What is the best antibiotic for an infected toenail?

Treatment of Infected Toenails

For infected toenails, oral terbinafine is the first-line antibiotic treatment due to its superior efficacy and safety profile compared to other antifungal agents. 1

Diagnostic Considerations

Before initiating treatment, it's crucial to determine the type of infection:

• Fungal infection (onychomycosis): Most common cause of toenail infections
  • Dermatophytes are the primary pathogens (70-80% of cases)
  • Candida and non-dermatophyte molds less common
• Bacterial infection (paronychia): Often involves the surrounding tissue
  • Usually caused by Staphylococcus aureus or Streptococcus species

Treatment Algorithm

For Fungal Infections (Onychomycosis):

1. First-line treatment: Terbinafine

   • Dosage: 250 mg orally once daily
   • Duration: 12 weeks for toenail infections 1, 2
   • Superior efficacy: 70% mycological cure rate and 59% effective treatment rate 2
   • Fungicidal action against dermatophytes 2

2. Second-line treatment: Itraconazole

   • Dosage: 200 mg daily continuously for 12 weeks, or
   • Pulse therapy: 400 mg daily for 1 week per month for 3-4 months 1
   • Less effective than terbinafine for dermatophyte infections 1
   • Preferred for Candida infections 1

3. Alternative treatment: Fluconazole

   • Dosage: 450 mg once weekly
   • Duration: 6-9 months for toenail infections 3
   • Mycological cure rates: 47-62% for toenail infections 4
   • Convenient weekly dosing may improve compliance 3

For Bacterial Infections (Paronychia):

• For mild to moderate bacterial infections:

  • Topical antiseptics combined with warm soaks
  • Imidazole lotion alternating with antibacterial lotion 1

• For more severe bacterial infections:

  • Oral antibiotics targeting Staphylococcus and Streptococcus species

Important Considerations

• Confirm diagnosis before treatment: Mycological confirmation through KOH preparation and culture is essential before starting systemic therapy 1

• Treatment duration: Toenail infections require longer treatment (12 weeks) compared to fingernail infections (6 weeks) due to slower growth rate and thicker nail plate 2

• Monitoring:

  • Baseline liver function tests before starting oral antifungals
  • Monitor for adverse effects during treatment
  • For terbinafine: watch for taste disturbance, skin reactions, and liver toxicity 2

• Treatment failure: If standard treatment fails, consider:

  • Poor compliance
  • Poor drug absorption
  • Immunosuppression
  • Dermatophyte resistance
  • Subungual dermatophytoma requiring partial nail removal 1

Expected Outcomes

• Complete cure may take time even after successful treatment due to slow nail growth
• Mean time to overall success: approximately 10 months for toenail infections 2
• Clinical relapse rate: approximately 15% within one year after completing terbinafine therapy 2

Common Pitfalls

1. Starting treatment without mycological confirmation - leads to unnecessary treatment and potential side effects

2. Inadequate treatment duration - toenails require longer treatment than fingernails

3. Failure to consider non-dermatophyte infections - different pathogens may require different treatments

4. Ignoring drug interactions - particularly with itraconazole which has numerous interactions with common medications

5. Not addressing predisposing factors - such as trauma, poor footwear, or underlying conditions that may contribute to recurrence

Terbinafine remains the gold standard for dermatophyte onychomycosis with the highest cure rates and lowest relapse rates according to the British Association of Dermatologists guidelines 1.