What are the guidelines for using anticholinergic medications?

Guidelines for Using Anticholinergic Medications

Anticholinergic medications should be avoided whenever clinically possible, particularly in older adults and postoperative patients, due to their significant risks of delirium, cognitive impairment, falls, and other serious adverse effects that outweigh benefits in most situations. 1, 2

Primary Clinical Contexts Where Anticholinergics Are Used

Postoperative Delirium Prevention

• Strongly avoid anticholinergic medications (including cyclobenzaprine, oxybutynin, prochlorperazine, promethazine, tricyclic antidepressants, paroxetine, diphenhydramine, and hydroxyzine) in older surgical patients to prevent postoperative delirium 1
• This recommendation is based on strong evidence linking anticholinergics to increased delirium risk, even though specific medication studies provide low-level evidence 1
• The only exception: patients requiring treatment to prevent withdrawal complications (e.g., chronic benzodiazepine users) or severe allergic/transfusion reactions 1

Extrapyramidal Symptom Management

• Do NOT use anticholinergics routinely for preventing extrapyramidal side effects from antipsychotics 1, 3
• Reserve anticholinergic use only for treating significant extrapyramidal symptoms when dose reduction and medication switching have failed 3
• For acute dystonia specifically: benztropine 1-2 mg IM/IV is appropriate as first-line emergency treatment 3
• After treating acute dystonia, maintain anticholinergic medications even after antipsychotic discontinuation to prevent delayed symptom emergence 3

Critical caveat: Anticholinergic medications like benztropine can cause delirium, drowsiness, and paradoxical agitation, particularly in elderly patients with Alzheimer's disease receiving typical antipsychotics—avoid benztropine or trihexyphenidyl entirely in this population 3, 2

Sialorrhea in Neuromuscular Disease

• For patients with neuromuscular disease and sialorrhea, a therapeutic trial of an inexpensive oral anticholinergic medication is suggested as first-line therapy 1
• Continue use only if benefits outweigh side effects 1
• Consider more expensive anticholinergic patch medications as first- or second-line alternatives for potentially longer-acting effects 1
• If inadequate response or intolerance to anticholinergic side effects occurs, switch to botulinum toxin therapy to salivary glands 1

Motion Sickness and Postoperative Nausea

• Scopolamine transdermal system (1 mg/3 days) is FDA-approved for motion sickness prevention and postoperative nausea/vomiting 4
• Apply at least 4 hours before antiemetic effect is required for motion sickness 4
• For postoperative nausea (non-cesarean surgeries), apply the evening before surgery and remove 24 hours post-surgery 4

Absolute Contraindications

• Angle closure glaucoma (absolute contraindication) 4
• Hypersensitivity to anticholinergic agents or belladonna alkaloids 4

High-Risk Populations Requiring Extreme Caution

Elderly Patients

• Older adults are particularly vulnerable to anticholinergic adverse effects due to baseline cognitive impairment and reduced physiologic reserve 2, 5
• Anticholinergic burden in elderly patients is associated with falls, cognitive decline, confusion, delirium, and severe cognitive impairment 2, 5, 6
• Deprescribing anticholinergic medications can prevent falls and reverse cognitive decline 2

Patients with Specific Medical Conditions

• Monitor more frequently in patients with suspected intestinal obstruction, pyloric obstruction, or impeded urine flow 4
• Avoid in patients with severe preeclampsia due to risk of eclamptic seizures 4
• Monitor for increased intraocular pressure in patients with open-angle glaucoma 4
• Discontinue if signs of acute angle closure glaucoma, difficulty urinating, or psychiatric symptoms develop 4

Comprehensive Side Effect Profile

Central Nervous System Effects

• Agitated delirium, confusion, hallucinations, disorientation, anxiety, seizures 2
• Drowsiness, cognitive impairment, memory problems 2, 5, 7
• Impaired mental and physical abilities 4
• Classic mnemonic: "Red as a beet, dry as a bone, hot as a hare, blind as a bat, mad as a hatter, full as a flask" 2

Peripheral Effects

• Dry mouth (most common), dry eyes, constipation 2, 8
• Blurred vision, mydriasis (pupil dilation) 2, 8
• Tachycardia, mild hyperthermia 2
• Urinary hesitancy and retention 2, 8
• Hot, dry, erythematous skin 2
• Hypoactive or absent bowel sounds 2

Post-Removal Symptoms

• Anticholinergic withdrawal symptoms may occur 24 hours or more after discontinuation 4
• Gradual tapering is preferred over abrupt discontinuation to avoid withdrawal or rebound worsening 2

Stepwise Management Algorithm for Reducing Anticholinergic Burden

Step 1: Identify and Prioritize

• Review all medications for anticholinergic properties 2
• Prioritize discontinuation of anticholinergics used to manage side effects of other drugs (e.g., benztropine for antipsychotic-induced extrapyramidal symptoms) 2
• Maintain anticholinergics treating primary conditions while exploring alternatives 2

Step 2: Dose Reduction

• Reduce doses to minimum effective levels when discontinuation is not feasible 2
• Use gradual tapering rather than abrupt cessation 2

Step 3: Medication Switching Strategies

For antipsychotics causing extrapyramidal symptoms:

• Switch from high-potency typical antipsychotics (haloperidol) to atypical antipsychotics with lower extrapyramidal symptom risk: olanzapine, quetiapine, or clozapine 3
• For risperidone specifically: use lowest effective dose (2-4 mg/day in adults; 0.25 mg/day starting dose in elderly) as extrapyramidal symptom risk increases significantly above 2 mg/day 3

For antidepressants:

• Switch from tertiary amine tricyclics to secondary amines (nortriptyline or desipramine) which have reduced anticholinergic effects 2

For overactive bladder:

• Consider switching to beta-3 adrenergic receptor agonists which carry less urinary retention risk 2

Step 4: Long-term Monitoring

• Conduct periodic medication reviews to assess continued need for all anticholinergic medications 2
• Educate patients to avoid over-the-counter anticholinergic medications 2
• Monitor for improvements in side effects, memory, and quality of life after anticholinergic burden reduction 7

Management of Severe Anticholinergic Toxicity

• Immediately discontinue the precipitating drug 2
• Provide supportive care including benzodiazepines for agitation 2
• Physostigmine (reversible anticholinesterase) can reverse both central and peripheral anticholinergic effects with dramatic improvement within minutes of IV administration 2

Special Considerations for Specific Medications

Metoclopramide

• Can cause extrapyramidal symptoms, particularly in pregnancy-related nausea 3
• Immediately withdraw upon reporting of extrapyramidal symptoms 3

Scopolamine Transdermal System

• Avoid eye contact to prevent blurred vision 4
• Wash hands thoroughly after application 4
• Do not cut the transdermal system 4
• Upon removal, fold in half with sticky sides together and discard to prevent accidental contact 4

Quality of Life Impact

• Reducing anticholinergic burden results in significant improvements in side effects, memory, and quality of life 7
• One-third to one-half of medicines commonly prescribed for older people have anticholinergic activity, making cumulative burden a major concern 9
• Anticholinergic burden is a predictor of cognitive and functional impairments, adverse health outcomes, and falls in older adults 9