geriatrics
Pharmacodynamics in Older Adults
Introduction
In contrast to pharmacokinetic effects, Overview of Pharmacodynamics is defined as what the drug does to the body or the response of the body to the drug; it is affected by receptor binding, postreceptor effects, and chemical interactions (see Older adults are particularly sensitive to anticholinergic drug effects. Many drugs (eg, tricyclic antidepressants, sedating antihistamines, urinary antimuscarinic agents, some antipsychotic drugs, antiparkinsonian drugs withatropine-like activity, many over-the-counter hypnotics and cold preparations) have anticholinergic effects. Older adults, most notably those with cognitive impairment, are particularly prone to central nervous system (CNS) adverse effects of such drugs and may become more confused and drowsy. Anticholinergic drugs also commonly cause constipation, urinary retention (especially in older men with benign prostatic hyperplasia), blurred vision, orthostatic hypotension, and dry mouth. Even in low doses, these drugs can increase risk of heatstroke by inhibiting diaphoresis. In general, older adults should avoid drugs with anticholinergic effects when possible. 