A List of Anticholinergics and How They Work

Anticholinergics are substances that block the actions of acetylcholine, a compound that acts as a neurotransmitter in the brain. Acetylcholine plays a number of important functions in the body, including communicating between the neurons of the central nervous system (CNS) and peripheral nervous system (PNS). 

It plays a part in muscle contractions as well as brain functions including cognition, learning, memory, attention, and REM sleep. Blocking the function of this neurotransmitter may help relieve the symptoms of some health conditions, including those linked to muscle movements such as Parkinson's disease.

This article describes some of the anticholinergics that are commonly prescribed, what they are used to treat, and how they work. It also explores some of the common side effects that might occur as well as warnings you should understand before taking these medications.

How Anticholinergics Work

Acetylcholine plays an important role in different functions throughout the body. In addition to helping control the movements of the muscles throughout the body, it also plays a part in brain functions including sleep, memory, learning, arousal, and attention.

Treatments for such conditions often involve the use of anticholinergics. They work by blocking acetylcholine so that it cannot bind to acetylcholine receptors in the brain and body. In doing so, it helps block nerve impulses that control digestion, mucus secretion, involuntary muscle movements, urination, and salivation.

Uses For Anticholinergics

Anticholinergics can be used to treat a variety of health conditions. Some of these include:

• Asthma
• Chronic obstructive pulmonary disorder (COPD)
• Diarrhea, irritable bowel syndrome (IBS), and other gastrointestinal disorders
• Dizziness
• Eye inflammation
• Insecticide or toxic mushroom poisoning
• Motion sickness
• Overactive bladder
• Urinary incontinence
• Symptoms of Parkinson's disease

For Parkinson's disease, anticholinergics can help block the involuntary muscle movements that are associated with the condition.

List of Anticholinergics

There are a number of different anticholinergic medications available. The specific type that your doctor prescribes may depend on factors such as your medical history and the reason it is being prescribed.

• Atropine: Used to treat heart rhythm problems and certain types of poisoning.
• Belladonna alkaloids: Relieves symptoms of IBS and other stomach issues.
• Benztropine mesylate: Used to treat extrapyramidal symptoms that can occur when taking antipsychotics as well as symptoms of Parkinson's disease.
• Clidinium bromide: Slows the intestines and decreases stomach acid, which can relieve symptoms of cramping and stomach pain. 
• Cyclopentolate: Used to dilate the pupils during eye exams.
• Darifenacin: Works to relax bladder muscles in order to help treat overactive bladder. 
• Dicyclomine: Relaxes the muscles of the stomach and intestines, slowing the movements of the gut and relieving stomach cramping associated with irritable bowel syndrome.
• Fesoterodine: Used to treat overactive bladder by relaxing bladder muscles in order to minimize uncontrolled or frequent urination.
• Glycopyrrolate: Used to reduce excess stomach acid production and manage heart rate during surgery.
• Homatropine hydrobromide: Used to dilate pupils of the eye and treat inflammatory eye conditions such as uveitis.
• Hyoscyamine: Reduces the production of stomach acid; reduces sweat and saliva production, and relaxes muscles of the stomach, intestines, gallbladder, and kidneys.
• Ipratropium: Used to treat chronic obstructive pulmonary disease (COPD).
• Orphenadrine: Relieves muscle pain and spasms by relaxing skeletal muscles.
• Oxybutynin: Used to treat overactive bladder in order to relieve urgent, frequent, or uncontrollable urination.
• Propantheline: Relieves excess sweating, involuntary urination, and stomach cramps.
• Solifenacin: Treats a bladder condition called neurogenic detrusor overactivity, which causes increased or involuntary contractions of bladder muscles.
• Tiotropium: Treats symptoms of asthma and COPD by relaxing the smooth muscles of the airways in order to prevent bronchospasms.
• Trihexyphenidyl: Reduces stiffness, improves muscle control, and relieves tremors and spasms in people who have Parkinson's disease.
• Trospium: Relaxes muscles of the bladder to help relieve symptoms of incontinence and reduce the frequent urge to urinate.
  

Side Effects of Anticholinergics

Anticholinergics can also have side effects that can vary in severity. Some of these side effects are more pronounced in certain populations, such as older adults. Some of the most common side effects that may occur when taking anticholinergics include:

• Blurry vision
• Confusion
• Constipation
• Dizziness
• Dry eyes
• Dry mouth
• Hallucinations
• Inability to sweat
• Increased body temperature
• Problems concentrating
• Sore throat

If you are experiencing side effects while taking anticholinergics, talk to your healthcare provider. Your prescriber may adjust your dosage, switch to a different type of anticholinergic medication, or change you to a different class of medications in order to treat your condition. 

Warnings

Before you take anticholinergics, it is important to be aware of some of the warnings associated with these medications.

Heat Exposure

Because anticholinergics affect the body's ability to sweat, taking these medications can lead to an increase in body temperature. If you combine this increased body temperature with activities that heat the body or exposure to hot temperatures, it can increase your risk of experiencing heat stroke or heat exhaustion. 

Overdose and Toxicity

Taking too much of an anticholinergic can also lead to medical complications. This can result in an overdose that may cause unconsciousness and can potentially be fatal. 

Symptoms of an anticholinergic overdose include:

• Blurry vision
• Confusion
• Dangerous increase in body temperature
• Dizziness
• Dry mouth
• Flushed, warm skin
• Hallucinations
• Rapid heartbeat
• Severe drowsiness
• Trouble breathing
• Urinary retention
  

Medical professionals may administer physostigmine, a medication that can counteract the overdose. The medication must be used carefully, however, since too much can cause acetylcholine toxicity (cholinergic poisoning).

Drug Interactions

Combining anticholinergics with other medications or substances can increase the risk of overdose, cause side effects, or alter how either medication works.

Potential interactions may occur if anticholinergics are taken with:

• Other medications that have anticholinergic effects
• Antidepressants, including amitriptyline, Prozac (fluoxetine), Pamelor (nortriptyline), and Paxil (paroxetine)
• Antihistamines
• Ipratropium bromide
• Monoamine oxidase inhibitors (MAOIs)
• Potassium chloride
• Tiotropium

You should avoid consuming alcohol while taking anticholinergics since it can cause an overdose. You should avoid Benedryl (diphenhydramine), an antihistamine that is used to treat allergies, and that also acts blocks the actions of acetylcholine.

Who Shouldn’t Take Anticholinergics?

People with the following conditions should also not take anticholinergics:

• Down syndrome
• Enlarged prostate
• Glaucoma
• Heart failure
• Hiatal hernia
• High blood pressure
• Hyperthyroidism
• Liver disease
• Myasthenia gravis
• Urinary tract blockage

People in certain age groups or with certain conditions should not take anticholinergics. The American Geriatrics Society suggests that people over the age of 65 should not use anticholinergic medications. Not only are they at an increased risk for side effects, but research has also found that older adults are also at a higher risk of experiencing memory problems and decreased mental functioning.

Anticholinergic syndrome can occur when a person suddenly stops taking an anticholinergic after long-term use. Symptoms can include anxiety, heart palpitations, and restlessness. Gradually lowering the dose over a period of time can minimize this risk.