Atropine – Uses, Mechanism and Side Effects
Atropine is an anticholinergic drug derived from the belladonna plant, used in emergency medicine, anesthesia, and ophthalmology.
Things worth knowing about "Atropine"
Atropine is an anticholinergic drug derived from the belladonna plant, used in emergency medicine, anesthesia, and ophthalmology.
What is Atropine?
Atropine is a naturally occurring alkaloid originally extracted from the deadly nightshade plant (Atropa belladonna). It belongs to the class of anticholinergic drugs and works by blocking the neurotransmitter acetylcholine at muscarinic receptors. Atropine is used across multiple medical disciplines, including emergency medicine, anesthesiology, and ophthalmology.
Mechanism of Action
Atropine acts as a competitive antagonist at muscarinic acetylcholine receptors (M1–M5). By blocking these receptors, it inhibits parasympathetic nerve signals. The main pharmacological effects include:
- Increased heart rate (positive chronotropic effect)
- Reduced secretion of saliva, sweat, and mucus
- Bronchodilation (relaxation of airway smooth muscle)
- Pupil dilation (mydriasis) and inhibition of the accommodation reflex
- Relaxation of smooth muscle in the gastrointestinal tract
Indications
Atropine is used in a variety of clinical situations:
- Bradycardia: To treat dangerously slow heart rate, including during cardiac resuscitation
- Premedication: Before surgery to reduce excessive secretions
- Poisoning: As an antidote for organophosphate poisoning (e.g., nerve agents and pesticides) and muscarine toxicity from certain mushrooms
- Ophthalmology: As a mydriatic agent for eye examinations and treatment of intraocular inflammation
- Antispasmodic: To relieve spasms of the gastrointestinal tract or urinary system
Dosage and Administration
The dosage of atropine depends on the specific indication and must be individually adjusted:
- Bradycardia / Resuscitation (adults): 0.5–1 mg intravenously, repeated as needed up to a total of 3 mg
- Premedication: 0.3–0.6 mg subcutaneously or intramuscularly
- Eye drops: 0.5%–1% solution, depending on the indication
- Children: Dosed by body weight under strict medical supervision
Atropine has a narrow therapeutic window and must always be administered under medical supervision.
Side Effects
The side effects of atropine reflect its anticholinergic properties and are collectively referred to as the anticholinergic syndrome:
- Dry mouth and dry skin
- Increased heart rate (tachycardia)
- Dilated pupils and blurred vision
- Urinary retention
- Constipation
- Skin flushing and a sensation of warmth
- In overdose: confusion, hallucinations, seizures, coma
Contraindications
Atropine should not be used, or used only with great caution, in patients with:
- Narrow-angle glaucoma
- Myasthenia gravis
- Benign prostatic hyperplasia with urinary retention
- Tachyarrhythmias
- Severe heart failure
Drug Interactions
Atropine can interact with numerous medications. The anticholinergic effect is enhanced by other anticholinergics, tricyclic antidepressants, and antihistamines. Concurrent use with metoclopramide may reduce its prokinetic effect.
References
- Katzung B.G., Trevor A.J.: Basic and Clinical Pharmacology. 15th edition. McGraw-Hill Education, 2021.
- European Resuscitation Council (ERC): Guidelines for Resuscitation 2021. Resuscitation, 2021.
- World Health Organization (WHO): Model Formulary 2008 – Atropine. WHO Press, Geneva.
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