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# Atropine
## Overview
Atropine is a naturally occurring belladonna alkaloid that acts as a competitive antagonist at muscarinic acetylcholine receptors. It is a potent anticholinergic agent used to reverse vagally mediated bradycardia and counteract the effects of organophosphate poisoning or nerve agent exposure.
## Primary Indications
* Symptomatic bradycardia
* Organophosphate or carbamate poisoning (adjunct for muscarinic symptoms)
* Pre-anesthetic medication (to decrease secretions and prevent reflex bradycardia)
* Symptomatic second-degree (Mobitz I) or third-degree AV block
## Adult Dosing
* **Symptomatic Bradycardia:** 1 mg IV/IO every 3–5 minutes as needed; maximum total dose of 3 mg (as per ACLS guidelines).
* **Organophosphate/Nerve Agent Poisoning:** 2–6 mg IV/IM, doubling the dose every 5–10 minutes until bronchorrhea and bronchospasm resolve ("atropinization"). Severe cases may require significantly higher titration.
## Pediatric Dosing
* **Symptomatic Bradycardia:** 0.02 mg/kg IV/IO (minimum single dose 0.1 mg; maximum single dose 0.5 mg in children, 1 mg in adolescents). May repeat once after 3–5 minutes.
* **Organophosphate/Nerve Agent Poisoning:** 0.05–0.1 mg/kg IV/IM every 10–20 minutes until airway secretions are controlled.
## Dose Adjustments
* **Renal/Hepatic:** No formal guidelines exist for dose adjustment, but use with caution in patients with significant hepatic or renal impairment due to reduced metabolic clearance.
* **Geriatrics:** Dose with caution (Beers Criteria) due to high risk of confusion, urinary retention, and constipation.
## Contraindications
* Known hypersensitivity to atropine or belladonna alkaloids.
* Angle-closure glaucoma (may increase intraocular pressure).
* Obstructive uropathy (e.g., bladder neck obstruction).
* Myasthenia gravis (relative).
* Tachycardia or significant coronary ischemia (relative, as tachycardia increases myocardial oxygen demand).
## Adverse Effects
* **Common:** Tachycardia, palpitations, dry mouth (xerostomia), blurred vision (mydriasis/cycloplegia), urinary retention, and constipation.
* **Serious:** Delirium, hallucinations, hyperthermia, and paradoxical initial bradycardia (rare, associated with low doses or rapid administration).
## Key Drug Interactions
* **Anticholinergics:** Enhanced effect with antihistamines, tricyclic antidepressants, and antipsychotics; increases risk of anticholinergic toxicity.
* **Pilocarpine:** Antagonistic effect; avoid concurrent use.
* **Potassium Chloride:** Increased risk of gastrointestinal ulceration with oral formulations.
## Monitoring
* Heart rate and rhythm (ECG).
* Blood pressure.
* Neurological status (mental status change).
* Oxygen saturation and airway/secretions (in toxicity).
* Urinary output (monitors for retention).
## Clinical Pearls
* **"Atropine Flush":** High doses may cause cutaneous flushing, common in pediatric patients.
* **Bradycardia Context:** Atropine is ineffective for symptomatic bradycardia caused by high-degree heart block (infranodal) or post-transplant patients (denervated heart); transcutaneous pacing is preferred.
* **Toxicity Treatment:** Physostigmine may be considered as an antidote for severe systemic anticholinergic delirium, but use only by experienced providers as it carries its own risks (seizures, cardiac arrest).
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**Disclaimer:** This information is for educational purposes only. Always verify standard dosing protocols via local institutional policies, current FDA-labeled prescribing information, and resources such as Lexicomp or Micromedex before administration.
