**3.2. Fondaparinux, idraparinux, and idrabiotaparinux**

Fondaparinux is a synthetic heparin-like compound that acts as indirect factor Xa inhibitor [50]. Idraparinux and idrabiotaparinux are second and third generation pentasaccharides derived from fondaparinux.

After subcutaneous administration, fondaparinux is cleared by kidneys and has an elimination half-life of 17 h in healthy volunteers and 29 h in patients with moderate renal insufficiency, and therefore, it is contraindicated in patients with severe renal insufficiency. In this specific condition, laboratory monitoring is performed with anti-Xa assay, aPTT, and PT [50]. Fondaparinux is approved as an alternative for heparin or LMWH in the initial treatment of VTE in conjunction with a vitamin K antagonist (VKA) and, in Europe, for ACS in patients for whom PCI is not indicated [56].

Idraparinux has a longer elimination half-time of 120 h after a single administration and accumulation does occur and after more than 6 months of treatment, the elimination half-time is increased up to 60 days. It is administered once weekly and is thereby suitable for long-term anticoagulation [57]. Idrabiotaparinux was evaluated for treatment of VTE and for stroke prevention in patients with AF, resulting as safe and efficient as idraparinux [58].
