They are the drugs of choice because they have the highest benefit and the lowest risk as sleep-promoting drugs. Hypnotics differ by half-life as well as chemical structure. Half-life refers to how long a drug is active in the body. Drugs that have a shorter half-life are effective in the body for a shorter time. Shorter half-lives are usually preferred so that daytime functioning is not impaired the next day or after waking.
Hypnotics also differ in the dose range over which they are effective.
Scientists have established the effective dose range for each hypnotic. Dose becomes a problem when higher doses than those established as effective are used. Use of high doses increases the risk of rebound insomnia . Rebound insomnia occurs when a person stops taking the medication and experiences one or two nights of insomnia that is worse than they experienced before treatment. It only occurs with short half-life hypnotics and can be avoided by gradually tapering the dose.