Dosage	Dosage adjustment in patientswith renal impairment	Half-life	Reversibility	Monitoring	Comparisons
Unfractionated heparin*†
333 units per kg SC firstdose, followed by 250 unitsper kg SC twice daily	No adjustment	0.5 to2 hours	Protamine	Activated partial thromboplastintime or anti–factor Xa levels Unfractionated heparin can bemonitored using the activatedpartial thromboplastin time withan institution-specific goal range orwith anti–factor Xa levels, typicallyusing a goal of 0.3 to 0.7 IU per mL	Unfractionated heparin vs. LMWH Considered equally effective and safe Unfractionated heparin may be better for patients with highbleeding risk because of short half-life and reversibility Unfractionated heparin may be favorable in patients with CrCl <30 mL/min/1.73 m² LMWH has lower incidence of heparin-inducedthrombocytopenia
LMWH*
Enoxaparin (Lovenox) 1 mg per kg SC every12 hours or 1.5 mg per kgSC every 24 hours†	1 mg per kg SC every 24 hours if CrCl< 30 mL/min/1.73 m²	3 to 6 hours	NA	Anti–factor Xa levels in selectedpatients A peak level (4 hours after the doseis given) can be measured, witha goal of 0.6 to 1 unit per mL fortwice-daily enoxaparin and 1.05units per mL for dalteparin	Unfractionated heparin vs. LMWH Considered equally effective and safe Unfractionated heparin may be better for patients with highbleeding risk because of short half-life and reversibility Unfractionated heparin may be favorable in patients with CrCl <30 mL/min/1.73 m² LMWH has lower incidence of heparin-inducedthrombocytopenia
Dalteparin (Fragmin)† 200 units per kg SC oncedaily	Use with caution and monitor anti–factor Xa levels in patients with CrCl< 30 mL/min/1.73 m²	3 to 5 hours	NA
Tinzaparin (Innohep) 175 anti–factor Xa IU per kgSC once daily for ≥ 6 days	Contraindicated in persons 90 yearsand older with CrCl ≤ 60 mL/min/1.73 m² Use with caution and monitor anti–factor Xa levels in patients with CrCl< 30 mL/min/1.73 m²	3 to 4 hours	NA
Fondaparinux (Arixtra)
Weight < 111 lb (50 kg):5 mg SC daily Weight 111 to 220 lb (50 to100 kg): 7.5 mg SC daily Weight > 220 lb (100 kg):10 mg SC daily	Use with caution in patients with CrCl30 to 50 mL/min/1.73 m² Contraindicated in patients with CrCl≤ 30 mL/min/1.73 m²	18 hours	NA	Anti–factor Xa levels (only iffondaparinux is the referencestandard for the assay)	LMWH vs. fondaparinux Comparable effectiveness and safety Longer half-life for fondaparinux is advantageous (daily dosing)and potentially troublesome (adverse effects and lack ofreversibility)