By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Not commercially available but usually compounded into 1 mg capsules
Estrogens are potent female hormones produced naturally by the ovary and needed for the normal development of the female reproductive tract as well as for normal female fertility. In the past, synthetic estrogens have had assorted medical and industrial uses. In the 1960s, researchers found that sphincter-related incontinence in post-menopausal women was alleviated with the administration of estrogens. Soon, the sphincter incontinence that is common in spayed female dogs was also being treated with diethylstilbestrol (DES) with good success.
Decades ago DES was used commercially as a growth promoting agent in livestock, as a human medication to help maintain pregnancy, and decades ago in the treatment of prostate cancer in humans but was removed from these uses due to human carcinogenicity issues. As the uses of DES dwindled to a few veterinary uses, its manufacturer found it unprofitable to continue production and DES went off the market in the late 1990s. Fortunately for the numerous incontinent female dogs hoping to lead indoor lives, the human carcinogenicity issues have not crossed over into the canine health arena. The low doses and infrequent dosing schedule has positioned DES as a medication of unparalleled safety and convenience in the treatment of canine incontinence. Compounding pharmacies now make this medication readily available to patients who need it on a prescription basis.
How this Medication is Used
As mentioned, DES has only one primary use: the treatment of sphincter tone incontinence in female dogs. DES is used at extremely low doses, thus avoiding any toxicity issues that have been a problem for estrogen-derivative medications.
For control of incontinence, DES capsules are given daily for one week. If the incontinence is not controlled after that time, then it will not help to raise the dose; DES will not be effective for this patient. If the incontinence is successfully controlled after this time period, the medication is discontinued and the patient is observed for the return of incontinence. This interval will determine the medication administration interval (for example, if the patient begins leaking in 4 days, then the medication is given every 3 days. If the patient is leaking after 5 days then the medication is given every 4 days.) In this way, the least amount of medication necessary can be given.
DES can be used to induce abortion (a morning after pill) in dogs but it is not as reliable as other abortion methods.
DES is also sometimes used to treat some forms of prostate disease and to induce estrus.
No side effects are expected at the doses of DES used to treat urinary incontinence. At higher doses, estrogens such as DES can be suppressive to the bone marrow leading to dangerous drops in red cell count, white cell count, and/or platelet count.
Interactions with other Drugs
Some more refractory cases of urinary incontinence may require the use of DES in combination with phenylpropanolamine, another medication used in the treatment of incontinence. These two medications together may succeed when either may have failed alone.
DES may not work as well with phenobarbital, phenylbutazone (an NSAID), or rifampin (an antibiotic). These medications all act by inducing the liver's enzyme systems used in ridding the body of drugs.
DES enhances the activity of corticosteroids such as prednisone and dexamethasone.
Anticoagulants may not work as well in the presence of DES.
Concurrent use of DES with antifungal medications (such as ketoconazole, itraconazole, and fluconazole) can increase estrogen levels as can concurrent use of DES with the antacid cimetidine.
Concerns and Cautions
Because of its ability to induce abortion, DES should not be used in pregnant pets and should not be handled by pregnant women.
DES should not be used in females with mammary tumors or other estrogen-responsive tumors.
DES is not safe for use in cats.
If a dose is accidentally skipped, incontinence may resume. Give the skipped pill when you remember to give it. If incontinence remains a problem, contact your veterinarian.
Store medication at room temperature protected from light.
It is our policy not to give dosing information over the Internet.