Adverse drug reaction

• An adverse drug reaction (ADR) refers to an unintended and harmful response to a medication.
• It occurs when a drug, prescribed or taken as instructed, produces an undesirable or unexpected effect on the body.
• Adverse drug reactions can range from mild side effects to severe and life-threatening conditions.
• Understanding ADRs is crucial for healthcare professionals, patients, and regulatory bodies to ensure the safe and effective use of medications.

Drug eruption1

Classification of Adverse Drug Reactions

• Adverse drug reactions can be classified into several categories based on different criteria.

• The most common classification system divides ADRs into the following types:

Type A (Augmented)

• Type A reactions are the most common type of adverse drug reactions and are predictable based on a drug's known pharmacological properties.
• These reactions are dose-dependent and usually related to the drug's therapeutic effect or its interaction with specific receptors or enzymes.
• Type A reactions are typically mild to moderate and include side effects such as nausea, dizziness, and headache.

Type B (Bizarre)

• Type B reactions are unpredictable and unrelated to the known pharmacological action of a drug.
• They occur infrequently and are often severe or life-threatening.
• Type B reactions are typically not dose-dependent and can vary between individuals.
• Examples of type B reactions include severe allergic reactions (anaphylaxis), drug-induced liver injury, and blood dyscrasias.

Type C (Chronic)

• Type C reactions are associated with the long-term use of a drug.
• They arise from the cumulative effects of a medication over time.
• Examples of type C reactions include drug-induced osteoporosis, tardive dyskinesia caused by long-term use of antipsychotics, and drug-induced endocrine disorders.

Type D (Delayed)

• Type D reactions occur after a significant delay following drug administration.
• These reactions can manifest weeks, months, or even years after initiating treatment.
• Examples of type D reactions include certain drug-induced cancers, such as bladder cancer associated with long-term use of certain diabetes medications.

Type E (End-of-treatment)

• Type E reactions occur when a drug is abruptly stopped or withdrawn.
• They are often related to a rebound effect or withdrawal syndrome.
• Examples include rebound hypertension after discontinuing antihypertensive medications or seizures following abrupt withdrawal of antiepileptic drugs.

Risk Factors for Adverse Drug Reactions

• Several factors can contribute to the occurrence of adverse drug reactions.

These include:

• Age: Elderly individuals and children may be more susceptible to ADRs due to differences in drug metabolism, organ function, and physiological characteristics.
• Polypharmacy: Taking multiple medications simultaneously increases the risk of drug interactions and adverse effects.
• Genetic Factors: Genetic variations can influence how an individual responds to certain drugs, potentially increasing the likelihood of ADRs.
• Pre-existing Conditions: Certain medical conditions, such as liver or kidney impairment, can affect drug metabolism and increase the risk of ADRs.
• Drug Allergies: Individuals with known drug allergies or hypersensitivity reactions may experience severe ADRs upon exposure to the specific medication.
• Concomitant Diseases: Coexisting medical conditions can interact with drugs and increase the risk of adverse effects.

Prevention and Management

• Prevention and management of adverse drug reactions involve various strategies:

• Proper Medication Selection: Healthcare professionals should carefully consider a patient's medical history, allergies, and potential drug interactions before prescribing medications.
• Patient Education: Patients should be educated about the potential side effects and risks associated with their medications. They should be encouraged to report any unusual symptoms to their healthcare provider.
• Monitoring and Surveillance: Regular monitoring of patients receiving medications can help detect and manage ADRs promptly.
• Pharmacovigilance: Pharmacovigilance programs and regulatory systems play a crucial role in monitoring and reporting ADRs at a population level. This helps identify potential safety concerns and take appropriate regulatory actions if needed.
• Adherence to Guidelines: Healthcare professionals should follow evidence-based guidelines for prescribing medications and adjust dosage or therapy based on individual patient characteristics.
• Reporting and Documentation: ADRs should be reported to the relevant regulatory authorities or pharmacovigilance programs to contribute to the overall understanding of drug safety profiles.

See Also

• Pharmacovigilance
• Medication Safety
• Drug Interactions
• Anaphylaxis
• Polypharmacy

• Dailymed label info on Adverse drug reaction
• FDA Adverse drug reaction

Adverse drug reaction Resources
Need Help Finding a Doctor? WikiMD's DocFinder can help find general and specialist physicians.	Latest articles Most recent articles Ongoing trials.