Alternative to Terbinafine for Onychomycosis
Itraconazole should be used as the first-line alternative when terbinafine is not tolerated, with fluconazole as a second-line option if both terbinafine and itraconazole cannot be used.
Primary Alternative: Itraconazole
The British Association of Dermatologists guidelines explicitly identify itraconazole as "the next best alternative" when terbinafine cannot be used 1. This recommendation is based on:
Dosing Regimens
- Continuous therapy: 200 mg daily for 12 weeks
- Pulse therapy: 400 mg daily for 1 week per month
- 2 pulses for fingernail onychomycosis
- 3 pulses for toenail onychomycosis 1
Efficacy Considerations
While itraconazole is less effective than terbinafine (26% complete cure vs. 55% with terbinafine at 72 weeks), it remains significantly superior to older agents like griseofulvin 1. The long-term data shows mycological cure rates of 13% for itraconazole versus 46% for terbinafine at 5 years, with higher relapse rates (53% vs. 23%) 1.
Important Monitoring Requirements
- Contraindications: Heart failure, hepatotoxicity 1
- Absorption: Must be taken with food and requires acidic pH for optimal absorption 1
- Monitoring: Hepatic function tests recommended in patients with:
- Pre-existing abnormal liver function
- Continuous therapy >1 month
- Concomitant hepatotoxic drug use 1
- Common adverse effects: Headache and gastrointestinal upset 1
Second-Line Alternative: Fluconazole
Fluconazole (Strength of Recommendation B) should be considered when both terbinafine and itraconazole cannot be tolerated 1.
Dosing Protocol
- Fingernail infections: 150-450 mg weekly for 3 months
- Toenail infections: 450 mg weekly for at least 6 months 1
- Higher doses (450 mg/week) and longer duration (9-12 months) yield better cure rates 1
Efficacy Profile
- Mycological cure rates: 47-62% (toenails), 89-100% (fingernails)
- Clinical cure rates: 28-36% (toenails), 76-90% (fingernails) 1
- Less effective than both itraconazole and terbinafine 1, 2
Key Advantages
- Once-weekly dosing improves compliance compared to daily regimens 1
- Fewer drug interactions than itraconazole
- Long half-life allows convenient dosing schedule
Monitoring Requirements
- Contraindications: Hepatic impairment, renal impairment 1
- Baseline testing: Liver function tests and complete blood count 1
- Ongoing monitoring: LFTs in high-dose or prolonged therapy 1
- Dose adjustment needed based on creatinine clearance 1
Clinical Decision Algorithm
First choice when terbinafine not tolerated: Itraconazole
- Use pulse therapy for better tolerability
- Ensure adequate gastric acidity (avoid PPIs if possible)
- Monitor for heart failure symptoms
If itraconazole contraindicated or not tolerated: Fluconazole
- Use 450 mg weekly dosing
- Extend treatment duration (minimum 6 months for toenails)
- Accept lower cure rates but better compliance
Last resort: Griseofulvin (Strength of Recommendation C)
- Only if all other options unavailable or contraindicated
- Requires 12-18 months for toenails
- Significantly lower efficacy (30-40% mycological cure) 1
Critical Pitfalls to Avoid
- Do not use fluconazole as first alternative - itraconazole has superior efficacy despite being less effective than terbinafine 1, 2
- Avoid itraconazole with proton pump inhibitors - requires acidic pH for absorption 1
- Do not undertreat with fluconazole - inadequate duration is a common cause of failure; use at least 6 months for toenails 1
- Screen for heart failure before itraconazole - this is an absolute contraindication 1
- Monitor liver function - all oral antifungals carry hepatotoxicity risk 1
Emerging Resistance Considerations
Recent evidence shows emerging terbinafine resistance, particularly with Trichophyton indotineae 3, 4. In these cases, itraconazole has shown effectiveness as an alternative, though relapse rates remain concerning 4. This reinforces itraconazole's role as the primary alternative when terbinafine fails or cannot be tolerated.