The Nature of the Drug: Introduced in 2011, Xarelto (rivoraxaban) is one of the most popular blood thinners on the market. It a member of the class of drugs called Factor Xa inhibitors, which counter blood-clot formation. Xarelto is prescribed for atrial fibrillation (irregular heartbeat), deep-vein thrombosis, and pulmonary embolism (blood clots in the lung). Doctors also prescribe it to stroke victims, and to patients having hip- or knee-replacement surgery. The drug is manufactured by Bayer, and marketed in the United States by Johnson & Johnson’s subsidiary Janssen Pharmaceuticals.