Anticholinergic effects are caused by drugs that block the action of acetylcholine. Acetylcholine is a chemical messenger (neurotransmitter) released by a nerve cell to transmit a signal to a neighboring nerve cell or a cell in a muscle or gland. Acetylcholine helps cells talk to each other. Acetylcholine helps with memory, learning, and concentration. It also helps control the functioning of the heart, blood vessels, airways, and urinary and digestive organs. Drugs that block the effects of acetylcholine can disrupt the normal functioning of these organs.

Many commonly used drugs have anticholinergic effects. Most of these drugs were not designed to have these unwanted effects. Anticholinergic effects include the following:

• Confusion

• Blurred vision

• Constipation

• Dry mouth

• Light-headedness and loss of balance

• Difficulty urinating

However, anticholinergic drugs can also have useful effects, such as helping control tremors, nausea, or overactive bladder.

Older people are more likely to experience anticholinergic effects because the amount of acetylcholine in the body decreases with age. Consequently, anticholinergic drugs block a higher percentage of acetylcholine, so that the aging body is less able to use what little acetylcholine is present. Also, cells in many parts of the body (such as the digestive tract) have fewer sites where acetylcholine can attach. As a result, doctors usually try to avoid using drugs with anticholinergic effects in older people if possible.