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.

• HeparinActs 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.
• EnoxaparinActs mainly on factor Xa; protamine neutralizes only about 60% of that effect, and HIT and osteoporosis are less common than with unfractionated heparin.

• Preventing and treating deep vein thrombosis
• Pulmonary embolism
• Acute coronary syndromes (unstable angina, heart attack)
• Clots linked to atrial fibrillation
• Stopping clotting in surgery, dialysis and bypass circuits

• BleedingKnown forSerious
• Heparin-induced thrombocytopenia (HIT)Known forSerious
• Spinal or epidural hematoma after spinal proceduresSerious
• Mild fall in platelet count
• High potassium (hyperkalemia)Serious
• Osteoporosis with long-term use
• Raised liver enzymes
• Bruising or irritation at the injection site
• Allergic reactions
• Skin necrosisSerious

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Check platelet counts during treatment; if HIT is suspected, stop every heparin source and switch to a non-heparin anticoagulant.
• Spinal or epidural anesthesia or puncture: a spinal hematoma can cause lasting paralysis, so doses are timed around the procedure.
• Protamine sulfate neutralizes unfractionated heparin, but it reverses only about 60% of the anti-Xa effect of enoxaparin.
• Kidney impairment: low-molecular-weight heparins are cleared more slowly and build up, which raises the risk of bleeding.

Written for biofideX in plain words, after checking these references:

• Heparin sodium in sodium chloride injection: label (DailyMed)
• Enoxaparin sodium injection: label (DailyMed)
• Low Molecular Weight Heparin (NCI Thesaurus)
• Heparin (NCI Thesaurus)

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.