Anticoagulant and Antiplatelet Reversal

Find the drug, read across to the reversal. Each row is one anticoagulant or antiplatelet group, and doses are the labeled ones. Follow local protocols and medical direction.

1. Confirm the drug, dose and time of the last dose. Use the patient, family, pill bottles or the medication list. Note the weight in kg.
2. Reverse for life-threatening or uncontrolled bleeding, not for a stable minor bleed. The reversal labels use this indication wording.
3. Start hemorrhage control and resuscitation at the same time. Reversal does not replace them.
4. Re-check the clotting tests after reversal, for example PT/INR or aPTT, and watch for rebound bleeding or re-thrombosis.

Warfarin: 4F-PCC dose by pre-treatment INR

Kcentra labeling. Dose by body weight, up to 100 kg. Use the potency printed on the vial. It varies by lot. Balfaxar is the other FDA-approved 4F-PCC for warfarin reversal, and it has its own labeled dosing. Do not apply this table to it.

Take an INR of 5.0 (range 4–6) in an 80 kg patient. That is 35 units/kg × 80 kg = 2,800 units. Then read the vial potency before you draw up.

Take a heparin infusion at 1,000 units/hr for 2 hours. That is about 2,000 units, so give 20 mg. Stop the infusion first. Cap each dose at 50 mg.

Take 80 mg of enoxaparin given 3 hours earlier. The rule says 80 mg of protamine. The cap holds it at 50 mg per dose.

• Pediatrics: The Kcentra label says pediatric safety and efficacy have not been studied. The Kcentra table does not cover children. Pediatric reversal doses are set by a specialist. Neonatal vitamin K (Hospira label): 0.5–1 mg within one hour of birth for prophylaxis; 1 mg subcutaneously or intramuscularly for treatment; benzyl alcohol-free products are preferred in neonates.
• Pregnancy: Both the Kcentra and protamine labels say the data are lacking. Give the drug only if it is clearly needed. Warfarin and DOAC bleeding in pregnancy needs obstetric and hematology input.
• Renal Impairment: The labels used here state no specific dose change for reversal. Recheck the clotting tests. When clearance is reduced, expect the anticoagulant effect to last longer.
• Older Adults: No specific adjustment is established. Age raises the risk of both bleeding and thrombosis after reversal.

• Error: Ordering andexanet alfa in the US. AstraZeneca ended US commercial sales on December 22, 2025. FDA had concluded that its risks outweighed its benefits. In ANNEXA-I, FDA reported thrombosis in 14.6% vs 6.9% of patients on usual care. Thrombosis-related deaths at day 30 were 2.5% vs 0.9%. Use 4F-PCC per local protocol. Do not follow older andexanet dosing as current US practice.
• Error: Forgetting the thrombotic risk. The Kcentra boxed warning covers arterial and venous thromboembolic complications. Weigh the bleed against the clot risk. Restart anticoagulation as soon as it is safe. Kcentra is contraindicated with known anaphylactic or severe systemic reactions to Kcentra or its components, including heparin. It is also contraindicated in disseminated intravascular coagulation and in known heparin-induced thrombocytopenia.
• Error: Protamine overdose or fast push. Excess protamine causes bleeding. Give it slowly, over 10 minutes, and cap each dose at 50 mg. Severe hypotension, anaphylaxis and pulmonary reactions are labeled risks. Fish allergy, prior protamine or NPH insulin exposure, and severe left ventricular dysfunction all raise the risk.
• Error: Fast or IM vitamin K. The label boxes fatal hypersensitivity with IV or IM use. The label prefers subcutaneous use whenever possible. If IV use is unavoidable, IV must not exceed 1 mg/min. For an urgent or life-threatening warfarin bleed, give vitamin K by slow IV infusion, no faster than 1 mg/min, and watch for anaphylaxis. Do not give it IM. Subcutaneous absorption is slower and less predictable. So the subcutaneous preference is for non-urgent INR correction, not for an active major bleed.
• Error: Using vitamin K alone for an urgent bleed. Vitamin K acts in hours. On its own it is too slow. Give 4F-PCC for the acute effect. Add vitamin K to keep that effect from wearing off.
• Error: Dosing PCC by vial strength. Kcentra vial potency changes by lot: 400–620 units for the 500-unit kit. Dose from the potency printed on the carton.
• Error: Transfusing platelets for an antiplatelet bleed. In the PATCH trial, platelet transfusion was associated with higher odds of death or dependence at 3 months than standard care (adjusted OR 2.05). In-hospital deaths: 24% with transfusion vs 17% with standard care. Do not give it routinely.

• EMS: Many services stock protamine and vitamin K. 4F-PCC and idarucizumab are usually hospital-only. Whether your crew may give any reversal agent varies by state and agency protocol.
• Transport: Kcentra is reconstituted from its kit. It is infused at 0.12 mL/kg/min, up to 8.4 mL/min (label). Protamine goes in over 10 minutes. Have resuscitation equipment ready.
• Handoff: Name the drug and dose, the time of the last dose, weight, INR or aPTT, the agent and dose given, and the time it was started.