Thrombotic Microangiopathy Cases Prompt Update to Antifungal Drug Labeling
The labeling for Lamisil (terbinafine hydrochloride) Tablets and Oral Granules has been updated to include a new warning regarding the risk of thrombotic microangiopathy.
Specifically, the labeling states that cases of thrombotic microangiopathy, including thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, have been reported with the use of terbinafine. If clinical symptoms and lab findings are consistent with thrombotic microangiopathy, patients should discontinue use of terbinafine. Unexplained thrombocytopenia and anemia in patients being treated with terbinafine should prompt further evaluation and a diagnosis of thrombotic microangiopathy should be considered.
Lamisil, an allylamine antifungal, is indicated for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes (tinea unguium). Prior to initiating treatment, appropriate nail specimens for lab testing should be obtained to confirm the diagnosis of onychomycosis. In addition, patients should be evaluated for evidence of chronic or active liver disease as the drug is contraindicated in this patient population.
Terbinafine inhibits biosynthesis of ergosterol, an essential component of fungal cell membrane, via inhibition of squalene epoxidase enzyme. This results in fungal cell death primarily due to the increased membrane permeability mediated by the accumulation of high concentrations of squalene but not due to ergosterol deficiency.
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