An Adverse Drug Reaction (ADR) is a harmful or unpleasant reaction that occurs after the administration of a medication or a combination of medications. ADRs can vary in severity from mild, transient symptoms to severe, life-threatening reactions. They are distinct from medication side effects, which are known and expected reactions to a drug.
ADRs can be classified into several types:
- Type A (Augmented): These are dose-dependent and predictable reactions based on the drug’s pharmacological properties. Examples include bleeding from anticoagulants or hypoglycemia from insulin.
- Type B (Bizarre): These reactions are dose-independent, unpredictable, and not related to the pharmacological action of the drug. They include allergic reactions and idiosyncratic reactions.
- Type C (Chronic): Reactions that occur as a result of long-term drug therapy, such as corticosteroid-induced osteoporosis.
- Type D (Delayed): These reactions occur as a delayed response to a drug, such as carcinogenic effects from long-term use of certain medications.
- Type E (End of use): Reactions occurring when stopping a drug, such as withdrawal symptoms.
- Type F (Failure): This refers to drug failure, where the medication does not work as intended.
ADRs can happen to anyone but are more common in certain groups, such as the elderly, children, and people taking multiple medications. They can have a significant impact on a patient’s health and quality of life, and therefore, it’s important for healthcare providers to monitor for potential ADRs and manage them appropriately when they occur.