ZK-93426 (ethyl-5-isopropoxy-4-methyl-beta-carboline-3-carboxylate) is a drug from the beta-carboline family.

It acts as a weak partial inverse agonist of benzodiazepine receptors,[1] meaning that it causes the opposite effects to the benzodiazepine class of drugs and has anxiogenic properties,[2] although unlike most benzodiazepine antagonists it is not a convulsant and actually has weak anticonvulsant effects.

[3] In human tests it produced alertness, restlessness and feelings of apprehension,[clarification needed] and reversed the effect of the benzodiazepine lormetazepam.

[4][5] It was also shown to produce nootropic effects[6][7] and increased release of acetylcholine.

[8][9]