Anticholinergic Drugs

Balancing the Benefits and Risks of Treatment

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Anticholinergics are a broad class of drug used to treat a variety of medical conditions that affect the contraction and relaxation of muscles.

They include medications used to treat overactive bladder, Parkinson's disease, diarrhea, vomiting, asthma, chronic obstructive pulmonary disease (COPD), muscle spasms, irritable bowel syndrome (IBS), and other conditions which involve involuntary muscle movement.

How the Drugs Work

Acetylcholine is a substance produced by the body that functions as a neurotransmitter. 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 the lungs. The cells involved in the contraction of these muscles have nerve receptors. Those receptive to acetylcholine are considered cholinergic.

When faced with abnormal muscle function, there are drugs that can block acetylcholine by binding to the cholinergic receptors. Without the means to deliver the chemical messages, the contractions can be stopped and the symptoms relieved.

We refer to this as the anticholinergic effect.

Anticholinergic Side Effects

In addition to muscle contractions, certain types of acetylcholine regulate memory, learning, and sensations.

Since anticholinergic drugs aren’t specific to the types of receptor they block, they can trigger a range of side effects impacting both the body and mind.

These 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
  • Urinary incontinence when sleeping
  • Bowel leakage
  • Confusion
  • Memory problems
  • Incoherence
  • Inability to concentrate
  • Tendency to be startled easily
  • Hallucinations
  • Dementia

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 lungs are blocked.

Antispasmodics are one class of drug in which the anticholinergic effect is considered beneficial. While side effects are common, short-term use combined with low dosage usually means that the symptoms are manageable.

Antispasmodic drugs with an anticholinergic effect include:

Unintended Anticholinergic Effects

On the other hand, there are drugs that have an unintended anticholinergic effect.

They include certain antidepressants and antipsychotics which increase or decrease dopamine and serotonin neurotransmitters to alter a person’s mood. In some cases, 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.

Antidepressants and antipsychotics with anticholinergic effects include:

  • Elavil (amitriptyline)
  • Norpramin (desipramine)
  • Tofranil (imipramine)
  • Pamelor (nortriptyline)
  • Paxil (paroxetine)
  • Thorazine (chlorpromazine)
  • Clozaril (clozapine)
  • Zyprexa (olanzapine)
  • Mellaril (thioridazine)

In between both of these extremes, 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 the anticholinergic effect, doctors can find the right drug and dosage by which to deliver treatment without the burden of side effects.

A Word From Verywell

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

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

Source:

Fox, C.; Smith, T.; Maidment, I. et al. "Effect of medications with anticholinergic properties on cognitive function, delirium, physical function and mortality: a systematic review". Age and Ageing. 2014; 43(5): 604-15. DOI: 10.1093/ageing/afu096.