Vetdrugs 2.0Protamine sulfate is a strongly basic protein preparation used to neutralize heparin anticoagulation. Its principal veterinary role is reversal of residual unfractionated heparin when anticoagulation is excessive or no longer desired. Its action depends on the heparin remaining in the circulation rather than a universal patient-weight-based replacement requirement.
Group
Heparin reversal agent
Mechanism of Action
Positively charged protamine binds negatively charged heparin and forms an inactive ionic complex. Neutralization reduces heparin’s ability to enhance antithrombin-mediated inhibition of coagulation enzymes. The effect is more complete for unfractionated heparin than for low-molecular-weight preparations, whose anti-factor-Xa activity may be only partly neutralized. Unbound protamine has additional effects on coagulation.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Unfractionated heparin reversal | Reference only | IV | Approximately 1 mg protamine neutralizes 80–100 units of residual unfractionated heparin. Adjust for elapsed time and route of heparin administration and measured coagulation. Administer slowly with immediate monitoring; this is not an mg/kg regimen. | |
| Alternative heparin neutralization ratio | Reference only | IV | A slow-IV alternative uses 1–1.5 mg protamine per 100 units heparin. One timing scheme halves the amount for each elapsed 30 minutes; SC heparin absorption can make this inaccurate. Do not exceed 50 mg over 10 minutes; adjust to measured coagulation. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Unfractionated heparin reversal | Reference only | IV | Approximately 1 mg protamine neutralizes 80–100 units of residual unfractionated heparin. Adjust for elapsed time and route of heparin administration and measured coagulation. Administer slowly with immediate monitoring; this is not an mg/kg regimen. | |
| Alternative heparin neutralization ratio | Reference only | IV | A slow-IV alternative uses 1–1.5 mg protamine per 100 units heparin. One timing scheme halves the amount for each elapsed 30 minutes; SC heparin absorption can make this inaccurate. Do not exceed 50 mg over 10 minutes; adjust to measured coagulation. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical bracken-fern poisoning adjunct | Reference only | IV | Once | One injection of 10 mL of 1% protamine sulfate (100 mg total) with 2.25–4.5 L whole blood was described. This is a blood-product combination, not a stand-alone treatment of marrow injury. |
Indications
- Reversal of clinically important unfractionated-heparin anticoagulation or overdose in veterinary patients.
- Neutralization of residual unfractionated heparin after selected extracorporeal or surgical procedures.
- Partial reversal of selected low-molecular-weight-heparin-associated bleeding within a specialist treatment plan.
Contraindications
- Serious protamine hypersensitivity
Interactions
- Excess protamine itself may impair coagulation.
- Low-molecular-weight heparin anti-Xa activity is not fully reversed by a simple unfractionated-heparin ratio.
Adverse effects
- Hypotension
- Bradycardia
- Severe anaphylactoid reaction
- Pulmonary vascular effects
Toxicity
Overdose may worsen bleeding. Stop administration for major hypotension or hypersensitivity and support circulation and ventilation.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Protamine sulfate injection 10 mg/mL Slow IV administration only; calculate from residual heparin and coagulation status. | Injection | 10 mg / mL | IV |
Monitoring and Administration
Estimate heparin remaining from dose, route, elapsed time and measured coagulation; do not use a universal mg/kg conversion.
A veterinary report used 1 mg protamine per 100 units heparin, given slowly IV, and documented severe shock. Use close cardiovascular and coagulation monitoring.
Do not retain diluted solutions for later use.
Observe for recurrent anticoagulation and bleeding several hours after reversal; residual SC heparin or release from the heparin–protamine complex can cause rebound. Follow blood pressure, heart rate, breathing and coagulation.
Use formulation-specific storage instructions. Described products include both ready-made injection and reconstituted powder, whose storage periods are not interchangeable.