Temazepam sleeping tablet and packaging. Temazepam is used to treat insomnia, the inability to sleep. It is a hypnotic drug that is only available on prescription and belongs to a group of drugs known as the benzodiazepines. It promotes sleep by enhancing the effects of the neurotransmitter gamma-aminobutyric acid (GABA), which inhibits nerves and brain activity. The drug has a short half-life (the time it takes for half the substance to be removed from an organism by a physical or chemical process) and so does not cause drowsiness the next morning.