The high prevalence of multiple chronic disorders and polypharmacotherapy expose elderly patient to an increased risk of adverse drug reactions. Aging is associated with relevant morphological and functional changes in the kidney, with consequent changes in the pharmacokinetics of hydrosoluble drugs. Changes in renal function are not always clinically evident, and a concealed renal failure can lead to an increased risk of adverse drug reactions to hydrosoluble drugs. Targeting these at-risk patients could contribute to reduce the risk of adverse drug reactions with relevant cost saving.