large number of drugs are introduced every year, and new interactions between medications are increasingly reported. The interaction may increase (or) decrease the effectiveness of the drug, it also may result in a new side effects. Drug - Drug interactions (DDIs) may lead to adverse drug reactions that can be severe enough to necessitate hospitalization. Approximately 37-60% of patients admitted to the hospital may have one or more potentially interacting drug combinations at admission. The proportion of hospital admissions due to DDIs ranges from 0% to 3.8%. In inpatients, the risk of having potentially interacting drug combinations can additionally increase, because new drugs are often added to the existing drug therapy. Recent studies could show that 2.2-65.0% of inpatients may have one or more potential DDIs and that 41.1- 69.7% of patients have a potential interacting drug combination at discharge. In inpatients, drug modifications shortly before discharge may be of most importance to reduce DDIs because in general the clinical and therapeutic monitoring of patients after discharge significantly declines.
