Diethylstilbestrol (DES) is a synthetic, non-steroidal estrogen compound prescribed by veterinarians to manage specific conditions in dogs. It mimics the biological effects of naturally occurring estrogen. Understanding how DES works and the protocols surrounding its use is important for owners whose pets require this long-term medical treatment. This article explains the nature of DES, its primary application, and the necessary steps for safe administration in canine patients.
What is Diethylstilbestrol?
DES is classified as a synthetic, non-steroidal estrogen agent with potent hormonal effects. Although developed in the 1930s and historically used in human medicine, it was phased out due to safety concerns. While no longer commercially manufactured in the United States, DES remains a valuable tool in veterinary medicine. It is primarily obtained through veterinary compounding pharmacies, which create specialized formulations based on a veterinarian’s prescription, allowing for precise dosing. Due to its classification, DES is considered an extra-label drug, requiring close supervision by a licensed veterinarian.
The Primary Veterinary Application of DES
The primary reason for prescribing DES is to treat Estrogen-Responsive Urinary Incontinence (ERUI), especially in spayed female dogs. This condition often appears months or years after spaying and is linked to declining estrogen levels. The lack of natural estrogen weakens the muscles surrounding the urethra, causing involuntary urine leakage.
DES replaces the reduced estrogen, increasing the tone and responsiveness of the urethral sphincter muscle. This improved function enhances the urethra’s closure pressure, helping the dog maintain continence. Success rates for controlling leakage with estrogen therapy are generally high. Although historically used for conditions like benign prostatic hypertrophy in intact male dogs, its modern role is overwhelmingly focused on managing female canine urinary incontinence.
Safe Administration and Monitoring Protocols
DES is typically administered orally as compounded tablets or liquid. Treatment begins with a short-term, higher “loading dose,” given daily until initial control of incontinence is achieved. The veterinarian then transitions the dog to a much lower “maintenance dose.”
The goal is to find the lowest effective dose required to prevent leakage, minimizing side effects while maintaining therapeutic benefit. This minimum effective dose is often given infrequently, sometimes only once or twice a week. Strict monitoring is necessary throughout long-term treatment. Veterinarians require routine blood work, specifically a Complete Blood Count (CBC), to check for potential negative effects on the blood-producing systems. These periodic tests catch early changes in white blood cell and platelet counts, allowing for immediate adjustment of the treatment plan.
Understanding Potential Adverse Effects
Although DES is generally well-tolerated at modern, low-dose levels, owners must be aware of potential adverse effects. The most serious concern is dose-dependent bone marrow suppression, which can lead to aplastic anemia. This happens when the estrogen compound interferes with the bone marrow’s ability to produce blood cells, including red cells, white cells, and platelets.
Other side effects relate to the drug’s hormonal activity. If the dose is too high, female dogs may show signs associated with estrus, such as vaginal swelling or discharge. In unspayed females, DES increases the risk of pyometra, a severe uterine infection. Gastrointestinal upset, such as vomiting or diarrhea, is also a possible adverse reaction. Owners should watch for signs like lethargy, easy bruising, or pale gums, which signal a blood-related issue, and report them to the veterinarian immediately.