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reh-SER-peen - Pronunciation guide

Brand Names

  • Rakelin
  • Serpasil


Rx symbolReserpine is an alkaloidal chemical derived from the plant Rauwolfia serpentina, sometimes used for long-term sedation of horses. Reserpine works by blocking the storage of some of the brain's chemical messengers, including a neurotransmitter called norepinephrine.

This drug takes many hours to fully take effect and has subtle sedating effects long after the last dose is given. Although some trainers routinely administer it to nervous or excitable horses, many trainers and veterinarians are against this practice because of side effects and the fact that other ways can be used to achieve the same results with most horses, without giving them a chemical medication that may increase health risks.


Reserpine is used as a long-acting tranquilizer to subdue excitable or difficult horses and has been used illicitly for the sedation of show horses, for-sale horses, and in other circumstances where a "quieter" horse might be desired. Currently, accurate tests are available that can determine if a horse has been given reserpine.

Dosage and Administration

Prescription medicationReserpine
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 0.002-0.008 mg/kg 1 0.1 mg/tablet Daily NA
Oral 0.002-0.008 mg/kg 1 0.25 mg/tablet Daily NA
Intramuscular injection 0.002-0.008 mg/kg 1 0.5 mg/ml Daily NA
Intramuscular injection 0.002-0.008 mg/kg 1 2.5 mg/ml Daily NA


  • 1Reserpine is a narrow therapeutic index drug. Doses above this range have resulted in severe toxicity. No antidote is available for reserpine toxicity.Drug interactions with reserpine can be life-threatening.
  • Horses treated with reserpine within the previous 60 days may be at risk for profound hypotension (even death) when exposed to xylazine, detomidine or ketamine.
  • 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

Horses vary greatly in their sensitivity to reserpine. Common side effects include colic, gastrointestinal upset, long-term diarrhea, sweating, depression, droopy eyes, and a dropped penis.


Little information has been published on the clinical use of reserpine in horses. Much available information is anecdotal and not backed by research.

Reserpine is not FDA approved for use with horses and is a prescription drug restricted by U. S. federal law to use by or on the lawful written or oral order of a licensed veterinarian.

Reserpine is prohibited in most sanctioned competitions and is a frequent cause of drug violations. The proper regulatory group should be consulted regarding rules and regulations.


Reserpine may interact with drugs used for general anesthesia. Accurate records should be kept of its use in case an animal is referred to an equine hospital for care or surgery.


Overdose results in increased risk and severity of the above mentioned side effects.

The antidote to reserpine is methamphetamine.


Rakeline Reserpine InjectionRakeline Reserpine Injection

Reserpine InjectionReserpine 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.