Diethylstilbesterol

What is diethylstilbestrol?

Diethylstilbestrol (DES; brand names: Apstil®, Boestrol®, Destibenol®, Distibene®, Honvol®, Stilbestrol®) 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 (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 diethylstilbestrol given?

• Diethylstilbestrol is given by mouth in the form of a tablet, a compounded liquid, or a chewable tablet.
• Measure liquid forms carefully.
• Diethylstilbestrol may be given with or without food.
• If vomiting occurs when dosed on an empty stomach, give future doses with food.

Diethylstilbestrol is considered a hazardous drug, so it is essential avoid accidental exposure. Wear gloves when handling the medication and do not handle it if you are pregnant or nursing. If it is necessary, wear gloves and wash your hands immediately after administration. If your pet vomits after giving this drug, wear gloves while cleaning up.

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 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?

Diethylstilbestrol may cause the following side effects:

• Mild vaginal spotting (uncommon if used at the appropriate lowest effective dose)

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

• Weakness
• Fever
• Bleeding, bruising
• Bloody diarrhea
• Infection
• Uterine infection that causes vaginal discharge
• Vomiting, lack of appetite
• Excessive water consumption or urination
• Lethargy
• Mammary tumor development
• Vomiting, diarrhea, lack of appetite (in cats)
• Breathing difficulty (in cats)
• Severe tiredness (in cats)

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. 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?

DO NOT USE diethylstilbestrol in:

• Pets that are allergic to it
• Pets with anemia or low white blood cell counts
• Female pets with estrogen-sensitive tumors
• Pets that are pregnant or lactating (unless medically essential)
• Animals intended to be used for food

USE WITH EXTREME CAUTION in:

• Cats

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with diethylstilbestrol:

• Azole antifungals
• Corticosteroids
• Clarithromycin
• Phenobarbital
• Tricyclic antidepressants

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 may perform complete blood cell counts, including platelet counts and liver function tests, before starting the medication and monthly, if using long-term.
• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• 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 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. Be prepared to provide information about the product and your pet's weight and symptoms.