Pradaxa and Xarelto are blood thinners and alternatives to warfarin that cause concerns for heart doctors.   
Pradaxa is a product of Boehringer Ingelheim and Xarelto is a product of Bayer and Johnson & Johnson. The risks from these drugs are similar to their predecessor, warfarin.

Warfarin, marketed since the 1950s, has known risks, like severe bleeding, that have been deterrents for patients. The new drugs, especially Pradaxa, have high risks, but the average patient is not familiar with the risks.
For instance, Pradaxa does not always mix well with other medications, and people issued a Pradaxa prescription need to have proper kidney function. With poor kidney function, the drug’s concentration level in the bloodstream can become dangerously high.
FiercePharma reports that the FDA reported over 500 deaths related to Pradaxa, while only 72 deaths were connected to warfarin. Though there haven’t been a distinct number of fatalities related to Xarelto, there are similar concerns with the new drug, which was approved last November.
Pradaxa and Xarelto do not require blood monitoring as warfarin does, so there is greater risk of stroke, blood clots and severe bleeding.
In addition to this difference, there is no antidote for Pradaxa and Xarelto, as there is for warfarin. This increases a patient’s risk – especially in those with weak kidney function.
If doctors test kidney function prior to writing prescriptions, problems can be avoided. Doctors need to be careful when prescribing these blood thinners, because the majority of problems related to Pradaxa are due to improper use.