Adult: Mild to moderate poisoning: Initially, 1-2 mg via IV inj, followed by an additional 2 mg dose via IV/IM inj every 5-60 minutes until muscarinic signs and symptoms disappear. Severe poisoning: Initially, 2-6 mg via IV inj, then a subsequent 2-6 mg dose via IV/IM inj every 5-60 minutes until muscarinic signs and symptoms subside. Alternatively, atropinisation may be maintained for at least 2 days in moderate to severe cases. Individualise dose according to the severity of poisoning and patient response. May be given in combination with a cholinesterase reactivator (e.g. pralidoxime). Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines). Child: 0.05-1 mg/kg via IM/IV inj every 10-30 minutes until muscarinic signs and symptoms subside. Dose may be repeated if symptoms reappear. Alternatively, 0.02 mg/kg (Max: 2 mg per dose) via IV inj every 5-10 minutes until signs and symptoms disappear. Individualise dose according to the severity of poisoning and patient response. May be given in combination with a cholinesterase reactivator (e.g. pralidoxime). Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Adult: To inhibit excessive salivary and bronchial secretions: 0.3-0.6 mg via IV inj immediately before induction of anaesthesia or via IM/SC inj 30-60 minutes before induction of anaesthesia. Child: Patients weighing <3 kg: 0.1 mg; 7-9 kg: 0.2 mg; 12-16 kg: 0.3 mg; ≥20 kg: 0.4-0.6 mg. Doses may be given via IM/SC inj 30-60 minutes before surgery. Alternatively, 0.01-0.02 mg/kg via IM inj 30-60 minutes prior to anaesthesia induction. Max: 0.6 mg per dose. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Intravenous Bradycardia
Adult: For the management of haemodynamically compromising bradycardia and AV block due to excessive vagal tone, or used in CPR to manage acute MI and symptomatic sinus bradycardia with hypotension and increased ventricular irritability: 0.5-1 mg via IV inj every 3-5 minutes. Max total dose: 3 mg. Child: For the management of patients with symptomatic bradycardia secondary to increased vagal activity or primary AV block: 0.02 mg/kg via IV inj, may repeat once every 5 minutes. Max single dose: 0.5 mg. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Intravenous Prophylaxis of cholinesterase inhibitor induced muscarinic adverse effects
Adult: To block the adverse muscarinic effects of anticholinesterase agents (e.g. neostigmine) when they are used after surgery in the reversal of competitive block: 0.6-1.2 mg via IV inj for each 0.5-2.5 mg neostigmine methylsulfate. Administer atropine concurrently with (in a separate syringe) or a few minutes before the anticholinesterase agent. Child: 0.02 mg/kg via IV inj for each 0.04 mg/kg neostigmine methylsulfate. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Ophthalmic Iritis, Uveitis
Adult: As 1% ophthalmic solution: Instil 1-2 drops into the affected eye(s) up to 4 times daily. As 1% ophthalmic ointment: Apply a small amount into the conjunctival sac 1-2 times daily. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines). Child: As 1% ophthalmic ointment: Same as adult dose. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Ophthalmic Myopia
Child: To control the progression of myopia in patients with >0.5 dioptres per year documented myopic progression: As 0.01% ophthalmic solution: 6-12 years Instil 1 drop once daily at night. Duration of treatment is based on regular clinical assessment. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Ophthalmic Mydriasis and cycloplegia for refraction
Adult: As 1% ophthalmic solution: Instil 1 drop into the eye(s) 1 hour before the procedure. As 1% ophthalmic ointment: Apply a small amount into the conjunctival sac 1-2 times daily. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines). Child: As 1% ophthalmic solution: Instil 1 drop into each eye bid for 1-3 days prior to the procedure. As 1% ophthalmic ointment: Same as adult dose. Dosage recommendations may vary among individual products or between countries (refer to specific product or local guidelines).
Angle-closure glaucoma or predisposition to angle-closure glaucoma (e.g. narrowing or closure of the anterior chamber angle); gastrointestinal obstruction, achalasia of the oesophagus, paralytic ileus, pyloric stenosis, severe ulcerative colitis, toxic megacolon, intestinal atony; obstructive uropathy (e.g. bladder neck obstruction due to prostatic hypertrophy), urinary retention due to prostatic or urethral disease; myasthenia gravis (unless used to decrease muscarinic adverse effects of anticholinesterases).
Special Precautions
Patient with arrhythmia, acute MI, myocardial ischaemia, heart failure, tachyarrhythmias (e.g. sinus tachycardia), coronary heart disease, hypertension; COPD, diarrhoea, gastric ulcer, mild to moderate ulcerative colitis, oesophageal reflux, hiatal hernia (associated with reflux oesophagitis), hyperthyroidism, thyrotoxicosis, autonomic neuropathy, partial pyloric stenosis; brain damage, Down syndrome, spastic paralysis. Febrile patients or those who are exposed to high ambient temperatures. Patients with darkly pigmented iris may be more resistant to pupillary dilation (ophthalmic). Patients undergoing cardiac surgery. Renal and hepatic impairment. Neonates, children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Hypersensitivity reactions (e.g. anaphylactic reactions); heat-related injury or hyperthermia (particularly in patients exposed to warm environment); tachycardia, increased blood pressure, worsening of ischaemia; thickening of bronchial secretions and formation of viscid bronchial plugs; decreased gastrointestinal motility, urinary retention; precipitation of acute glaucoma, blurred vision, photophobia; confusion (especially in elderly), psychosis (particularly in high doses or sensitive patients). Cardiac disorders: Transient bradycardia, palpitation, arrhythmia. Eye disorders: Mydriasis, inhibition of accommodation; local eye irritation, eye hyperaemia, eyelid oedema, follicular conjunctivitis, decreased lacrimation, eye pain, transient stinging sensation (ophthalmic). Gastrointestinal disorders: Dry mouth, difficulty swallowing, constipation, reflux, loss of taste, nausea, vomiting, bloated feeling. General disorders and administration site conditions: Fever; inj site redness or irritation (parenteral). Metabolism and nutrition disorders: Thirst. Nervous system disorders: Dizziness, drowsiness, excitement, ataxia, incoordination. Psychiatric disorders: Hallucination. Renal and urinary disorders: Difficulty in micturition. Respiratory, thoracic and mediastinal disorders: Reduced bronchial secretion. Skin and subcutaneous tissue disorders: Anhidrosis, urticaria, rash, dry skin. Vascular disorders: Flushing.
This drug may cause dizziness, drowsiness or transient blurring of vision, if affected, do not drive or operate machinery. Ophthalmic: Remove contact lenses before administration and wait for at least 15 minutes before reinsertion. After administration, protect the eyes from bright light as atropine may increase the sensitivity to light.
Monitoring Parameters
Monitor blood pressure, heart rate, mental and respiratory status. Ophthalmic: Monitor the reduction in visual acuity. Determine IOP and estimate the depth of the angle of the anterior chamber prior to treatment initiation. Assess for signs and symptoms of local and systemic toxicity.
Overdosage
Symptoms: Dilated pupils, dry mouth and tongue, difficulty in swallowing, tachycardia, dry skin, hyperpyrexia, nausea, vomiting, hypertension, rash, excitement, restlessness, tremor, confusion, incoordination, ataxia, hallucinations, paranoid and psychotic reactions, delirium, and convulsions. In severe cases, CNS depression, coma, and circulatory or respiratory failure may occur. Management: Symptomatic and supportive treatment. Maintain adequate airway and fluid intake. May give activated charcoal within 1 hour to reduce absorption of oral overdose. Methods of cooling (e.g. cold packs, sponging with tepid water) may be done to help reduce fever. May consider IV sodium bicarbonate for persistent metabolic acidosis despite correction of hypoxia. May administer diazepam or a short-acting barbiturate to control marked excitement and convulsions. In severe cases, give IV physostigmine for extreme delirium or agitation, repetitive seizures, severe sinus or supraventricular tachycardia, and unresponsive severe hyperthermia. Consider giving IV propranolol for supraventricular tachyarrhythmias if contraindicated or unresponsive to physostigmine. Urinary catheterisation may be needed. Artificial respiration with oxygen may be necessary for respiratory depression.
Drug Interactions
Enhanced anticholinergic effects with other drugs with anticholinergic activity (e.g. MAOIs, TCAs, phenothiazines, neuroleptic drugs, clozapine, amantadine, antispasmodics, disopyramide, quinidine, mequitazine, promethazine). May antagonise the gastrointestinal effects of cisapride and metoclopramide. May antagonise the antiglaucoma and miotic actions of ophthalmic long-acting cholinergic antiglaucoma agents (e.g. demecarium, echothiophate). May increase the toxic effects of antimyasthenics, K citrate, or K supplements. May interfere with or antagonise the actions of synthetic choline esters (e.g. bethanechol, carbachol), anticholinesterase drugs (e.g. neostigmine, physostigmine), and pilocarpine.
Action
Description: Mechanism of Action: Atropine is a tertiary amine antimuscarinic agent that competitively inhibits the action of acetylcholine at parasympathetic sites in the smooth muscle, cardiac muscle, exocrine glands and CNS. It depresses the vagus nerve, thereby increasing heart rate. Atropine acts as a competitive acetylcholine antagonist at muscarinic receptors to reverse the muscarinic effects of cholinergic poisoning (due to agents with acetylcholinesterase inhibitor activity). In the eyes, it inhibits acetylcholine action to induce mydriasis by relaxing the cholinergically innervated iris sphincter muscle and causes cycloplegia by paralysing the ciliary muscle. Onset: IV: 2-4 minutes (increased heart rate). IM: Approx 15-30 minutes (increased heart rate); within 30 minutes (inhibition of salivation). Ophthalmic: Within minutes. Duration: IM: ≤4 hours (inhibition of salivation). Ophthalmic: 7-12 days (mydriasis); ≥14 days (cycloplegia). Pharmacokinetics: Absorption: Readily and well absorbed from the gastrointestinal tract, mucous membranes or eyes, and following IM inj. Bioavailability: 19-95% (ophthalmic). Time to peak plasma concentration: 30 minutes (IM); 3-60 minutes (ophthalmic). Distribution: Widely distributed throughout the body. Crosses the placenta and blood-brain barrier; enters breast milk (small amounts). Plasma protein binding: 14-44%. Metabolism: Incompletely metabolised in the liver via hydrolysis. Excretion: Via urine (13-50% as unchanged drug and metabolites). Elimination half-life: 3 ± 0.9 hours (IV/IM); 2.5 ± 0.8 hours (ophthalmic).
Chemical Structure
Atropine Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 174174, Atropine. https://pubchem.ncbi.nlm.nih.gov/compound/Atropine. Accessed Oct. 28, 2024.
Storage
Tab/solution for inj: Store between 15-30°C. Ophthalmic solution/ointment: Store below 25°C. Protect from light.
A03BA01 - atropine ; Belongs to the class of belladonna alkaloids, tertiary amines. Used in the treatment of functional gastrointestinal disorders. S01FA01 - atropine ; Belongs to the class of anticholinergics used as mydriatics and cycloplegics.
References
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