Anticholinergics
Key Points
- Anticholinergics (parasympatholytics) block muscarinic acetylcholine receptors → reverse parasympathetic “rest and digest” effects
- Classic adverse effects: ABCDE — Anorexia/dry mouth, Blurred vision, Constipation, Drowsiness/delirium, Excretion (urinary retention)
- Beers Criteria: Anticholinergics in older adults increase risk of delirium, falls, cognitive impairment, and urinary retention
- Atropine: Prototype anticholinergic; reverses bradycardia, blocks secretions before surgery, antidote for cholinergic crisis
- Oxybutynin: Overactive bladder treatment; significant anticholinergic burden — avoid in older adults (Beers Criteria)
- Ipratropium/Tiotropium: Respiratory anticholinergics — see bronchodilators for complete inhaler management
Drug Class Overview
Anticholinergics block the binding of acetylcholine at muscarinic (M1, M2, M3) receptors of the parasympathetic nervous system. The parasympathetic “SLUDGE” effects are reversed:
SLUDGE (cholinergic effects blocked by anticholinergics):
- Salivation → reduced (dry mouth)
- Lacrimation → reduced (dry eyes)
- Urination → reduced (urinary retention)
- Defecation → reduced (constipation)
- GI motility → reduced (decreased peristalsis)
- Emesis → reduced (antiemetic effect)
Major Drug Classes and Clinical Uses
Cardiovascular / Emergency
Atropine (prototype): Blocks M2 receptors in SA node → increases heart rate.
Indications:
- Symptomatic bradycardia (first-line pharmacologic treatment): 0.5 mg IV, may repeat every 3–5 minutes (max 3 mg)
- Pre-operatively: dries secretions, reduces vagal stimulation during intubation
- Antidote for cholinergic crisis (organophosphate poisoning, AChE inhibitor overdose)
Adverse Effects: Tachycardia, dry mouth, blurred vision, urinary retention, constipation, confusion (especially older adults).
Contraindications: Tachycardia, narrow-angle glaucoma, prostatic hyperplasia, myasthenia gravis.
Gastrointestinal
Dicyclomine (Bentyl): Relaxes GI smooth muscle.
Indications: Irritable bowel syndrome (IBS) — treats cramping and pain.
Hyoscyamine (Levsin): For IBS, peptic ulcer disease, diverticulitis.
Adverse Effects: Classic anticholinergic effects — dry mouth, constipation, blurred vision, urinary retention.
Urinary — Overactive Bladder
Overactive bladder (OAB) is characterized by urinary urgency, frequency, and urge incontinence. Anticholinergics relax the detrusor muscle of the bladder → reduce involuntary contractions.
| Drug | Notes |
|---|---|
| Oxybutynin (Ditropan) | Most commonly used; also patch (Oxytrol); may be used for postoperative bladder spasms; Beers Criteria — avoid in older adults |
| Tolterodine (Detrol) | More bladder-selective than oxybutynin; fewer CNS effects |
| Trospium (Sanctura) | Less CNS penetration — potentially better tolerated by older adults |
| Solifenacin (VESIcare) | Once-daily dosing; selective muscarinic M3 antagonist |
| Mirabegron (Myrbetriq) | NOT anticholinergic — β3 adrenoceptor agonist alternative with fewer anticholinergic effects |
Shared Adverse Effects: Dry mouth, blurred vision, constipation, urinary retention, cognitive impairment.
In selected postoperative urologic care (for example after TURP), oxybutynin may be prescribed short-term to reduce painful bladder spasms; continue retention and cognitive-status monitoring.
Contraindications: Urinary retention, uncontrolled narrow-angle glaucoma.
Respiratory
Ipratropium (Atrovent — SAMA), Tiotropium (Spiriva — LAMA): Block muscarinic receptors in bronchial smooth muscle → reduce bronchoconstriction and secretions.
Primary use: COPD maintenance; acute asthma (ipratropium + albuterol combination).
See bronchodilators for complete respiratory anticholinergic profiles and dosing.
Antiemetic
Scopolamine (Transderm Scōp): Transdermal patch behind ear for motion sickness and PONV prevention.
See antiemetics for full scopolamine profile.
Parkinson’s Disease
Benztropine (Cogentin), trihexyphenidyl: Reduce EPS symptoms (tremor, rigidity) caused by antipsychotic-induced dopamine blockade.
Classic Anticholinergic Adverse Effects (ABCDE)
| Mnemonic | Effect | Clinical Significance |
|---|---|---|
| A — Anorexia/Dry mouth | Decreased salivation | Difficulty swallowing, dental caries with long-term use |
| B — Blurred vision | Mydriasis, cycloplegia | Contraindicated in narrow-angle glaucoma |
| C — Constipation | Decreased GI motility | Monitor bowel function |
| D — Drowsiness/Delirium | CNS anticholinergic effects | Especially severe in older adults — confusion, hallucinations |
| E — Excretion impaired | Urinary retention | Contraindicated in prostatic hyperplasia; monitor urine output |
Additional: Tachycardia (blocked cardiac M2 receptors), hyperthermia (blocked sweat glands).
Anticholinergics and Older Adults — Beers Criteria
Anticholinergic medications are on the AGS Beers Criteria for Potentially Inappropriate Medications in Older Adults. They are associated with increased risk of delirium, cognitive impairment, falls, and urinary retention. Use with extreme caution or avoid in patients >65 years. Consider alternatives (e.g., mirabegron for OAB instead of oxybutynin).
Nursing Assessment
Before Administration:
- Assess for contraindications: narrow-angle glaucoma (blurred vision/elevated IOP risk), urinary retention, prostatic hyperplasia, myasthenia gravis
- Bowel history: existing constipation worsened by anticholinergics
- Older adults: assess cognitive baseline (delirium risk)
- Heart rate: atropine contraindicated in tachycardia
Ongoing Monitoring:
- Urinary output — monitor for retention (especially in males with BPH)
- Bowel function — prevent and treat constipation
- Intraocular pressure for patients with glaucoma history
- Cognitive status in older adults (confusion, hallucinations)
- Hydration status — impaired sweating may cause overheating
Patient Education:
- Expect dry mouth — sip water frequently; use sugar-free candy/gum
- Change positions slowly (orthostatic hypotension)
- Report inability to urinate, vision changes, or severe constipation
- Avoid hot environments — anticholinergics impair sweating
- Avoid driving until CNS effects are known (drowsiness, blurred vision)
Related Concepts
- bronchodilators — Respiratory anticholinergics (ipratropium, tiotropium)
- antiemetics — Scopolamine for motion sickness and PONV
- bladder-assessment — Overactive bladder management
- geriatric-assessment-and-polypharmacy-safety — Beers Criteria and anticholinergic burden in older adults
- medication-related-urinary-elimination-changes — Anticholinergics as cause of urinary retention
- psychotropic-medications — Benztropine for antipsychotic-induced EPS
Self-Check
- An 80-year-old patient is prescribed oxybutynin for overactive bladder. What concerns would you bring to the provider’s attention, and what alternative medication might be preferred?
- A patient receiving atropine for symptomatic bradycardia develops difficulty urinating. What is the mechanism of this adverse effect?
- A patient on an anticholinergic medication in a hot environment becomes confused and has dry, flushed skin. What complication do you suspect, and what is the priority intervention?