Buy Ambien online is a sedative, also called a hypnotic. Zolpidem affects chemicals in the brain that may be unbalanced in people with sleep problems insomnia). Ambien is used to treat insomnia. The immediate-release tablet is used to help you fall asleep when you first go to bed. The extended-release form, Ambien CR, has a first layer that dissolves quickly to help you fall asleep, and a second layer that dissolves slowly to help you stay asleep. Your doctor will determine which form of Ambien is best for you.