What Are Anticholinergics?

An array of medication on a table

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What Are Anticholinergics?

Anticholinergics are a class of drugs used to treat a wide range of medical conditions, from asthma to the side effects of certain psychiatric medications. They are also used to treat some symptoms of Parkinson’s disease.

They can help to decrease the involuntary movement of muscles in your body that are part of the disease. For instance, with Parkinson’s disease, anticholinergics are used to control tremors that are commonly characteristic of the condition. 

History

Anticholinergics were originally derived from atropine-containing plants like deadly nightshade and thorn apple. For many centuries, atropine-containing plants were burned and the smoke was inhaled, and used as a treatment for diseases that obstruct the airways.

However, when these plants were burned, other compounds like scopolamine and hyoscyamine, were released. These compounds had intoxicating and sometimes poisonous effects. 

Anticholinergics are a popular asthma treatment today. They were originally taken in the form of a cigarette or tobacco pipe for its medicinal benefits. This wasn’t very different from the centuries-old method of using atropine-containing plants and inhaling the smoke, to treat conditions that obstructed the airways.

In the 19th century, anticholinergic agents were introduced into medication for Parkinson’s. They were the first form of treatment for the condition.

As other more effective drugs for the condition were developed, the use of anticholinergics to treat Parkinson’s disease has since declined. This is largely due to the more severe side effects the medication can have on older people. 

How Anticholinergics Work

Anticholinergics work by blocking the action of a chemical messenger called acetylcholine. Acetylcholine is responsible for transferring signals that affect communication between nerves and certain types of muscles and organs in several parts of your body.

Anticholinergics block this chemical messenger from binding to its receptors on the cells. 

One of the most common uses of anticholinergics is as a treatment for asthma. They help to ease asthma symptoms by relaxing and enlarging the airways, which makes breathing easier. They are also used to treat a variety of conditions like urinary incontinence and motion sickness. 

Types 

Anticholinergics can be split into two broad categories. Some medications are primarily anticholinergic while some are meant for other medical purposes, but could produce anticholinergic effects. 

Primary Anticholinergics

There are many types of pure anticholinergic medications and they all work in the same way—by blocking the actions of acetylcholine.

These types of anticholinergics generally can’t be bought over the counter, they can only be prescribed by a doctor.

The exact anticholinergic your doctor might prescribe for you depends on the condition that is being treated:

  • Cogentin (benztropine mesylate) and Artane (trihexyphenidyl): Used to treat some symptoms of Parkinsons’ disease and side effects of certain psychiatric medications.
  • Enablex (darifenacin): Used to treat urinary incontinence. 
  • Tudorza Pressair (aclidinium): Used to treat respiratory conditions like asthma.
  • Atropine: Treats eye conditions such as uveitis. It’s also used to reduce secretions of saliva and mucus in your airways during surgery.
  • Ditropan (oxybutynin): Is used to treat overactive bladders.

Other Anticholinergic Drugs

Some prescription and over-the-counter medications also have anticholinergic properties. This means that they can block the actions of acetylcholine, even though they are not formulated for that purpose. Medications that fall into this category include the following: 

  • Tricyclic antidepressants: Amitriptyline, Anafranil (clomipramine), and Pamelor (nortriptyline)
  • Antihistamines: Drugs like Dimetapp (brompheniramine), Benadryl (diphenhydramine), and Avil (pheniramine)
  • Antipsychotic medication: Thorazine (chlorpromazine), Clozaril (clozapine), Zyprexa (olanazapine)

Uses

There are anticholinergics that are used to treat many conditions including: 

  • Asthma 
  • Diarrhea 
  • Motion sickness 
  • Gastrointestinal disorders 
  • Certain symptoms of Parkinson’s disease
  • Allergies
  • Overactive bladder 
  • Urinary incontinence 
  • Poisoning
  • Muscle spasms 
  • Chronic obstructive pulmonary disease (COPD)
  • Hyperhidrosis

Anticholinergics can also be used during surgery, to relax the muscles, reduce the secretion of saliva, and keep your heartbeat steady. 

Common Side Effects

Anticholinergics are relatively safe but some people who take the medication might experience: 

  • Dry mouth and eyes 
  • Headaches 
  • Difficulty urinating  
  • Constipation 
  • Anxiety
  • Insomnia

It’s important to know that, unless necessary, the use of anticholinergics should be avoided in older people as side effects are far more common in the elderly, particularly cognitive effects.

Severe Side Effects

When anticholinergics are used at high doses, one may experience more severe side effects. Some of these include: 

  • Flushing
  • Decreased sweating
  • Confusion 
  • Loss of memory 
  • Hallucinations
  • Seizures
  • Impaired vision 
  • Hyperthermia
  • Urinary retention

These more severe side effects are often an indication of an overdose on anticholinergic agents. This is known as anticholinergic poisoning or anticholinergic toxicity and requires immediate medical attention. 

More severe side effects are also more common in older people, which is why anticholinergics are used with caution, if at all, in the elderly.

Some research suggests that long-term use of anticholinergics may contribute to cognitive decline. A 2018 study evaluated the risk of older people who have used anticholinergics long-term developing dementia and Alzheimer’s disease.

The results of the study showed there was an association for those who used them for an extended period and an increased risk of developing dementia. 

Precautions

Certain precautions need to be taken when using anticholinergics. They include:

  • Overheating: It’s important to prevent your body from overheating by staying hydrated when on anticholinergics, especially if one of the side effects you experience is decreased sweating. When there’s a decrease in how much you sweat, your body temperature rises, and you are more likely to experience heat strokes. 
  • Overdose: Taking a combination of several anticholinergic drugs could result in an overdose. An overdose of any anticholinergic can be fatal. Signs of an overdose include confusion, hallucinations, rapid heartbeat, fevers, and dizziness. 
  • Use with alcohol: Like with almost all medication, the use of anticholinergics with alcohol is strongly discouraged.
  • Other medical conditions: People with certain medical conditions are discouraged from using anticholinergics. Talk with your physician if you have any medical conditions before taking anticholinergic drugs.
  • Use with other drugs: People who are already taking certain other drugs shouldn’t take anticholinergics. Discuss with your doctor or pharmacist any potential interactions with other medications if you take anticholinergic agents.
  • Use of multiple anticholinergics: Using multiple drugs with anticholinergic effects may result in greater risk of complications and toxicity as a result of the collective side effects. If you are using any over-the-counter drugs with anticholinergic effects it’s best to talk to your doctor about the potential drug interactions. 
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