Halcion is used for medicating insomnia which also helps to treat trouble falling or staying asleep. The typical dosage is one tablet by mouth before bedtime. This medication helps you sleep, but it should only be used for a short period of time, typically for 7 to 10 days at a time. In addition to sleepiness, this medication can cause side effects like headaches and dizziness. Like other benzodiazepines, Halcion also has other serious risks and interactions with other medications.