I've been on Plavix, and am now on Coumadin, as is my best friend. Plavix (they also had me nifepidine to help relax the arteries after the surgery to remove the clot i developed in the left brachial artery in my arm) totally killed my energy levels, and the calcium channel blocker was like a governor on my motor, I just could not go hard at all. Once I was switched to Coumadin my energy levels returned, but I do notice I don't recover from hard efforts as well, and I am colder than I used to be.
Is your brother on a true anti-coagulant or an anti-platelet like Plavix?