Rivaroxaban (BAY 59-7939) is an oral anticoagulant invented and manufactured by Bayer;[3][4] in a number of countries it is marketed as Xarelto.[1] In the United States, it is marketed by Janssen Pharmaceutica.[5] It is the first available orally active direct factor Xa inhibitor. Rivaroxaban is well absorbed from the gut and maximum inhibition of factor Xa occurs four hours after a dose. The effects last approximately 8–12 hours, but factor Xa activity does not return to normal within 24 hours so once-daily dosing is possible.