Sign of something else wrote:
Rat poison of other types is actually used as human medicine.
This. Coumadin only "thins" the blood. Perhaps he's on an agent that is increasing his viscosity, and doesn't want to die? I'm not sure why one would want thin blood otherwise...? It's a different mechanism, but aspirin also decreases clotting.
Kirwa was on strychnine, not warfarin. Strychnine acts as a stimulant in small doses.