1.3 - Anticholinergic effects  pp. 18-23

Anticholinergic effects

By David M. Gardner, Michael D. Teehan and Ross Baldessarini

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Background

Antipsychotic-induced anticholinergic effects occur frequently and result from a blockade of muscarinic receptors (M1–M5) in the brain and periphery (Table 1.3.1). In addition to antipsychotics, numerous other commonly used medications have anticholinergic properties (Table 1.3.2).

Common adverse anticholinergic effects include dry mouth, blurred vision, constipation, urinary retention, and cognitive impairment, such as memory difficulties, confusion, and delirium. The cognitive effects caused by anticholinergic medications are especially troublesome in elderly patients. Other less common effects include tachycardia or paradoxical bradycardia, acute closed-angle glaucoma, paralytic ileus, bowel obstruction, psychosis, and sweating impairment with associated hyperthermia.

Although anticholinergic effects are often viewed as detrimental, it is important to keep in mind that they can also be beneficial. Anticholinergic medications (such as benztropine) are often used to treat or prevent selected antipsychotic-induced extrapyramidal symptoms (EPS). It should be noted that both desired and undesired anticholinergic effects can result from such treatments.

The severity and consequences of a drug's anticholinergic effects are determined by several patient and drug factors. Patient factors include age, comorbid medical conditions (e.g. narrow-angle glaucoma, benign prostatic hypertrophy, urinary retention, dementia, hyperthyroidism, hypertension, congestive heart failure, coronary artery disease), and the concurrent use of other drugs with antimuscarinic effects. Drug factors include dosage, CNS bioavailability, and muscarinic receptor binding affinity (Table 1.3.3).

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