Overview
Module covers cholinergic and anticholinergic medications, their indications, mechanisms, adverse effects, overdose signs, contraindications, and patient education.
Indications
- Cholinergic: glaucoma to reduce intraocular pressure.
- Cholinergic: myasthenia gravis to improve muscle strength.
- Cholinergic: Alzheimer’s disease to increase acetylcholine in the brain.
- Anticholinergic: overactive bladder to reduce urinary frequency and urgency.
- Anticholinergic: asthma to help open airways.
- Anticholinergic: nausea management by drying secretions.
- Anticholinergic: Parkinson’s disease to reduce tremors.
Mechanisms of Action
- Cholinergic response: mimics acetylcholine; stimulates parasympathetic nervous system.
- Parasympathetic system: rest and digest functions are enhanced.
- Example cholinergic: bethanechol stimulates bladder for urinary retention.
- Anticholinergic response: blocks acetylcholine action; inhibits parasympathetic activity.
- Anticholinergic effect: resembles sympathetic activation in the body.
- Example anticholinergic: scopolamine blocks acetylcholine to prevent nausea and vomiting.
Comparative Summary
| Category | Cholinergic (Parasympathetic mimetic) | Anticholinergic (Parasympathetic blocker) |
|---|
| Primary actions | Enhance rest and digest; increase secretions and motility | Reduce secretions and motility; sympathetic-like effects |
| Key examples | Bethanechol for urinary retention | Scopolamine for nausea and vomiting |
| Cardiovascular | Bradycardia; hypotension | Tachycardia; possible hypertension |
| Respiratory | Not primary focus here | Bronchodilation benefit in asthma |
| GI/GU effects | Increased salivation; diarrhea; nausea; vomiting | Dry mouth; constipation; urinary retention |
| CNS effects | Not emphasized | Altered mental status, especially in elderly |
| Ocular effects | May be used in glaucoma | Dry eyes; blurry vision; avoid in glaucoma |
Adverse Effects
- Cholinergic: increased salivation and sweating.
- Cholinergic: bradycardia and hypotension.
- Cholinergic: diarrhea, nausea, and vomiting.
- Anticholinergic: altered mental status, especially elderly.
- Anticholinergic: dry mouth and constipation.
- Anticholinergic: urinary retention; dry eyes or blurry vision.
Toxicity and Overdose Signs
- Cholinergic crisis: neuromuscular overstimulation causing muscle weakness and respiratory failure.
- Cholinergic overdose signs: excessive salivation, sweating, muscle weakness.
- Anticholinergic overdose signs: agitation and confusion.
- Anticholinergic overdose signs: dilated pupils, dry skin, tachycardia, urinary retention.
Assessment and Monitoring
- Monitor vital signs with cholinergic drugs.
- Pay special attention to heart rate and blood pressure.
- Cholinergic therapy: watch for bradycardia and hypotension.
- Anticholinergic therapy: watch for tachycardia and potential hypertension.
- Assess for overdose signs based on expected system effects.
Contraindications
- Cholinergic: contraindicated in hypotension due to further BP lowering.
- Cholinergic: contraindicated in bradycardia due to further HR lowering.
- Anticholinergic: contraindicated in glaucoma; increases intraocular pressure.
- Anticholinergic: contraindicated in urinary retention; worsens retention.
- Anticholinergic: contraindicated in myasthenia gravis; exacerbates weakness.
Patient Education
- Cholinergic: recognize excessive salivation, sweating, muscle weakness as warning signs.
- Anticholinergic: expect dry mouth, constipation, possible confusion; monitor severity.
- Seek medical attention if usual side effects worsen or new severe symptoms appear.
- Report signs of overdose promptly to prevent complications.
Key Terms & Definitions
- Parasympathetic nervous system: rest and digest branch controlling baseline functions.
- Cholinergic response: drug effect mimicking acetylcholine; activates parasympathetic system.
- Anticholinergic response: drug effect blocking acetylcholine; inhibits parasympathetic system.
- Bradycardia: slower than normal heart rate.
- Hypotension: lower than normal blood pressure.
- Tachycardia: faster than normal heart rate.
Action Items / Next Steps
- Verify baseline HR and BP before starting therapy.
- Educate patients on expected effects and overdose signs.
- Monitor elderly closely for anticholinergic CNS effects.
- Avoid contraindicated conditions when selecting therapy.