Levsin and Levbid both contain hyoscyamine, a medication that treats overactive bladder, stomach cramps, and symptoms related to Parkinson's disease. Levsin is an immediate-release tablet you'll typically take every 4 hours. Levbid, on the other hand, is an extended-release formula that you'll typically ake just twice a day. Side effects of both medications include dry mouth and feeling fuzzy-headed, but Levbid may be better tolerated because of it's formulation.