What kind of pharmacy..

Walgreens? CVS? Right-Aide?

I don't know if you're aware of this but I've already changed things. I killed Ben Linus.
--Sayid

Drug Mart, the other ones listed, plus there are pharmacies in Target, Giant Eagle and others.

Wow. Only in America!

They state outright that it's a Right Aid in the show dialogue. Pay attention.