Atropine
Mechanism :
Atropine is commonly classified as an anticholinergic drug. More precisely, however, it is termed an antimuscarinic agent since it antagonizes the muscarine-like actions of acetylcholine and other choline esters.
Indication :
- As an anti-sialagogue when reduction of secretions of the respiratory tract are needed
- To temporarily increase heart rate or decrease AV-block until definitive intervention can take place in bradycardia or AV-block
- As an antidote for overdose of cholinergic drugs or for cholinesterase poisoning such as organophosphorus insecticides
- As an antidote for mushroom poisoning in certain species of fungus such as Amanita muscaria
- It is used to prevent vagal stimulation prior to procedures in, prolonged cardiac arrest
- For causing mydriasis.
- Pylorospasm and other spastic conditions of GI tract
Contraindications :
Atropine generally is contraindicated in patients with glaucoma, pyloric stenosis, thyrotoxicosis, fever, urinary tract obstruction and ileus.
Dosing :
Pre-anaesthetic:
Neonates and children <5 kg: 0.02 mg/kg/dose 30-60 min pre-operatively and then 4-6 hourly as and when required; use of a minimum dosage of 0.1 mg in neonates.
Children >5 kg:
0.01 mg-0.02 mg/kg/dose IV/IM/SC to a maximum dose 0.4 mg/dose 30 min preoperative. Minimum dose: 0.1 mg.
Sinus bradycardia:
IV 0.02 mg/kg (Minimum dose 0.1 mg; maximum single dose 0.5 mg in children and 1 mg adolescents). May be repeated every 5 mins for 2-3 doses as and when required. Maximum total dose is 1 mg in children and 2 mg in adolescents.
Bronchospasm:
Inhalational 0.025-0.05 mg/kg in 2.5 ml of normal saline 3-4 times/day via a nebulizer; maximum: 2.5 mg/dose.
Refraction-Ophthalmic:
Infants: Instill 1 drop of 0.25% solution 3 times/day for 3 days before the procedure.
Children 1-5 years: Instill 1 drop of 0.55 solution 3 times/day for 3 days before the procedure.
Children >5 years or children with dark irides: Instill 1 drop of 1% solution 3 times/day for 3 days before the procedure.
For OPC or Carbamate poisoning:
IV:
0.03 mg-0.05 mg/kg IV/IM/ET every 10-20 min till atropine effect (tachycardia, mydriasis, fever), then every 1-4 hours for at least 24 hours.
I.M (AtroPen):
Children 6 months-4 years: 0.5 mg (blue pen)
Children 4-10 years: 1 mg (dark red pen)
Children >10 years: 2 mg (green pen)
Mild symptoms: 1 injection as soon as exposure is known or suspected.
Severe symptoms: 2 additional injections (3 total) given in rapid succession 10 minutes after receiving the first injection.
Uveitis (off-label):
Ophthalmic:
Instill 1 drop of 0.5% solution 1-3 times daily.
Sialorrhea, pylorospasm and other spastic conditions of the GIT:
3-7 kg: 0.1 mg IV single dose.
8-11 kg: 0-.15 kg IV single dose.
11-18 kg: 0.2 mg IV single dose.
18-29 kg: 0.3 mg IV single dose.
≥30 kg: 0.4 mg IV single dose.
Adverse Effect :
Anti-muscarinic effects (dryness of the mouth, blurred vision, photophobia, tachycardia), hypersensitivity reactions, palpitation, dilated pupils, difficulty in swallowing, hot dry skin, thirst, dizziness, restlessness, tremor, fatigue and ataxia. Toxic doses lead to hallucinations, delirium and coma.
Interaction :
Antihistamines, disopyramide, tricyclic anti-depressants: Increased adverse effects.
Metoclopramide, domperidone: Antagonism.
Ketoconazole: Affects absorption.
Hepatic Dose :
No dosage adjustments are recommended.