synthetic pentasaccharides
Last reviewed 01/2018
- pentasaccharides are synthetic drugs that accelerate the interaction between
factor Xa and antithrombin
- induce a conformational change in antithrombin
- unlike unfractionated and low-molecular-weight heparins, pentasaccharides do not affect the interaction of antithrombin with thrombin and thus selectively inhibit factor Xa activity
- fondaparinux is a pentasaccharide with a half-life of approximately 17 hours
- idraparinux is a long-acting pentassacharide, with a half-life of about 80 hours
- induce a conformational change in antithrombin
A table comparing the properties of pentasaccarides to low molecular weight heparin is presented below:
| Property | Pentasaccarides | Low molecular weight heparin |
| monitoring requirement | no* | no* |
| bioavailability | complete | very high |
| plasma protein binding | none | low |
| renal clearance | yes | yes |
| dose-dependent clearance | no | no |
| risk of heparin-induced thrombocytopaenia | no** | low |
| safety in pregnancy | not known | yes |
| route of administration | subcutaenous | subcutaneous |
| neutralised by protamine sulphate | no | partial |
| half-life (hours) | 3-6 hours | fondaparinux 17 hours |
* monitoring is required in patients with a creatinin clearance of less than 30 ml/min by anti-Xa concentrations.
** low-molecular-weight heparins are less likely to induce thrombocytopenia than unfractionated heparin, because these interact less with platelets and platelet factor 4 (an essential feature of heparin-induced thrombocytopenia). Pentasaccharides do not interact with platelet factor 4 and platelets and thus are very unlikely to induce thrombocytopaenia (1).
Trial evidence suggest that fondaparinux is as good as, and possibly better than, low molecular-weight heparin for the prophylaxis of post-operative deep venous thrombosis in patients undergoing hip replacement (2).
Reference:
- (1) Savi P et al. Effect of fondaparinux on platelet activation in the presence of heparin-dependent antibodies: a blinded comparative multicenter study with unfractionated heparin. Blood 2005;105 (1): 139-144.
- (2) BMJ. 2006 Jan 28;332(7535):215-9.