Anticholinergic vs. Cholinergic Drugs

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  • 0:04 The Nervous System
  • 1:03 How They Work
  • 2:13 Uses
  • 3:40 Side Effects
  • 5:08 Lesson Summary
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Lesson Transcript
Instructor: Kaitlin Baker

Kaitlin has taught nursing students and has a master's degree in nursing leaderhsip, as well as a bachelor's degree in English literature.

This lesson will describe cholinergic and anticholinergic drugs in terms of their effects on the parasympathetic and sympathetic nervous systems. You'll learn about how these drugs work, what conditions they treat, and what side effects may result.

The Nervous System

In order to understand cholinergic drugs and anticholinergic drugs, you first have to have a basic knowledge of how the nervous system operates. Suppose you're taking a leisurely walk through the forest, when a bear appears and begins running after you. At this point, your sympathetic nervous system (otherwise known as the ''fight-or-flight'' response) kicks in and your heart rate increases, your blood vessels narrow to pump blood to your heart and muscles, movement of the digestive tract is slowed, and your blood pressure increases. All of this is supposed to allow you to either run and escape the bear, or fight it off.

Finally, you have escaped the bear. You return home, take a shower, put on a fresh set clothes, and settle down in front of a fire for dinner with your family. When you're in a relaxed state, the parasympathetic nervous system, also known as your rest and digest system, kicks in and your heart rate slows, muscles and blood vessels relax throughout the body, digestive muscles start to move again, and your blood pressure falls again.

How They Work

Cholinergic drugs are a wide variety of drugs used to work on the parasympathetic nervous system. These drugs work by enhancing the actions of acetylcholine, a neurotransmitter or chemical messenger in the brain. Effects of increased acetylcholine are considered the everyday work of the body, such as salivation, digestion, and skeletal muscle relaxation. An alternative way in which cholinergic drugs work is by blocking the enzyme that breaks down acetylcholine, which results in naturally occurring acetylcholine being able to work longer.

If cholinergic drugs work to enhance the parasympathetic nervous system, then anticholinergic drugs work to enhance the sympathetic nervous system. By blocking acetylcholine from sending chemical messages, anticholinergic drugs cause a decrease in parasympathetic effects. The results of blocking parasympathetic effects are referred to as anticholinergic effects, and they include: reduced smooth muscle spasm, reduced digestive tract movement, pupil dilation, decreased production of secretions, increased heart rate, airway relaxation, and reduced urine output.


By enhancing acetylcholine and increasing the actions of the parasympathetic nervous system, cholinergic drugs are able to help with several issues. Some are used during surgeries to reduce the risk of urinary retention, or holding urine inside the body. Others are used to help diagnose and treat glaucoma, a disease that is caused by increased pressure inside the eye. By increasing the dilation or widening of blood vessels, these drugs are able to reduce pressure in the eye. Cholinergic drugs can also increase muscle strength in patients with myasthenia gravis, a condition that causes progressive muscle weakness.

Anticholinergic drugs treat a wide variety of issues. Drugs originally designed to treat certain issues are sometimes used for different issues because of their anticholinergic effects, such as antidepressants being used in the treatment of irritable bowel syndrome when diarrhea is the primary symptom. Anticholinergics drugs can also treat urinary incontinence and overactive bladder.

The ability of these drugs to reduce secretions and relax airways can help treat chronic obstructive pulmonary disorder (COPD) and asthma. Another use is to block involuntary muscle movements associated with nervous system diseases such as Parkinson's. These drugs are also used as muscle relaxants during surgery to maintain a normal heartbeat, and decrease saliva secretions. Anticholinergics may also decrease excessive sweating.

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