Terbinafine Use in Onychomycosis with Mild ALT Elevation
Terbinafine can be used cautiously in patients with mild ALT elevation of 50, but baseline liver function tests must be documented and the patient requires close monitoring during treatment, as active or chronic liver disease represents a contraindication but mild transaminase elevation alone does not preclude therapy. 1, 2, 3
Risk Assessment Framework
The British Association of Dermatologists explicitly states that active or chronic liver disease is a contraindication to terbinafine, but distinguishes this from patients with isolated mild transaminase elevations. 1, 2 An ALT of 50 (assuming normal range upper limit ~40) represents approximately 1.25 times the upper limit of normal, which does not constitute active liver disease in the absence of other hepatic pathology. 1
Mandatory Pre-Treatment Requirements
Before initiating terbinafine in this patient, you must:
- Document baseline liver function tests (ALT, AST) and complete blood count as recommended for all adult patients, particularly those with any hepatic abnormality history. 1, 3
- Investigate the cause of the ALT elevation to rule out active hepatitis, chronic liver disease, heavy alcohol use, or concomitant hepatotoxic medications—all of which would shift the risk-benefit calculation. 1, 2
- Obtain informed consent after discussing the risk of hepatotoxicity, which can lead to liver transplant or death in rare cases. 3
Treatment Protocol
If you proceed with terbinafine:
- Administer 250 mg daily for 12-16 weeks for toenail onychomycosis or 6 weeks for fingernail infection. 1
- Monitor liver function tests during therapy, particularly if treatment extends beyond one month or if the patient takes concomitant hepatotoxic drugs. 1
- Instruct the patient to immediately report symptoms of hepatotoxicity: persistent nausea, anorexia, fatigue, vomiting, right upper abdominal pain, jaundice, dark urine, or pale stools. 3
Common Pitfall to Avoid
The FDA label and British guidelines both emphasize that measurement of serum transaminases is advised for all patients before taking terbinafine, not just those with known liver disease. 3 Many clinicians mistakenly believe baseline testing is optional—it is not. This is particularly critical in your patient who already has documented ALT elevation. 1, 3
Alternative Considerations
If the ALT elevation represents undiagnosed chronic liver disease or if the patient has additional hepatotoxicity risk factors:
- Itraconazole may be considered as first-line alternative, though it also carries hepatotoxicity risk and requires similar monitoring in patients with pre-existing deranged liver function tests. 1
- Topical therapy alone (amorolfine 5% lacquer or ciclopirox 8% lacquer) may be appropriate for superficial or distal onychomycosis if systemic therapy poses excessive risk. 1
Evidence Quality Note
The British Association of Dermatologists guidelines provide Grade A evidence supporting terbinafine as first-line therapy for dermatophyte onychomycosis, with superior efficacy compared to itraconazole (76% vs 38% mycological cure at 72 weeks). 4 However, these efficacy data come from populations without significant hepatic impairment, making individualized risk assessment essential in your patient. 4, 5