The therapeutic armamentarium of parenteral anticoagulants available to clinicians is mainly composed by unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), fondaparinux, recombinant hirudins (i.e. bivalirudin, desirudin, lepirudin) and argatroban. These drugs are effective and safe for prevention and/or treatment of thromboembolic diseases but they have some drawbacks. Among other inconveniences, UFH requires regular anticoagulant monitoring as a result of variability in the anticoagulant response and there is a risk of serious heparin-induced thrombocytopaenia (HIT). LMWH, fondaparinux and recombinant hirudins are mainly cleared through the kidneys and their use in patients with severe renal insufficiency may be problematic. LMWH is only partially neutralized by protamine while fondaparinux and recombinant hirudins have no specific antidote. Novel anticoagulants in development for parenteral administration include new indirect activated factor Xa (FXa) inhibitors (idrabiotaparinux, ultra-low-molecular-weight heparins [semuloparin, RO-14], new LMWH [M118]), direct FXa inhibitors (otamixaban), direct FIIa inhibitors (flovagatran sodium, pegmusirudin, NU172, HD1-22), direct FXIa inhibitors (BMS-262084, antisense oligonucleotides targeting FXIa, clavatadine), direct FIXa inhibitors (RB-006), FVIIIa inhibitors (TB-402), FVIIa/tissue factor inhibitors (tifacogin, NAPc2, PCI-27483, BMS-593214), FVa inhibitors (drotrecogin alpha activated, ART-123) and dual thrombin/FXa inhibitors (EP217609, tanogitran). These new compounds have the potential to complement established parenteral anticoagulants. In the present review, we discuss the pharmacology of new parenteral anticoagulants, the results of clinical studies, the newly planned or ongoing clinical trials with these compounds, and their potential advantages and drawbacks over existing therapies.
