An adverse drug reaction (ADR) is any noxious, unintended, and undesired response to a medicine that occurs at doses normally used in humans for prophylaxis, diagnosis, or therapy. Unlike side effects, which are often predictable and may even be utilized for therapeutic advantage, ADRs are typically harmful and require intervention. The Rawlins and Thompson classification system categorizes these reactions into two main types based on their predictability and dose-dependence.
While Types A and B cover the most common presentations, pharmacovigilance frameworks expand the classification to capture chronic and delayed drug behaviors.
Adverse drug reactions can mimic common disease states, making diagnosis challenging. Nurses must look out for sudden changes in organ function. Gastrointestinal upsets like nausea, vomiting, and diarrhea are frequent, while dermatological signs range from mild maculopapular rashes to life-threatening conditions like Stevens-Johnson syndrome. Hematological abnormalities such as unexplained bruising, bleeding, or fatigue point toward bone marrow suppression. Neuropsychiatric symptoms, including confusion, tremors, and lethargy, frequently affect older adults on multiple medications. Recognizing these patterns early prevents misdiagnosis and stops inappropriate escalation of drug therapy.
Certain individuals face a higher statistical likelihood of experiencing adverse drug reactions. Assessing patient history is the cornerstone of safe nursing care. Key risk factors include:
| Risk Factor | Mechanism / Reason |
|---|---|
| Extreme Age | Neonates and older adults have altered drug clearance and metabolic capacities. |
| Polypharmacy | Taking multiple drugs increases the mathematical probability of drug-drug interactions. |
| Organ Impairment | Renal or hepatic disease delays excretion, causing drug accumulation and toxicity. |
| Genetics | Variations in hepatic enzymes alter the speed of drug metabolism. |
When an adverse reaction occurs, immediate action determines patient safety. The first step is stopping the offending medication unless the reaction is trivial and benefits outweigh the risks. Supportive care follows, tailored to the specific symptom presentation. In severe anaphylactic reactions, immediate administration of intramuscular epinephrine is lifesaving, alongside airway maintenance and intravenous fluid resuscitation. Antidotes may be administered if specific toxicity is confirmed, such as naloxone for opioid overdose or phytomenadione (vitamin K) for warfarin-induced bleeding. Documenting the event clearly in the patient chart prevents future re-exposure.
Preventing ADRs requires meticulous clinical practice, patient education, and active reporting systems. Nurses must perform thorough drug histories, check for known allergies, and calculate dosages carefully, especially for weight-based pediatric regimens. In Nigeria, reporting suspected adverse drug reactions is coordinated through the National Pharmacovigilance Centre (NPC) under the National Agency for Food and Drug Administration and Control (NAFDAC). Using the NAFDAC spontaneous reporting yellow form allows healthcare workers to contribute to national safety data, helping identify rare or delayed signals that clinical trials missed.