Anticholinergic Drugs: Benefits and Side Effects

Anticholinergics are any drugs that block the action of the neurotransmitter acetylcholine. This chemical messenger is involved in involuntary muscle movements and certain functions of the body, such as digestion and urination.

Anticholinergic drugs can be beneficial in treating a wide array of health conditions ranging from allergies and depression to irritable bowel syndrome (IBS) and Parkinson's disease. However, given the extent of anticholinergic effects, these drugs can affect the body negatively too.

Side effects of anticholinergics include blurred vision, impaired coordination, and bowel leakage, to name a few. Long-term use is linked to dementia.

This article discusses different anticholinergic drugs, how they work, and how they are used. It also covers anticholinergic side effects and warnings to consider.

How Anticholinergic Drugs Work

Anticholinergic drugs work by binding to nerve receptors that are sensitive to acetylcholine. These receptors are considered "cholinergic," hence the name of the drugs.

Nerve receptors are molecules on or in a cell that bind to substances in order to produce a certain effect. Acetylcholine is one of those substances. It acts on nerve cells to deliver chemical messages to the brain.

By doing so, acetylcholine can regulate certain biological functions either by speeding them up or slowing them down. These include skeletal muscles involved in movement and smooth muscles found in the heart, stomach, intestines, urinary tract, and lungs.

Acetylcholine is powerful, but it can only be so if it is received by nerve cells.

When acetylcholine's effects are having a negative impact on the body, such as abnormal muscle contractions, anticholinergic drugs can be used to block acetylcholine from cells' receptors.

With the cells having no means of delivering the chemical messages responsible for the muscle contractions, they can be stopped and symptoms relieved.

This is referred to as the anticholinergic effect.

When Anticholinergics Are Used

Anticholinergic drugs are used to treat a variety of conditions, including:

• Allergies
• Chronic obstructive pulmonary disease (COPD)
• Depression
• Heart disease
• Insomnia
• Irritable bowel syndrome (IBS)
• Muscle spasms
• Parkinson's disease
• Urinary incontinence
  

Benefits of the Anticholinergic Effect

A number of drugs achieve their therapeutic goals because of the anticholinergic effect. By slowing bowel movement, for example, a person may find relief from diarrhea.

Similarly, the breathing restriction associated with asthma and COPD can be improved when the cholinergic receptors of the lungs are blocked.

Antispasmodics—drugs that temper muscle spasms related to gastrointestinal and other issues—are one class of drugs in which the anticholinergic effect is considered beneficial.

Antispasmodic drugs with an anticholinergic effect include:

• Bentyl (dicyclomine)
• Buscopan (hyoscine butylbromide)
• Levsin (hyoscyamine)
• Lomotil (atropine/diphenoxylate)
• Enablex (darifenacin)
• Pamine (methylscopalamine)
• Spiriva (tiotropium bromide)
• Symmetrel (amantadine)
• Vesicare (solifenacin)

Side Effects of Anticholinergics

Since anticholinergic drugs aren’t specific to the types of receptors they block, they can trigger a range of side effects.

In addition to muscle contractions, certain types of acetylcholine regulate memory, learning, and sensations. That means that side effects can affect both the mind and body.

Potential side effects of anticholinergics include:

• Dry mouth due to the inhibition of the salivary glands
• Sore throat due to decreased mucus production
• Absence of sweating
• Increased body temperature
• Light sensitivity due to slowed pupil dilation
• Blurred vision or double vision
• Increased heart rate to compensate for changes in vascular function
• Poor coordination due to altered muscle control, which can make it dangerous to drive or engage in certain other activities
• Urinary incontinence when sleeping
• Bowel leakage
• Confusion
• Memory problems
• Incoherence
• Inability to concentrate
• The tendency to be startled easily
• Hallucinations

Higher doses and longer use increase the risk of these occurring.

Anticholinergic effects typically improved by gradually decreasing the dosage, though this should only be done per advice from your healthcare provider.

Drugs With Unintended Anticholinergic Effects

There are also drugs that can have anticholinergic effects that are unexpected.

They include certain antidepressants and antipsychotics that increase or decrease dopamine and serotonin, neurotransmitters to alter a person’s mood. In some cases, and though unintended, the drugs can block acetylcholine and lead to anticholinergic side effects.

The challenge, of course, is that antidepressants and antipsychotics are often prescribed over the long term, making the management of symptoms all the more difficult.

That said, there are times when low-dose antidepressants can be used to treat chronic pain and IBS. A similar effect is achieved with certain low-dose antipsychotics and Parkinson's disease.

By weighing the pros and cons of a possible anticholinergic effect, healthcare providers can find the right drug and dosage by which to deliver treatment without the burden of side effects.

Warnings and Considerations

There are certain people for whom anticholinergics may not be recommended. Those that do use these drugs should be aware of certain risks, such as potential overdose, overheating, and dementia.

Possible Contraindications

Anticholinergic medications should be used with caution in people over 65 years of age or with dementia.

In addition, the following conditions may worsen with the use of anticholinergics:

• Glaucoma
• Hyperthyroidism
• Prostate Hypertrophy
• Tachyarrhythmia
  

Anticholinergic Overdose

Since many medications have anticholinergic effects, it is possible to be prescribed more than one anticholinergic drug at a time. Taking multiple anticholinergics at once can cause an overdose.

Signs of overdose include:

• Confusion
• Difficulty breathing
• Dizziness
• Fever
• Flushed skin
• Hallucinations
• Increased heart rate
• Loss of coordination
• Severe drowsiness
• Slurred speech

Do not drink alcohol if you are taking anticholinergics. Alcohol can intensify the risk of overdose. If you suspect an overdose of anticholinergic medications, seek emergency medical help.

Overheating

Anticholinergics hinder your ability to sweat and can lead to heat exhaustion or heat stroke. Use caution in hot weather, during exercise, or when taking hot baths or showers. Signs of heat stroke include:

• Confusion or altered mental status
• Hot, dry skin
• Loss of consciousness
• Seizures
• Slurred speech
• Very high body temperature

If you suspect someone is overcome by heat, cool them off by wetting their clothes with cold water, circulate the air around them, move them to a cooler location, and call 911.

A Word From Verywell

If you are experiencing intolerable side effects due to the anticholinergic effects of a drug, speak with your healthcare provider. Depending on your healthcare provider, the practitioner may be able to decrease the dosage or find the appropriate substitution.

However, you should not discontinue any drug without first speaking with your healthcare provider. Doing so can sometimes cause ill effects (especially with certain antidepressants) unless treatment is gradually tapered off.