Anticholinergic side effects occur when drugs block the action of acetylcholine, a neurotransmitter involved in various functions of the body. These side effects can be caused by medications that are intended to have anticholinergic effects, as well as by those for which this is an unintended side effect. Common anticholinergic side effects include:
- Dry Mouth (Xerostomia): Reduced saliva production.
- Blurred Vision: Difficulty focusing the eyes, due to effects on the ciliary muscles of the eye.
- Constipation: Reduced gut motility leading to difficulty in bowel movements.
- Urinary Retention: Difficulty in urinating due to relaxation of the bladder muscles.
- Cognitive Impairment: Memory problems, confusion, and in severe cases, delirium, especially in the elderly.
- Drowsiness and Sedation: Though some people may experience the opposite effect (excitement).
- Tachycardia: Increased heart rate, as a result of blocking the parasympathetic effects on the heart.
- Dry and Flushed Skin: Decreased sweating can lead to an inability to cool down in hot environments.
Common drugs and drug classes that can cause anticholinergic side effects include:
- Antihistamines: Especially first-generation antihistamines like diphenhydramine (Benadryl) and promethazine (Phenergan)
- Tricyclic Antidepressants: Such as amitriptyline, imipramine, and nortriptyline.
- Antipsychotics: Particularly older ones like chlorpromazine and thioridazine, but some atypical antipsychotics also have anticholinergic properties.
- Antimuscarinics for Overactive Bladder: Such as oxybutynin (Ditropan) and solifenacin (Vesicare).
- Certain Anti-Parkinson’s Drugs: Like benztropine (Cogentin)
- Anti-nausea Medications: Such as prochlorperazine (Stemetil)
- Antispasmodics: Used for gastrointestinal disorders, like hyoscine (Buscopan)
Elderly patients are particularly susceptible to the cognitive and delirious effects of anticholinergic medications.