Antimuscarinic drugs 💊
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⚙️ Mode of Action
- Anticholinergic drugs block acetylcholine (ACh) at muscarinic receptors.
- Result: ↓ parasympathetic activity → smooth muscle relaxation, ↓ secretions, ↑ heart rate, mydriasis.
💊 Indications & Uses
- 🧠 Neurology: Parkinson’s disease & parkinsonism (reduce tremor/rigidity).
- 💧 Urology: Overactive bladder & incontinence (oxybutynin, tolterodine, solifenacin, darifenacin, trospium, fesoterodine, propiverine).
- 🍽️ Gastroenterology: Reduce motility in IBS/diverticular disease (e.g. dicycloverine, propantheline, hyoscine butylbromide – Buscopan).
- ❤️ Cardiology: Atropine for bradyarrhythmias (↑ heart rate).
- 🌬️ Respiratory: Historically for asthma/COPD (now replaced by selective inhaled agents like ipratropium, tiotropium).
- 🚢 ENT / Travel: Hyoscine hydrobromide for motion sickness.
- 👁️ Ophthalmology: Mydriasis & cycloplegia for eye exams.
- ☠️ Toxicology: Antidote in organophosphate poisoning.
🔄 Interactions
- ⚠️ Avoid with other antimuscarinics (↑ side effect risk).
- Can potentiate anticholinergic burden from TCAs, antihistamines, antipsychotics.
⚠️ Cautions
- 🚗 May impair ability to drive or operate machinery.
- 👶👵 Children, elderly, and people with Down’s syndrome are more sensitive.
- 🧔 Prostatic hypertrophy → risk of urinary retention.
⛔ Contraindications
- Myasthenia gravis.
- Intestinal obstruction / paralytic ileus.
- Pyloric stenosis.
- Severe ulcerative colitis / toxic megacolon.
- Untreated angle-closure glaucoma.
🤒 Side Effects
- 🍽️ GI: Constipation, nausea, vomiting.
- ❤️ CVS: Bradycardia (initial) → tachycardia, palpitations, arrhythmias.
- 💧 GU: Urinary retention, urgency.
- 👁️ Ophthalmic: Mydriasis, blurred vision, photophobia, angle-closure glaucoma.
- 🌬️ Respiratory: Reduced bronchial secretions → risk of thick sputum plugs.
- 😮💨 Skin/mucous: Dry mouth, dry skin, flushing.
- 🧠 CNS: Confusion (esp. elderly), dizziness, hallucinations.
📚 References
