Regadenoson
"I took the Lexiscan stress test yesterday.  The hardest part of the test was lying still for 45 min.  The chemical was injected during the last 10min and I felt no real side effects.  I had a slight taste in my mouth for maybe 20 seconds and I noticed that my heart rate increased.  After a couple of minutes my heart started slowing and after the 10min period, I felt normal.  If you are scheduled for the test, stop worrying, it's not that bad.  Don't stress out from all the horror stories you read on the Internet."