Atropine

Emergency & Prehospital

• Symptomatic bradycardia: sinus bradycardia or AV block at the AV node level, causing hypotension, altered mental status, ischemic chest pain, acute heart failure or shock. It is the first drug in the AHA 2025 adult bradycardia algorithm. Treat the reversible causes at the same time.
• Organophosphate or carbamate insecticide poisoning: give it right away for bronchorrhea, bronchospasm, seizures or significant bradycardia (AHA 2025 Part 10, rec 1, COR 1, LOE A). Pralidoxime joins it for organophosphate poisoning. A benzodiazepine handles seizures or agitation.
• Nerve agent exposure (sarin, soman, tabun, VX): autoinjectors treat the muscarinic symptoms (AtroPen, DuoDote, ATNAA). Mass-casualty stock sits forward in CHEMPACK containers.
• Pediatric bradycardia from increased vagal tone or primary AV block: oxygenate and ventilate first. Then give it alongside the epinephrine and CPR priorities in the PALS 2025 algorithm.

ED / ICU / Transport

• Toxic bradycardia (β-blocker, calcium channel blocker, digoxin or other cardiac glycoside, local anesthetic): give it as part of standard ACLS/PALS bradycardia care. Expect a variable response, and often a poor one. AHA 2025 dropped the toxin-specific atropine recommendations from the 2023 toxicology update. For glycosides, atropine and pacing are standard ALS measures. Start toxin-specific therapy early.
• Muscarinic mushroom poisoning: labeled indication. Titrate to drying of secretions
• Muscarinic effects of cholinesterase inhibitors: paired with neostigmine (atropine or glycopyrrolate) to block bradycardia and secretions during neuromuscular-blockade reversal
• Antisialagogue and vagal blockade: drying secretions and preventing reflex vagal bradycardia during procedures (labeled)
• Pediatric emergency intubation: premedication to prevent bradycardia may be reasonable in infants and children (PALS 2025, COR 2b, LOE C-LD; weak evidence). In practice you see it when bradycardia risk is high: young infants, succinylcholine, repeat laryngoscopy. It is off-label.

Other Uses

• Bradyasystolic cardiac arrest: still on the FDA label. The AHA arrest algorithm dropped routine atropine for asystole or PEA in 2010, and the 2025 algorithm does not include it.
• Amniotic fluid embolism: AHA 2025 recommends against atropine without bradycardia in peripartum patients with life-threatening suspected amniotic fluid embolism (COR 3: No Benefit, LOE C-EO). That covers the case-report atropine-ondansetron-ketorolac ("A-OK") regimen. Atropine may worsen V/Q mismatch. A faster rate also shortens diastolic filling, which matters with RV pressure overload. Treat true bradycardia as usual.

Doses vary by protocol; follow local protocols and medical direction. Adult doses start with the 2025 AHA Guidelines for CPR and ECC (algorithms and Part 10), wherever those state a dose. Where they don't, the US label takes over. Pediatric numbers live in the table below. A row marked "Differs from FDA label" is where the label says something different.

Available Forms

• Prefilled syringe, adult strength: 0.1 mg/mL in 5 mL (0.5 mg) and 10 mL (1 mg) single-dose syringes for IV use; the 1 mg/10 mL syringe is the form EMS and crash carts usually carry
• Prefilled syringe, pediatric strength: 0.05 mg/mL in 5 mL (0.25 mg)
• Vials: 0.4 mg/mL and 1 mg/mL in 1 mL single-dose vials; 0.4 mg/mL in 20 mL (8 mg) multiple-dose vials (CHEMPACK), labeled for IV, IM, subcut, IO and endotracheal use. After first use, discard within 24 hr. The 20 mL multiple-dose vial holds benzyl alcohol 9 mg/mL (about 22.5 mg per mg of atropine). Gasping syndrome in neonates has been linked to more than 99 mg/kg/day. In neonates and small infants, use preservative-free syringes or single-dose vials where you can. Over a long, high-dose course, keep a running tally of the benzyl alcohol (label W&P 5.7)
• Atropine autoinjectors (IM): AtroPen 0.25 mg (yellow), 0.5 mg (blue), 1 mg (red) and 2 mg (green); Rafa atropine 2 mg (FDA-approved in 2018 for adults and children over 41 kg, now listed as discontinued in Drugs@FDA but still stocked in CHEMPACK; Rafa 0.5 mg and 1 mg pediatric strengths are authorized for emergency use only, e.g. in CHEMPACK). AtroPen strengths are stated as atropine sulfate (the 2 mg device delivers 1.67 mg atropine base)
• Combination autoinjectors (IM): DuoDote (civilian) and ATNAA (military) deliver atropine 2.1 mg (stated as atropine base) and pralidoxime chloride 600 mg through one needle

Adult Dosing

Pediatric Dosing

Start with AHA/AAP 2025 for any dose it gives. Then check the NASEMSO National Model EMS Clinical Guidelines v3.0 (2022), then the US label. No source gives a dose? Then the table shows none. No pediatric maximum goes above the adult one (NASEMSO Universal Care Guideline, p. 13). Unless marked labeled, the doses are off-label.

Weight-based dose checks: pediatric weight-based dosing and Broselow tape.

Continuous Infusion

Preparation & Administration

• Push: give undiluted as an IV/IO bolus from the prefilled syringe, then flush with saline.
• Full doses: Small doses can slow the heart briefly before the rate climbs (FDA label). Don't shave the adult dose. Give the full 1 mg. For pediatric bradycardia, give at least 0.1 mg per the PALS 2025 algorithm. Intubation premedication has no minimum dose.
• Concentration for organophosphate escalation: At 0.1 mg/mL, 32 mg comes to 320 mL. As doses climb, move to 0.4 mg/mL or 1 mg/mL vials. In neonates and small infants, reach for preservative-free single-dose vials, not the benzyl alcohol-containing 20 mL vial (see Available Forms).
• Autoinjector technique: mid-lateral thigh, through clothing with pockets emptied, at 90 degrees; hold about 10 seconds; bend the needle back on a hard surface and leave or pin used devices on the patient so the next provider can count them.
• Route: The AHA 2025 bradycardia algorithms give atropine IV or IO. Get vascular access instead of relying on the endotracheal route. Without IV/IO access in cholinergic poisoning, give IM atropine: an autoinjector, or the 0.4 mg/mL 20 mL multiple-dose vial. That vial's labels list IV, IM, subcut, IO and endotracheal use, so IM from it is on-label. Prefilled syringes are labeled IV only. Then switch to IV titration as soon as possible.

Contraindications

• None absolute in the FDA labels. Once organophosphate or nerve agent poisoning is life-threatening, no condition stands in the way of atropine.
• Heart transplant without autonomic reinnervation: do not use it for sinus bradycardia (ACC/AHA/HRS Class 3: Harm). Denervated hearts have responded to atropine with paradoxical high-grade AV block and sinus arrest. Reach for pacing or an adrenergic agonist. Aminophylline or theophylline is reasonable (ACC/AHA/HRS Class 2a).
• Prior anaphylaxis to atropine (relative): if atropine is still essential, give it under medical supervision.

Precautions

• Infranodal AV block (Mobitz II, third-degree with a wide-QRS escape): atropine works at the SA and AV nodes. Here it is unlikely to help. Speeding the atrial rate can worsen the block (e.g. 2:1 to 3:1) and slow the ventricles. The FDA label warns against relying on it. You may try it while the pads go on. Never delay pacing or an adrenergic infusion for it.
• Coronary artery disease or acute MI: faster rates push up myocardial O₂ demand, and that can prolong ischemia.
• Narrow-angle glaucoma: it can set off acute angle closure.
• Bladder outflow obstruction or pyloric stenosis: can cause complete urinary retention or obstruction.
• Paralytic ileus, severe ulcerative colitis or toxic megacolon: slowed gut motility can worsen all three.
• Tachyarrhythmia-prone states (e.g. thyrotoxicosis): vagal blockade adds to the rate.
• Myasthenia gravis: avoid routine use. Still, atropine blocks the muscarinic effects of anticholinesterase therapy, and cholinergic crisis still calls for it.
• Chronic lung disease: thickened secretions and mucus plugs.
• Heat, PPE and small children: blocked sweating causes hyperthermia.

Hold / Reassess If

• Bradycardia not improved after 3 mg total: stop atropine; pace or start epinephrine or dopamine
• New tachyarrhythmia, ischemic chest pain or ST change
• Organophosphate infusion with a clear chest but delirium, hyperthermia, absent bowel sounds or urinary retention: pause and reduce the rate

Common

• Dry mouth, thirst
• Blurred vision, photophobia, mydriasis
• Tachycardia, palpitations
• Flushing and decreased sweating (heat intolerance)
• Urinary hesitancy, constipation, especially in older adults
• Headache, dizziness, confusion; CNS effects appear earlier and at lower doses in children

These come from post-approval reports in the labels. Frequencies are not established.

Serious / Life-Threatening

Overdose & Toxicity Management

• Signs: antimuscarinic toxidrome: tachycardia, hot dry skin, flushing, dilated poorly reactive pupils, fever, urinary retention, absent bowel sounds, delirium. Severe cases progress to coma, respiratory depression and circulatory collapse. In children, 10 mg or less may be fatal (FDA label).
• Immediate management: start with airway, oxygen and ventilation. Keep a continuous ECG and cool actively. Place a bladder catheter and give IV fluids to maintain urine output. Use a benzodiazepine for agitation or seizures. Avoid large sedative doses, because late central depression can follow.
• Antidote: physostigmine reverses severe antimuscarinic delirium. Adult: 0.04 mg/kg (2 mg) slow IV, no faster than 1 mg/min, then 1–4 mg every 20 min if needed. Child: 0.02 mg/kg, no faster than 0.5 mg/min, repeated every 5–10 min to a total of 2 mg. Monitor the ECG the whole time. It is contraindicated with suxamethonium. Only a toxicologist directs it. Never use it in organophosphate, carbamate or nerve agent poisoning. The US label covers an unapproved product used in shortage (Anticholium).
• Extracorporeal removal: dialysis does not remove atropine.

Clinically Significant Interactions

IV Compatibility

• Give undiluted by IV/IO push through a flushed line.
• Do not mix with other drugs in the same syringe unless compatibility is confirmed.
• Organophosphate infusions: use the institution's standard concentration and a dedicated pump channel.
• Verify with an institutional compatibility resource.

• Pediatrics: Dose by weight, with a 0.1 mg minimum and a 0.5 mg single-dose cap for bradycardia. Over 40 kg or over 14 yr, use the adult dose (1 mg every 3–5 min, max 3 mg). Organophosphate doses double every 5 min. No single dose goes above the adult dose. See the Pediatric Dosing table. Children show CNS effects and atropine fever at lower doses.
• Neonates: Neonatal resuscitation runs on ventilation and epinephrine, not atropine. The half-life more than doubles under 2 yr (about 6.9 hr). Extreme hyperthermia has been reported in a newborn after very small oral doses.
• Pregnancy: It crosses the placenta. Observational cohorts and surveillance studies have not shown a consistent increase in malformations. They cannot exclude risk, though, and no animal reproduction studies exist. Untreated symptomatic bradycardia or organophosphate poisoning can be fatal. Never withhold life-sustaining atropine.
• Lactation: Trace amounts reach breast milk. After an IV dose, the label suggests pumping and discarding milk for 24 hr if the infant's exposure worries you.
• Older Adults: The half-life runs about 10 hr at 65–75 yr, against 3 hr in younger adults. Delirium and urinary retention come more often. Do not withhold it in an emergency. Reassess before repeat dosing.
• Renal Impairment: There is no labeled adjustment. 13–50% is excreted unchanged in urine, so effects may last longer. Keep urine output up during toxicity.
• Hepatic Impairment: It has not been studied. Most of the drug is hydrolyzed in the liver. Titrate to effect.
• Obesity / Dosing Weight: Adult doses are fixed. They are not weight-based. Pediatric doses use actual body weight, within the caps.
• Heart Transplant Recipients: A denervated heart does not respond to vagal blockade. Atropine has caused paradoxical high-grade AV block and sinus arrest. See Contraindications.

• Scope: IV/IO atropine: Paramedic, RN and critical-care transport. Nerve agent autoinjectors: trained EMS providers. AtroPen may also be given by a caregiver or the patient when no trained provider is available. It varies by state and agency protocol.
• Storage & Stability: 20–25°C (68–77°F), excursions 15–30°C (59–86°F). Keep autoinjectors from freezing and protected from light in their pouch or carton. Opened 20 mL multiple-dose vial: discard 24 hr after first use. Discard any discolored solution.
• No IV/IO Access: unstable high-degree AV block: consider immediate transcutaneous pacing while access is obtained (AHA 2025, COR 2b). Cholinergic poisoning: give IM atropine until access is in, then switch to IV titration (see Preparation & Administration).
• Carried Concentration: The 1 mg/10 mL (0.1 mg/mL) syringes treat bradycardia, but they hold too little for poisoning. Know where vials and autoinjectors are stocked before a cholinergic call.
• Mass Casualty and CHEMPACK: CHEMPACK containers sit in hospitals and fire stations, and the Strategic National Stockpile manages them. They hold atropine, DuoDote or ATNAA autoinjectors, 20 mL atropine vials, pralidoxime and benzodiazepines. EMS containers treat up to 454 people. Hospital containers treat up to 1,000. State and local officials open them without a federal request.
• Scene Safety: PPE and decontamination come first. Remove clothing and wash the skin. Unprotected providers have been poisoned by contact with contaminated patients.
• Altitude / Environment: Atropine blocks sweating. Heat, exertion and chemical-protective suits raise the risk of hyperthermia.
• Handoff Essentials: time and total atropine dose (mg) and number and type of autoinjectors (show the used devices), current infusion rate, last chest examination, HR, BP, temperature, pralidoxime and benzodiazepine doses, and the suspected agent.

Mechanism of Action

• It is a competitive, surmountable antagonist at muscarinic acetylcholine receptors. It has little effect at nicotinic receptors.
• SA and AV node: It blocks vagal tone, which gives a faster sinus rate and better AV-nodal conduction. Small doses can slow the rate first. Large doses occasionally cause AV block.
• Glands and smooth muscle: Salivary and bronchial secretions drop and the bronchi dilate. The gut slows. Urinary retention, mydriasis and loss of sweating follow.
• It crosses the blood-brain barrier. High doses cause restlessness, delirium and hallucinations.

Pharmacokinetics

• Half-life: about 3 hr in adults, about 10 hr at 65–75 yr, about 6.9 hr under 2 yr and 2.5 hr in older children. The kinetics are nonlinear after 0.5–4 mg IV. The label says the half-life more than doubles under 2 yr and over 65 (Fresenius label, sections 8 and 12.3).
• Metabolism: enzymatic hydrolysis, mainly in the liver: noratropine, atropine N-oxide, tropine, tropic acid (Fresenius label, section 12.3). Organophosphate pesticides inhibit atropine metabolism.
• Elimination: 13–50% unchanged in urine. Dialysis does not remove it.
• Distribution: wide. It crosses the placenta, and traces reach breast milk.

Generic Name

Atropine sulfate. AtroPen strengths are stated as the sulfate (2 mg = 1.67 mg atropine base); the DuoDote and ATNAA 2.1 mg dose is stated as atropine base

Brand Names

AtroPen (autoinjector); DuoDote and ATNAA (atropine with pralidoxime chloride); also in diphenoxylate-atropine tablets (Lomotil) and ophthalmic solutions

Pharmacologic Class

Muscarinic antagonist (antimuscarinic anticholinergic); belladonna alkaloid

Therapeutic Class

Vagolytic; antidote for organophosphate, carbamate and nerve agent poisoning; antisialagogue

Controlled Substance

Not controlled

ISMP High-Alert

No

Look-Alike / Sound-Alike

None on the ISMP confused drug names list. Concentration mix-ups are the real risk: 0.1 mg/mL syringes, 0.4 and 1 mg/mL vials, and four autoinjector strengths