Treatment of Onychomycosis
First-Line Treatment: Oral Terbinafine for Dermatophyte Infections
Oral terbinafine 250 mg daily is the recommended first-line treatment for dermatophyte onychomycosis, given for 6 weeks for fingernails and 12 weeks for toenails, achieving cure rates of 70-90%. 1, 2
Why Terbinafine is Preferred
- Terbinafine demonstrates superior efficacy compared to itraconazole and fluconazole for dermatophyte infections both in vitro and in clinical trials. 1, 3, 4
- The drug has fungicidal (not just fungistatic) activity against dermatophytes, allowing for shorter treatment duration. 5, 6
- Terbinafine achieves mycological cure rates of 76% ± 3% across 18 randomized controlled trials. 7
- It has minimal drug interactions, making it safer for patients on multiple medications. 6, 7
Critical Pre-Treatment Requirement
Never initiate treatment without mycological confirmation through KOH preparation, fungal culture, or nail biopsy—this is the most common cause of treatment failure. 3, 2, 8
Baseline Monitoring
- Obtain liver function tests (ALT and AST) and complete blood count before starting terbinafine, especially in patients with history of alcohol consumption, hepatitis, or liver disease. 1, 3
- Common adverse effects include gastrointestinal disturbances (49% of side effects), taste disturbance, and dermatological reactions (23%). 5
- Rare but serious: hepatotoxicity, subacute lupus-like syndrome, and psoriasis aggravation. 1, 5
Alternative Treatment: Itraconazole for Candida and Non-Dermatophyte Infections
When Candida species invade the nail plate, itraconazole is the most effective agent and should be used instead of terbinafine. 1, 3
Itraconazole Dosing Regimens
- Pulse therapy (preferred): 400 mg daily for 1 week per month—2 pulses for fingernails, 3-4 pulses for toenails. 1, 3
- Continuous therapy: 200 mg daily for minimum 4 weeks (fingernails) or 12 weeks (toenails). 1
- Itraconazole achieves cure rates of 92% for Candida onychomycosis when given as pulse therapy. 1
Important Contraindications
- Itraconazole is contraindicated in congestive heart failure due to negative inotropic effects. 1
- It must be taken with food and acidic pH for optimal absorption. 1
- Monitor liver function tests in patients on continuous therapy >1 month or with concomitant hepatotoxic drugs. 1
Special Populations
Diabetic Patients
Terbinafine is the preferred agent in diabetics due to low risk of drug interactions and no hypoglycemia risk. 1, 5, 3
- Onychomycosis is a significant predictor for foot ulcers and cellulitis in diabetics, making treatment critical to prevent serious complications. 1, 3
- Avoid itraconazole in diabetics with cardiac disease due to increased prevalence of heart failure in this population. 1
Immunocompromised Patients (HIV, Transplant Recipients)
Terbinafine is preferred over itraconazole in immunocompromised patients due to lower risk of drug interactions with antiretrovirals and immunosuppressive medications. 1, 3
- Prevalence of onychomycosis in HIV-positive patients is approximately 30%. 1
- Griseofulvin should be avoided as it is the least effective oral antifungal in HIV-positive patients. 3
Pediatric Patients (Ages 1-12 Years)
Both terbinafine and itraconazole are first-line options for children, with higher cure rates (94-100%) than adults. 1, 3
Terbinafine Dosing by Weight:
- <20 kg: 62.5 mg daily
- 20-40 kg: 125 mg daily
40 kg: 250 mg daily
- Duration: 6 weeks for fingernails, 12 weeks for toenails 1, 3
Itraconazole Pulse Therapy:
- 5 mg/kg daily for 1 week per month
- 2 pulses for fingernails, 3 pulses for toenails 1
Topical Therapy: Limited Role
Topical treatments are inferior to systemic therapy except in very limited cases of distal or superficial white onychomycosis without matrix involvement. 3, 8
When to Consider Topical Therapy
- Mild-to-moderate infections without lunula involvement. 1, 8
- Patients with contraindications to systemic therapy. 1
- As adjunct to systemic therapy (not as monotherapy for moderate-severe disease). 1
Topical Options
- Amorolfine 5% lacquer: Apply once or twice weekly for 6-12 months. 1, 3
- Ciclopirox 8% lacquer: Apply once daily for up to 48 weeks, achieving complete cure in only 5.5-8.5% of patients. 1, 8
- Both require monthly removal of unattached infected nail by healthcare professional. 8
Management of Treatment Failure (20-30% of Cases)
Common Causes of Failure
- Incorrect diagnosis without mycological confirmation (most common). 3
- Poor adherence to treatment regimen. 3
- Dermatophytoma (compact fungal mass preventing drug penetration). 3
- Immunosuppression or drug resistance. 3
Strategies for Treatment Failure
Switch to alternative systemic agent: if terbinafine was used, switch to itraconazole or vice versa. 3
- Consider partial nail removal or avulsion for dermatophytoma. 3
- Reevaluate diagnosis with repeat mycological testing. 3
- Assess for underlying immunosuppression or poor drug absorption. 3
Follow-Up and Realistic Expectations
- Reevaluate patients 3-6 months after initiating treatment to assess response. 3
- Complete clinical normalization may not occur even with mycological cure, as nails may have pre-existing dystrophy from trauma or non-fungal disease. 3
- Treatment duration appears adequate at 12 weeks for toenails based on cure rates of 71-82% at follow-up. 9
Prevention of Recurrence
- Wear protective footwear in communal bathing facilities, gyms, and hotel rooms. 3
- Apply absorbent antifungal powders and wear cotton socks. 3
- Keep nails short, avoid sharing toenail clippers, and discard old footwear. 3
- Thoroughly dry between toes after bathing and change socks daily. 5
Drugs to Avoid
Griseofulvin is no longer recommended as first-line treatment due to low efficacy (30-40% mycological cure), higher relapse rates, and prolonged treatment duration of 12-18 months. 1, 3