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Isoxsuprine for Horses

By Barbara Forney, VMD

Last reviewed: 7/13/2022

Commonly prescribed for: Navicular Disease or Laminitis

Species: Horses

Therapeutic Class: Vasodilator

General Drug Information and Indications

Isoxsuprine is a human drug that is sometimes used in horses to treat navicular disease or laminitis. This drug works by relaxing the smooth muscle that surrounds small blood vessels causing "vasodilation" and potentially increasing blood flow to the hooves. The use of oral isoxsuprine in the horse is not universally accepted because it has been shown that horses only absorb a very small amount of this drug through their digestive tracts. Nevertheless, there are many veterinarians who feel that it is helpful in selected cases.

Isoxsuprine is used in human medicine to treat premature labor and prevent abortion. Because of its demonstrated effectiveness in humans, some veterinarians use isoxsuprine for the same purpose in broodmares. Its effectiveness in the broodmare has not been well evaluated.

Like many other drugs in veterinary medicine, isoxsuprine is not FDA approved for use in animals and is not available from a veterinary pharmaceutical manufacturer. Instead, it is compounded by a specialty pharmacy.

How to Give this Medication

Give this medication to your horse exactly as your veterinarian prescribes. If you miss giving your horse a dose of isoxsuprine, give the next dose as soon as you remember or, if it is close to the next scheduled dose, return to the regular schedule. Do not double dose to catch up.

Wash your hands after giving your pet this medication.

Despite the low level of oral absorption, isoxsuprine can be found in a horse's urine for many weeks after treatment is discontinued. If your horse is competing in a sanctioned competition where there are drug rules, you should consult with a knowledgeable veterinarian regarding the withdrawal time for isoxsuprine.

Side Effects

Be sure to discuss any side effects with your veterinarian immediately.

Side effects after oral administration are rare in the horse because of the low absorption. Possible side effects could include low blood pressure, increased heart rate, and possible irritation of the digestive tract.


Keep this and all drugs out of reach of children. This drug should only be given to the animal for which it was prescribed. Do not give this medication to a person.

Federal law restricts this drug to use by or on the order of a licensed veterinarian.

Isoxsuprine should not be used in mares immediately after foaling or horses that are actively bleeding.

There are no safety studies on isoxsuprine use in pregnant or lactating mares. There are no safety studies regarding the effects on semen in breeding stallions.

Drug Interactions

Be sure to review with your veterinarian any medications or supplements your pet may be receiving.

Drug interactions are unlikely with oral isoxsuprine.


If you suspect your pet or another animal has been accidentally overdosed or has eaten this medication inadvertently, contact your veterinarian or the A.S.P.C.A.'s Animal Poison Control Center at 888.426.4435. Always have the prescription container with you when you take your pet for treatment.

If you or someone else has accidentally ingested this medication call the National Capital Poison Center at 800.222.1222.


Different strengths or dosage forms of isoxsuprine may have different storage requirements. Read the label or ask your pharmacist for the storage requirements of the prescription you receive.
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