I guess this would depend on (1) the extent to which unnecessary sympathy effects my daily life and (2) how the consideration of hypothetical events would effect the evolution of my moral system with respect to this new constraint.

The former is negligible to me, but the latter seems potentially dangerous. I don't know exactly how not being a psychopath effects my reasoning, so I don't think I would be comfortable taking the pill. Maybe if I could backup my mind...