Is Augmentin (amoxicillin‑clavulanate) an appropriate first‑line treatment for a nail infection?

Augmentin Is Not Appropriate for Nail Infections

Augmentin (amoxicillin-clavulanate) is not indicated for nail infections because the vast majority of onychomycosis cases are caused by fungi—not bacteria—and require antifungal therapy, not antibiotics. 1, 2

Why Augmentin Does Not Treat Nail Infections

• Dermatophytes cause the overwhelming majority of nail infections, with Trichophyton rubrum being the most common pathogen worldwide. 1, 3
• Mycological confirmation (microscopy and culture) is mandatory before starting any treatment because only about 50% of nail dystrophies are actually fungal, and the remainder are due to trauma, psoriasis, or other non-infectious causes. 1, 2
• Augmentin is an antibacterial agent that targets bacterial cell walls and has no activity against fungi. 4

When Bacteria Do Infect the Nail: Paronychia

• Bacterial paronychia (infection of the nail fold, not the nail plate itself) is caused by Staphylococcus aureus or mixed anaerobic/aerobic organisms in children with finger-sucking habits. 5
• In bacterial paronychia, amoxicillin-clavulanate or clindamycin is appropriate initial therapy, coupled with incision and drainage if an abscess has formed. 5
• This is distinct from onychomycosis, which involves fungal invasion of the nail plate and requires systemic antifungal agents. 1, 2

Correct First-Line Treatment for Fungal Nail Infections

For Dermatophyte Onychomycosis (Most Common)

• Oral terbinafine 250 mg once daily is the first-line treatment: 6 weeks for fingernails, 12 weeks for toenails. 2, 6
• Terbinafine achieves 70–80% mycological cure rates for toenails and 80–90% for fingernails, far superior to all other agents. 1, 2
• Baseline liver function tests and complete blood count are required before starting terbinafine. 2, 6

For Candida Onychomycosis (Less Common)

• Itraconazole is the preferred agent for Candida nail infections, achieving 92% cure versus only 40% with terbinafine. 2
• Pulse dosing: 400 mg daily for 1 week per month, repeated for 2 months (fingernails) or 3–4 months (toenails). 1, 2
• Itraconazole must be taken with food and acidic beverages to optimize absorption. 2

For Candida Paronychia (Nail Fold Only, No Plate Invasion)

• Topical imidazole (clotrimazole or miconazole) applied to the nail folds is first-line therapy. 1, 2
• Continue application until cuticle integrity is restored, which may take several months. 1, 2
• If bacterial co-infection is suspected, alternate antifungal with topical antibacterial lotion. 1, 2

Common Pitfalls to Avoid

• Do not prescribe antibiotics for nail discoloration or thickening without confirming bacterial infection. The default assumption should be fungal until proven otherwise. 1, 2
• Do not start systemic antifungals without mycological confirmation, as this leads to unnecessary treatment of non-fungal nail disease. 1, 2
• Yeasts and non-dermatophyte molds are often secondary colonizers or saprophytes in previously damaged nails; culture results must be interpreted in clinical context. 1
• Pseudomonas aeruginosa can cause green or black nail discoloration and is treated with topical or oral ciprofloxacin, not amoxicillin-clavulanate. 3

Algorithm for Nail Infection Management

1. Obtain mycological confirmation (KOH prep and fungal culture) before any systemic therapy. 1, 2
2. If dermatophyte confirmed: prescribe terbinafine 250 mg daily (6 weeks for fingers, 12 weeks for toes). 2, 6
3. If Candida confirmed with nail plate invasion: prescribe itraconazole pulse therapy (400 mg daily × 1 week/month for 2–3 pulses). 1, 2
4. If Candida paronychia only (no plate invasion): prescribe topical imidazole. 1, 2
5. If bacterial paronychia confirmed (erythema, warmth, purulence around nail fold): prescribe amoxicillin-clavulanate or clindamycin plus incision/drainage if abscess present. 5
6. If green/black discoloration: suspect Pseudomonas and prescribe ciprofloxacin. 3