Estriol: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Incurin, Oestriol

Species with doses

Dogs

Routes

PO

Last reviewed

1 October 2026

Indications

• Urinary incontinence from urethral sphincter mechanism incompetence (USMI) in spayed bitches
• Oestrogen-responsive incontinence (alternative/adjunct to phenylpropanolamine)

Estriol dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• USMI urinary incontinence (spayed bitch): Papich 5e: start 2 mg per dog per day (may combine with phenylpropanolamine); after 1 week 1.5 mg/day for 1 week, then 1 mg/day for 1 week, then every other day, every third day and so on toward 0.5 mg once weekly. Plumb’s 10e gives a different taper (next rows). Reduce if oestrus-type signs (vulvar swelling, attractiveness to males) appear.
• Oestrogen-responsive incontinence — label regimen (Plumb’s 10e): Plumb’s 10e p.484 (label dosage; FDA-approved): initially 2 mg/dog (NOT mg/kg) PO once daily for a minimum of 14 days; after incontinence is controlled decrease to 1 mg/dog once daily, then 0.5 mg/dog once daily, then 0.5 mg/dog every other day until the lowest effective dose is found. Allow at least 7 days between adjustments. Maximum 2 mg/dog per day; re-assess the diagnosis if there is no response.
• Sphincter mechanism incompetence — 1 mg start (Plumb’s 10e): Plumb’s 10e p.485 (extra-label): initially 1 mg/dog (NOT mg/kg) PO once daily for 7–14 days. If effective, decrease to 0.5 mg/dog once daily, then try every other day — never below 0.5 mg/dog per day. If ineffective, increase to 2 mg/dog once daily (maximum); if 2 mg works, reduce to 2 mg every other day. Allow 7 days between changes.

Contraindications

Intact (entire) bitches and pregnancy (oestrogen effects). Oestrogen-dependent neoplasia. Diabetes (oestrogens can worsen control). Known hypersensitivity. Handle with care (pregnant women should avoid handling — oestrogen). Not for males (different incontinence management).

Species-specific warnings

Dogs: For spayed females only — not for entire/pregnant bitches. Watch for oestrogenic signs and monitor CBC on higher doses (oestrogen marrow effect, though low with short-acting oestriol).

Adverse effects

• Signs of oestrus / vulval swelling, attractiveness to males (dose-related — reduce dose)
• Vomiting, inappetence
• Rare bone-marrow suppression (far less than long-acting oestrogens like DES)
• Mammary/vulval changes at higher doses

Drug interactions

• Phenylpropanolamine (alpha-agonist): synergistic for USMI (oestriol increases alpha-receptor responsiveness) — sometimes combined in refractory cases
• Corticosteroids: oestrogens may potentiate effects
• Drugs affecting oestrogen metabolism: altered levels

Pregnancy and lactation

Contraindicated in pregnancy/entire bitches (oestrogen effects).

Monitoring

• Continence response and titration to the lowest effective dose
• Oestrogenic signs (vulval swelling/oestrus behaviour) — reduce dose if seen
• CBC periodically with higher/longer use (marrow surveillance)
• Confirm the bitch is spayed and not pregnant

Toxicity and overdose

At label doses, oestrogenic side effects (oestrus signs, vulval swelling) are the main issue and are dose-related (reduce dose). Unlike older long-acting oestrogens (diethylstilbestrol), short-acting oestriol carries a much LOWER risk of the dose-dependent, potentially fatal bone-marrow suppression (aplastic anaemia) — but caution and monitoring remain sensible.

Management: No specific antidote. Reduce/withhold dose; supportive care. For oestrogenic signs, lower the dose. Monitor CBC if high/prolonged exposure (marrow-suppression surveillance). Generally self-limiting at the lower doses used.

Clinical pearls

• The licensed oestrogen for spayed-bitch USMI incontinence — improves urethral tone by up-regulating alpha-receptor responsiveness; titrate to the LOWEST effective dose (often every other day)
• Short-acting oestriol is much safer than old long-acting DES (far lower marrow-suppression risk), but still watch for oestrogenic signs and monitor CBC on higher doses
• Can be combined with phenylpropanolamine in refractory incontinence (synergy)
• Reduce the dose if vulval swelling/oestrus behaviour appears; handle tablets with gloves

Mechanism of action

Estriol is a short-acting oestrogen that binds oestrogen receptors in the lower urinary tract, increasing the number/sensitivity of alpha-adrenergic receptors in urethral smooth muscle and improving urethral muscle tone, mucosal coaptation and closure pressure — restoring continence in oestrogen-responsive (USMI) incontinence. Its short duration of action gives a more favourable safety profile than long-acting oestrogens (lower marrow-suppression risk).

Formulations and products

• 1 mg tablet (Incurin)
• Incurin (MSD Animal Health) — 1 mg tablet, Tablet

Storage

Tablets: 15–30 °C, dry, protect from light; handle with gloves (pregnant women should avoid handling).

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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Frequently asked questions