Terbinafine-induced Myositis: A Case Report

We report a case of terbinafine-induced myositis in a 37-year-old Asian male patient treated for Tinea cruris. The patient complained of severe generalized body aches, weakness, fever, fatigue, and passing of concentrated urine after consuming one dose of terbinafine 250 mg tablet, which worsened after the second dose. At the presentation, the patient was afebrile, fatigued, and had difficulty moving. All the laboratory parameters were normal, except N-acetyl-cysteine-(NAC)-activated creatine kinase, which was elevated to 276 U/L. There was a slight elevation in alanine transaminase (ALT) levels (44 U/L) and albumin-to-globulin ratio (1.8). The oral terbinafine was stopped. Patient was prescribed with tablet acetaminophen 650 mg thrice daily for two days and as needed thereafter, to manage myalgia. The patient reported being symptomatically better after six days of terbinafine withdrawal. The Naranjo’s causality assessment scale score was eight, indicating a probable relation between drug exposure (terbinafine use) and adverse drug reaction (myositis). The severity of terbinafine-induced myositis in this patient was moderate (level 3) as categorized by the Modified Hartwig and Siegel scale.