Carbamates

Carbamate esters of propanediols — meprobamate, tybamate, carisoprodol, and the anticonvulsant felbamate. They act at GABA-A, at a site distinct from where benzodiazepines bind, so flumazenil is not their reversal, and the sedation is barbiturate-like in character: cross-tolerant with the rest of this subject and without a comparable ceiling.

Carisoprodol is sold as a muscle relaxant and is metabolised to meprobamate, so anyone taking it is taking both, and that conversion runs through CYP2C19, which varies between people — the same tablet is a different drug in different bodies. Felbamate is the odd member, an anticonvulsant carrying aplastic anaemia and liver failure warnings rather than a sedative anyone seeks out. The class harms are additive respiratory depression, particularly alongside opioids and benzodiazepines, and a dependence and withdrawal syndrome that includes seizures.