Drug reference
protamine sulfate
Heparin antagonist · Antidote
Heparin antagonistAntidote
CDSCO approved
EXCRETION
—
not curated
INTERACTIONS
—
none in our sources
PREGNANCY
—
not curated
Mechanism
Protamine sulfate, a strongly basic protein, neutralizes heparin by binding to it. In the absence of heparin, it acts as a weak anticoagulant by interacting with platelets and fibrinogen.
Indications
Neutralization of heparin (e.g., after cardiac or vascular surgery)Treatment of heparin-induced bleedinglife-threatening or intracranial hemorrhage due to heparin or LMWH
Dosing
- Adult
- 1 mg for every 100 U of heparin (i.v.)
Side effects
Common
Flushing (rapid i.v. injection)Breathing difficulty (rapid i.v. injection)
Serious
- Histamine release
- Hypersensitivity reactions
- Hypotension (rapid i.v. injection)
- Bradycardia (rapid i.v. injection)
- Arrhythmias (rapid i.v. injection)
Related guidelines
Preoperative cardiac evaluation for non-cardiac surgery
AHA · Cardiology · 2025
GI bleeding on antiplatelet or anticoagulant therapy
CSI · Cardiology · 2020
Abnormal uterine bleeding
FOGSI · Obstetrics & Gynaecology · 2016
Cardiovascular disease prevention
ESC · Cardiology · 2021
Primary prevention of cardiovascular disease
AHA · Cardiology · 2019
Ask House about protamine sulfate
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Sources: KD Tripathi 7e, Harrison 22e·Verified: 2026-05-10 · House clinical team