Adverse Effects

Definition

Adverse effects (adverse drug reactions, ADRs) are harmful, unintended responses to a medication administered at normal doses. They differ from expected side effects, which are typically mild and tolerable.

Classifications

• Type A (Augmented): Dose-related and predictable (bleeding from warfarin).
• Type B (Bizarre): Unpredictable, often immune-mediated (anaphylaxis to penicillin).
• Toxic effect: Occurs at high or accumulating doses.
• Idiosyncratic: Unusual patient-specific response.

High-Risk Adverse Effects to Recognize

Stevens-Johnson syndrome (sulfa drugs, phenytoin), serotonin syndrome (SSRIs), neuroleptic malignant syndrome (antipsychotics), ototoxicity (aminoglycosides), nephrotoxicity (vancomycin), and agranulocytosis (clozapine).

Nursing Responsibilities

Assess baseline labs and allergies before administration; monitor patients closely after first doses; recognize early warning signs; hold the medication and notify the provider for severe reactions; document and report ADRs to the FDA MedWatch program.

NCLEX Relevance

Pharmacology questions often require distinguishing expected side effects (transient nausea) from adverse effects that require stopping the medication (tinnitus from aspirin).