1) Our most comprehensive source for drug information is Lexicomp Online. It contains complete drug monographs, identification, doses, mechanisms of action, interactions, adverse effects, calculators, patient education, and more.
2) StatRef has AHFS Drug Information, a comprehensive, evidence-based source of drug information complete with therapeutic guidelines and off-label uses.
3) DynaMed offers a medication information for each disease or condition, when applicable, and rates the information according to level of evidence.
5) EE+ POEM Archive (available from UCentral) has a drug section that provides best-evidence answers to drug questions. Each answer has a "level of evidence" rating and a "bottom line" summary for quick analysis. Available via desktop and fully downloadable to a mobile device.
6) Embase is a large biomedical and pharmacological literature database. It encompasses everything published in Medline (PubMed), but has content and indexing favoring drug information.