Muscarinic receptor antagonist (vagolytic)REQUIRES MONITORING

Atropine

Atropin Viatris · Atropin Abboxia · Atropine Accord

First-line treatment for symptomatic bradycardia, but only when the bradycardia is vagally mediated or located in the sinus node or AV node. Atropine blocks muscarinic receptors and thereby removes parasympathetic braking — if there is no such brake to remove, nothing happens, which is the entire explanation for why the drug is ineffective in infranodal block. The effect comes within one minute and fades over an hour or so, making it a bridge to pacing rather than a treatment.

BOXED WARNING

In AV block type II Mobitz 2 and complete heart block with wide QRS complexes, the block is below the AV node and atropine has no effect — do not waste time but proceed immediately to external pacing or isoprenaline. Doses below 0,5 mg may cause paradoxical bradycardia through central vagal stimulation.

Dosing in adults

By indicationuppdaterad 2026-08-22

Indication	Regimen	Comment
Symptomatic bradycardia	0,5 mg iv, repeat every 3–5 min to a total maximum of 3 mg	never give less than 0,5 mg per dose
Vagal reflex bradycardia during anaesthesia or intubation	0,5–1 mg iv	may be given prophylactically during repeated laryngoscopy in children
Organophosphate or nerve agent poisoning	2 mg iv, double the dose every 5 min until secretions dry	no upper maximum dose; titrate to secretions, not to heart rate
Reversal of neuromuscular blockade	0,5–1 mg iv per 2,5 mg neostigmine	given simultaneously to counteract bradycardia
Children with bradycardia	0,02 mg/kg iv, minimum dose 0,1 mg, maximum dose 0,5 mg	hypoxia must be excluded and corrected first

Renal impairment

No established dose adjustment for single doses. Approximately half is excreted unchanged renally, so repeated dosing in severe renal impairment may prolong anticholinergic effects.

Hepatic impairment

No established dose adjustment.

Children

0,02 mg/kg iv (minimum 0,1 mg, maximum 0,5 mg per dose); may be repeated once.

Pitfall

Do not continue giving atropine in AV block type II Mobitz 2 or complete heart block with wide QRS complexes, and in heart transplant recipients whose heart is denervated — in both cases there is no vagal tone to block, and atropine may even worsen the situation by increasing the sinus rate without improving conduction. Proceed to pacing.

Pharmacokinetics

ONSET: under 1 minute iv, maximal effect 2–4 min
EFFECT DURATION: 1–2 hours on heart rate
t½: 2–4 hours (longer in children and the elderly)
Vd: 2 l/kg
PROTEIN BINDING: approximately 20 %
METABOLISM: Hepatic hydrolysis and conjugation
EXCRETION: Renal, approximately 50 % unchanged
CROSSES: Blood–brain barrier and placenta

Adverse effects by frequency

≥ 10 %

Dry mouth, accommodation disturbance and blurred vision, tachycardia, skin flushing

1–10 %

Urinary retention, constipation, anhidrosis with hyperthermia, confusion in the elderly

< 1 %

Anticholinergic delirium, acute angle-closure glaucoma, tachyarrhythmia with myocardial ischaemia

Monitoring schedule

ECG and heart rate: continuously during treatment
Blood pressure and perfusion: every 5 min until stable
Mental status (anticholinergic syndrome): after repeated doses
Bladder filling and urine output: with repeated dosing and in elderly men

Interaction burden

18clinically significant

1 contraindicated · 5 major · 12 moderate. Additive anticholinergic burden with tricyclic antidepressants, antihistamines, antipsychotics, antiparkinson drugs, and urological antimuscarinics — in the elderly it is the sum of these that precipitates delirium. Counteracts the effect of cholinesterase inhibitors.

Formulation & cost

Injection solution 0,5 mg/ml, 1 ml ampoule: 0,5 mg per ampoule
Pre-filled syringe 0,1 mg/ml, 5 ml: 0,5 mg, ready-to-use emergency syringe
Restriction: in organophosphate poisoning, large quantities are often required from emergency stockpiles