Overview of Megestrol Acetate for Dogs and Cats

Megestrol acetate belongs to a class of drugs known as progestins. Megestrol Acetate, also known as Ovaban® and Megace®,  is used in dogs and in cats to control heat cycles. Megestrol has also been used to treat behavior and skin conditions in cats. 

Megestrol acetate is similar to the naturally occurring hormone progesterone.

Megestrol acetate demonstrates anti-estrogen properties and has some steroidal effects.

Megestrol acetate affects the function of the adrenal glands through its steroid effects.

Megestrol acetate is used in humans patients as a palliative treatment for some breast and uterine cancers. In animals, it is used to treat dogs with certain reproductive problems. An extra-label use is treatment of behavioral/skin problems in cats.

Megestrol acetate is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.

Brand Names and Other Names of Megestrol Acetate

This drug is registered for use in humans and animals.

Human formulations: Megace® (Bristol-Myers) and various generic preparations

Veterinary formulations: Ovaban® (Schering)

Uses of Megestrol Acetate for Dogs and Cats

Megestrol acetate is used in dogs and in cats to control heat cycles (estrus) and in bitches to treat false pregnancy.

Extra-label uses of megestrol acetate include treatment of certain behavioral and skin problems in cats.

Megestrol can be used to treat benign prostatic hypertrophy in male dogs. 

Precautions and Side Effects

While generally safe and effective when prescribed by a veterinarian, megestrol acetate causes side effects in some animals.

Megestrol acetate should not be used in animals with known hypersensitivity or allergy to the drug.

Megestrol acetate should be avoided in pregnant animals.

Megestrol acetate should also be avoided in animals with uterine disease, diabetes or breast cancer.

Megestrol acetate may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with megestrol acetate. Such drugs include certain antibiotics and steroids.

Repeated use of megestrol to control heat cycles (estrus) in dogs and cats (instead of spaying), increases the risk for future reproductive problems such as infections of the uterus.

Care must be taken to monitor patients, especially cats, receiving megestrol acetate. Due to profound effects on the adrenal gland, insufficiency of the adrenal gland (creating Addison’s disease -like syndrome) may occur after a few weeks of administering the drug.

Adverse effects include lethargy, vomiting, and diarrhea (also associated with Addison-like syndrome)

Some cats may develop transient diabetes mellitus after administration of the drug.

A few reports have linked megestrol acetate treatment to liver disease in cats.

Because of these adverse effects, extra-label use of megestrol in cats has decreased in recent years.

How Megestrol Acetate Is Supplied

Megestrol acetate is available as 5 mg, 20 mg and 40 mg tablets.

Dosing Information of Megestrol Acetate for Dogs and Cats

Medication should never be administered without first consulting your veterinarian.

The dose of megestrol depends on the purpose for its use.

In dogs to control heat cycles (estrus) or to treat false pregnancy, Megestrol is dosed at  0.25 mg per pound (0.5 mg/kg) once daily for eight days is recommended.

In cats to suppress heat cycles (estrus), Megestrol is dosed at 5 mg per cat per day is recommended.

In cats for various skin and behavioral concerns, a dose range of between 2.5 and 5 mg per cat per day is recommended.

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 pet appears to be feeling better, the entire treatment plan should be completed to prevent relapse.