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Tripelennamine for Horses

By Barbara Forney, VMD

Last reviewed: 7/14/2022

Commonly prescribed for: Hives, Bee Stings, Itchy Skin and Allergic Skin Conditions

Species: Horses

Therapeutic Class: Antihistamine

Basic Information

Tripelennamine is an antihistamine. It competitively inhibits histamine binding at the H1 receptors on sensitive cells in the respiratory tract, intestines, blood vessels, and skin. When compared to other antihistamines, tripelennamine has minimal anticholinergic properties and is only moderately sedating.


Tripelennamine is used in horses to treat allergic problems such as hives and itchy skin reactions or more urgent allergic problems such as tongue or facial swelling due to bee sting, insect bites, or contact with an irritating plant. Oral antihistamines generally take 20 - 45 minutes to exert an effect, whereas injectable antihistamines such as tripelennamine or pyrilamine maleate act more rapidly. Injectable antihistamines, however, are more likely to cause adverse side-effects.

If antihistamines alone are unable to control all of the allergic signs, they may be used with corticosteroids allowing use of a lower dose of the corticosteroids.

Tripelennamine Side Effects

  • Sedation, CNS depression, and decreased coordination are the most-common side effects with any antihistamine use. Less-common side effects include excitement, fine tremors, whole body tremors, and seizures. Gastrointestinal side-effects such as colic or loss of appetite are possible.
  • Antihistamines may thicken mucous in the respiratory tract. Extra caution should be used in horses with respiratory problems due to excess mucous.


  • High doses of antihistamines have been shown to cause birth defects in laboratory animals. It is not known if tripelennamine is excreted in milk. It should be used in pregnant or lactating animals only if the benefits outweigh the risks.
  • Tripelennamine should not be administered intravenously in the horse due to potential CNS stimulation.
  • Individual animals may react differently to antihistamines. Very young animals and very old animals may be more sensitive to the sedating side-effects of antihistamines. When using antihistamines in these populations, they should be used at the lowest possible dose.
  • Tripelennamine has some abuse potential for human drug abusers. One should be aware of unusual requests for this drug.
  • Antihistamines should be discontinued prior to skin testing.

Drug Interactions

  • Antihistamines have an additive effect when combined with other CNS depressant drugs, such as tranquilizers.
  • Antihistamines may affect the activity of anticoagulants like warfarin.


Overdoses can cause either increased sedation and ataxia, or CNS excitement and seizures.
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