What are examples of anticholinergic medications?

Anticholinergic Medications

Anticholinergic medications are drugs that block the neurotransmitter acetylcholine in the brain and peripheral tissues, and include several major medication classes such as first-generation antihistamines, certain antipsychotics, tricyclic antidepressants, bladder antimuscarinics, and certain muscle relaxants. 1

Common Anticholinergic Medications by Class

First-Generation Antihistamines

• Diphenhydramine (Benadryl) 2, 1
• Hydroxyzine 2, 1
• Promethazine 2
• Chlorpheniramine 3

Antipsychotics

• Clozapine - has significant anticholinergic activity 4
• Thioridazine 3
• Olanzapine 3
• Chlorpromazine 3
• Quetiapine (lower anticholinergic activity) 3

Tricyclic Antidepressants

• Amitriptyline - high anticholinergic activity 3
• Doxepin - high anticholinergic activity 3
• Nortriptyline - moderate anticholinergic activity 3
• Paroxetine - moderate anticholinergic activity (unlike other SSRIs) 3

Bladder Antimuscarinics

• Oxybutynin 2, 3
• Tolterodine 2, 3
• Solifenacin 3
• Darifenacin 3

Gastrointestinal Antispasmodics

• Dicyclomine 5
• L-hyoscyamine 3
• Glycopyrrolate 2

Muscle Relaxants

• Cyclobenzaprine 2, 1
• Orphenadrine 3

Respiratory Agents

• Ipratropium bromide (nasal spray/inhaler) 2
• Tiotropium 3

Antiparkinson Agents

• Benztropine 4, 6
• Trihexyphenidyl 6

Other Medications with Anticholinergic Properties

• Ranitidine (H2 blocker) - low anticholinergic activity 3
• Cimetidine (H2 blocker) 4
• Warfarin - minimal anticholinergic activity 3
• Digoxin - minimal anticholinergic activity 3
• Furosemide - minimal anticholinergic activity 3

Clinical Considerations

Anticholinergic Side Effects

• Peripheral effects: dry mouth, blurred vision, constipation, urinary retention, tachycardia 1, 7
• Central nervous system effects: confusion, memory impairment, delirium, hallucinations 1, 8
• Increased risk of falls in older adults 1
• Cognitive impairment, especially in elderly patients 2, 1

Anticholinergic Burden

• The cumulative effect of multiple medications with anticholinergic properties significantly increases risk of adverse outcomes 1, 9
• One-third to one-half of medications commonly prescribed for older people have some degree of anticholinergic activity 9
• Anticholinergic burden is associated with cognitive decline, functional impairment, and increased mortality in older adults 7

Special Populations at Risk

• Older adults are particularly vulnerable to anticholinergic side effects due to age-related changes in pharmacokinetics and pharmacodynamics 2, 1
• Patients with dementia or cognitive impairment are at higher risk for worsening cognition 2, 8
• Patients with narrow-angle glaucoma should avoid anticholinergics 5
• Patients with benign prostatic hyperplasia may experience worsening urinary symptoms 1

Drug Interactions

• Anticholinergics may antagonize the effects of antiglaucoma agents 5
• When combined with other CNS-active substances, anticholinergics can cause enhanced performance impairment and sedation 1
• Antacids may interfere with the absorption of anticholinergic agents 5
• Anticholinergics may affect gastrointestinal absorption of various drugs by altering gastrointestinal motility 5

Recommendations for Clinical Practice

• Avoid anticholinergic medications in older adults whenever possible 2, 1
• When treating allergic conditions, second-generation antihistamines are preferred over first-generation antihistamines due to reduced anticholinergic effects 1
• For patients requiring anticholinergic medications, use the lowest effective dose for the shortest duration possible 1
• Regularly review medication regimens to identify and reduce anticholinergic burden 1
• Consider alternative treatments with lower anticholinergic burden when available 9, 7