Pyrilamine Maleate

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peye-RIL-uh-meen MA-le-ate - Pronunciation guide

Brand Names

  • Ani-Hist
  • Hist-ALL
  • Hist-EQ Powder
  • Histagranules
  • Tri-Hist Granules


Rx symbolPyrilamine maleate is an antihistamine drug used in horses to reduce or prevent allergic reactions to histamines.


Pyrilamine is an antihistamine drug used to treat hypersensitivity reactions caused by foreign proteins or allergens in the horse's body. The skin and respiratory tract are the target for most allergic reactions in horses.

Dosage and Administration

Prescription medication Pyrilamine Maleate
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 0.3 mg/lb 600 mg/ounce Every 12 hours NA
Intravenous injection 40-60 mg/100lb 20 mg/ml Repeat in 6 to 12 hours if needed NA


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • Extra-label use of drugs in treating animals is allowable only by licensed veterinarians within the context of a valid veterinarian-client-patient relationship, and does not include drug use in treating animals by the layman (except under the supervision of a licensed veterinarian).
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your equine appears to feel better, the entire treatment plan should be completed to prevent relapse.
  • This medication may be available in forms and concentrations not noted in the above table. Always check the label and literature provided with the medication about the form and concentration and DO NOT USE the calculator if the information differs.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Side effects may include nervousness, convulsions, tremors, palpitations, GI disturbances, sedation, muscular weakness, anorexia, lassitude, and lack of coordination.


Pyrilamine maleate is not approved for use in horses intended for food.

Pyrilamine is a prescription drug according to U. S. federal law, available only on the written or oral order of a licensed veterinarian.

Pyrilamine maleate is prohibited or regulated in most sanctioned competitions. It is important to check with the individual regulatory group. .


Increased sedation can occur if pyrilamine maleate is combined with other CNS depressant drugs. It may partially counteract the anticoagulation effects of heparin or warfarin. Pyrilamine may enhance the effects of epinephrine.


Treatment of overdosage is supportive and symptomatic. The manufacturer suggests using "careful titration" of barbituates to treat convulsions, and analeptics, such as caffeine or amphetamines, to treat CNS depression.


AniFlex Pyrilamine Maleate Powder  AniFlex Pyrilamine Maleate Powder

Pyrilamine Maleate Vaccine InjectionPyrilamine Maleate Vaccine 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.