First Aid is sufficient. Of the 20 or so pharm questions I had, I can think of only two questions I had absolutely no idea about -- and would spending hours and hours with other pharm texts would have given me the knowledge to answer those questions? Probably not. (i.e. they were really obscure drug-drug interaction questions, and I'm hoping they were experimental!)
I think your time would be better off spent studying any weak points in physiology or microbiology you may have.
A friend of mine took the boards last week and reported that High Yield Biochem (Lippincott) is pretty good. THe main things discussed are rate-limiting steps and what would result if you lost the cofactor for a certain reaction.