Atropine

Approved Indications:

• Bradyarrhythmias: Treatment of symptomatic sinus bradycardia, atrioventricular (AV) block, or asystole during cardiac arrest.
• Preanesthetic medication: To reduce salivary, respiratory, and gastric secretions.
• Organophosphate or carbamate poisoning: Antidote for cholinergic toxicity due to pesticides or nerve agents.
• Ophthalmic use: Induction of mydriasis and cycloplegia for diagnostic procedures.
• Intraoperative use: To block vagal reflexes during surgery.
• Bronchial hypersecretion: Management of excessive secretions in palliative care or anesthesia.
• Reversal of neuromuscular blockade: Used with anticholinesterase agents (e.g., neostigmine) to prevent muscarinic side effects during reversal of non-depolarizing muscle relaxants.

Clinically Accepted Off-label Uses:

• Infantile hypertrophic pyloric stenosis (diagnostic test)
• Asthma exacerbations (rare and severe cases)
• Urinary incontinence (bladder spasms, though less preferred)

Route of Administration:

• Intravenous (IV), Intramuscular (IM), Subcutaneous (SC), Endotracheal (ET), Ophthalmic (eye drops), Oral (rare)

Adult Dosage:

• Bradycardia (IV): 0.5 mg every 3–5 minutes as needed; max total dose: 3 mg
• Organophosphate poisoning:
• Initial dose: 1–2 mg IV every 5–15 minutes until muscarinic symptoms are controlled.
• May require higher or continuous infusion in severe toxicity.
• Preanesthetic medication (IM/SC/IV): 0.4–0.6 mg 30–60 minutes before induction.
• Reversal of neuromuscular blockade (IV): 0.015 mg/kg with neostigmine.

Pediatric Dosage:

• Bradycardia (IV/IO): 0.02 mg/kg; minimum dose: 0.1 mg, maximum single dose: 0.5 mg (children), 1 mg (adolescents); may repeat once.
• Organophosphate poisoning: 0.02–0.05 mg/kg IV/IM every 10–30 minutes until signs of atropinization appear.

Elderly: Use cautiously due to increased sensitivity to anticholinergic effects (e.g., confusion, urinary retention).

Renal/Hepatic Impairment: No specific dose adjustment required, but caution advised due to prolonged elimination in severe impairment.

Ophthalmic Use (Adults & Children):

• 1% atropine sulfate eye drops: 1–2 drops instilled 1 hour before procedure or as directed.

Atropine Sulfate is a competitive antagonist of muscarinic acetylcholine receptors (M1–M5) located in smooth muscle, cardiac tissue, glands, and the central nervous system. By blocking parasympathetic stimulation, it inhibits vagal effects on the heart, leading to increased heart rate and improved AV conduction. In smooth muscles and glands, it reduces secretions, relaxes bronchial and GI smooth muscle, and inhibits salivation, lacrimation, and urination. In toxicological contexts, atropine opposes excessive cholinergic stimulation due to organophosphate poisoning, thereby preventing overstimulation of muscarinic receptors.

• Absorption: Rapidly absorbed after IM, SC, or oral administration. IV administration has immediate onset.
• Onset of Action:
• IV (cardiac use): Within 1–2 minutes
• IM/SC: 15–30 minutes
• Ophthalmic: Mydriasis begins in 30–40 minutes
• Peak Effect: 2 minutes (IV), 30 minutes (IM)
• Duration of Action:
• IV (cardiac use): 30–60 minutes
• Ophthalmic: Up to 7–14 days for mydriasis
• Distribution: Crosses blood-brain barrier and placenta; widely distributed.
• Protein Binding: 14–22%
• Metabolism: Hepatic via enzymatic hydrolysis.
• Half-life:
• Adults: 2–4 hours
• Children: 6.5 hours (prolonged)
• Excretion: Primarily renal (urine) as metabolites and unchanged drug.

Pregnancy:

• FDA Category C (historical): No adequate and well-controlled studies in humans.
• Animal studies show potential adverse effects at high doses.
• Crosses placenta; use only if clearly needed and benefits outweigh potential risks.

Lactation:

• Atropine is excreted in breast milk.
• Potential for anticholinergic effects in infants, such as dry mouth, tachycardia, or CNS disturbances.
• Use cautiously; brief exposure (e.g., preoperative) unlikely to harm infant. Monitor for signs of adverse effects if repeated doses are required.

• Primary Class: Anticholinergic / Antimuscarinic Agent
• Subclass: Belladonna alkaloid derivative
• Pharmacologic Type: Parasympatholytic

• Known hypersensitivity to atropine or any component of the formulation
• Glaucoma (especially narrow-angle type)
• Prostatic hypertrophy with urinary retention
• Myasthenia gravis (unless used as adjunct to anticholinesterase reversal)
• Severe ulcerative colitis or toxic megacolon
• Obstructive gastrointestinal or urinary tract disease

• High-risk groups: Elderly, children, patients with Down syndrome, and those with underlying cardiac disease.
• CNS effects: May cause confusion, hallucinations, or delirium, especially in older adults.
• Ophthalmic use: Risk of angle-closure glaucoma; intraocular pressure should be monitored.
• Hyperthermia: Inhibits sweating; caution in hot environments or with fever.
• Organophosphate poisoning: Repeated dosing or infusion may be necessary; monitor for both under- and over-atropinization.
• Cardiac patients: Use with caution in ischemic heart disease; may increase myocardial oxygen demand.

Common Side Effects (by system):

• Cardiovascular: Tachycardia, palpitations
• CNS: Dizziness, confusion, restlessness, headache (especially in elderly)
• Gastrointestinal: Dry mouth, nausea, constipation
• Ophthalmic: Blurred vision, photophobia, pupil dilation
• Genitourinary: Urinary retention
• Skin: Flushing, dry skin

Serious or Rare Side Effects:

• Anaphylaxis (rare)
• Hallucinations, psychosis
• Ventricular arrhythmias (rare)
• Coma (in overdose)

Onset/Severity:

• Most side effects are dose-related and transient, resolving as plasma levels fall.
• CNS effects and anticholinergic toxicity are more likely with high doses or repeated use.

Major Interactions:

• Other anticholinergics (e.g., scopolamine, antihistamines, tricyclic antidepressants): Additive anticholinergic effects.
• Cholinesterase inhibitors (e.g., donepezil): Antagonizes their effects.
• Potassium chloride tablets/capsules: Risk of GI irritation or ulceration.
• Amantadine and quinidine: May increase atropine toxicity.
• Antacids and adsorbents: May reduce absorption if given orally.

Metabolism & Enzyme Systems:

• Not primarily metabolized via CYP450; minimal involvement of major hepatic isoenzymes.

Food & Alcohol Interactions:

• Alcohol may enhance CNS side effects such as dizziness or confusion.

• No recent FDA or WHO changes to indications or safety warnings.
• Updated toxicology guidelines emphasize prompt and aggressive atropine use in severe organophosphate poisoning.
• Current ACLS protocols recommend IV atropine as first-line for symptomatic bradycardia, reinforcing its role in emergency cardiac care.
• Modern use shifting towards selective muscarinic antagonists in some settings due to more favorable side effect profiles.

• Temperature: Store at 20°C to 25°C (controlled room temperature).
• Protection: Protect from light and excessive heat.
• Refrigeration: Not required for most formulations.
• Handling:
• Do not use if the solution is discolored or contains particulates.
• Use single-dose vials immediately after opening.
• Ophthalmic solutions must be used within prescribed period once opened.