Atropine

ATROPEN

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Pronunciation: A-troe-peen (at-ROE-pen)

Atropine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Atropine ballicule

What it isAntimuscarinic; symptomatic bradycardia, organophosphate poisoning and secretion control.

Why this oneIt reverses vagally mediated bradycardia within a minute, and in organophosphate poisoning it is titrated to drying of secretions with no ceiling dose.

What limits itIt crosses into the CNS, causing delirium in the elderly. Ineffective in infranodal block and in transplanted hearts.

Atropine molecular structure (skeletal formula) — Molecular structure: Atropine

FDA-approved for

bradycardia/organophosphate poisoning (~1960)

Off-label

clozapine-induced sialorrhea (sublingual drops)

FDA label

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FDA dosing	Population	Start	Target	Max
Antisialagogue / other antivagal use	Adults	0.5-1 mg IV	Repeat q1-2h PRN	Titrate to HR, PR interval, BP, symptoms
Organophosphorus or muscarinic mushroom poisoning	Adults	2-3 mg IV	Repeat q20-30min PRN	Titrate to effect
Bradyasystolic cardiac arrest	Adults	1 mg IV	Repeat q3-5min	3 mg total
All uses (not well studied)	Pediatric	0.01-0.03 mg/kg IV initial	Titrate to effect	Undefined

Renal Undefined

Hepatic Undefined

Repeat-dose spacing is per indication (q1-2h antivagal; q20-30min poisoning; q3-5min arrest, 3 mg cap)

Instructions

IV administration; titrate based on heart rate, PR interval, blood pressure, and symptoms
Single-dose syringe — discard unused portion; do not administer unless solution clear and seal intact
Coronary artery disease: limit total dose to 0.03-0.04 mg/kg (2-3 mg) to avoid tachycardia-driven myocardial oxygen demand

Available strengths

inj 0.25, 0.5, 1 mg
drops 1 %
sol 8 mg/20 mL
ointment 10 mg/g

Cautions

Tachycardia: in CAD, restrict total dose to 2-3 mg (max 0.03-0.04 mg/kg)
May precipitate acute glaucoma
May convert partial organic pyloric stenosis into complete obstruction
May cause complete urinary retention in prostatic hypertrophy
May inspissate bronchial secretions and form viscid plugs in chronic lung disease

Adverse reactions

Common (antimuscarinic): dry mouth, blurred vision, photophobia, tachycardia
Anhidrosis with heat intolerance
Elderly: constipation, difficulty in micturition
Occasional hypersensitivity — skin rashes, sometimes progressing to exfoliation

Pregnancy Animal reproduction studies not conducted; unknown whether atropine causes fetal harm — Undefined risk

Lactation Trace amounts found in breast milk; clinical impact unknown

Cost

Atropine (ATROPEN)

Strength		#/mo	CostPlus
0.25 mg	inj	per unit	not offered
0.5 mg	inj	per unit	not offered
1 mg	inj	per unit	not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Atropine is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Other forms: Atropine eyedrops (ISOPTO ATROPINE)

Available combined with: Difenoxin (in MOTOFEN) · Diphenoxylate (in LOMOTIL) · diphenoxylate / atropine

Generic entry2020

NO BOXED WARNINGS

Principal riskDelirium in the elderly from CNS penetration

Classes and tags

Clinical profile

Therapeutic safety burden2 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism4 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryC

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.

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