Adverse Drug Reaction – Definition

adverse drug reaction

Adverse Drug Reaction – an undesired, negative, and often unpleasant response to a medication. People commonly refer to adverse drug reactions as side effects, which is not entirely accurate because a side effect may have therapeutic value whereas an adverse drug reaction is potentially harmful. Adverse drug reactions are common, affecting more than two million Americans each year.

They can occur with any drug a person takes or uses, ranging in severity from upset stomach or headache, which often subside after taking the drug for several doses, to urticaria (hives) or anaphylaxis (life-threatening closure of the airways), which are usually allergic reactions. Rash and itching are also common adverse reactions. Adverse drug reactions may also affect the composition of the blood or the function of organs such as the heart, liver, and kidneys.

Risk Factors for Adverse Drug Reactions

Intentional misuse of a drug, including taking more than recommended or in combination with other drugs, increases the likelihood of adverse drug reaction.

All drugs have some identified potential adverse reactions. These are the events that usually surface during the human testing phase of clinical research studies. Some such reactions may be inherent to the properties of the drug—that is, result from the drug itself. Many antibiotic medications, for example, kill bacteria in the intestines at the same time they kill bacteria that are causing infection, resulting in diarrhea because intestinal bacteria are essential for proper digestion. Nausea, vomiting, and hair loss are known adverse reactions with chemotherapy drugs.

Other such reactions may result from drug interaction with other medications the person is using or from the ways in which the body responds to the drug over the long term. Tardive dyskinesia is a known adverse reaction to long-term use of antipsychotic medications, for example. long-term use of corticosteroid medications, such as taken to treat inflammatory bowel disease (ibd) or Addison’s disease, ave numerous adverse effects on the body.

Adverse drug reactions may be localized, such as dermatitis, or systemic (involve multiple body systems). Doctors generally classify adverse drug reactions as immunologic (those that involve an immune response) or nonimmunologic (those that do not involve an immune response).

People who are immunocompromised (such as those who have hiv/aids or take immunosuppressive therapy), have an autoimmune disorder such as rheumatoid arthritis or systemic lupus erythematosus (sle), have liver or kidney disease, take multiple medications (often called polypharmacy), or are age 60 or older have increased risk for adverse drug reactions.

Most drug reactions occur within several days to three weeks of beginning the drug, though some long-term adverse reactions occur up to years after the drug’s initiation.

Common Adverse Drug Reactions

Allergic responseAnaphylaxisAnemia
PruritusRash on trunkTardive dyskinesia

It is important, when beginning treatment with a new medication or adding a different drug to a treatment regimen, to know the expected results and possible adverse reactions. People who take multiple drugs, including over-the-counter (otc) drugs and medicinal herbs and botanicals, should make sure the prescribing physician and the dispensing pharmacist know all of them. Numerous products interact with one another in ways that alter their effects in the body, increasing the risk for adverse drug reactions.

Many countries have regulatory requirements for documenting and reporting adverse drug reactions. Such requirements help oversight agencies and health-care professionals monitor issues with drugs that may not have been apparent during preapproval testing. In the United States the US Food and Drug Administration (FDA) oversees compliance with these requirements and works with pharmaceutical manufacturers to resolve issues that arise.


How did you like this article?

Page last reviewed:

About Us