Comparative properties of unfractionated heparin, low molecular weight heparins (LMWH), and fondaparinux.
| . | Unfractionated Heparin . | LMWH . | Fondaparinux . |
|---|---|---|---|
| Source | Animal | Animal | Synthetic |
| Structure | Heterogeneous | Heterogeneous | Homogeneous |
| Targets | Multiple | Multiple | Single (factor Xa) |
| Pharmacologic Effect | Activity expressed as IU (anti-Xa = anti-IIa) | Activity expressed as IU (anti-Xa > anti-IIa) | Activity expressed gravimetrically as μg or μmol |
| Administration | Intravenously or two to three times daily, subcutaneously | One to two times daily subcutaneously | Once daily subcutaneously |
| HIT Response | — | ~80% crossreactivity with heparin-induced thrombocytopenia (HIT) antibodies | No crossreactivity with HIT antibodies |
| Bioavailability | Variable | High | High |
| Half-life | Dose-dependent ~1–1.5 hours (IV) | ~4 hours | ~17 hours |
| Mode of Excretion | Reticuloendothelial, urinary | Urinary | Urinary |
| Antidote | Protamine sulfate | Protamine sulfate (partial neutralization) | None |
| . | Unfractionated Heparin . | LMWH . | Fondaparinux . |
|---|---|---|---|
| Source | Animal | Animal | Synthetic |
| Structure | Heterogeneous | Heterogeneous | Homogeneous |
| Targets | Multiple | Multiple | Single (factor Xa) |
| Pharmacologic Effect | Activity expressed as IU (anti-Xa = anti-IIa) | Activity expressed as IU (anti-Xa > anti-IIa) | Activity expressed gravimetrically as μg or μmol |
| Administration | Intravenously or two to three times daily, subcutaneously | One to two times daily subcutaneously | Once daily subcutaneously |
| HIT Response | — | ~80% crossreactivity with heparin-induced thrombocytopenia (HIT) antibodies | No crossreactivity with HIT antibodies |
| Bioavailability | Variable | High | High |
| Half-life | Dose-dependent ~1–1.5 hours (IV) | ~4 hours | ~17 hours |
| Mode of Excretion | Reticuloendothelial, urinary | Urinary | Urinary |
| Antidote | Protamine sulfate | Protamine sulfate (partial neutralization) | None |