Doctors prescribe Ambien to treat insomnia and other sleep disorders. It belongs to the class of drugs known as sedative-hypnotics, which affect brain chemicals that may be out of balance in people who have sleep problems. Even though Ambien can be purchased with a prescription, it is not recommended to buy drugs online without first consulting a healthcare provider. In order to purchase Ambien online, only reputable sites and pharmacies that require a valid prescription should be used.