Adverse Drug Reactions in the Elderly

Can We Stem the Tide?

Shari J. Lynn

Am Nurs Journal. 2012;7(1)

Defining and Classifying ADRs

The World Health Organization (WHO) defines an ADR as "any response to a drug which is noxious and unintended, and which occurs at doses normally used in man." WHO also defines the related terms unexpected adverse reaction, side effect, adverse event or experience, serious adverse event, and signal. (See the box below.)

Some experts classify ADRs according to cause, as type A, B, C, or D.

Type A reactions are expected, based on the drug's pharmacologic properties. Usually dose-dependent, they account for most ADRs. Examples include bleeding with warfarin use and hyperkalemia with spironolactone use.

Type B reactions are idiosyncratic, unexpected, and more serious than Type A reactions. Usually, they aren't dose-dependent or related to the drug's pharmacologic properties, and subside only with drug withdrawal. Examples include anaphylaxis and malignant hyperpyrexia.

Type C reactions are chronic effects related to long-term drug use, such as analgesic nephropathy.

Type D reactions are delayed drug effects, such as cancer or teratogenesis.

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Next Section

Abstract and Introduction
Incidence of ADRs
Defining and Classifying ADRs
Polypharmacy and Drug Interactions
Drug Interactions: Pharmacokinetic vs Pharmacodynamic
Beers Criteria
Know Your Professional Responsibility
Obtaining Medication History From an Older Adult
References

Defining terms
An unexpected adverse reaction is a reaction whose nature or severity isn't consistent with the drug's current labeling. A side effect is an unintended effect that occurs at normal drug dosages and relates to the drug's properties. An adverse event or experience is a medical occurrence that may arise during treatment but doesn't have a causal relationship with the drug in question. A serious adverse event is a fatal, life-threatening, or permanently disabling event that requires extensive hospitalization, leads to a congenital anomaly, or requires an intervention to avert permanent impairment or damage. A signal is an observed possible adverse event that is unknown or wasn't previously documented.

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