Zolpidem Tart ER 12.5 mg tab is used to treat a certain sleep problem (insomnia). Zolpidem 12.5 ER may help you fall asleep faster, stay asleep longer, and lessen how often you wake up during the night, so you can get a better night's rest. Zolpidem belongs to a class of drugs called sedative-hypnotics. It acts on your brain to produce a calming effect.