What is "z-drug"

Z-drugs are a group of nonbenzodiazepine drugs with effects similar to benzodiazepines, which are used in the treatment of insomnia, and most of whose names start with the letter "Z". Some Z-drugs may have advantages over benzodiazepines. Benzodiazepines actually worsen sleep architecture, whereas the Z-drug zaleplon (Sonata) may have less or no disruption of sleep architecture.