One of the lesser known aspects of an anticoagulant drug is the reversal agent, or antidote. There are times, like an emergency surgery, where the drug in the patient's system would need to be reversed so the surgery could be performed. This is not a very common occurence, but when it happens it is memorable.
When it first came out around 2011, there was no Xarelto reversal agent. This becomes a big risk then for a Xarelto patient that has to undergo emergency surgical procedures. In 2014, Portola Pharmaceuticals began clinical testing Andexanet Alfa as a reversal drug for Xarelto and Apixaban. However, as of March 2016 Andexanet Alfa has not been approved by the US Food and Drug Administration.