Estriol
Oestriol
Also known as: Incurin · Oestriol
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Urethral sphincter mechanism incompetence (USMI) in spayed bitches | Starting dose: 1 mg/dog. If successful, reduce to 0.5 mg/dog. If unsuccessful, increase to 2 mg/dog. Minimum effective dose: 0.5 mg/dog. Maximum dose: 2 mg/dog. | PO | q24h (can consider q48h for maintenance once response is seen) | Long-term | 🌍 EU |
- Urethral sphincter mechanism incompetence (USMI) in spayed bitches: Alternate-day dosing can be considered once a response has been seen.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| All indications | Do not use. | PO | N/A | N/A | 🌍 EU |
- All indications: Contraindicated or not recommended for use in cats.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Estriol is a synthetic, short-acting estrogen with a high affinity for estrogen receptors in the lower urogenital tract. It is primarily used in veterinary medicine for the management of urethral sphincter mechanism incompetence (USMI) in spayed female dogs. By increasing resting urethral muscle tone, it improves urodynamic function and helps resolve urinary incontinence.
Clinical Warning: Estriol should not be used in intact bitches or animals under 1 year of age. Long-term use carries a low risk of bone marrow suppression.
Mechanism of action
Estriol binds to estrogen receptors in the lower urogenital tract → increases resting urethral muscle tone and mucosal vascularity → improves urodynamic function and urethral closure pressure.
Safety & warnings
Contraindications
- Intact bitches
- Polyuria/polydipsia (PU/PD) of unknown origin
- Animals < 1 year old
Adverse effects
- Oestrogenic effects (swollen vulva, attractiveness to males) in 5-9% of dogs at 2 mg/day
- Bone marrow suppression (rare, but possible with long-term use)
- Gastrointestinal upset (mild)
Precautions
Human Safety Warning: Pregnant or breastfeeding women should handle this medication with caution. Wash hands after administration or wear gloves.
Drug interactions
Concurrent administration may potentiate efficacy in treating urinary incontinence (synergistic effect).
Monitoring
- Clinical response (resolution of urinary incontinence)
- Complete Blood Count (CBC) periodically for long-term use to monitor for bone marrow suppression
- Signs of estrogenic side effects (vulvar swelling)
Pharmacokinetics
Half-life
Absorption
Rapidly absorbed from the gastrointestinal tract after oral administration.
Distribution
Widely distributed, with high affinity for estrogen receptors in the urogenital tract.
Metabolism
Undergoes hepatic metabolism and enterohepatic recirculation.
Elimination
Excreted primarily in the urine as conjugates.
Overdose
Overdose may lead to exaggerated estrogenic effects, including pronounced vulvar swelling, attractiveness to male dogs, and potentially an increased risk of bone marrow suppression (anemia, thrombocytopenia, leukopenia). Treatment is supportive and symptomatic; discontinue the drug until signs resolve.
Available products
Formulations
- 1 mg oral tablet
Veterinary
- Incurin 1 mg tablets
Human-labeled
- Ovestin (various strengths, creams/tablets)
Regulatory status
Approved for control of estrogen-responsive urinary incontinence in ovariohysterectomized dogs.
POM-V classification.
POM-V classification.
No regulatory data for: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature in a dry place, protected from light. Keep out of reach of children and animals.
Client information
Administer this medication exactly as directed by your veterinarian.
Important Safety Warning: Pregnant or breastfeeding women should handle this medication with caution (wear gloves or wash hands immediately after handling).
Monitor your dog for signs of 'heat' (such as a swollen vulva or being attractive to male dogs) and report these to your vet. Do not exceed the prescribed dose, as high doses can cause serious blood disorders.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.