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ALIMENTARY TRACT AND METABOLISM › DRUGS FOR FUNCTIONAL GASTROINTESTINAL DISORDERS › BELLADONNA AND DERIVATIVES, PLAIN › Belladonna alkaloids, tertiary amines
atropine
A03BA01
Forms & Strengths
- Injection: 0.1 mg/mL, 0.4 mg/mL, 0.5 mg/mL, 1 mg/mL
- Ophthalmic Solution: 1%
- Ophthalmic Ointment: 1%
Adult Dosing
- Bradycardia: 0.5 mg IV every 3-5 minutes as needed; maximum total dose: 3 mg
- Organophosphate poisoning: 2-5 mg IV/IM repeated every 10-15 minutes until symptoms resolve
- Preoperative antisialagogue: 0.4-0.6 mg IV/IM/SC 30-60 minutes before anesthesia
- Uveitis (Ophthalmic): 1-2 drops into the eye(s) up to qid
Pediatric Dosing
- Bradycardia: 0.02 mg/kg IV/IO (minimum dose: 0.1 mg); may repeat once; maximum single dose: 0.5 mg in children, 1 mg in adolescents
- Organophosphate poisoning: 0.05 mg/kg IV/IM every 10-15 minutes until atropinization
- Preoperative: 0.01-0.02 mg/kg SC/IV/IM; maximum dose: 0.4 mg
Indications
- Acute symptomatic bradycardia
- Organophosphate or carbamate insecticide poisoning
- Preanesthetic medication to reduce salivary and bronchial secretions
- Mydriasis and cycloplegia for ophthalmic examinations or uveitis
Mechanism of Action
- Competitive antagonist at muscarinic acetylcholine receptors (M1, M2, M3)
- Blocks parasympathetic nerve impulses, leading to increased heart rate, reduced secretions, and smooth muscle relaxation
Contraindications
- Narrow-angle glaucoma
- Glaucoma predisposition
- Tachycardia secondary to cardiac insufficiency or thyrotoxicosis
- Obstructive uropathy (e.g., prostatic hypertrophy)
- Obstructive disease of the gastrointestinal tract (e.g., pyloric stenosis, paralytic ileus)
Adverse Reactions
- Xerostomia (dry mouth)
- Blurred vision and mydriasis
- Tachycardia and palpitations
- Constipation and urinary retention
- Confusion, hallucinations, and central nervous system toxicity (especially in elderly)
Drug Interactions
- Amantadine and other anticholinergics: Enhanced anticholinergic adverse effects
- Antihistamines with anticholinergic properties: Increased risk of urinary retention and constipation
- Phenothiazines and tricyclic antidepressants: Potentiation of antimuscarinic effects
- Metoclopramide: Antagonism of gastrointestinal motility effects
Curated Content: Needs Vetting Before Put to Clinical Use