Medroxyprogesterone Acetate

What is medroxyprogesterone acetate?

Medroxyprogesterone acetate (brand names: Provera®, Meprogest®, Proclim®) is a progestin hormone used to treat sexually driven behavior problems in cats, such as male-male aggression, spraying, roaming, and mounting.

In dogs, it has been used for many conditions, including certain dwarfisms, skin conditions, reproductive conditions, and behaviors. In horses, it has been used for many conditions such as reproductive conditions and behaviors.

Its use in cats, dogs, and horses to treat reproductive, behavioral, and other conditions is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is medroxyprogesterone acetate given?

• Medroxyprogesterone acetate is given by mouth, in the form of a tablet. It can also be given as an injection in the hospital.
• Give the tablet form with or without food; however, if stomach upset occurs when dosed on an empty stomach, give future doses with food.

This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly, so laboratory tests may be needed to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Medroxyprogesterone acetate may cause the following side effects:

• Increased appetite
• Increased thirst
• Weight gain
• Sleepiness
• Changes in personality

Serious adverse reactions may occur. If any of the following signs develop, stop giving medroxyprogesterone acetate and contact your veterinarian immediately:

• Changes to mammary tissue
• Diabetes (increased drinking and/or urination)
• Decreased thyroid hormone levels (poor haircoat, weight gain)
• Uterine infection (lethargy, decreased appetite, increased drinking and/or urination, vulvar discharge)

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.  

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This long-acting medication lasts for at least 4 to 6 weeks, and may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

DO NOT USE medroxyprogesterone acetate in:

• Pets that are allergic to it
• Young pets that have not reached puberty
• Pets that are pregnant
• Pets that had a heat cycle 1–2 months earlier
• Pets with diabetes
• Pets with uterine bleeding
• Pets with a prolonged heat cycle

USE WITH CAUTION in:

• Pets that are lactating

DO NOT USE medroxyprogesterone acetate to treat false pregnancy.

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with medroxyprogesterone acetate, including:

• Corticosteroids
• Cyclosporine
• Selegiline
• Theophylline

This medication may interact with thyroid tests. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Your veterinarian should monitor your pet’s weight, mammary tissue, blood sugar levels, and adrenal gland function before your pet starts this medication and periodically while using this medication.
• Your veterinarian may monitor your pet to be sure that the medication is working.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store medroxyprogesterone acetate?

• Store the tablets in a tight container at room temperature, between 68°F and 77°F (20°C and 25°C).
• Keep the container out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.