephalexin if MRSA is likely: Research shows that while some MRSA skin infections may respond to incision and drainage alone, cephalexin has no activity against MRSA 5, 6
- Distinguish bacterial from fungal etiology: Patients with chronic paronychia, occupational exposure (wet work), or immunosuppression are more likely to have Candida involvement requiring antifungal therapy rather than antibiotics 4
- Adjust dose in renal impairment: Patients with creatinine clearance less than 30 mL/min require dose reduction proportional to their reduced renal function 7