Protamine Sulfate

ED / ICU / Transport

• Unfractionated heparin (UFH) overdose or excess effect with bleeding: The labeled indication, heparin overdosage. See heparin
• UFH overdose or high aPTT without bleeding: usually not needed. Stop or hold the heparin instead. Its effect fades within hours, with a half-life of about 60–90 min.
• UFH-associated intracranial hemorrhage: reversal is reasonable here, per AHA/ASA 2022
• UFH before an urgent procedure or surgery: reverse when leftover heparin effect would cause bleeding
• Low-molecular-weight heparin (LMWH)-associated major bleeding: enoxaparin or dalteparin. Partial reversal only. It may be considered for ICH per AHA/ASA 2022. See enoxaparin

Other Uses

• End of cardiopulmonary bypass (CPB): routine heparin neutralization. Anesthesia and perfusion titrate it.
• Heparin rebound after cardiac surgery: guide repeat doses or a low-dose infusion with coagulation tests.
• End of vascular, catheter-based and hemodialysis procedures: reverse procedural heparin when residual effect threatens bleeding. Follow operator and institutional protocol.
• Not indicated: protamine has no effect on these drugs. Bleeding on apixaban, rivaroxaban, edoxaban, dabigatran, warfarin, fondaparinux, argatroban or bivalirudin is not a protamine case.

The label dose is 1 mg per 100 units of heparin still circulating. Give it by very slow IV injection over 10 min. Not more than 50 mg in any 10-min period. The label notes that about half the dose may be enough if given 30 min after the heparin. The time bands below come from protocol, not the label. The subcutaneous UFH and bypass rows defer to protocol, because no numeric regimen was verified.

Available Forms

• IV injection: 10 mg/mL in 5 mL (50 mg) single-dose vial, preservative-free; the vial used outside the operating room
• Large vial: 10 mg/mL in 25 mL (250 mg) single-dose vial, 5 times the drug in the 5 mL vial; intended for neutralizing large surgical heparin doses

Adult Dosing

Pediatric Dosing

For heparin units/kg regimens used to estimate the units received, see weight-based dosing.

Preparation & Administration

• Dilution: use it undiluted at 10 mg/mL. If you dilute it, use D5W or 0.9% sodium chloride, and don't store the mixture, since it has no preservative
• Push rate: very slow IV injection over 10 min; never more than 50 mg in any 10-min period
• Line: give alone; do not mix with other drugs, especially cephalosporins and penicillins
• Readiness: vasopressors, epinephrine and resuscitation equipment at the bedside before the first mL

Contraindications

• Previous intolerance to protamine
• Bleeding without prior heparin use (boxed warning): protamine has nothing to bind, and it adds its own anticoagulant effect

Precautions

• Prior protamine exposure: a previous heparin reversal or cardiac surgery can sensitize the patient through a humoral immune response. Re-exposure can bring severe reactions.
• Protamine-containing drugs: NPH insulin, protamine zinc insulin and certain beta-blockers (label). Prior exposure can cause life-threatening reactions, and large IV doses of protamine can cause fatal anaphylaxis. Severe reactions can happen even with no reaction to the subcutaneous insulin (label).
• Fish allergy or previous vasectomy: Boxed-warning risk factors (label). No link between fish allergy and protamine reactions has been established (label).
• Male infertility: Antiprotamine antibodies have been reported in the blood serum of infertile or vasectomized men. Those men may react to protamine (label).
• Severe left ventricular dysfunction or abnormal preoperative pulmonary hemodynamics: A boxed-warning risk factor (label).
• High, rapid or repeated doses: They raise the risk of reactions and can cause paradoxical bleeding

Hold / Reassess If

• Watch for a sudden fall in BP, heart rate or SpO₂, bronchospasm or rising PA pressure during the dose. Stop, and treat it as a reaction.
• If aPTT or ACT is already normal and nothing is still bleeding, give no further dose.

Common

• Sudden hypotension and bradycardia, mostly with rapid injection
• Transient flushing and warmth
• Dyspnea
• Nausea, vomiting and lassitude
• Back pain in awake patients (for example during cardiac catheterization)

Serious / Life-Threatening

Overdose & Toxicity Management

• Signs: Watch for bleeding (protamine weakly anticoagulates platelets and fibrinogen, label), bradycardia, dyspnea, flushing and severe hypotension with rapid dosing. Hypertension has also occurred.
• Rebound vs excess: Heparin effect can come back 30 min–18 hr after reversal, and that needs more protamine. Excess protamine needs none. Tell them apart with heparin titration, anti-Xa or viscoelastic testing.
• Management: no antidote; stop protamine, replace blood loss with red cells and plasma, and treat hypotension with fluids, epinephrine, dobutamine or dopamine

Clinically Significant Interactions

IV Compatibility

• Diluents: D5W or 0.9% sodium chloride if dilution is wanted
• Incompatible: Several cephalosporins and penicillins are incompatible with it. Without compatibility data, don't mix it with any drug.
• Line: give alone and flush before and after
• Check an institutional compatibility resource first.

• Pediatrics: The label says safety and effectiveness are not established. Guidelines still use the same per-100-unit ratios, with a 50 mg cap (see the Pediatric Dosing table).
• Neonates: neonatal sources don't match the child bands. Count UFH over the last 2 hr only. Enoxaparin gets 1 mg per 1 mg only within 3–4 hr of the dose. Follow the NICU protocol and hematology advice. Dose from the heparin units actually received, flushes and circuits included. After subcutaneous heparin, a prolonged infusion may be needed.
• Pregnancy: there are no animal reproduction or adequate human data, so fetal risk is unknown. Don't withhold it for life-threatening heparin-associated bleeding.
• Lactation: it is unknown whether it enters breast milk. The label advises caution. Acute reversal should not be delayed.
• Older Adults: no specific adjustment is established. Dose by heparin exposure.
• Renal Impairment: no specific adjustment is established. Protamine is cleared mainly by the kidneys. Enoxaparin builds up in renal failure, so a dose given more than 12 hr ago may still need reversal. Guide it by aPTT or anti-Xa.
• Hepatic Impairment: no specific adjustment is established.
• Obesity / Dosing Weight: not weight-based. The dose follows the heparin units or LMWH mg given, and those doses were often weight-based.
• Diabetes on Protamine-Containing Insulin: exposure is a label risk factor for anaphylaxis with large IV doses. Give slowly, with resuscitation ready (label).

• Scope: This is not a standard EMS drug. RN and critical-care transport (RN/CCT) teams may give it under medical direction, or receive patients after reversal. Scope varies by state and agency protocol.
• Storage & Stability: Store at 20–25°C (68–77°F). Don't freeze it. Discard any diluted solution, since it has no preservative. Keep it out of vehicle heat and cold extremes.
• Carried Concentration: both vials are 10 mg/mL. The 25 mL (250 mg) vial holds 5 times the drug in the 5 mL (50 mg) vial. Draw only the calculated mg.
• Infusions in Transport: give it over 10 min, with continuous ECG and SpO₂ and frequent NIBP. Have epinephrine and a vasopressor ready before you start.
• Altitude / Environment: altitude has no specific effect. Noise and motion hide early wheeze and distress, so watch the monitor.
• Handoff Essentials: record the anticoagulant, dose and time. Record protamine mg (each dose and the total), time and rate. The patient is now protamine-exposed, a label risk factor for reactions to later doses. Include aPTT, ACT or anti-Xa before and after, any reaction, and NPH insulin or prior protamine exposure. Plan a repeat aPTT at 2–4 hr after LMWH reversal.

Mechanism of Action

• Protamine is an arginine-rich, strongly cationic protein from salmon sperm. It binds strongly anionic heparin and forms a stable, inactive salt. The anticoagulant activity of both is lost.
• Long UFH chains bind fully, so reversal is complete. Shorter LMWH chains with less sulfate bind only partly. Anti-IIa is reversed, but anti-Xa only partly.
• Fondaparinux is too small to bind, so it is not reversed.
• Free protamine is a weak anticoagulant, acting on platelets and fibrinogen among other proteins. Excess dosing causes bleeding (label).
• Complement activation by heparin–protamine complexes, and prostaglandin and thromboxane generation, are linked to anaphylactoid reactions (label, Adverse Reactions).

Pharmacokinetics

• Half-life: about 5–7 min
• Metabolism: the fate of the heparin–protamine complex is not fully known. It may be partly broken down (fibrinolysin), freeing heparin.
• Elimination: predominantly renal
• Distribution: volume of distribution about 12 L

Generic Name

Protamine sulfate (Protamine Sulfate Injection, USP)

Brand Names

No US brand name; generic 10 mg/mL injection

Pharmacologic Class

Cationic protein; heparin antagonist

Therapeutic Class

Anticoagulant reversal agent (antidote)

Controlled Substance

Not controlled

ISMP High-Alert

No (the heparins it reverses are high-alert)

Look-Alike / Sound-Alike

protamine / Protonix (pantoprazole)