Z-Drugs

Three unrelated skeletons — the imidazopyridine zolpidem, the cyclopyrrolones zopiclone and eszopiclone, the pyrazolopyrimidine zaleplon — that all act at the benzodiazepine site of GABA-A, with more selectivity for the receptor subtypes carrying sedation than for those carrying anxiolysis. Non-benzodiazepine describes their chemistry and not their pharmacology: cross-tolerance with the benzodiazepines is real, respiratory depression adds to other depressants the same way, and withdrawal after sustained use looks like a benzodiazepine's.

They differ mainly in duration, from zaleplon at the short end to eszopiclone at the long. Complex sleep behaviours — walking, eating, driving, holding conversations, with no memory of any of it afterwards — are documented across the class and are the reason for its strongest label warning. They are commoner when the drug is taken and the person then stays up, and when alcohol is on board.