Atropine Sulfate

(atropine sulfate)



Veterinary Availability

  • Injectable for IV ; IM; or SQ use: 0.5 mg/mL in 30mL vial and 2 mg /mL in 100mL vial

Human Availability

  • Tablets: 0.4 mg
  • Injectable: several concentrations


Atropine, a belladonna alkaloid, is both a central and a peripheral muscarinic blocking agent. It inhibits acetylcholine or other cholinergic stimulants at postganglionic parasympathetic neuroeffector sites.

The pharmacologic effects of atropine are dose related. When given in small doses it inhibits salivary and bronchial secretions. Given in moderate doses atropine can dilate pupils and increase heart rate. At large doses atropine decreases GI motility and inhibits gastric acid secretion.

Atropine is readily absorbed following oral administration, IM injection, inhalation, or when given via endotracheal administration. It is well distributed in the body crossing into the central nervous system, and across the placenta. It has also been found distributed in breast milk in small quantities.

Atropine is metabolized in the liver and excreted into urine with 30-50% being excreted unchanged.


In pet rats it is used for: treatment of overdose of cholinergic agents, and as an antidote for organophosphate insecticide poisoning.

Drug Interactions or Contraindications

  • Atropine activity may be increased by the following:
    • Antihistamines
    • Procainamide
    • Meperidine
    • Benzodiazepines
    • Phenothiazines
  • Atropine may increase the activity of thiazide diuretics and sympathomimetics.
  • *In humans atropine is contraindicated where narrow-angle glaucoma is suspected.*

Adverse Reactions

CNS:  stimulation, lethargy, ataxia (staggering gait, uncoordinated movement), seizures, respiratory depression

CV: bradycardia (low heart rate) at low doses, tachycardia (high heart rate) at higher doses, arrhythmias (irregular heart rate )

EENT: increased intraocular pressure when used topically in the eye

GI: dry mouth, thirst, constipation

GU: urinary retention

Other: anaphylaxis

Dosage Recommendations

0.05 mg/kg to 0.5 mg/kg, SQ, IM (cardiac issues) 34, 41, 44(*Note for veterinarians: rat’s possess serum atropine esterase, which rapidly hydrolyzes atropine.)


Up to 10 mg/kg, SQ, IM, IV every 20 minutes, in organophosphate overdose until muscarinic signs disappear. 1, 26, 34, 41, 44


  • This drug can cause urinary retention. Monitor the rat’s fluid intake and output.
  • Keep in closed container at room temperature.


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