Diethylstilbestrol for Female Dogs: Uses, Side Effects, and Safe Use for Urinary Incontinence

By Dr Duncan Houston

Introduction

Urinary incontinence in spayed female dogs is common, frustrating, and often upsetting for owners. Many dogs are otherwise bright and healthy but start leaking urine while sleeping, resting, or lying down, especially as they get older.

Diethylstilbestrol, usually shortened to DES, is one of the medications used to help manage this problem. It can be very effective in the right dog, but it is a drug that needs to be used carefully, at the lowest effective dose, and with the right case selection.

If your dog has been prescribed DES, the key questions are:

• What is it actually treating?

• How is it used safely?

• What side effects matter most?

Quick Answer

Diethylstilbestrol, or DES, is a synthetic estrogen used mainly to treat sphincter mechanism incontinence in spayed female dogs. It is often effective at low doses and may only need to be given every few days once control is achieved, but it must be used carefully because higher doses or inappropriate use can cause serious side effects, including bone marrow suppression.

What Is DES?

DES is a synthetic estrogen. In veterinary medicine, its main use today is to improve urethral sphincter tone in incontinent female dogs, especially spayed dogs with hormone-responsive leakage.

This is not the same as treating a urinary tract infection, bladder stones, spinal disease, or a behavioral house-soiling problem. DES is specifically used when the issue is weak urethral closure pressure.

Clinical insight:
The classic history is a spayed female dog that leaks urine when relaxed or asleep, not a dog that is deliberately urinating in the house.

What Is DES Used For?

The main use of DES is sphincter tone urinary incontinence in female dogs. It is most commonly used in spayed dogs.

Other uses have existed historically, but in practice, urinary incontinence is the reason most dogs receive it now. The source material also notes occasional use for estrus induction or prostate-related conditions, but those are not its main everyday role.

How Does DES Help Incontinence?

DES helps increase urethral sphincter tone. In simple terms, it helps the outlet of the bladder stay closed more effectively.

That is why it is useful in dogs with hormone-responsive incontinence after spaying. The goal is not to change urine production. The goal is to improve urine retention between trips outside.

What matters most:
If the dog is leaking because of a urinary infection, bladder inflammation, neurologic disease, or a structural problem, DES may not solve the problem. Diagnosis still matters.

How Is DES Given?

DES is typically started with an initial induction phase, often daily for about one week. Once continence improves, the dose is reduced to the lowest effective frequency, which may be every few days in some dogs.

This step-down approach matters because the aim is always:

• lowest effective dose

• lowest effective frequency

• long-term control with minimal risk

If leakage returns during maintenance, the plan may need adjusting under veterinary guidance.

Severity Framework: When Is DES a Good Fit?

Mild

• occasional leaking during sleep

• otherwise bright and well

• no straining, no pain, no increased urination

This is a classic situation where DES may help.

Moderate

• frequent urine leakage

• repeated bedding accidents

• skin irritation around the vulva or hind end

These dogs often benefit from treatment, but still need proper rule-outs first.

Severe or complicated

• constant dribbling

• recurrent urinary tract infections

• straining to urinate

• blood in the urine

• neurologic weakness

• marked thirst or increased urination

These cases need a fuller workup before assuming simple sphincter incontinence.

Poor candidate or caution case

• pregnancy

• nursing

• estrogen-responsive tumors

• cats

• cases with no improvement after an initial treatment period

These are situations where DES may be unsafe or inappropriate.

When Should DES Not Be Used?

DES should not be used in:

• pregnant dogs

• nursing dogs

• dogs with mammary tumors or other estrogen-responsive tumors

• cats

The source material specifically notes that DES is not safe for use in cats and should be avoided in dogs with estrogen-responsive cancer concerns.

Clinical insight:
If a dog has urine leakage plus other concerning signs like blood, straining, pain, or increased thirst, do not assume it is a DES-type case until other causes are ruled out.

Side Effects of DES

At the low doses used for canine incontinence, side effects are uncommon. That is one reason DES remains useful. But uncommon does not mean impossible.

Important side effects

• bone marrow suppression

• lethargy

• reduced appetite

• unusual behavior changes

• abnormal estrus-like effects in some cases

The most serious concern is bone marrow suppression, which can reduce red cells, white cells, or platelets. This is rare at incontinence doses, but it is the side effect that gives this drug its reputation and why careful dosing matters.

Decision checkpoint:
A dog that becomes unusually quiet, weak, off food, or unwell while on DES should not just be observed casually. That needs reassessment.

What If DES Does Not Work?

If a dog does not improve after the initial treatment period, that matters. The source text specifically notes that if incontinence does not improve after one week, DES should not simply be continued blindly.

That can mean:

• the diagnosis is wrong

• the dose or frequency needs rethinking

• another medication may be more appropriate

• combination therapy may be needed

Phenylpropanolamine is one of the better-known alternatives or add-on options in some dogs, and the source material notes that some cases respond best to a DES plus phenylpropanolamine combination.

Drug Interactions to Know About

DES can interact with several medications.

Examples listed in the source text include:

• phenylpropanolamine

• phenobarbital

• phenylbutazone

• rifampin

• corticosteroids such as prednisone or dexamethasone

• anticoagulants

• antifungals such as ketoconazole or itraconazole

These interactions may:

• reduce DES effectiveness

• increase estrogen effects

• increase side effect risk

• alter clotting-related risk

What matters most:
If a dog is on long-term medication for seizures, inflammation, fungal disease, or clotting issues, DES should not be treated as a simple add-on without review.

When Is This an Emergency?

Seek veterinary care promptly if your dog develops:

• marked lethargy

• weakness

• loss of appetite

• pale gums

• bruising or unusual bleeding

• sudden worsening in overall health

These signs may suggest a more serious adverse effect such as bone marrow suppression.

Also seek prompt care if leaking is accompanied by:

• straining

• pain

• blood in the urine

• fever

• major change in thirst or urination

That pattern suggests the problem may be bigger than simple sphincter incontinence.

What Should You Do Next?

If your dog has been prescribed DES:

1. give it exactly as directed

2. follow the induction and maintenance plan carefully

3. use the lowest effective frequency once continence is controlled

4. monitor for appetite, energy, and any unusual changes

5. contact your vet if leakage does not improve or returns quickly

Key point:
The goal with DES is not daily forever by default. The goal is the minimum effective schedule.

Common Mistakes Owners Make

• assuming all urine leakage is simple spay incontinence

• continuing treatment without reassessment if it is not helping

• overlooking blood, pain, or straining

• forgetting that DES is not safe in all patients

• using more often than needed once control is achieved

• missing subtle illness signs that could suggest a side effect

Can DES Cure Incontinence?

DES does not cure the underlying tissue tendency permanently. It manages the problem.

Many dogs do very well on it, sometimes with infrequent maintenance dosing. But if the medication is stopped, leakage may return.

The goal is:

• control

• comfort

• cleaner sleep and bedding

• better quality of life

Will My Dog Improve on DES?

Many spayed female dogs with true sphincter mechanism incontinence improve significantly on DES.

You may notice:

• less leaking during sleep

• drier bedding

• fewer urine accidents

• reduced skin irritation from urine scald

If there is no improvement, that is useful information too. It means the diagnosis or plan may need revisiting.

FAQs

What is DES mainly used for in dogs?
It is mainly used for urinary incontinence in spayed female dogs.

Does DES have to be given every day forever?
Not always. It is often started daily, then reduced to the lowest effective frequency, sometimes every few days.

Is DES safe in cats?
No. The source material states that DES is not safe for cats.

What is the most serious side effect?
Bone marrow suppression is the most important serious concern.

Can DES be combined with phenylpropanolamine?
Yes, in some cases the combination may be more effective than either drug alone.

Final Thoughts

DES remains a useful medication for urinary incontinence in spayed female dogs, especially when used carefully and at low doses. It can make a real difference for dogs leaking during sleep and for owners constantly washing bedding and managing urine scald.

But it is still a hormone drug, and it needs respect. The right diagnosis matters, the lowest effective dose matters, and side effects, while uncommon, still matter. Used properly, it can be a very effective long-term management tool.

If you are unsure whether your dog’s leaking is likely to be hormone-responsive incontinence, whether their medication is working properly, or whether another cause needs ruling out, ASK A VET™ can help you track patterns and decide when reassessment is needed.