By Rania Gollakner, BS, DVM, MPH

What is diethylstilbestrol?

Diethylstilbestrol (brand names: Apstil®, Boestrol®, Destibenol®, Distibene®, Honvol®, Stilbestrol®, also known as DES) is a hormonal agent and a synthetic estrogen used to treat urinary incontinence and other diseases responsive to estrogen. This medication is no longer commercially available in the United States, but may be available from compounding pharmacies.

Its use in dogs to treat urinary incontinence is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is diethylstilbestrol given?

Diethylstilbestrol is given by mouth in the form of a tablet or a compounded liquid or chewable tablet. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure liquid forms carefully. Pregnant women should NOT handle this medication; if it is necessary, wear gloves and wash hands immediately after administering.

This medication should take effect within 1 to 2 days, and improvements in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are uncommon if used at the appropriate lowest effective dose, but may include mild vaginal spotting. Serious side effects include blood cell abnormalities that lead to weakness, fever, bleeding, bruising, bloody diarrhea, or infection; uterine infection that causes vaginal discharge, vomiting, lack of appetite, excessive water consumption or urination, and/or lethargy; or mammary tumor development. In cats, serious side effects have included pancreatic, liver, and heart damage which can cause vomiting, diarrhea, lack of appetite, breathing difficulty, or severe tiredness.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Diethylstilbestrol should not be used in pets that are allergic to it, in females with estrogen-sensitive tumors, in pets with anemia or low white blood cell counts, or in animals that are intended to be used for food. It should be used with extreme caution in cats. Do not use in pets that are pregnant or lactating unless it is medically necessary.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with diethylstilbestrol: azole antifungals, bupropion, cimetidine, corticosteroids, erythromycin, clarithromycin, phenobarbital, phenytoin, rifampin, tricyclic antidepressants, or warfarin. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Complete blood cell counts including platelet counts and liver function tests may be performed prior to starting the medication and monthly if using long-term. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store diethylstilbestrol?

Store commercially produced tablets at room temperature between 59°F and 86°F (15°C and 30°C) in a tight container. For compounded medications, follow the storage directions on the label.

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.

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