Pharmacy Practice

thus: “two or more drugs interacting in such a manner that the effectiveness or toxicity of one or more drugs is altered”.[2‑5] DDI in patients receiving multidrug therapy is a major concern. Such interactions may lead to an increased risk of hospitalization and higher health care costs.[6] The incidence of actual occurrence of drug interactions has been reported to be much smaller, ranging from 0 to 1.3%.[7,8] Some studies have found that up to 11 % of patients experience symptoms associated with DDIs and that DDIs are responsible for up to 2.8 % of hospital admissions.[9,10] Research has also shown that DDIs are associated with increased health care use.[11] According to a recently published study, 1 % of all hospital admissions are caused by DDIs, and 0.05 % emergency department visits, 0.6 % of the hospital admissions and 0.1 % o