Incidence and predisposing factors for flucloxacillin-related hepatotoxicity in children.

BACKGROUND: Flucloxacillin-induced hepatotoxicity is well established in adults. However, there are few paediatric studies of flucloxacillin-induced hepatotoxicity despite this drug being among the most commonly prescribed in children. We aimed to determine the incidence of flucloxacillin-induced hepatotoxicity in children receiving IV therapy as well as identify risk factors for this adverse drug reaction. METHODS: We undertook a 2 year retrospective audit of children aged 0-18 years admitted to the Royal Children's Hospital (March 2019 to March 2021) who had liver function tests determined before and after receiving IV flucloxacillin for at least 24 hours duration. Causality was assessed using the Roussel Uclaf Causality Assessment Method and Naranjo criteria. RESULTS: Overall, the incidence of hepatotoxicity was 66/393 (17%). The median age of children with hepatotoxicity was 1.1 years (IQR 0.3-11.9), 43 (65%) received two or more concomitant hepatotoxic medications and 23 (35%) were receiving total parenteral nutrition. The median timing of onset of hepatotoxicity after commencement of flucloxacillin was 4 days (range 2-7). Severe hepatotoxicity (Common Terminology Criteria for Adverse Events grade 3 or above) occurred in 9/66 (14%) for bilirubin, 13/66 (20%) for ALT and 10/66 (15%) for GGT. Predisposing factors for hepatotoxicity were increasing age (OR 1.06 per additional year, 95% CI 1.01-1.10, P = 0.02), with adolescents aged 12-18 years having the highest risk (OR 5.10, 95% CI 2.02-12.85, P = 0.001), and two or more concomitant hepatotoxic medications (OR 2.51, 95% CI 1.02-6.18, P = 0.05). The median time to resolution of hepatotoxicity after cessation of flucloxacillin was 5 days (range 2-10). CONCLUSIONS: In children, older patients and those receiving two or more concomitant hepatotoxic medications are at greater risk of flucloxacillin-induced hepatotoxicity.