Amongst numerous promising anticoagulant molecules, rivaroxaban (Xarelto(®)), 
dabigatran (Pradaxa(®)) and apixaban (Eliquis(®)) have been registered outside 
the USA in the prevention of thromboembolic events in patients undergoing total 
hip or knee prosthetic replacement. Rivaroxaban however has been granted 
authorisation by the FDA for the thromboprophylaxis after surgery for total hip 
or knee surgery. Dabigatran has been granted authorisation by the FDA in 
non-valvular atrial fibrillation (RE-LY trial) while rivaroxaban is expecting 
approval in this same indication (ROCKET trial). Phase III results in the 
treatment and in the secondary prevention of established venous thrombosis and 
pulmonary embolism are encouraging. These small molecules are obtained by 
chemical synthesis, their molecular weight is lower than 500 daltons. Many 
coagulation tests may be affected by these molecules. Those modifications should 
be known in order to avoid misinterpretation of the tests but could also be used 
to measure plasma concentrations of these products. The choice of a non specific 
global and readily available test has been documented (Quick time for 
rivaroxaban and aPTT for dabigatran). Anti-Xa (for rivaroxaban) and anti-IIa 
(for dabigatran) activities should however be preferred, expressed in ng/ml with 
calibrated plasmas (containing predetermined concentration of the tested drug). 
The half-life is around 8 to 12 hours, with a peak activity 2 to 4 hours after 
ingestion. Dabigatran is mainly eliminated via the kidney, hence requiring 
dose-adjustment in case of moderate renal insufficiency, and contra-indicated in 
case of severe renal insufficiency. Rivaroxaban being excreted via kidney and 
liver, some precautions should apply in case of liver insufficiency. No data are 
available in pregnancy or pediatrics, clinical trials are ongoing. There are few 
interactions with concomitant drugs, which should not be ignored. The short 
half-life of these new agents compensates for the lack of any specific antidote 
in many instances. Their oral administration, without the need for dose 
adjustment, and without requirement for a laboratory monitoring will increase 
their use in a large number of patients, in those indications for which an 
approval has been granted by health authorities.