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Anticholinergic Pregnancy: Should not be used during pregnancy unless clearly necessary. Atropine rapidly crosses the placental barrier; IV administration during pregnancy or at term may cause tachycardia in the fetus and mother.

Atropine

Brand names: Atropine Sulphate

Atropine is an antimuscarinic agent used in emergencies to treat haemodynamically significant bradycardia and as an antidote in cholinergic crisis, including organophosphate poisoning.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 0.5 mg IV (sinus bradycardia), every 2-5 minutes until desired heart rate is achieved
Route: Intravenous injection
Frequency: Repeated every 2-5 minutes (sinus bradycardia) or every 3-5 minutes for AV block, to a maximum of 3 mg
Max: 3 mg (total maximum dose in adults)
Treatment of haemodynamically compromising bradycardia, AV block, cardiopulmonary resuscitation: sinus bradycardia 0.5 mg IV every 2-5 minutes until desired heart rate achieved; AV block 0.5 mg IV every 3-5 minutes (maximum 3 mg). Pre-anaesthetic medication: 0.3-0.6 mg IV immediately before surgery (or IM 30-60 minutes before). In combination with neostigmine to limit its muscarinic effects: 0.6-1.2 mg IV. As an antidote to organophosphates (pesticides, nerve gases), cholinesterase inhibitors and muscarinic mushroom poisoning: 0.5-2 mg IV, can be repeated after 5 minutes and subsequently every 10-15 minutes until signs and symptoms disappear (this dose may be exceeded many times). Atropine should not delay implementation of external pacing for unstable patients, particularly those with high-degree (Mobitz type II second-degree or third-degree) block.

Paediatric dose

Dose: 0.02 mg/kg
Route: Intravenous injection
Frequency: Single dose (bradycardia/AV block/CPR); for organophosphate poisoning may be repeated several times until signs and symptoms disappear
Max: 0.6 mg per dose
Bradycardia, AV block, cardiopulmonary resuscitation: 0.02 mg/kg IV in a single dose (maximum 0.6 mg). Pre-anaesthetic medication: usual dose 0.01-0.02 mg/kg (maximum 0.6 mg per dose). In combination with neostigmine: 0.02 mg/kg IV. Antidote to organophosphates: 0.02 mg/kg IV, possibly repeated several times until signs and symptoms disappear. Not appropriate to deliver a dose of less than 0.5 ml, so not for use in neonates with body weight below 3 kg. Total maximum dose in children usually 0.6 mg.

Dose adjustments

Renal

Caution advised in patients with renal or hepatic impairment (no specific dose adjustment stated).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Bradycardia, AV block, cardiopulmonary resuscitation: 0.02 mg/kg IV in a single dose (maximum 0.6 mg). Pre-anaesthetic medication: usual dose 0.01-0.02 mg/kg (maximum 0.6 mg per dose). In combination with neostigmine: 0.02 mg/kg IV. Antidote to organophosphates: 0.02 mg/kg IV, possibly repeated several times until signs and symptoms disappear. Not appropriate to deliver a dose of less than 0.5 ml, so not for use in neonates with body weight below 3 kg. Total maximum dose in children usually 0.6 mg.

Verify in a children's formulary

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients
  • Closed-angle glaucoma
  • Risk of urinary retention because of prostatic or urethral disease
  • Achalasia of the oesophagus, paralytic ileus, and toxic megacolon
  • (These contraindications are not relevant in life-threatening emergencies such as bradyarrhythmia or poisoning)

Side effects

  • Visual disturbances (mydriasis, inhibition of accommodation, blurred vision, photophobia)
  • Dryness of the mouth (difficulty swallowing/talking, thirst)
  • Tachycardia (with palpitations and arrhythmias; transient exacerbation of bradycardia may precede)
  • Constipation and reflux; reduced bronchial secretion; anhidrosis/dry skin; flushing
  • Excitement, incoordination, mental confusion and/or hallucinations (especially with higher doses); urinary retention

Interactions

  • Other drugs with anticholinergic activity (tricyclic antidepressants, some H1-antihistamines, antiparkinsonian drugs, disopyramide, mequitazine, phenothiazines, neuroleptics, atropinic antispasmodics, clozapine, quinidine) - risk of potentiation of atropinic adverse effects (urinary retention, constipation, dry mouth)

Clinical monograph

How it works

It competitively antagonises acetylcholine at muscarinic receptors, blocking vagal tone at the sinoatrial and atrioventricular nodes to increase heart rate and reducing secretions in cholinergic excess.

Prescribing in practice

  • Avoid using very small intravenous increments for bradycardia because subtherapeutic dosing can paradoxically worsen bradycardia through a central vagotonic effect.
  • It is generally ineffective and may be inappropriate in Mobitz type II and complete heart block, where transcutaneous pacing or chronotropic infusions are preferred.
  • Antimuscarinic effects such as urinary retention, dry mouth, blurred vision and confusion are common, with particular caution in the elderly and in acute angle-closure glaucoma.

Monitoring

Use continuous ECG and blood pressure monitoring and observe the heart-rate response and for antimuscarinic adverse effects after dosing.

Counselling the patient

  • In organophosphate poisoning much larger cumulative doses titrated to secretions may be needed.
  • Anticipate dry mouth, blurred vision and urinary retention.
  • Have pacing available if bradycardia is unresponsive.

Evidence & guidelines

Atropine is the recommended first-line drug for symptomatic bradycardia in Resuscitation Council UK bradycardia algorithms.

Reference: NICE; UK ALS Guidelines 2021; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

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Atropine is a core drug in the following exam-focused workups on our sister siteReviseMRCEM.

MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.