i find alot of help with my med questions on crazy meds.com. from the common to the freakishly rare even the ones that the dr doesnt tell you and its in plain english not medical medical terms. it might be worth checking out.
rxlist.com and drugs.com are also very good and quite authoritative. Of the two, rxlist.com provides the most detail, but drugs.com has a medication interactions checker.
Regards, Red