Atropine

Atropine

Clinical data
Drug class	Anticholinergic
Uses	Treatment of bradycardia, Antidote for acetylcholinesterase inhibitor toxicity
Contraindications	Known hypersensitivity
Routes of administration	IV, IM, PO, oral or endotracheal inhalation, ophthalmic solution
Dosage	Treatment of bradycardia: 1 mg every 3 to 5 minutes (3mg max), repeat until obtaining desired heart rate Treatment of acetylcholinesterase inhibitor toxicity: 2 to 3 mg every 20 to 30 min Antisialagogue/anti-vagal: 0.5 to 1mg every 1 to 2 hours Pediatric: 0.01 mg/kg to 0.03 mg/kg every 3 to 5 minutes. Minimum dose is 0.1 mg. Maximum dose is 0.5mg (child) or 1 mg (adolescent).
Dosage
Pharmacodynamics
Mechanism of action	Muscarinic acetylcholine antagonism
Pharmacokinetics
Metabolism	Enzymatic hydrolysis in the liver
Protein binding	14-22%
Physical and chemical data
Formula	C17H23NO3
Molar mass	289.369 g/mol
Article quality
Editor rating	Comprehensive
User likes	0

Atropine is a tertiary amine extracted from belladonna alkaloid as a racemic mixture of d and l-hyoscyamine, which vary in their potency as anticholinergic agents. It reversibly binds to peripheral muscarinic acetylcholine receptors where it acts a competitive inhibitor. Its primary uses include treatment of bradycardia or bradycardia-induced cardiac arrest, treatment of cholinergic effects of organophosphate, nerve agent, or insecticide toxicity, or in ophthalmic surgery to produce mydriasis and cycloplegia. It can also be utilized in conjunction with cholinesterase inhibitors for reversal of neuromuscular blockade in order to reduce their muscarinic effects.

Uses

- Treatment of bradycardia (vasovagal response, AV block, bradyarrhythmias)

- Treatment of acetylcholinesterase inhibitor toxicity (chemical nerve agents, carbamate, organophosphates)

- Perioperatively for reduction of secretions and vagal responses

- Perioperatively for prophylaxis against muscarinic effects when anticholinesterase agents (neostigmine, physostigmine, pyridostigmine) are used to reverse neuromuscular blockade

- For ophthalmic surgery, to induce mydriasis or cycloplegia

- Treatment of amblyopia

Contraindications

Absolute contraindications

- Atropine or belladonna alkaloids hypersensitivity. Note: IM/IV administration of atropine can cause flushing of face and trunk, which is not associated with a hypersensitivity response.

Precautions

- Coronary artery disease, acute myocardial infarct, congestive heart failure, tachycardia, or hypertension

- Chronic lung disease

- Obstructive gastrointestinal disease, including toxic megacolon, paralytic ileus, pyloric stenosis

- Obstructive urinary disease, including uropathy and prostatic hypertrophy

- Acute-angle glaucoma

- Myasthenia gravis

- Insufficient data regarding atropine use during pregnancy to determine risk of adverse developmental outcomes

Pharmacology

Pharmacodynamics

Mechanism of action

Atropine is a competitive inhibitor at autonomic postganglionic cholinergic receptors. Atropine’s activity is primarily due to the l-hyoscyamine enantiomer.  Atropine binds receptors found in GI and pulmonary smooth muscle, exocrine glands, heart and eye; it does not block acetylcholine’s action at the NMJ. It does not inhibit nicotonic cholingeric receptors at typical doses. Atropine’s primary clinical effects include changes in heart rate, reduction in salivary, bronchial, and sweat gland secretions, bronchodilation, mydriasis and cycloplegia, decreased GI motility and gastric secretions, and contraction of the bladder detrusor muscle.

Adverse effects

- Dry mouth (xerostomia)

- Blurred vision, including photophobia and loss of visual acuity

- GI symptoms: dysphagia, constipation, nausea, vomiting

- Bradycardia (at doses of 0.4-0.6mg)

- Tachycardia (at doses of 1-2mg)

- Palpitations, arrhythmias, aystole

- Flushing

- Urinary retention

- Delirium and coma at high doses

Pharmacokinetics

- IV administration has a distribution half life of about 1 minute, with rapid decline in concentration within the first 8-10 minutes.

- Crosses the blood-brain barrier and the placenta

- Undergoes enzymatic hydrolysis in the liver into active metabolites

- Atropine and its metabolites are primarily exreted renally, with small contributions from pulmonary and fecal routes of excretion. 13-57% of atropine is excreted unchanged in the urine.