I use the paid version of Epocrates, as it is a quick and easy one to use, and is especially useful for the drug interaction check. I use Up to Date as well, but much less frequently. I haven’t updated it recently, but I used to use the Sanford Guide App a lot for antibiotics. Back in the days of paper books, I would carry a Washington Manual of Medical Therapeutics, and a Harriet Lane Handbook (perds), and a Tarascon Pocket Pharmacopoeia in the pocket of my lab coat, but I no longer wear one, so don’t have room to carry any books in my scrubs. (And going back a long, long time ago, I used to make 4x6 index cards with a ring attachment with all the information I needed about most of the medications I used Most frequently).