Heparin
An injected anticoagulant used to prevent and treat venous clots and pulmonary embolism, and to stop clotting in surgery and dialysis.
Also called unfractionated heparin (full name) or UFH (abbreviation).
Drug card
- Class
- Heparin
- How it works
- Boosting antithrombin, which then switches off thrombin and factor Xa
- Used for
- Preventing and treating venous thrombosis
- Pulmonary embolism
- Clots linked to atrial fibrillation
- Stopping clotting in surgery, dialysis and bypass circuits
- Known for
- Bleeding
- Heparin-induced thrombocytopenia (HIT)
- Its name
- -parin means a heparin or low-molecular-weight heparin
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does heparin work?
A mix of long sulfated sugar chains that binds antithrombin and activates it. Unlike low-molecular-weight heparins, which act mainly on factor Xa, it inactivates thrombin and factor Xa about equally, along with factors IX, XI and XII. It is given only by injection and has a short, dose-dependent half-life of about 0.5 to 2 hours.
Like other heparins: Heparins bind antithrombin (heparin cofactor) and activate it. With unfractionated heparin, antithrombin then inactivates thrombin and factor Xa about equally; the shorter chains of low-molecular-weight heparins steer it mainly against factor Xa. They stop new clots forming and existing ones growing, but they do not dissolve a clot that is already there.
Uses
What is heparin used for?
- Preventing and treating venous thrombosis
- Pulmonary embolism
- Clots linked to atrial fibrillation
- Stopping clotting in surgery, dialysis and bypass circuits
Side effects
Side effects of heparin
- BleedingKnown forSerious
- Heparin-induced thrombocytopenia (HIT)Known forSerious
- Early, mild fall in platelet count
- High potassium (hyperkalemia)Serious
- Osteoporosis with long-term high doses
- Raised liver enzymes (ALT, AST)
- Allergic reactions with chills, fever and hives
- Anaphylactoid reactions, rarely shockSerious
- Irritation, bruising or ulcers at the injection site
- Skin necrosisSerious
- Delayed, temporary hair loss
- Spinal hematoma after spinal tap or anesthesiaSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Full-dose treatment is adjusted by the aPTT; check platelet count and hematocrit throughout.
- Suspected HIT: stop every heparin source, flushes included, and use a non-heparin anticoagulant.
- Bleeding or overdose: protamine sulfate neutralizes heparin.
- Contraindicated after HIT, with uncontrolled active bleeding, or with allergy to heparin or pork products.
Good to know: Acts on thrombin and factor Xa about equally, is adjusted by aPTT at full dose and is neutralized by protamine; enoxaparin acts mainly on Xa and protamine reverses it only partly.
Remember it
A way to remember it
PATHOS
- P
- Protamine reverses them (fully only for unfractionated heparin)
- A
- Antithrombin is the partner they work through
- T
- Thrombocytopenia, including HIT
- H
- Hyperkalemia
- O
- Osteoporosis with long-term use
- S
- Spinal or epidural hematoma
Written for biofideX
Its name
-parin means heparin or low-molecular-weight heparin
Covers heparin itself and low-molecular-weight heparins such as enoxaparin and dalteparin. Fondaparinux, a synthetic factor Xa inhibitor, ends in -parinux.
- Every drug name stem
Its class
Heparins
Other heparins with a card:
Easily mixed up with direct factor Xa inhibitors, direct thrombin inhibitors and vitamin K antagonists.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Heparin sodium in sodium chloride injection: label (DailyMed)
- Heparin (NCI Thesaurus)
- Enoxaparin sodium injection: label (DailyMed)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood clots and cholesterol
Heparin is one of 19 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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