Inflammation is associated with downregulation of the expression and activity of cytochrome P450 enzymes (CYP450) involved in hepatic drug metabolism. Elevated plasma drug levels and increased toxicity might be the consequences of this downregulation. Few clinical studies have investigated these consequences of inflammation in children, who are prescribed many off-label or unlicensed drugs. This review describes the impact of inflammation on CYP450 drug metabolism and drug effect in children, with the consequent implications for drug studies and clinical therapy in this group.