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
Safety
Uterine health (ultrasound)Vaginal discharge monitoringOphthalmic exam with prolonged use
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.
References
References
Textbooks & handbooks
- Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
- Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
- Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
- National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
- The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/
Clinical guidelines & consensus
- Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
- American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.
Journals & peer-reviewed studies
- Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
- Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
- ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control
Regulatory & approvals
- Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/
Databases
- Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
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.
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