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Diethylstilbestrol (DES) 101: What You Need to Know if Your Pet is Prescribed Diethylstilbestrol

Developed in collaboration with Kelly Cairns, DVM, MS, DACVIM | Vice President of Medical Excellence and Education | Thrive Pet Healthcare

Last reviewed: 10/12/2023

What is Diethylstilbestrol (DES)?

Diethylstilbestrol (or DES) is a non-steroidal synthetic female hormone (estrogen) agent. It is commonly prescribed by veterinarians to treat estrogen-responsive urinary incontinence in spayed female dogs. It is also used in the treatment of some cancers in both male and female dogs.

Your veterinarian may prescribe Diethylstilbestrol under the brand names Apstil®, Boestrol®, Destibenol®, Distibene®, Honvol®, or Stilbestrol®. It is given orally in tablet, compounded liquid, or chewable tablet form. DES is well-absorbed from the gastrointestinal tract.

DES is FDA-approved as a human medicine but not as a veterinary medication. However, veterinarians can legally prescribe the FDA-approved drugs for off-label use. It is also compounded by a specialty pharmacy like Wedgewood Pharmacy and prescribed by veterinarians when they determine that the FDA-approved drug is not appropriate.

Key Facts
  • Diethylstilbestrol is also known as DES. It is a synthetic estrogen that is commonly used to treat urinary incontinence in spayed female dogs.
  • It is not available from a veterinary pharmaceutical manufacturer, only through a specialty compounding pharmacy, though veterinarians can prescribe it for off-label use.
  • It works by mimicking the effects of the natural female hormone, estrogen, and used as hormone replacement therapy.
  • It can produce side effects, the most serious being bone marrow suppression (aplastic anemia).
  • Compounded forms of DES that make giving it easier and dosing more accurate.

How Diethylstilbestrol Works

Diethylstilbestrol mimics the effects of the natural female hormone, estrogen. It is often used in combination with phenylpropanolamine to treat urinary incontinence. It works by improving the function of the nerves of the urinary sphincter.

The urinary sphincter is a part of a dog’s urinary tract. It is what makes a dog able to hold their bladder and not leak. Estrogen decreases after a female dog is spayed. Over time, it can result in incontinence (the inability to fully close their urinary sphincter). This is also called urethral incompetence.

Also, estrogen production declines with age. Older, non-spayed female dogs sometimes experience urinary incontinence related to lower estrogen.

They can also develop PUPD (polyuria and polydipsia) from an underlying condition. This can also result in clinical incontinence in dogs with marginal urethral sphincter competence.

Possible Side Effects of Diethylstilbestrol

The most serious side effect of diethylstilbestrol is bone marrow suppression (aplastic anemia). DES can inhibit the production of blood cells in the bone marrow, which can be fatal. This can lead to anemia (low red blood cell count), leukopenia (low white blood cell count), or thrombocytopenia (low platelet count). This can make your pet more prone to infections, fatigue, and bleeding issues.

Bone marrow suppression is more common after large or repeated doses. But it may occur after the recommended dose. If you notice that your dog is tired, or bruises easily, or bleeds easily, alert your veterinarian immediately. These may be early warning signs of serious blood disorder side effects.

Other side effects include signs of being in heat, including vaginal discharge or spotting, infection of the uterus in intact female dogs (pyometra), cystic endometrial hyperplasia and other abnormalities of the reproductive system, diarrhea, vomiting, lack of energy, increased water consumption, increased urination, and feminization of male dogs.

Side effects are more common in older pets.

Additional Precautions

  • Administer with extreme care in cases where the pet has an existing infection or bone-marrow depression.
  • DES is not usually used in cats because they are more likely to develop liver, heart, and pancreas problems.
  • It increases the risk for fetal malformations administered to pregnant or lactating females. 
  • Avoid using in males that are intended for breeding.
  • Humans should take precautions when handling this medication. Wear gloves when administering Diethylstilbestrol and when cleaning up urine, feces, or vomit. Wash your hands thoroughly afterward.
  • Pregnant women should not administer Diethylstilbestrol.

Drug Interactions

Use diethylstilbestrol with caution when giving with azole antifungals, bupropion, cimetidine, corticosteroids, erythromycin, clarithromycin, phenobarbital, phenytoin, rifampin, tricyclic antidepressants, or warfarin.

Be sure to tell your vet about any medications (including vitamins, supplements, or herbal therapies) that your pet takes.

Wedgewood Pharmacy provides medication options that help ensure accurate dosing, especially for hard to medicate pets. Click below for a complete list of Wedgewood’s dosing forms and strengths.


What To Do if You Miss a Dose

If you miss giving your pet a dose, 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 give two doses (double dose) to catch up. If you are not sure what to do, call your veterinarian and follow their directions.

What to Do in the Case of a Diethylstilbestrol Overdose

An overdose of diethylstilbestrol can cause seizures and a lower-than-normal number of red and white blood cells and platelets in the blood (pancytopenia). This can be life-threatening and requires immediate veterinarian intervention. Contact your veterinarian immediately if you suspect an overdose.

If you suspect your pet or another animal has accidentally overdosed or has eaten this medication inadvertently, immediately contact your veterinarian or the A.S.P.C.A.’s Animal Poison Control Center at 888-426-4435.

Remember to take your prescription container with you when you take your pet for treatment. If you or someone else has ingested this medication, call the National Capital Poison Center at 800-222-1222.

Cost of Diethylstilbestrol

Wedgewood Pharmacy’s diethylstilbestrol preparations start at $0.26 per dose. Your veterinarian will prescribe a specific dosage based on the pet’s weight, condition, and other factors.

Compounded medicines are prepared for the exact strength your veterinarian prescribes. The price of the medication will depend on the dosage and the medication form, with certain dosage forms and higher strengths generally being more expensive.

In addition, the cost of a medication will depend upon the price of the other active pharmaceutical ingredients and may increase the cost of the finished drug.


Looking for Diethylstilbestrol

Looking for Diethylstilbestrol?

We can let your veterinarian know that you are interested in our compounded Diethylstilbestrol.

Frequently Asked Questions

Frequently Asked Questions for Diethylstilbestrol

Are There any Risk Factors for Diethylstilbestrol?

Diethylstilbestrol should not be given to females with estrogen-sensitive tumors or to pets with anemia or low white blood cell counts. Use with extreme caution in cats. Do not give to pets that are pregnant or lactating unless the benefits outweigh the risks.

How Long Can a Dog Be on DES?

Oral DES is typically initially given daily for one week for control of incontinence. If it doesn’t improve symptoms after that time, then it will not be effective for that particular dog and a different medication is necessary.

If incontinence is successfully controlled, diethylstilbestrol is discontinued. The dog is then observed for the return of incontinence. The medication administration interval is determined by when the incontinence returns.

The medication administration interval is how often a drug is given over a period of time. That is usually one day before the return of symptoms. In other words, if the dog is incontinent after 4 days, DES will be given every 3 days. This way, the least amount of medication necessary can be given, which limits side effects, especially if it is needed long-term.

Is There Any Monitoring That Needs to Be Done with Diethylstilbestrol?

Your veterinarian will most likely monitor your pet’s complete blood count (CBC), platelet counts, and liver function monthly, especially if given long-term. You should also watch your pet at home to make sure the medication is working and for side effects.

Is DES Bad for Dogs?

There are potential toxic side effects of DES. But when used at the lowest effective dose to treat urinary incontinence, it is usually well-tolerated. You should monitor your pet for signs of bone marrow toxicity and pyometra (infected uterus).

Is There a Cure for Incontinence in Dogs?

There is no cure for urinary incontinence in spayed female dogs, but it can be successfully treated and managed with medications like diethylstilbestrol (DES).

This article is meant to provide general and not medical advice. We strongly recommend that a veterinarian be consulted for the specific medical needs of your animal.



Merch Veterinary Manual
VCA Animal Hospitals