Keflex (Cephalexin) for Paronychia
Yes, Keflex (cephalexin) is an effective and appropriate first-line oral antibiotic for acute paronychia when signs of bacterial infection are present, though oral antibiotics should only be used after initial topical therapy or when infection is suspected. 1
When to Use Oral Antibiotics
The decision to use oral antibiotics like Keflex depends on the severity and characteristics of the paronychia:
Grade 1 paronychia (mild erythema/swelling without discharge): Oral antibiotics are NOT needed—use topical povidone iodine 2% twice daily with topical antibiotics and corticosteroids instead 2
Grade 2 paronychia (nail fold edema/erythema with pain, discharge, or nail plate separation): Oral antibiotics should be added if infection is suspected, but obtain bacterial/viral/fungal cultures first 3, 1, 2
Grade 3 or intolerable Grade 2: Oral antibiotics are indicated along with consideration for surgical drainage 1, 2
Why Cephalexin is Appropriate
Cephalexin is specifically recommended by the American Academy of Dermatology as a preferred oral antibiotic agent for paronychia with signs of infection. 1 The rationale includes:
- Provides excellent coverage against the most common pathogens: Staphylococcus aureus and Streptococcus species 4
- Up to 25% of paronychia cases have secondary bacterial superinfections involving both gram-positive and gram-negative organisms 3, 1, 5
- Oral cephalosporines achieve high tissue concentrations in the affected areas 6
Alternative Antibiotics if Cephalexin Fails
If initial treatment with cephalexin fails, switch to sulfamethoxazole-trimethoprim (Bactrim) as it provides broader coverage including MRSA. 1 Other alternatives include:
- Amoxicillin-clavulanate (Augmentin 500/125 mg every 12 hours) 1
- Fluoroquinolones (ciprofloxacin or levofloxacin) for suspected Pseudomonas, particularly if green pus is present 5, 6
Avoid clindamycin as it lacks adequate coverage for some streptococcal species and has increasing resistance patterns. 1
Critical Treatment Algorithm
Start with topical therapy first: Apply povidone iodine 2% twice daily combined with topical antibiotics and mid-to-high potency corticosteroid ointment 1, 2
Add warm water soaks: 15 minutes 3-4 times daily or white vinegar soaks (1:1 dilution) for 15 minutes daily 1
Obtain cultures before starting oral antibiotics: This is essential for grade 2 or higher cases, especially in severe cases or treatment failures 1, 2
Add oral cephalexin if: Signs of infection are present (discharge, significant pain, spreading erythema) 1
Reassess after 2 weeks: If no improvement, escalate therapy or consider surgical drainage 3, 1, 2
Important Caveats
Oral antibiotics are usually not needed if adequate drainage is achieved, unless the patient is immunocompromised or severe infection is present 1, 7
Determine if abscess is present: Any abscess formation mandates drainage, and oral antibiotics alone are insufficient 1, 7
Avoid topical steroids if purulent drainage is present until infection is adequately treated 2
For drug-induced paronychia (from EGFR inhibitors): This is primarily an inflammatory process rather than primary infection, so the same topical approach applies first, with oral antibiotics reserved for confirmed secondary infection 3, 2
Special Consideration for Green Pus
If green pus and significant swelling are present, this suggests Pseudomonas aeruginosa infection and requires immediate surgical drainage followed by oral fluoroquinolone (ciprofloxacin or levofloxacin) rather than cephalexin. 5