it seems like he was able to figure out what was drugging him, after Angela came into the dream.
He either learned how to avoid it, or learned how to stop it from effecting his brain.


very cool, i knew drugs couldn't keep him down

Drugs could never have kept Sylar down. We'd seen it in the fist season.

This time, he even said it himself, he felt like he belonged there, sedated, in a cage, because he still feels repentant for what he's done, but when Angela told him in his dream to snap out of it and go out there and fight, he just got up.