# Atropine (dl-Hyoscyamine)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/atropine-dl-hyoscyamine
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-02
**Evidence Score:** 1 / 10
**Category:** Compound
**Also Known As:** Atropine sulfate, Atropine (derived from Atropa belladonna and related Solanaceae), Atropine (Atropa belladonna alkaloid), Tropine tropate, Atropa belladonna alkaloid, 1αH,5αH-Tropan-3α-ol (±)-tropate, dl-Hyoscyamine

## Overview

Atropine is a competitive, reversible antagonist at all five subtypes of muscarinic [acetylcholine](/ingredients/condition/cognitive) receptors (M1–M5), blocking parasympathetic neurotransmission by preventing acetylcholine binding and thereby increasing heart rate, reducing secretions, relaxing smooth muscle, and dilating pupils. Its most clinically decisive application is the emergency reversal of organophosphate or carbamate poisoning, where intravenous doses of 2–4 mg (titrated to drying of secretions) can be life-saving, and low-concentration ophthalmic formulations of 0.01–0.05 wt% have demonstrated statistically significant slowing of axial eye elongation in pediatric myopia trials.

## Health Benefits

- **Reversal of Organophosphate/Nerve Agent Poisoning**: Atropine competitively blocks muscarinic receptors flooded by excess [acetylcholine](/ingredients/condition/cognitive) from cholinesterase inhibition, rapidly reversing bronchospasm, excessive secretions, bradycardia, and miosis; high-concentration formulations of 10 mg/mL are approved in several countries specifically for this indication.
- **Bradycardia and Cardiac Arrest Management**: By blocking cardiac M2 muscarinic receptors, atropine increases sinoatrial node firing rate and atrioventricular conduction velocity, making it a first-line ACLS agent for symptomatic sinus bradycardia at doses of 0.5–1 mg IV.
- **Myopia Progression Control in Children**: Low-dose atropine ophthalmic solutions (0.01–0.05 wt%) reduce axial elongation of the pediatric eye through poorly fully elucidated mechanisms likely involving retinal M1/M4 receptor modulation, with multiple randomized trials showing 50–77% reduction in myopia progression over two years compared to placebo.
- **Cycloplegia and Mydriasis for Ophthalmic Examination**: Atropine 1% ophthalmic solution produces prolonged ciliary muscle paralysis (cycloplegia) and pupil dilation lasting up to 14 days, enabling accurate refraction measurement in children and facilitating fundoscopic examination.
- **Amblyopia (Lazy Eye) Treatment**: Penalization therapy using 1% atropine drops in the stronger eye blurs its vision and forces use of the amblyopic eye, offering a non-occlusive alternative to patching with comparable efficacy demonstrated in large pediatric trials.
- **Preoperative Antisialagogue and Anesthetic Adjunct**: Atropine reduces salivary and bronchial secretions preoperatively by blocking M3 receptors on exocrine glands, historically dosed at 0.4–0.6 mg IM 30–60 minutes before induction to maintain a clear surgical airway.
- **Antidote for Muscarinic Drug Overdose**: Atropine reverses the excessive parasympathomimetic effects of muscarinic agonists (e.g., pilocarpine, bethanechol) and certain mushroom poisonings (Clitocybe/Inocybe species containing muscarine), restoring autonomic balance through direct receptor competition.

## Mechanism of Action

Atropine acts as a competitive, surmountable antagonist at all five muscarinic [acetylcholine](/ingredients/condition/cognitive) receptor subtypes (M1–M5), which are G-protein-coupled receptors (GPCRs); it binds with high affinity to the orthosteric acetylcholine binding site within the receptor's transmembrane domain, preventing acetylcholine from inducing the conformational change required for downstream G-protein activation, without itself activating the receptor. At M2 receptors in the sinoatrial and atrioventricular nodes, blockade releases inhibitory Gi-protein tone, increasing cAMP, enhancing If (funny current), and accelerating cardiac automaticity; at M3 receptors on smooth muscle and secretory glands, blockade prevents Gq/IP3-mediated calcium release, relaxing smooth muscle and drying secretions. At the neuromuscular junction and autonomic ganglia, atropine has negligible effect at therapeutic doses because those junctions use nicotinic (not muscarinic) receptors, preserving voluntary motor function. The compound crosses the blood-brain barrier due to its lipophilicity (logP ≈ 1.83), enabling central effects including sedation at low doses, excitation and hallucinations at toxic doses, mediated predominantly through M1 receptor blockade in the cortex and limbic system.

## Clinical Summary

In emergency and anesthesia contexts, atropine's clinical role is codified in ACLS protocols (0.5–1 mg IV for bradycardia) and WHO essential medicines guidelines for organophosphate poisoning (initial 2–4 mg IV, repeated every 5–10 minutes until secretions dry), with evidence derived from large observational cohorts and military/occupational case series rather than prospective RCTs. The most robust modern RCT data concerns pediatric myopia: the LAMP trial demonstrated that 0.05% atropine reduced mean spherical equivalent progression by 0.55 D/year versus 0.81 D/year in the placebo group (p < 0.001) while 0.01% reduced progression by 0.27 D/year, establishing a clear dose-response relationship. In the PEDIG amblyopia RCTs, weekend atropine penalization (2 days/week) achieved outcomes statistically equivalent to full-time patching for moderate amblyopia (20/100 to 20/400), with a clinically meaningful improvement in compliance-dependent outcomes. Overall confidence in atropine's pharmacodynamic effects is extremely high given mechanistic clarity and decades of clinical application, though formal placebo-controlled trials for its life-saving emergency indications are absent by necessity.

## Nutritional Profile

Atropine is a pure pharmacological compound, not a nutritional substance, and possesses no macronutrient, micronutrient, or dietary fiber content relevant to human nutrition. As a tropane alkaloid (molecular formula C17H23NO3, MW 289.37 g/mol), it is present in Solanaceae plant tissues at concentrations that are toxicologically significant but nutritionally irrelevant; its pharmaceutical preparations are administered in microgram-to-milligram doses far below any caloric or micronutrient contribution. The compound is water-soluble at 2200 mg/L at 25°C and exhibits a pKa of approximately 9.9, rendering it predominantly ionized at physiological pH, which influences renal reabsorption and elimination half-life (approximately 2–3 hours). Atropine sulfate monohydrate (MW 694.82 g/mol per mmol) is the predominant pharmaceutical salt form, selected for its superior aqueous stability and sterility compatibility compared to the free base.

## Dosage & Preparation

- **Intravenous Injection (Emergency Bradycardia)**: 0.5–1 mg IV bolus, may repeat every 3–5 minutes to a maximum of 3 mg total; available as 0.1 mg/mL and 0.4 mg/mL solutions for injection.
- **Intravenous/Intramuscular (Organophosphate Poisoning)**: Initial dose 2–4 mg IV (severe poisoning); repeated every 5–10 minutes until pulmonary secretions dry; high-concentration autoinjectors (10 mg/mL) available in Germany, Portugal, and military contexts; titration to effect, not fixed dose ceiling.
- **Ophthalmic Solution 1% (Cycloplegia/Amblyopia)**: 1–2 drops of 1% (10 mg/mL) solution instilled in affected eye(s); cycloplegia persists 6–12 days; amblyopia penalization typically 1 drop in the non-amblyopic eye once daily or on weekends.
- **Ophthalmic Solution Low-Dose (Myopia Control)**: 0.01–0.05 wt% formulated at pH 5.5–6.0 with ≤50 mM sodium phosphate buffer and ≤0.01 wt% EDTA as stabilizer; 1 drop once nightly in both eyes; solutions at these concentrations require careful stabilization to prevent hydrolysis to tropic acid.
- **Atropine Sulfate Oral/Intramuscular (Preoperative)**: 0.4–0.6 mg IM or IV 30–60 minutes before anesthesia induction; pediatric dosing 0.01–0.02 mg/kg (minimum 0.1 mg to avoid paradoxical bradycardia).
- **Atropine Sulfate in Antidiarrheal Combinations**: ≥25 µg atropine sulfate per dosage unit combined with diphenoxylate ≤2.5 mg or difenoxin ≤0.5 mg per tablet; sub-therapeutic atropine dose serves as abuse deterrent.
- **Veterinary Formulations**: Initial dose 0.05 mg/lb body weight IV/SC for organophosphate toxicity, followed by 0.15 mg/lb IM as maintenance; reflects higher sensitivity differences versus humans.

## Safety & Drug Interactions

At therapeutic doses, atropine produces predictable anticholinergic adverse effects including dry mouth, urinary retention, constipation, tachycardia, decreased sweating with risk of hyperthermia, blurred vision, and mydriasis; mnemonic 'dry as a bone, blind as a bat, red as a beet, hot as a hare, mad as a hatter' encapsulates the anticholinergic toxidrome seen in overdose, which may progress to delirium, hyperthermia, respiratory depression, and death. Critical drug interactions include additive anticholinergic burden with tricyclic antidepressants (e.g., amitriptyline), first-generation antihistamines (e.g., diphenhydramine), antipsychotics (e.g., clozapine), and other muscarinic antagonists (e.g., ipratropium, oxybutynin), potentially precipitating anticholinergic syndrome; atropine also antagonizes the effects of prokinetic agents (metoclopramide, bethanechol) and miotic ophthalmic drugs (pilocarpine). Absolute contraindications include narrow-angle glaucoma (risk of acute angle-closure crisis from mydriasis-induced anterior chamber shallowing), obstructive uropathy, paralytic ileus, myasthenia gravis (worsens neuromuscular junction dysfunction), and known hypersensitivity; relative contraindications include tachyarrhythmias, hyper[thyroid](/ingredients/condition/hormonal)ism, and prostatic hyperplasia. Atropine crosses the placenta and enters breast milk; it is classified FDA Pregnancy Category C, indicating risk cannot be ruled out, and its use in pregnancy and lactation requires careful benefit-risk assessment; the minimum lethal dose in adults is estimated at 10 mg, while children are significantly more sensitive.

## Scientific Research

Atropine carries one of the strongest evidence profiles of any pharmaceutical compound given its century-long clinical use, with its efficacy in bradycardia, organophosphate poisoning, and cycloplegia supported by extensive observational data, case series, and inclusion in international treatment guidelines rather than modern placebo-controlled RCTs (conducting such trials in emergencies is ethically constrained). The myopia control indication is supported by the highest-quality modern RCT evidence: the ATOM1, ATOM2, and LAMP (Low-concentration Atropine for Myopia Progression) trials are randomized, placebo-controlled studies conducted in Southeast Asian pediatric populations (n = 400–438 per study), demonstrating dose-dependent reduction in myopia progression of 50–77% at 0.01–0.05% concentrations over 1–2 years with acceptable side-effect profiles. For amblyopia treatment, the PEDIG (Pediatric Eye Disease Investigator Group) multi-site RCTs (n > 400) established non-inferiority of atropine penalization versus patching for moderate amblyopia in children, with visual acuity improvements of approximately 3.16 lines in the atropine group versus 3.53 lines in the patching group (no statistically significant difference). Analytical detection studies confirm reliable quantification of atropine at 0.1–0.9 mg/L in biological matrices using reversed-phase HPLC at 215–220 nm or GC-MS, supporting toxicological monitoring in poisoning cases.

## Historical & Cultural Context

The Solanaceae plants yielding atropine—particularly Atropa belladonna and Mandragora officinarum—have one of the most documented histories in pharmacology and folklore, with use traceable to ancient Egypt, Greece, and Rome for anesthesia, analgesia, and ritual purposes; the genus name Atropa references Atropos, the Greek Fate who cuts the thread of life, underscoring the plant's lethal potential. During the Renaissance, Italian noblewomen applied belladonna extracts as eye drops to dilate pupils for cosmetic effect, giving rise to the name belladonna ('beautiful woman'), with the active principle being the atropine-class alkaloids causing the observed mydriasis. The pure alkaloid l-hyoscyamine was first isolated from Hyoscyamus niger in 1833 by Geiger and Hesse, and the racemic atropine form was characterized by Mein in 1831; Scottish physician Douglas Argyll Robertson's clinical descriptions of its ophthalmic effects in the 1860s formalized its medical use in ophthalmology. Its role in anesthesia premedication, established in the early 20th century to prevent dangerous vagal reflexes and 'ether death,' remained standard practice for decades and cemented atropine as one of the foundational compounds of modern clinical pharmacology.

## Synergistic Combinations

In organophosphate poisoning management, atropine is synergistic with pralidoxime (2-PAM), an oxime reactivator of [acetylcholine](/ingredients/condition/cognitive)sterase: atropine addresses muscarinic receptor overstimulation while pralidoxime regenerates the inhibited enzyme before 'aging' (irreversible phosphorylation) occurs, with combined therapy demonstrably superior to either agent alone in animal models and standard-of-care protocols. In the treatment of nerve agent or pesticide poisoning with pronounced CNS involvement, benzodiazepines (e.g., diazepam, midazolam) are added as a third synergistic agent to suppress atropine-resistant seizure activity mediated by glutamatergic mechanisms, forming the classic three-drug antidote protocol. The combination of atropine with diphenoxylate or difenoxin in antidiarrheal preparations exploits a pharmacodynamic pairing where atropine's antisecretory and antispasmodic properties complement the opioid-receptor-mediated reduction in intestinal motility, while simultaneously serving as an abuse-deterrent due to dysphoric anticholinergic effects at supratherapeutic opioid doses.

## Frequently Asked Questions

### What is atropine used for clinically?

Atropine is used in emergency medicine for symptomatic bradycardia (0.5–1 mg IV per ACLS protocol) and as the primary antidote for organophosphate and nerve agent poisoning (2–4 mg IV, repeated until secretions dry). In ophthalmology, it serves as a cycloplegic agent for refraction, as amblyopia penalization therapy at 1% concentration, and increasingly as low-dose (0.01–0.05%) eye drops to slow myopia progression in children.

### Does low-dose atropine work for myopia in children?

Yes—multiple randomized controlled trials including the ATOM1, ATOM2, and LAMP studies conducted in Southeast Asian pediatric populations (n = 400–438) demonstrated that 0.01–0.05% atropine eye drops reduce myopia progression by 50–77% over two years compared to placebo, with axial elongation also significantly slowed. The 0.05% concentration showed the greatest effect but with more rebound on discontinuation, while 0.01% offered the best balance of efficacy and minimal side effects such as glare and near blur.

### What are the main side effects of atropine?

Atropine's anticholinergic side effects are dose-dependent and include dry mouth, urinary retention, constipation, blurred near vision, mydriasis (pupil dilation), tachycardia, flushing, and decreased sweating with consequent risk of hyperthermia. At toxic doses, these progress to delirium, hyperthermia, and respiratory depression; the lethal dose in adults is estimated at approximately 10 mg, and children are considerably more sensitive, making accidental ingestion of belladonna-containing plants a medical emergency.

### How does atropine work as an antidote for organophosphate poisoning?

Organophosphates irreversibly inhibit acetylcholinesterase, causing accumulation of acetylcholine at muscarinic and nicotinic synapses; atropine competitively blocks all five muscarinic receptor subtypes (M1–M5), directly antagonizing the resulting bronchospasm, excessive secretions (the most life-threatening manifestation), bradycardia, and miosis. Atropine is combined with pralidoxime (an oxime reactivator that regenerates the enzyme) and benzodiazepines (for seizure control) as the standard three-drug antidote protocol, with atropine titrated to drying of pulmonary secretions rather than a fixed dose ceiling.

### Is atropine safe during pregnancy and breastfeeding?

Atropine is classified FDA Pregnancy Category C, meaning animal studies have shown adverse fetal effects but adequate human data are lacking; it crosses the placenta and can cause fetal tachycardia, and its use in pregnancy is therefore reserved for situations where benefits clearly outweigh risks, such as acute hemodynamic compromise. Atropine is excreted in breast milk, potentially suppressing lactation and causing anticholinergic effects in nursing infants, so breastfeeding is generally advised to be withheld for several hours after maternal dosing when clinically feasible.

### What is the difference between atropine and dl-hyoscyamine, and are they the same thing?

Atropine is the racemic mixture (equal parts of d- and l-isomers) of hyoscyamine, while dl-hyoscyamine refers to this same racemic form; l-hyoscyamine is the naturally occurring, more pharmacologically active isomer found in plants like belladonna. In clinical practice, atropine (dl-hyoscyamine) is used because it is more stable than the pure l-form, though l-hyoscyamine is approximately twice as potent on a milligram-per-milligram basis. Both are antimuscarinic agents with identical mechanisms of action, but dosing differs due to their potency difference.

### What drug interactions should I be aware of when taking atropine?

Atropine should not be combined with other anticholinergic medications (antihistamines, tricyclic antidepressants, certain antipsychotics, muscle relaxants) as this increases the risk of severe anticholinergic toxicity including urinary retention, confusion, and cardiac arrhythmias. Medications that inhibit acetylcholinesterase, such as cholinesterase inhibitors used in Alzheimer's disease treatment, directly antagonize atropine's effects. Additionally, atropine may reduce gastrointestinal motility and delay absorption of other oral medications, particularly those requiring stomach acid for dissolution.

### Who should avoid atropine and what medical conditions contraindicate its use?

Atropine should be avoided in patients with glaucoma (especially narrow-angle glaucoma), severe heart disease, tachycardia, hyperthyroidism, and severe liver or kidney impairment. Patients with gastrointestinal obstruction, urinary retention, myasthenia gravis, or hypersensitivity to belladonna alkaloids should not use atropine. Elderly patients are at higher risk for adverse effects due to increased sensitivity to anticholinergic effects and potential cognitive impairment, requiring dose adjustment or avoidance in vulnerable populations.

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