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Anticholinergic medications include a broad class of drugs that blocks the action of a chemical messenger
Side effects from anticholinergic medications are common, especially in the elderly. The probable side effects depend on the medical history of the person, dosage, and specific type of anticholinergics taken.
Sometimes, therapeutic effects in one organ system may have undesirable side effects in other organ systems.
Possible side effects of anticholinergic medications include:
- Dry mouth due to inhibition of the salivary gland
- Drowsiness or sedation
- Blurred vision or double vision
- Dry eyes
- Absence of or reduced sweating
- Hyperpyrexia (increased body temperature)
- Poor coordination due to altered muscle control
- Constipation
- Urinary incontinence
- Urinary retention
- Postural hypotension (decrease in blood pressure on standing or sitting from lying down position)
- Confusion or delirium
- Hallucinations
- Memory impairment
- Incoherence
- Inability to concentrate
- Increased heart rate
- Dementia (a complex disorder affecting the brain causing memory loss, personality changes, and impaired reasoning)
Anticholinergic medications should be avoided by people who have certain health conditions such as:
- Benign prostatic hypertrophy (BPH)
- Glaucoma
- Myasthenia gravis
- Alzheimer’s disease
- Chronic constipation
- Bowel blockage
- Urinary tract blockage or urinary hesitancy
- Unstable heart conditions
- Postural hypotension
- Severe colitis
- Dementia
- Cognitive impairment
- Delirium
- Pregnant and lactating women
The use of anticholinergics should be avoided by the elderly because anticholinergic side effects are particularly common and problematic in them.
Mechanism of action of anticholinergic medications
Anticholinergic medications work by blocking the action of the neurotransmitter acetylcholine.
A neurotransmitter is a chemical that is released by the nerve cells to send signals to other cells. Blocking the neurotransmitter acetylcholine inhibits involuntary muscle movements (muscle movements not under conscious control) in the lungs, gastrointestinal tract, urinary tract, and other areas of the body. Because anticholinergic medications affect various body functions involving digestion, urination, salivation, and movement, they help treat many health conditions.
Classification of anticholinergic medications
Anticholinergic medications are classified according to the receptors that they target:
- Antimuscarinic medications: This targets the muscarinic acetylcholine receptors found at the nerve endings at the smooth muscle cells, secretory glands, and eye. They are also found in the central nervous system. The majority of anticholinergic medications are antimuscarinics.
- Antinicotinic medications: These act on the nicotinic acetylcholine receptors located at the nerve endings of the neuromuscular junctions and are the target of muscle relaxing drugs.
Uses of anticholinergic medications
Anticholinergic medications have been used for treating many diverse conditions such as:
- Asthma
- Chronic obstructive pulmonary disease (COPD)
- Diarrhea
- Irritable bowel syndrome (IBS)
- Muscle spasms
- Overactive bladder (OAB)
- Urinary incontinence
- Parkinson's disease
- Surgery and anesthesia
- Muscle relaxation
- Vomiting
- Gastrointestinal disorders
- Insomnia
- Dizziness
- Motion sickness
- Poisoning due to insecticides and poisonous mushrooms
- Psychiatric disorders
Drug interactions of anticholinergic medication
Anticholinergic medications have potential interactions with medications that have cholinergic actions.
The use of multiple drugs with anticholinergic properties may be problematic because of their cumulative anticholinergic side effects. The combined use of two or more anticholinergic medications should be avoided to minimize the risk of adverse drug effects.
Medications with anticholinergic properties that should not be combined include:
- Antidepressants
- Antihistamines
- Muscle relaxants
- Antispasmodics
- Anti-diarrheal medications
- Parkinson’s medications
- Antiarrhythmic medications
- Antipsychotics
- Overactive bladder (OAB) medications
- Acetylcholinesterase inhibitors
- Motion sickness medications
- Certain antiemetic medications
- Respiratory medications
Appropriate choice of anticholinergic medications and their dose help minimize undesirable side effects. With a suitable prescription, anticholinergic medications are usually safe.