Heparin

Heparin is an anticoagulant that potentiates antithrombin to prevent new clot formation, used when rapid effect is needed. Monitor aPTT for IV therapy, and keep protamine sulfate available as the antidote; give subcutaneous doses in the abdomen without aspirating or massaging the site. Watch for heparin-induced thrombocytopenia, signaled by a falling platelet count, which requires stopping the drug.