Adverse drug reaction is a broad term comprising many problems associated with drug use. It includes side effects, toxicity, drug–drug interactions, drug–physiology interactions, drug–laboratory test interactions, allergic reactions, and idiosyncratic reactions. Food and Drug Administration (FDA) defines a serious adverse event as one in which the patient outcome is death, or life threatening, hospitalization, disability, congenital anomaly or required intervention to prevent permanent impairment or damage. ADRs are a major universal problem and are one of the leading causes of mortality and morbidity in health care facilities globally. The incidence of ADR varies with studies. A published meta-analysis of the incidence of adverse drug reactions (ADRs) in hospitalized patients concluded that ADRs rank as the fourth to sixth leading cause of death in the United States and the overall incidence of serious ADR accounted for 6.7% of hospitalized patients.