Terbinafine for onychomycosis
Dr. Kirby also discussed the rationale for ordering regular LFTs in patients taking terbinafine for onychomycosis. “There is a risk of drug-induced liver injury from taking terbinafine, but it’s rare,” she said. “Can we be thoughtful about which patients we expose?”
Evidence suggests that patients with hyperkeratosis greater than 2 mm, with nail matrix involvement, with 50% or more of the nail involved, or having concomitant peripheral vascular disease and diabetes are recalcitrant to treatment with terbinafine
(J Am Acad Dermatol. 2019 Apr;80[4]:853-67). “If we can frame this risk, then we can frame it for our patients,” she said. “We’re more likely to cause liver injury with an antibiotic. When it comes to an oral antifungal, itraconazole is more likely than terbinafine to cause liver injury. The rate of liver injury with terbinafine is only about 2 out of 100,000. It’s five times more likely with itraconazole and 21 times more likely with Augmentin.”
She recommends obtaining a baseline LFT in patients starting terbinafine therapy “to make sure their liver is normal from the start.” In addition, she advised, “let them know that there is a TB seroconversion risk of about 1 in 50,000 people, and that if it happens there would be symptomatic changes. They would maybe notice pruritus and have a darkening in their urine, and they’d have some flu-like symptoms, which would mean stop the drug and get some care.”
Dr. Kirby emphasized that a patient’s propensity for developing drug-induced liver injury from terbinafine use is not predictable from LFT monitoring. “What you’re more likely to find is an asymptomatic LFT rise in about 1% of people,” she said.
She disclosed that she has received honoraria from AbbVie, ChemoCentryx, Incyte, Janssen, Novartis, and UCB Pharma.