Anticholinergics are a class of drugs used to treat a wide range of conditions, but they can have unintended effects on the body. This drug class gets its name because it works by affecting acetylcholine, a neurotransmitter that plays a significant role in muscle movement and other functions in the body.

Intended Effects

Anticholinergic medications affect a wide range of body functions, including respiration, circulation, vision, and alertness. Many medications have anticholinergic effects, but in most cases, they are considered adverse reactions. A few drugs are prescribed specifically for their anticholinergic effects, to treat Parkinson’s, psychiatric disorders, allergies, and respiratory disorders like COPD and asthma.

Acetylcholine

Acetylcholine is a neurotransmitter that delivers messages to nerve cells and the brain. It plays a significant role in speeding up and slowing down functions like the movement of the skeletal and cardiac muscles. Researchers know a lot about how the nerves work in these movements, but little is known about how acetylcholine affects the central nervous system.

How They Work

Anticholinergics are competitive antagonists to acetylcholine. To deliver chemical messages, acetylcholine must bind with receptors on the organs or glands they are sent to activate. Anticholinergics block these receptors, preventing acetylcholine from binding with them. The chemical message does not get through, reducing the effects of the acetylcholine or stopping them altogether.

Uses for Anticholinergics

Anticholinergics have many uses. Patients take them to relieve cramps in the bladder or GI tract or to prevent motion sickness, menstrual cramps, or urinating during sleep. In surgery, anticholinergics keep the heart beating normally, and they can help relieve post-surgery nausea and vomiting.

Adverse Effects

Anticholinergics have many adverse effects centrally and peripherally. Central nervous system side effects include headache, memory problems, anxiety, and insomnia, even at low doses. People taking anticholinergics may also experience flushing, urinary retention, constipation, and diminished contraction in the muscles. These adverse effects are not life-threatening, but they can be signs that levels in the blood are elevated.

Toxicity

Toxicity from anticholinergics usually occurs from accidental medication misuse, though it can also occur in people taking the right dose. People taking oral anticholinergics are more likely to experience toxicity. This is especially true if they are taking multiple similar medications: the effects are synergistic and have a stronger effect when taken together than they would on their own.

Signs of Toxicity

Physical symptoms such as flushing, dilated pupils, change in mental status, and fever are classic signs of anticholinergic toxicity. Some anticholinergics cause arrhythmias when taken in excess. People experiencing toxicity will be dry — this means they have symptoms like urinary retention, lack of sweat, and dry mouth. Central nervous system effects occur, too, including hallucinations, restlessness, staccato speech, and confusion. Some people experience jerking or seizures.

Contraindications

Anticholinergics can be beneficial, but doctors and patients should consider the risk of adverse side effects and toxicity. There are many contraindications. Patients with dementia, COPD, and urinary incontinence may take multiple medications with anticholinergic effects and are at greater risk for toxicity.Other conditions that are negatively impacted by anticholinergics include hyperthyroidism, glaucoma, and arrhythmias that cause the heart to beat too fast.

Older Adults

Seniors are more sensitive to the effects of anticholinergics. They are also more likely to have conditions that require this treatment, like COPD and dementia. One study shows that the use of anticholinergics increases the risk of non-Alzheimers dementia. In this study, researchers attributed 10 percent of dementia cases to the use of anticholinergic medications.

Children

Children are more sensitive to anticholinergics than adults. Restlessness and irritability are common in children taking these medications, and side effects like shortness of breath can be severe. Kids taking anticholinergic medications may experience a rapid and dangerous increase in body temperature during hot weather and should be monitored closely.