What are the recommended oral treatments for onychomycosis (toenail fungus)?

Oral Treatments for Toenail Fungus

Terbinafine 250mg daily for 12-16 weeks is the first-line oral treatment for toenail fungus (onychomycosis) due to its superior efficacy and relatively low risk of side effects. 1

First-Line Oral Treatment Options

Terbinafine

• Dosage: 250mg once daily 2
• Duration: 12 weeks for toenails (6 weeks for fingernails) 1, 2
• Efficacy: Superior to other oral antifungals with mycological cure rates of 73-94% 3, 4
• Mechanism: Allylamine antifungal with fungicidal activity 5
• Monitoring: Baseline liver function tests and complete blood count recommended 1
• Contraindications: Hepatic impairment 6
• Common side effects: Headache, taste disturbance, gastrointestinal upset 6, 2
• Warning: Can aggravate psoriasis and cause subacute lupus-like syndrome 6

Itraconazole

• Dosage: 200mg daily continuous therapy or pulse therapy (200mg twice daily for 1 week per month, with 2 pulses for fingernails and 3 pulses for toenails) 6, 1
• Duration: 12 weeks for continuous therapy 6
• Efficacy: Lower than terbinafine (45.8% vs 73% mycological cure at 48 weeks) 4
• Contraindications: Heart failure, hepatotoxicity 6, 1
• Caution: More drug interactions than terbinafine 1
• Best absorbed: With food and acidic pH 6

Alternative Oral Treatments

Fluconazole

• Dosage: 150-450mg once weekly 6, 1
• Duration: At least 6 months for toenail infections 6
• Indication: Useful alternative when patients cannot tolerate terbinafine or itraconazole 6
• Contraindications: Hepatic impairment, renal impairment 6
• Monitoring: Baseline liver function tests and full blood count; monitor liver function in high-dose or prolonged therapy 6

Griseofulvin

• Dosage: 500-1000mg daily 6
• Duration: 12-18 months for toenail infections 6
• Efficacy: Lower efficacy and higher relapse rates compared to terbinafine and itraconazole 6, 1
• Contraindications: Liver impairment 6
• Administration: Should be taken with fatty food to increase absorption 6
• Note: No longer recommended as first-line due to inferior efficacy and longer treatment duration 1

Treatment Selection Algorithm

1. Assess infection type and severity:

   • For dermatophyte infections: Terbinafine is most effective 1, 4
   • For Candida infections: Itraconazole may be more effective 1

2. Consider patient factors:

   • Hepatic impairment: Avoid terbinafine, itraconazole, and griseofulvin; consider fluconazole with dose adjustment 6
   • Heart failure: Avoid itraconazole 1
   • High risk of drug interactions: Terbinafine preferred over azoles 1
   • Diabetic patients: Terbinafine preferred due to lower risk of drug interactions 1

3. Treatment regimen:

   • Start with continuous terbinafine therapy rather than pulse therapy (76.67% vs 26.67% clinical cure rate) 3
   • For non-responders to initial 12-week terbinafine course, a second 12-week course may increase mycological cure rates to 94% 7

Common Pitfalls and Caveats

• High recurrence rates: Onychomycosis has 40-70% recurrence rates even with established treatments 1
• Treatment failure factors: Poor compliance, poor absorption, immunosuppression, dermatophyte resistance, subungual dermatophytoma, and zero nail growth 1
• Liver monitoring: Essential for patients with history of heavy alcohol consumption, pre-existing liver disease, hepatitis, or hematological abnormalities 1
• Taste disturbance: Can be severe, prolonged, or permanent with terbinafine; discontinue if it occurs 2
• Incomplete treatment: 6 weeks of terbinafine is generally insufficient for toenail infections, while 12 weeks is optimal 5, 8

Prevention Strategies

• Keep nails short
• Avoid sharing nail clippers
• Wear protective footwear in public areas
• Apply antifungal powders in shoes and on feet
• Wear cotton, absorbent socks
• Treat concomitant fungal infections 1