What are the monitoring requirements for Terbinafine (Lamisil) therapy in the treatment of onychomycosis (fungal nail infection)?

From the Guidelines

Terbinafine for fungal nail infections typically requires minimal monitoring for most patients, with baseline liver function tests (LFTs) recommended before starting treatment due to the rare risk of hepatotoxicity, as noted in the British Association of Dermatologists' guidelines for the management of onychomycosis 2014 1. For standard treatment courses, which are typically 6 weeks for fingernails or 12 weeks for toenails at 250mg daily, routine monitoring of LFTs during treatment is not necessary for patients without pre-existing liver disease or risk factors. However, patients should be instructed to report symptoms of liver dysfunction immediately, including unexplained nausea, anorexia, fatigue, jaundice, dark urine, or right upper quadrant pain.

• Key considerations for monitoring include:
  • Baseline LFTs for all patients due to the potential for hepatotoxicity, as emphasized in the guidelines 1.
  • Periodic LFT monitoring (every 4-6 weeks) for patients with pre-existing liver disease, given the increased risk of liver effects in this population, as discussed by M. Ameen et al. 1.
  • A complete blood count may be considered before treatment in patients with risk factors for blood dyscrasias, acknowledging the potential for rare but serious hematological adverse effects.
• Treatment efficacy should be assessed clinically, with improvement typically visible as the nail grows out, though complete resolution may take 9-12 months for toenails.
• Terbinafine is generally well-tolerated but can interact with certain medications metabolized by CYP2D6, so a medication review before initiating therapy is important, as highlighted in the guidelines 1.
• Patients should be advised that alcohol consumption during treatment may increase the risk of liver effects, underscoring the need for cautious use in patients with a history of heavy alcohol consumption or liver disease, as noted by M. Ameen et al. 1.

From the FDA Drug Label

Prior to initiating treatment, appropriate nail specimens for laboratory testing (KOH preparation, fungal culture, or nail biopsy) should be obtained to confirm the diagnosis of onychomycosis The optimal clinical effect is seen some months after mycological cure and cessation of treatment. This is related to the period required for outgrowth of healthy nail Periodic monitoring of liver function tests is recommended. Terbinafine tablets should be immediately discontinued in case of elevation of liver function tests

Monitoring for fungal nail treatment with terbinafine includes:

• Obtaining nail specimens for laboratory testing before initiating treatment to confirm the diagnosis of onychomycosis
• Monitoring for liver function tests periodically during treatment
• Discontinuing treatment if liver function tests are elevated
• Monitoring for clinical effect after treatment cessation, which may take several months to be seen due to the time required for outgrowth of healthy nail 2

From the Research

Terbinafine Monitoring for Fungal Nail

• Terbinafine is a commonly used treatment for fungal nail infections, with studies showing its efficacy in treating toenail onychomycosis 3, 4.
• The recommended duration of treatment for toenail onychomycosis is typically 12 weeks, although some studies have investigated the effectiveness of shorter treatment durations 3.
• Monitoring for liver enzyme abnormalities is important when prescribing terbinafine, as it can cause elevated liver enzymes in some patients 5, 6, 7.
• Studies have shown that terbinafine can be used safely with close follow-up, and that baseline and regular laboratory monitoring for liver toxicity is recommended 5, 6, 7.
• The risk of liver injury requiring termination of treatment is relatively low, ranging from 0.11% to 1.22% for different oral antifungal treatments, including terbinafine 6.
• Other potential adverse events associated with terbinafine include cutaneous, cardiac, and neurological effects, although these are relatively rare 7.
• Antifungal stewardship is important to reduce the incidence of antifungal resistance, and laboratory testing of liver function tests is recommended prior to the administration of any oral antifungals 7.

Key Findings

• Mycological cure rates for terbinafine in the treatment of toenail onychomycosis have been reported to be around 72-77% 3, 4.
• Clinical cure rates are generally lower, ranging from 45-58% 3.
• The risk of adverse events associated with terbinafine is relatively low, although monitoring for liver toxicity is important 5, 6, 7.
• Terbinafine can be used safely with close follow-up, and antifungal stewardship is important to reduce the incidence of antifungal resistance 7.

Treatment Duration

• The recommended duration of treatment for toenail onychomycosis is typically 12 weeks 3, 4.
• Some studies have investigated the effectiveness of shorter treatment durations, although these may not be as effective 3.
• The treatment duration may depend on the extent of the disease and the patient's response to treatment 4.

Monitoring and Safety

• Monitoring for liver enzyme abnormalities is important when prescribing terbinafine 5, 6, 7.
• Baseline and regular laboratory monitoring for liver toxicity is recommended 5, 6, 7.
• The risk of liver injury requiring termination of treatment is relatively low, although other potential adverse events can occur 6, 7.