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Protamine Sulfate

Prescription
Heparin Antagonist
Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
1 available
Interactions
1 documented
Formulations
1

Mechanism of action

Positively charged protein derived from salmon sperm that binds ionically to negatively charged heparin molecules, forming a stable heparin-protamine complex that is pharmacologically inactive, reversing heparin anticoagulation within minutes.

At a glance

Class
Heparin Antagonist
Schedule
Prescription
Storage
Refrigerate 2–8°C; stable 24h at room temperature after withdrawal from vial

Dosing

🐕

Dog

Only for reversing unfractionated heparin overdose or post-procedural hepariniza
Dose
—
Route
PO
Frequency
Single dose; may repeat 50% dose if aPTT still prolonged after 30 min
🐈

Cat

Rarely needed in clinical feline practice
Dose
—
Route
IV
Frequency
Single dose

Formulations

💊

Other — 1

Strength
—

Storage

Refrigerate 2–8°C; stable 24h at room temperature after withdrawal from vial

Safety

Monitoring parameters

aPTT or ACT before and 15 min post-administrationBlood pressure (continuous during infusion)Signs of hypersensitivity for 30 min

Interactions

Moderate — 1

Enoxaparin
moderate
Protamine only partially reverses LMWH (~60% of anti-Xa activity neutralized, vs 100% for unfractionated heparin). Incomplete reversal.
Management: Give protamine 1 mg per 100 anti-Xa units of enoxaparin. Expect only partial reversal. May need repeat dosing. Monitor anti-Xa activity.

Brands

Other markets

Protamine Sulfate Injection

FAQs

Frequently asked questions

›What is Protamine Sulfate?
Protamine Sulfate is a heparin antagonist used in pets. Positively charged protein derived from salmon sperm that binds ionically to negatively charged heparin molecules, forming a stable heparin-protamine complex that is pharmacologically inactive, reversing heparin anticoagulation within minutes.
›What is Protamine Sulfate used for in pets?
Protamine Sulfate is used in veterinary medicine for: Only for reversing unfractionated heparin overdose or post-procedural hepariniza; Rarely needed in clinical feline practice.
›What is the Protamine Sulfate dose for dogs?
For dogs, Protamine Sulfate is typically dosed as follows — Only for reversing unfractionated heparin overdose or post-procedural hepariniza: undefined undefined PO Single dose; may repeat 50% dose if aPTT still prolonged after 30 min. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Protamine Sulfate dose for cats?
For cats, Protamine Sulfate is typically dosed as follows — Rarely needed in clinical feline practice: undefined undefined IV Single dose. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›Does Protamine Sulfate need a prescription?
Yes. Protamine Sulfate 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. Find a vet near you →