Estriol (Incurin®) for Dog Incontinence: How It Works, Risks, and What to Expect

By Dr Duncan Houston

Urinary incontinence in spayed female dogs is common, frustrating, and often misunderstood. Many owners assume it is behavioural or age related, but in most cases, it is a hormonal and sphincter control problem.

Estriol is one of the main treatments used for this condition. It can be very effective, but like all hormone therapies, it needs to be used carefully and adjusted properly over time.

Quick Answer

Estriol is a short-acting estrogen used to treat urinary incontinence in spayed female dogs. It works by improving bladder sphincter tone, helping prevent urine leakage. Most dogs respond well, but treatment requires dose adjustment, monitoring, and awareness of hormonal side effects.

Why Do Spayed Female Dogs Become Incontinent?

After spaying, estrogen levels drop.

This affects the urethral sphincter, which normally helps keep urine inside the bladder.

What happens clinically

• Reduced sphincter tone

• Leakage, often during rest or sleep

• Wet bedding or urine dribbling

Clinical insight:
This is not a training issue. It is a mechanical and hormonal problem, which is why medications like estriol can work so well.

How Does Estriol Work?

Estriol is a naturally derived estrogen.

It works by:

• Increasing urethral sphincter tone

• Improving closure pressure

• Reducing involuntary urine leakage

Why estriol is preferred

• Short acting compared to older estrogens

• Lower risk of serious complications like bone marrow suppression

Clinical insight:
Estriol is effective because it targets the underlying issue, not just the symptom.

How Is Estriol Given?

• Typically started once daily

• Dose is gradually reduced to the lowest effective level

Typical approach

1. Start with a standard daily dose

2. Assess response over 1 to 2 weeks

3. Reduce dose stepwise

4. Maintain lowest dose that controls leakage

Important limits

• Do not exceed 2 mg per day

• If ineffective at this level, reassessment is needed

Missed dose

• Give when remembered

• Do not double the next dose

Severity Framework

Mild

• Occasional leakage

• Happens during sleep

Often responds quickly to treatment.

Moderate

• Regular leakage

• Noticeable wet bedding

Requires dose adjustment and monitoring.

High

• Persistent incontinence despite treatment

• Partial response only

May need combination therapy or further diagnostics.

Critical

• No response at maximum dose

• Additional symptoms present

These cases require reassessment for underlying disease or alternative diagnoses.

Side Effects to Watch For

Common

• Reduced appetite

• Vomiting

• Increased thirst

Hormonal effects

• Vulvar swelling

• Increased attractiveness to male dogs

• Mild mammary enlargement

Rare but important

• Behavioural changes

• Persistent gastrointestinal signs

Decision checkpoint:
If side effects appear, reducing the dose often resolves them.

What If Estriol Doesn’t Work?

This is an important clinical moment.

Possible reasons include:

• Incorrect diagnosis

• Severe sphincter incompetence

• Neurological disease

• Structural abnormalities

Clinical insight:
Not all incontinence is hormone responsive. If estriol fails, you need to rethink the diagnosis, not just increase the dose.

Drug Interactions and Considerations

Use caution with:

• Other estrogen containing medications

• Thyroid medications

• Phenobarbital

• Ketoconazole

• Cyclosporine

These can alter estriol levels or increase side effects.

Special Precautions

• Not for male dogs

• Avoid in pregnant or lactating dogs

• Use caution in liver disease

• Handle carefully, especially for people sensitive to hormones

Consistency matters

• Give at the same time daily

• Monitor response closely

When Is This an Emergency?

Incontinence itself is not an emergency, but seek veterinary care if:

• Sudden change in urination pattern

• Blood in urine

• Pain when urinating

• Lethargy or systemic illness

These may indicate infection or other underlying disease, not simple incontinence.

What Should You Do Next?

If your dog has incontinence:

1. Confirm diagnosis with your vet

2. Start estriol if appropriate

3. Monitor response over 1 to 2 weeks

4. Adjust dose to lowest effective level

5. Reassess if no improvement

If your dog is already on estriol:

• Watch for side effects

• Adjust dose as needed

• Do not increase beyond recommended limits without guidance

Common Mistakes

• Assuming incontinence is behavioural

• Not adjusting the dose after improvement

• Increasing dose instead of reassessing

• Ignoring side effects

• Missing underlying causes

Can This Be Prevented?

Not always, but risk can be managed.

• Monitor for early signs after spaying

• Maintain healthy weight

• Regular veterinary checks

• Early treatment improves outcomes

FAQs

How quickly does estriol work?

Most dogs improve within 1 to 2 weeks.

Is this lifelong treatment?

Often yes, but at a reduced maintenance dose.

Can I stop once it improves?

Stopping usually leads to recurrence.

Is estriol safe long term?

Generally yes, with proper monitoring and dosing.

What if my dog is still leaking?

Further diagnostics or alternative treatments may be needed.

Final Thoughts

Estriol is one of the most effective treatments for hormone related urinary incontinence in dogs.

But success is not just about starting the medication. It is about adjusting it correctly, monitoring response, and knowing when to reassess.

If you are unsure whether your dog’s incontinence is hormone related, or you need help adjusting treatment and monitoring response, ASK A VET™ can help guide you with clear, practical support.