Adverse Effects

An adverse drug reaction is a noxious, unintended response to a health product. The term is broader than “allergy.” A predictable pharmacologic effect may become harmful when the dose is excessive, clearance falls, or the patient has little physiologic reserve. An immune-mediated reaction may occur even at a small dose. A medication error involves incorrect prescribing, dispensing, preparation, administration, or monitoring; a near miss reaches no patient or causes no harm, but still exposes a system vulnerability. Disease progression can imitate an adverse effect, so timing alone never proves causation. The first question is not “Which label fits?” It is “What threatens the patient now?” New wheezing, hypotension, shallow respirations, rapidly changing mental status, severe bleeding, or loss of airway protection takes priority over completing a medication history. In Canada, the nurse stabilizes the patient first, then follows organizational reporting, disclosure, and documentation processes. Report a suspected reaction even when the diagnosis is not confirmed and causality is uncertain. Hospitals have a statutory obligation under Vanessa’s Law to report serious adverse drug reactions and medical device incidents to Health Canada...