Bleeding is the chief sign of heparin overdosage.
Neutralization of Heparin Effect
When clinical circumstances (bleeding) require reversal of the heparin effect, protamine sulfate (1% solution) by slow infusion will neutralize heparin sodium. No more than 50 mg should be administered, very slowly, in any 10-minute period. Each mg of protamine sulfate neutralizes approximately 100 USP Heparin Units. The amount of protamine required decreases over time as heparin is metabolized. Although the metabolism of heparin is complex, it may, for the purpose of choosing a protamine dose, be assumed to have a half-life of about 1/2 hour after intravenous injection.
Because fatal reactions often resembling anaphylaxis have been reported with protamine, it should be given only when resuscitation techniques and treatment of anaphylactoid shock are readily available.
For additional information consult the labeling of Protamine Sulfate Injection.
Chat online with Pfizer Medical Information regarding your inquiry on a Pfizer medicine.
*Contact Medical Information. 8AM-9PM ET Monday to Friday; excluding holidays.
Submit a medical question for Pfizer prescription products.
To report an adverse event related to the Pfizer-BioNTech COVID-19 Vaccine, and you are
not part of a clinical trial* for this product, click the link below to submit your
*If you are involved in a clinical trial for this product, adverse
events should be reported to your coordinating study site.
If you cannot use the above website, or would like to report an adverse event related
to a different Pfizer product, please call Pfizer Safety at
You may also contact the U.S. Food and Drug Administration (FDA) directly to report
adverse events or product quality concerns either online at