Monitoring ALT, AST, and CBC after initiation of therapy has very low yield for terbinafine or griseofulvin

Reference

Stolmeier DA, Stratman HB, McIntee TJ, Stratman EJ. Utility of laboratory test result monitoring in patients taking oral terbinafine or griseofulvin for dermatophyte infections. JAMA Dermatol 2018; 154(12):1409-1416.

Synopsis

The package insert for terbinafine recommends a baseline measurement of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and a white blood cell count in patients with immunodeficiency who will be taking the medication for more than 6 weeks. However, physicians commonly order a baseline complete blood count (CBC) on all patients, and many obtain follow-up ALT and AST after some duration of treatment, often 1 month. This was a retrospective review of 4985 adults and children with a mean age of 43 years who had been given 4309 courses of terbinafine and 793 courses of griseofulvin. Patients were included if they were given the medication to treat an episode of dermatophyte infection, and excluded if they had a diagnosis of anemia, myelodysplastic syndrome, leukemia, or alcohol abuse. Laboratory results were divided into baseline results obtained between 90 days before and 7 days after starting the medication, and monitoring results obtained 7 days or more after the initiation of therapy. Of patients given terbinafine, 61% had at least one baseline test, 42% at least one monitoring test, and 32% had both tests. Testing was less frequent for patients taking griseofulvin (21%, 20%, and 9%, respectively). Approximately 1 in 3 patients given terbinafine and approximately 1 in 7 patients given griseofulvin had a baseline CBC. For both drugs, the rates of abnormal AST or ALT either at baseline or during monitoring was approximately 3%, of which less than 0.2% were grade 2 or worse elevations (> 3 times the upper limit of normal). The pattern was similar for griseofulvin. Only one patient developed hepatotoxicity and had the medication discontinued as a result.