Competitive antagonist/partial agonist of estrogen receptors (ERα). In estrogen-receptor-positive cancer cells, blocks estrogen-dependent growth signaling. In other tissues, may have partial agonist effects (uterus, bone).
At a glance
Class
Selective Estrogen Receptor Modulator (SERM)
Storage
Store at room temperature, protect from light and moisture
Dosing
CAUTION: Paradoxically stimulates uterine tissue in dogs (agonist effect), causi
Uterine stimulation risk applies to cats as well
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →Safety
Uterine health (ultrasound)Vaginal discharge monitoringOphthalmic exam with prolonged use
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →Interactions
No documented interactions.
FAQs
Frequently asked questions
›What is Tamoxifen?
Tamoxifen is a selective estrogen receptor modulator (serm) used in pets. Competitive antagonist/partial agonist of estrogen receptors (ERα). In estrogen-receptor-positive cancer cells, blocks estrogen-dependent growth signaling. In other tissues, may have partial agonist effects (uterus, bone).
›What is Tamoxifen used for in pets?
Tamoxifen is used in veterinary medicine for: CAUTION: Paradoxically stimulates uterine tissue in dogs (agonist effect), causi; Uterine stimulation risk applies to cats as well.
›What is the Tamoxifen dose for dogs?
For dogs, Tamoxifen is typically dosed as follows — CAUTION: Paradoxically stimulates uterine tissue in dogs (agonist effect), causi: 0.4–1 mg/kg PO q24h. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Tamoxifen dose for cats?
For cats, Tamoxifen is typically dosed as follows — Uterine stimulation risk applies to cats as well: undefined undefined PO N/A. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›Does Tamoxifen need a prescription?
Yes. Tamoxifen is a prescription medication and should only be administered under veterinary supervision.
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →References
References
The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.
Textbooks & handbooks — 5
- Plumb's Veterinary Drug Handbook
- Withrow & MacEwen's Small Animal Clinical Oncology
- Merck Veterinary Manual
- NRC Nutrient Requirements of Dogs and Cats
- Veterinary Pharmacology and Therapeutics (Riviere & Papich)
Clinical guidelines & consensus — 4
- ASPCA Animal Poison Control Center Guidelines
- AAHA Diabetes Management Guidelines
- ASPCA Poison Control Guidelines
- RECOVER CPR Guidelines
Journals & peer-reviewed studies — 2
- EPIC Study (J Vet Intern Med 2016)
- JVIM FAT CAT Study
Regulatory & approvals — 1
- CDSCO Veterinary Drug Approval Registry (1969–2026)
Databases — 1
- Washington State University VCPL MDR1 Database