Antimuscarinic (Anticholinergic) Agent 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 Sulfate

Brand names: Minims Atropine (eye drops), atropine injection — generic

Atropine sulfate is an antimuscarinic agent used in cardiology to treat symptomatic bradycardia and as an antidote in organophosphate or anticholinesterase 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

Patient weight (kg)

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 blocks muscarinic acetylcholine receptors, opposing vagal tone at the sinoatrial and atrioventricular nodes to increase heart rate and conduction.

Prescribing in practice

Avoid very low intravenous bolus doses for bradycardia because they can produce a paradoxical slowing of the heart rate.
It may be ineffective in infranodal (Mobitz II or complete) heart block, where pacing should be arranged rather than relying on atropine.
Antimuscarinic effects include urinary retention, dry mouth, blurred vision and confusion, so use caution in the elderly, in glaucoma and in prostatic enlargement.

Monitoring

Monitor heart rate, rhythm and blood pressure continuously during and after intravenous administration.

Counselling the patient

Expect a dry mouth, blurred vision and a faster heartbeat after a dose.
Report difficulty passing urine or marked confusion.
In the emergency setting, the team will watch your heart rhythm closely.

Evidence & guidelines

Atropine is the first-line drug for symptomatic bradycardia in resuscitation and peri-arrest guidance, and a recognised antidote in cholinergic poisoning.

Reference: UK Resuscitation Council Advanced Life Support Guidelines (2021); TOXBASE/National Poisons Information Service (organophosphate poisoning); RCOphth ophthalmic formulary; 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).

Curated clinical cross-links plus same-class fallbacks.

Pathways

Same specialty