Liver Injury due to Amoxicillin vs. Amoxicillin/Clavulanate: A Subgroup Analysis of a Drug-Induced Liver Injury Case-Control Study in Italy

Objective: Several studies showed that amoxicillin plus clavulanic acid (co-amoxiclav) is one of the most common agents associated to serious Drug Induced Liver Injury (DILI). We estimated the risk of acute serious DILI associated with amoxicillin alone compared with co-amoxiclav, through a multicenter case-control study carried out in nine Italian hospitals from October 2010 to January 2014. Methods: Cases were adults, with a diagnosis of acute liver injury. Controls presented acute clinical disorders, not related to chronic conditions and not involving the liver. Adjusted Odds Ratio (ORs) with 95% CI were calculated initially with a bivariate and then multivariate analysis. Results: We analysed 179 cases matched to 1770 controls. Seven cases were exposed to amoxicillin (adjusted OR 1.69, 95% CI 0.72-3.98) and 22 cases to co-amoxiclav (adjusted OR 3.00, 95% CI 1.76-5.40). Conclusions: Co-amoxiclav almost doubled the risk of serious acute liver injury compared to amoxicillin alone. The incidence of co-amoxiclav induced DILI is very low but the widespread use of this drug by the general population makes the risk clinically relevant. The often inappropriate prescription of antimicrobial agents, and in particular of co-amoxiclav, could expose a given patient to a life-threatening risk compared to a negligible clinical benefit.