A drug reaction or effect other than the intended or anticipated one that is unusual, undesirable, discomforting, or life-threatening.
An unexpected and potentially harmful response to a drug that is unrelated to its intended effect. Adverse drug reactions can occur because of the nature of the drug taken or because the person taking it is allergic to the drug. Adverse drug reactions can be mild, moderate, or severe and life-threatening. Because most drugs are taken orally, either as pills or capsules, and are digested in the gastrointestinal tract, the most common reactions are nausea, loss of appetite, and diarrhea. Rashes are also a common adverse drug reaction.
An undesired side effect or toxicity caused by the administration of a drug.
An unwanted response to a therapeutic drug. Health professionals are encouraged to report all adverse events related to drugs or medical devices to the manufacturer and the Food and Drug Administration (FDA) to aid in monitoring the safety of marketed medical products.