Rilmazafone

Rilmazafone (リスミー, Rhythmy, previously known as 450191-S) is a water-soluble prodrug developed by Shionogi. Inside the human body, rilmazafone is converted into several benzodiazepine metabolites that have sedative and hypnotic effects.

Rilmazafone is not a benzodiazepine, since there is no benzene ring fused with a diazepine ring in the compound; in fact, the parent drug has no diazepine ring. It is therefore not classified as a benzodiazepine in several countries, including the United States, where it is not designated a controlled substance. Rilmazafone has no effects on benzodiazepine receptors itself, nor does it produce any psychoactive effects prior to metabolism. However, once inside the body it is metabolized by aminopeptidase enzymes in the small intestine to form the principal active benzodiazepine rilmazolam. As can be seen in the molecular diagram below, the principal metabolite contains a benzodiazepine ring structure (i.e., a benzene ring fused with a diazepine ring), unlike the parent compound (rilmazafone), which has no diazepine ring. Rilmazafone has been identified as a NPS (new psychoactive substance) in the U.S. and Europe.