N-Methylclonazepam (also known as Ro05-4082, ID-690 and methylclonazepam) is a benzodiazepine derivative developed in the 1970s. It has sedative and hypnotic properties, and has around the same potency as clonazepam itself. It was never introduced into clinical use. It is a structural isomer of meclonazepam (3-methylclonazepam), and similarly has been sold as a designer drug, first being identified in Sweden in 2017. In July 2025, N-methylclonazepam was identified alongside fentanyl as a component in a batch of drugs linked to a mass overdose in Baltimore, Maryland. There were at least 27 hospitalisations, and many patients remained unconscious even after administration of naloxone; a NIST research chemist said this may have been due to the sedative effects of the methylclonazepam.
See also Cloniprazepam Flunitrazepam
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