Adverse Drug Reactions in the Elderly

Can We Stem the Tide?

Shari J. Lynn


Am Nurs Journal. 2012;7(1) 

In This Article

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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