Atropine (Tropane Alkaloid · Anticholinergic · Nerve Agent Antidote · Myopia Control)
| Compound | Atropine (dl-Hyoscyamine) |
| Chemical class | Alkaloid — Tropane (Tropinyl ester of tropic acid; racemic hyoscyamine) |
| CAS | 51-55-8 |
| Primary source | Atropa belladonna (deadly nightshade), Datura stramonium, Hyoscyamus niger |
| Key applications | Pharmaceutical anticholinergic; bradycardia, organophosphate poisoning, ophthalmology, premedication; informational reference |
| Claim strength | High (as pharmaceutical); Informational only |
| Typical form | Pharmaceutical injection (cardiac/toxicology emergency); ophthalmic drops; oral tablet; not a dietary supplement |
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Name origin: From Atropa belladonna (Atropa = Atropos, one of the three Fates in Greek mythology, who cuts the thread of life — reflecting belladonna’s deadly potential). Belladonna means “beautiful woman” in Italian — referring to the cosmetic use of belladonna extract drops to dilate pupils, considered attractive in Renaissance Italy. Atropine is the racemic mixture (50:50 R/S) of hyoscyamine; in belladonna plants, the pharmacologically active form is L-hyoscyamine (which racemises to atropine during extraction). Traditional use: Belladonna has one of the longest documented toxic/medicinal histories. Egyptian physicians used henbane (Hyoscyamus) preparations as early as 1550 BCE for pain. Renaissance Italian women used belladonna eye drops to dilate pupils cosmetically. Medieval European herbalists used belladonna for surgery, witches used nightshade preparations for hallucinogenic “flying ointments” (transdermal scopolamine/hyoscyamine). The first use of a pure alkaloid in surgery was the use of atropine to reduce secretions during chloroform anaesthesia (1867). Pharmacology — competitive muscarinic antagonist: Atropine competitively blocks muscarinic acetylcholine receptors (M1–M5) throughout the body: heart (M2 antagonism → increased heart rate), smooth muscle (M3 antagonism → relaxation), glands (M3 antagonism → reduced secretions), eye (M3 antagonism → mydriasis, cycloplegia), CNS (M1 antagonism → amnesia, delirium at high doses). Pharmaceutical applications: (1) Emergency bradycardia (IV 0.5–1 mg); (2) Organophosphate/nerve agent poisoning (competitive reversal of excess ACh; given with pralidoxime); (3) Ophthalmic mydriasis/cycloplegia; (4) Preoperative to reduce secretions; (5) Antidote for cholinergic crisis.
Atropine — Pharmaceutical and Historical Context
Organophosphate antidote — life-saving application: Atropine is the cornerstone antidote for organophosphate pesticide poisoning and nerve agent exposure (sarin, VX, novichok). Organophosphates irreversibly inhibit AChE, causing accumulation of ACh at all muscarinic and nicotinic synapses — producing the SLUDGE syndrome (Salivation, Lacrimation, Urination, Defaecation, GI distress, Emesis) and ultimately respiratory failure. Atropine competitively blocks the downstream muscarinic overstimulation (but not nicotinic), reversing bronchospasm and bronchosecretion. Doses of 2–4 mg IV (10–20× the cardiac emergency dose) are required for nerve agent exposure. Military personnel in conflict zones carry autoinjector atropine for this indication. Pharmaceutical evidence: High.
Ophthalmology — atropine for myopia control: A paradigm-shifting discovery: low-dose atropine eye drops (0.01–0.05%) significantly slow myopia (short-sightedness) progression in children in multiple Asian RCTs (ATOM1, ATOM2, LAMP studies) — reducing axial elongation by 50–70% over 2 years. This represents the strongest intervention for controlling childhood myopia progression. The mechanism appears to involve M4 receptor antagonism in the retina (not pupil dilation at low doses). Low-dose atropine for myopia control is now recommended in paediatric ophthalmology guidelines in many Asian countries and is gaining acceptance globally. Pharmaceutical evidence: High (multiple Asian RCTs).
Antimuscarinic toxidrome — belladonna poisoning: Belladonna poisoning (“hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter”) reflects atropine/hyoscyamine’s anticholinergic effects: hyperthermia (inability to sweat), mydriasis, dry skin/mouth, flushing, and anticholinergic delirium. This mnemonic is standard medical education. Treatment: physostigmine (reversible AChE inhibitor, increasing ACh to overcome competitive antimuscarinic antagonism). Critical toxicology reference.
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Frequently Asked Questions — Atropine
Why is atropine given before surgery?
Pre-operative atropine (now less commonly used than historically) was given to: (1) reduce airway secretions (salivation, bronchial secretions) that could obstruct anaesthetic airway management; (2) prevent bradycardia during intubation or ophthalmic surgery; (3) reduce the risk of vagal reflex-induced cardiac slowing during surgical manipulation. Modern anaesthetic agents have reduced pre-operative atropine use, but it remains the drug of choice for intra-operative bradycardia unresponsive to other measures.
What makes atropine the antidote for nerve agents?
Nerve agents (sarin, VX, novichok) irreversibly inhibit acetylcholinesterase (AChE), the enzyme that degrades ACh. Without AChE, ACh accumulates at all synapses. Atropine blocks the downstream effects at muscarinic receptors (bronchospasm, bronchosecretion, cardiovascular), buying time for the patient to survive. Pralidoxime (2-PAM) regenerates AChE if given early (before “ageing” of the organophosphate-AChE bond). Diazepam prevents seizures from CNS cholinergic excess. The auto-injector for military nerve agent exposure contains atropine + pralidoxime.
Is low-dose atropine eye drops available without a prescription for myopia control?
Regulatory status for low-dose atropine myopia control drops (0.01–0.05%) varies by country. In Singapore, Hong Kong, Taiwan, and increasingly Australia, low-dose atropine is prescribed by ophthalmologists for paediatric myopia control. In most Western markets, it requires prescription. Compounding pharmacies prepare low-dose atropine formulations where commercial products are unavailable. No OTC myopia control atropine product exists in regulated markets, and self-treatment of children without ophthalmologist supervision is not recommended.
What is the difference between atropine and scopolamine?
Both are tropane alkaloids from belladonna-family plants and competitive muscarinic antagonists. Key differences: atropine (racemic hyoscyamine) has stronger peripheral anticholinergic effects and is preferred for cardiac (bradycardia) and toxicological (organophosphate) applications. Scopolamine has greater CNS penetration and is preferred for: motion sickness (Transderm Scop patch), preoperative nausea, and it was historically used as “truth serum” due to its greater amnestic effect. Scopolamine is more potent for nausea; atropine is more potent for cardiac effects.
Related compounds: Scopolamine, Hyoscyamine, Pilocarpine, Arecoline
Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.
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