atropine
Brand: Atropen
Beers Criteria Prototype Drug
Drug Class: anticholinergic / antimuscarinic
Drug Family: GU agent
Subclass: competitive muscarinic receptor antagonist
Organ Systems: cardiovascularcnspns-autonomic
Mechanism of Action
Competitive antagonist at muscarinic ACh receptors; blocks parasympathetic (vagal) effects on heart increasing HR; blocks glandular secretions and smooth muscle; CNS stimulation at high doses.
muscarinic acetylcholine receptors (M1-M5)
Indications
- symptomatic bradycardia (ACLS)
- organophosphate/nerve agent poisoning (large doses)
- pre-anesthetic (antisialagogue)
- CPR (no longer recommended for asystole per 2010 ACLS)
- ophthalmic mydriasis
Contraindications
- acute angle-closure glaucoma
- GI/GU obstruction
- myasthenia gravis
- tachyarrhythmias
Adverse Effects
Common
- dry mouth
- urinary retention
- constipation
- blurred vision
- tachycardia
Serious
- paradoxical bradycardia at low doses (0.4 mg — pre-junctional stimulation)
- anticholinergic delirium (especially elderly)
- severe tachycardia
Pharmacokinetics (ADME)
| Absorption | well absorbed oral, IM, IV |
| Distribution | crosses BBB readily |
| Metabolism | hepatic |
| Excretion | renal |
| Half-life | 2-3 hours |
| Onset | variable |
| Peak | 15-30 min |
| Duration | 4-6 hours |
| Protein Binding | 14-22% |
| Vd | 2-3 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| other anticholinergics | additive anticholinergic toxicity | major |
| physostigmine | antidote for atropine toxicity | beneficial |
Nursing Considerations
- For bradycardia: 0.5 mg IV; may repeat to max 3 mg total
- Paradoxical bradycardia: doses <0.5 mg can actually SLOW HR (vagal stimulation via CNS) — always use ≥0.5 mg
- Organophosphate poisoning: massive doses may be needed (20+ mg); titrate to drying of secretions not HR
- Anticholinergic toxidrome mnemonic: dry as a bone, red as a beet, blind as a bat, hot as a hare, mad as a hatter
Clinical Pearls
- Paradoxical bradycardia: doses <0.5 mg stimulate vagal center in brain before peripheral blockade
- Organophosphate antidote: use until secretions dry up — not based on heart rate
- Physostigmine reverses central anticholinergic effects (crosses BBB)
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.