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ah-TROW-peen - Pronunciation guide

Brand Names

  • AtroJect SA
  • Atropine Sulfate Injection
  • Atropine Sulfate Injection 1/120 Grain
  • Atropine Sulfate Injection 15 mg/mL L.A.
  • Atropine Sulfate Injection SA


Rx symbolAtropine, which is a purified form of the tropane alkaloid found in the deadly nightshade plant, has been known and used for centuries. Atropine counteracts the effects of acetylcholine, which is a chemical compound that acts as a neurotransmitter in the peripheral, central, autonomic, and somatic nervous systems.

By competing with the receptors on sensitive muscle cells that are primarily not under conscious control in the heart, lungs, sweat glands, eyes, intestines, and urinary system, atropine is used to treat breathing problems, abnormal heart rhythms, eye problems, and in the treatment of overdoses with organophosphates found in older types of dewormers and some fly sprays and insecticides.


Injectable atropine is often used by veterinarians in emergency situations as a bronchodilator with horses having difficulty breathing during acute episodes of heaves or chronic obstructive pulmonary disease.

Atropine is used to treat abnormal heart rhythms, especially those that occur during anesthesia or in response to other drugs.

Veterinarians use atropine topically to dilate the pupil of the horse's eye during examinations and as a part of treatment to decrease the pain of recurrent uveitis and other diseases of the eye where dilating the pupil helps prevent formation of scars or adhesions that might permanently interfere with normal pupil function.

Atropine is used to treat poisoning or overdose with organophosphates contained in some types of older dewormers and fly sprays.

Dosage and Administration

Prescription medicationAtropine
Method Dosage
(click row for calculator)
Concentration Period Duration
Opthalmic 1 or 2 drops 1% Every 3 to 24 hours NA
Intravenous, Intramuscular or Subcutaneous injection 0.03-0.06 mg/kg2 0.54 mg/ml1 Treatment NA
Intravenous, Intramuscular or Subcutaneous injection 6.5 mg/100lb 0.15 mg/ml1 Treatment NA


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • 1CAUTION: Multiple concentrations available for injection. Check medication label for concentration.
  • The recommended average initial dose should be split, injecting 1/4 to 1/3 slowly intravenously, and the remainder intramuscularly or subcutaneously. After symptoms appear to be under control, repeated maintenance doses should be administered based upon the individual response of the animal
  • 2This drug is not approved for use in horses but may be prescribed for extra-label use.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Drug side effects are commonly dose-related and include increased heart and respiratory rates, slowing of gastrointestinal motility, abdominal pain, dilation of the pupil, and dry mouth and mucous membranes.


Some horses are susceptible to developing colic caused by the slowing of the gastrointestinal tract due to administration of atropine. Extreme caution should be taken with use in horses with kidney or liver disease due to increased severity of side effects.

Atropine should be used with extreme caution in foals.

Atropine is FDA-approved for use in horses and is a prescription-only drug. U.S. federal law mandates that this drug be used by or on the prescription of a licensed veterinarian.

Atropine is prohibited in most sanctioned competitions. It is important to check with the appropriate regulatory group.


Atropine interacts with antihistamines, phenothiazine tranquilizers, and some painkillers. The likelihood of side effects increases when long-term corticosteroids are used to treat a horse with chronic obstructive pulmonary disease.


Drug overdose increases the severity of side effects, and, in addition, may cause restlessness, muscular tremors, loss of coordination, convulsions, and respiratory depression, which, if severe, may lead to death.


Atropiine Opthalmalic SolutionAtropiine Opthalmalic Solution

Atropine Sulfate InjectionAtropine Sulfate Injection



About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.