Lexicomp >>> Epocrates...Epocrates is pretty horrible and lacking in detail for medications but great at disease states & differential diagnosis.
Lexicomp app includes tons of other features like laboratory test interpretation info (drug test interactions, diagnostic results, etc.) and "5-minute clinical consult" which has tons of common ailments with treatment algorithm approaches.
Clinical pharmacology (online version) is the most detailed for drug info; I have not used the app for this however.