What is the indication for repeating liver and kidney function tests in a 42-year-old male patient, for whom Lamisil (Terbinafine) 250mg once daily was prescribed?

From the Guidelines

The patient's Lamisil (terbinafine) 250 mg daily should remain on hold until the liver and kidney function test results are reviewed and confirm normal liver and kidney function, as recommended by the British Association of Dermatologists' guidelines for the management of onychomycosis 1. This approach is in line with the guidelines, which suggest that terbinafine is generally preferred over itraconazole for the treatment of dermatophyte onychomycosis, but it requires baseline liver function tests and a complete full blood count in adult patients with a history of hepatotoxicity or haematological abnormalities. Some key points to consider when prescribing terbinafine include:

• Hepatic impairment is a contraindication for terbinafine use
• Renal impairment is also a contraindication for terbinafine use
• Baseline liver function tests and a complete full blood count are recommended in adult patients with a history of hepatotoxicity or haematological abnormalities
• Monitoring of liver function tests is recommended during terbinafine therapy, especially in the first months of treatment. The patient should be informed about this temporary suspension and advised to report any symptoms such as persistent nausea, anorexia, fatigue, jaundice, dark urine, or right upper quadrant pain while waiting for the lab results. Regular monitoring of liver function is standard practice during Lamisil therapy, especially in the first months of treatment, as early detection of abnormalities can prevent serious hepatic injury, as noted in the British Association of Dermatologists' guidelines 1.

From the FDA Drug Label

1. 1 Hepatotoxicity ... Before prescribing terbinafine tablets, liver function tests should be performed since hepatotoxicity may occur in patients with and without pre-existing liver disease. Periodic monitoring of liver function tests is recommended. 5.8 Laboratory Monitoring Measurement of serum transaminases (ALT and AST) is advised for all patients before taking terbinafine tablets.

The decision to hold Lamisil 250 QD until lab results are obtained is a conservative approach, as the drug label recommends periodic monitoring of liver function tests and advises measuring serum transaminases before taking the medication 2. This suggests that liver function tests should be performed to minimize the risk of hepatotoxicity.

From the Research

Liver and Kidney Profile

• The patient's liver and kidney profile needs to be repeated as it was not performed last time.
• The decision to hold Lamisil 250 QD until lab results are obtained is likely due to the potential risk of liver injury associated with terbinafine therapy, as reported in studies 3, 4, 5.

Terbinafine-Induced Liver Injury

• Terbinafine has been associated with severe liver injury, including hepatobiliary dysfunction, in rare cases 3, 4, 5.
• The mechanism of terbinafine-induced hepatotoxicity is thought to involve the formation of a reactive metabolite, 7-dimethylhept-2-ene-4-ynal (TBF-A), which can bind to hepatobiliary proteins and lead to direct toxicity or immune-mediated reactions 4, 5.
• Studies suggest that monitoring liver function tests during terbinafine therapy may not be effective in preventing liver injury, and that patients should be advised to discontinue treatment and seek medical attention if symptoms of liver injury occur 3.
• However, another study recommends monitoring patients clinically and measuring liver biochemistry through periodic blood tests, after confirming normal liver function at the onset of therapy with terbinafine 5.

Relevance of Other Studies

• One study 6 investigated the effects of pulmonary metabolites of prostaglandins E2 and F2alpha on guinea-pig respiratory tract, which is not directly relevant to the patient's situation or terbinafine-induced liver injury.