Antibiotic Choice for Paronychia
For acute bacterial paronychia, oral antibiotics targeting Staphylococcus aureus are the first-line choice when systemic therapy is needed, with cephalexin or dicloxacillin being standard options; however, if MRSA is suspected or the infection fails to respond, switch to sulfamethoxazole-trimethoprim (Bactrim). 1, 2
Initial Assessment and Treatment Strategy
Severity-Based Approach
Mild paronychia:
- Apply topical povidone iodine 2% twice daily to the affected area 1, 2
- Add topical antibiotics or topical corticosteroids to reduce inflammation 1, 3
- Implement antiseptic soaks with dilute vinegar (50:50 dilution) or povidone-iodine for 10-15 minutes twice daily 3
Moderate to severe paronychia:
- Add oral antibiotics with coverage for Staphylococcus aureus and other gram-positive organisms 1
- Consider that up to 25% of paronychia cases have secondary bacterial or mycological superinfections, requiring broader coverage 1, 3, 2
- If abscess is present, drainage is mandatory before or concurrent with antibiotic therapy 4, 5
Specific Antibiotic Recommendations
First-Line Oral Antibiotics
- Standard therapy targets S. aureus, the most prevalent pathogen in adult paronychia 6, 7
- Oral cephalosporins (such as cephalexin) are appropriate initial choices 7
- Alternative first-line options include fluoroquinolones (ciprofloxacin, levofloxacin, or moxifloxacin) which have high in vitro activity against most isolated organisms 7
Second-Line for Treatment Failure
- Switch to sulfamethoxazole-trimethoprim (Bactrim) when initial antibiotics fail, as it provides broader coverage including MRSA 1, 2
- This switch is particularly important given that MRSA can cause paronychia, especially in certain populations 6
Special Populations
- In pediatric patients with oral self-soothing behaviors (finger sucking), mixed anaerobic and aerobic infections are more common 6
- For these cases, initial therapy with broad-spectrum antibiotics like amoxicillin/clavulanate or clindamycin is suggested 6
Critical Diagnostic Considerations
Before changing antibiotics in non-responsive cases:
- Obtain bacterial, viral, and fungal cultures to identify resistant organisms or non-bacterial causes 1, 3, 2
- Consider both gram-positive and gram-negative organisms as potential pathogens 1, 3
- Remember that 72% of organisms isolated from EGFR inhibitor-associated paronychia are gram-positive, 23% gram-negative, and 5% Candida species 7
When Antibiotics May NOT Be Needed
Chronic paronychia (symptoms ≥6 weeks):
- This represents an irritant contact dermatitis, not primarily an infection 4, 5
- Treatment focuses on topical steroids or calcineurin inhibitors rather than antibiotics 4
- Secondary fungal colonization may occur; an imidazole lotion alternating with an antibacterial lotion is usually effective 8
Paronychia associated with ingrown toenails:
- Systemic antibiotics are ineffective unless infection is proven 9
- Treatment should address the causal toenail problem 5
Common Pitfalls to Avoid
- Do not use systemic antibiotics routinely without evidence of bacterial infection 9
- Topical antibiotics alone may suffice when simple soaks relieve inflammation 4
- Oral antibiotics are usually not needed if adequate drainage is achieved, unless the patient is immunocompromised or severe infection is present 4
- Reassess after 2 weeks of treatment; if no improvement, consider referral to dermatology or hand surgery 3, 2