Anticholinergic medicines are drugs that block acetylcholine, a chemical messenger that helps control digestion, urination, sweating, and attention. Doctors use them for bladder problems, allergies, motion sickness, and some breathing or movement conditions. They can be helpful, but may also cause dry mouth, constipation, blurred vision, or confusion. Their risks depend on the specific medicine, dose, other medicines, age, and overall health.
How Do Anticholinergic Medicines Work?
Acetylcholine is a chemical messenger that helps nerve cells communicate with muscles, glands, and other parts of the body. It plays a role in many everyday functions, including saliva production, bowel movement, bladder emptying, sweating, and attention.
Anticholinergic medicines block the effects of acetylcholine at certain sites in the body. This reduces specific nerve signals, which can be useful when a body function needs to be controlled. For example, a medicine may relax the bladder, reduce excessive saliva, prevent motion sickness, or help open the airways. According to the Cleveland Clinic, these medicines have a wide range of uses, and their effects depend on the medicine and the condition being treated.
Which Medicines Have Anticholinergic Effects?
Anticholinergic effects are not limited to one group of medicines. Some drugs are designed specifically to block acetylcholine, while others have this effect as an additional property. Examples described in patient guidance from the North East and North Cumbria NHS include medicines used for bladder symptoms, allergies, depression, and sleep.
- Bladder control medicines: Oxybutynin, tolterodine, and solifenacin may be prescribed to reduce urinary urgency or frequent urination.
- Antihistamines: Some older allergy medicines, including diphenhydramine and chlorpheniramine, have anticholinergic effects. They may be found in allergy, cold, or sleep products.
- Antidepressants: Tricyclic antidepressants such as amitriptyline and nortriptyline can have anticholinergic effects. They may be prescribed for depression or certain types of pain.
- Motion sickness medicines: Scopolamine can help prevent nausea and vomiting associated with motion sickness.
- Inhaled medicines for breathing conditions: Ipratropium and tiotropium help manage airway symptoms in conditions such as chronic obstructive pulmonary disease (COPD).
- Medicines for movement disorders: Benztropine is one example of a medicine used for certain movement symptoms associated with Parkinsonism.
These examples do not mean that every medicine used for allergies, depression, breathing problems, or other conditions is anticholinergic. The strength of the effect also differs between medicines. Checking the exact active ingredient is more useful than relying on a product's general purpose or brand name.
What Side Effects Can Anticholinergic Medicines Cause?
Because acetylcholine helps control several body functions, blocking its effects can lead to unwanted changes in different organs. The Merck Manual Consumer Version describes a range of possible anticholinergic effects, including changes involving the mouth, eyes, digestive system, bladder, and mental alertness.
- Dry mouth and dry eyes: Less saliva or tear production can cause discomfort, difficulty swallowing dry foods, or eye irritation.
- Constipation: Slower bowel movement may make stools harder to pass.
- Difficulty passing urine: Some medicines can make it harder to start urinating or empty the bladder fully.
- Blurred vision: Changes in the eyes' focusing response can affect clear vision.
- Drowsiness or dizziness: Some medicines can affect alertness and balance, potentially increasing the risk of falls.
- Confusion or memory difficulties: Certain medicines can affect attention, thinking, or awareness, particularly in susceptible people.
- Rapid heartbeat: Some anticholinergic medicines can increase the heart rate.
- Reduced sweating and overheating: Blocking normal sweating can make it harder for the body to cool itself in hot conditions.
Not everyone experiences these effects, and their likelihood depends on the specific drug, dose, duration of use, and other medicines being taken. Some effects may be temporary, while persistent or disruptive symptoms deserve medical review. Sudden marked confusion, inability to pass urine, or significant overheating after taking a medicine requires urgent medical assessment, especially if an excessive dose may have been taken.
Who May Be More Affected by Anticholinergic Medicines?
Older adults are generally more vulnerable to anticholinergic side effects. They may be more likely to experience confusion, problems with balance, constipation, or difficulty emptying the bladder. The North East and North Cumbria NHS guidance also highlights that side effects may become more likely when someone takes several medicines, uses higher doses, or continues treatment for a long time.
Risk can be particularly relevant when several medicines with anticholinergic effects are taken together. A person may not realise that an everyday allergy tablet or non-prescription sleep aid contributes to the same overall effect as a prescribed medicine. This is one reason a complete medication review can be useful, especially after changes in memory, balance, bowel habits, or urination.
What Is Anticholinergic Burden?
Anticholinergic burden refers to the combined anticholinergic effects of all the medicines a person takes. A single medicine may have a relatively limited effect, while several medicines with these properties can add to the overall burden. Healthcare professionals may use medication lists and assessment tools to identify medicines that contribute to this effect. These tools differ in how they classify individual drugs, so their results need to be interpreted in the context of a person's treatment and health.
Reviewing anticholinergic burden does not necessarily mean that every medicine with these effects should be stopped. A medicine may be providing an important benefit, and stopping it could allow the treated condition to return or worsen. The aim is to weigh the benefits against potential harms and consider whether a safer or more suitable alternative is available.
Do Anticholinergic Medicines Increase the Risk of Dementia?
Research has found an association between anticholinergic medicine use and a higher risk of future dementia in older adults, particularly in studies examining longer-term exposure. However, an association does not prove that the medicines themselves cause dementia. Other health conditions, reasons for prescribing the medicines, and differences between study methods may affect the findings.
A Cochrane review found a possible link between anticholinergic medication use and future problems with memory and thinking but concluded that the available evidence could not establish a direct cause-and-effect relationship. This uncertainty is a reason to review long-term use thoughtfully, particularly in older adults, rather than to stop a prescribed medicine without medical advice.
Anyone experiencing new or worsening memory problems, confusion, or changes in daily functioning should discuss these concerns with a healthcare professional. Reviewing medicines is one part of that assessment, alongside the person's medical history, symptoms, and other relevant findings.
How Can You Use Anticholinergic Medicines Safely?
Anticholinergic medicines can be appropriate and effective treatments when their expected benefits outweigh their risks. Good medication management helps identify unwanted effects and reduces the chance of taking medicines with overlapping actions unnecessarily.
- Keep an up-to-date medicine list. Include prescription medicines, non-prescription products, herbal products, and supplements.
- Check cold, allergy, and sleep products. Some contain ingredients with anticholinergic effects, even when they are sold without a prescription.
- Ask about overlapping effects. A doctor or pharmacist can review whether multiple medicines contribute to dry mouth, constipation, drowsiness, confusion, or other unwanted effects.
- Discuss persistent side effects. Symptoms that affect daily activities, worsen over time, or make treatment difficult may prompt a review of the dose, medicine, or available alternatives.
- Do not change treatment on your own. Ask the prescribing professional before stopping a medicine or changing its dose. Some medicines need a planned adjustment rather than sudden discontinuation.
Seek timely professional advice if you develop new confusion, repeated falls, persistent difficulty urinating, or other concerning changes after starting a medicine or changing a dose. If the symptoms are sudden or serious, seek urgent care rather than waiting for a routine appointment.