Micromedex is awesome; but not cheap - though your hospital may have it as part of the ThomsonHC suite that includes a lot of things pharmacy tends to use.
Also, UpToDate has a pretty solid (though limited) patient instructions/information dbase.
Not perfect either, but if you can access JAMA you can pull their archives of "patient pages" - single sheet info pages written in layspeak. Covers a lot, but not ED specific. No copyright infringement such as with drugs.com as DMN refers to above. PDF & save on a jumpdrive.
Finally, all your d/c ought to end with something along the lines of: please follow up with your physician/referral in [time frame] as we discussed, and do not hesitate to return to the ED if your symptoms change, worsen, or if you feel you need sooner reevaluation.
Cheers!
-d
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