Atropine
Atropine
Generic Name
Atropine
Drug Class
Muscarinic antagonist (anticholinergic)
Mechanism
Competitive blockade of all muscarinic acetylcholine receptors (M1–M5). Increases heart rate, reduces secretions, dilates pupil, relaxes smooth muscle.
Contraindications
- Glaucoma with narrow angle (risk of acute angle‑closure)
- Mechanical ileus
- Severe peripheral vascular disease (risk of ischemia)
- History of pro‑arrhythmic QT‑prolongation (at high doses)
Clinical Pearls
- Pediatrics: 0.01–0.02 mg/kg IM/IV for bradycardia; 0.1 mg/kg eye drops for mydriasis.
- Pregnancy: Category C. Use only if benefits > dangers.
- Breastfeeding: Low transfer; minimal but avoid if mother is of child‑bearing potential.
Clinical Notes
Atropine
(Antimuscarinic alkaloid)
| Category | Details |
|---|---|
| Drug class | Muscarinic antagonist (anticholinergic) |
| Mechanism of action | Competitive blockade of all muscarinic acetylcholine receptors (M1–M5). Increases heart rate, reduces secretions, dilates pupil, relaxes smooth muscle. |
| Routes of administration | Ophthalmic, intramuscular, intravenous, oral, rectal, intranasal, transdermal (creams/gels). |
| Therapeutic uses | • Bradycardia from vagal/syncope (IV 0.5–1 mg, repeat ≤ 2 mg, max 3 mg) • Pre‑anesthetic atropinisation (0.01 mg/kg IM/IV) • Ophthalmic mydriasis (1 %) • Salivary/gastro‑ileal secretions in surgery • Treatment of organophosphate nerve‑agent poisoning (de‑atropinise + paralytic‑colchicine) |
| Contraindications | • Glaucoma with narrow angle (risk of acute angle‑closure) • Mechanical ileus • Severe peripheral vascular disease (risk of ischemia) • History of pro‑arrhythmic QT‑prolongation (at high doses) |
| Key adverse effects | • Tachycardia, palpitations, arrhythmias • Dry mouth, blurred vision, photophobia • Urinary retention, constipation • CNS: agitation, hallucinations, delirium (high doses) • In overdose: seizures, hyperthermia, seizures |
| Drug interactions | • Potentiates anticholinergic drugs (e.g., antihistamines, tricyclic antidepressants, antipsychotics). • Increases plasma ritonavir levels (e.g., HIV protease inhibitors). • May reduce the efficacy of β‑blockers (contradictory effect on HR). • Avoid with agents prolonging QT (e.g., quinidine, sotalol). |
| Pharmacokinetics (IV) | • Absorption: Immediate. • Distribution: 1.5–5.9 L/kg. • Half‑life: 2–2.5 h (IV). • Metabolism: Hepatic (oxidative de‑homo‑Atropine). • Elimination: ~73 % renal, 27 % biliary. • Protein binding: ~30 % (low). |
| Dose‑adjustment (renal/hepatic impairment) | • Note: no routine dose adjustment required for mild‑moderate CKD, but monitor for toxicity in severe CKD (CrCl < 30 mL/min) or hepatic dysfunction. |
| Special populations | • Pediatrics: 0.01–0.02 mg/kg IM/IV for bradycardia; 0.1 mg/kg eye drops for mydriasis. • Pregnancy: Category C. Use only if benefits > dangers. • Breastfeeding: Low transfer; minimal but avoid if mother is of child‑bearing potential. |
| Overdose management | • Staged treatment: 1. < 2 mg – monitor vitals, give activated charcoal, consider IV fluids. 2. > 2 mg – treat with charcoal, administer IV atropine 1 mg i.v. / i.m. every 5 min up to 6 mg, +benzodiazepine for seizures, consider lipid emulsion therapy if severe. 3. Severe – ICU, supportive care (ventilation, cardiac monitoring). |
| Key references | • Katzung BG. Basic & Clinical Pharmacology. 15th ed. 2023. • Woolley F, et al. Clinical Pharmacokinetics of Atropine. Drugs. 2022. • Lexicomp® Atropine; UpToDate “Use of atropine in adults with bradycardia.” 2025. |
Quick‑reference mnemonic
- A: Antimuscarinic → ↓ secretions, ↑ HR, dilate pupil
- B: Bradycardia → first‑line antidote
- C: Contraindications – narrow‑angle glaucoma, ileus, arrhythmias
Use the table as a concise, practitioner‑friendly overview.
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