meclonazepam meclonazepam meclonazepam ((s)-3-methylclonazepam) was discovered by a team at hoffmann-la roche in the 1970s and is a drug which is a benzodiazepine derivative similar in structure to clonazepam. it has sedative and anxiolytic actions like those of other benzodiazepines, and also has anti-parasitic effects against the parasitic worm schistosoma mansoni. meclonazepamclinical dataatc codenonelegal statuslegal status ca: schedule iv de: npsg (industrial and scientific use only) uk: under psychoactive substances act identifiers iupac name (3s)-5-(2-chlorophenyl)-3-methyl-7-nitro-1,3-dihydro-1,4-benzodiazepin-2-one cas number58662-84-3 npubchem cid3033985chemspider2298544 yuniirn43209smachemblchembl351821 ncomptox dashboard (epa)dtxsid10207366 chemical and physical dataformulac16h12cln3o3molar mass329.74 g·mol−13d model (jsmol)interactive image smiles o=n(c1=cc2=c(nc((c)n=c2c3=cc=cc=c3)=o)c=c1)=o inchi inchi=1s/c16h12cln3o3/c1-9-16(21)19-14-7-6-10(20(22)23)8-12(14)15(18-9)11-4-2-3-5-13(11)17/h2-9h,1h3,(h,19,21)/t9-/m0/s1 ykey:lmuvyjcafwgnsy-vifpvbqesa-n y ny (what is this?) (verify) meclonazepam was never used as medicine and instead appeared online as a designer drug. legal issues united kingdom in the uk, meclonazepam has been classified as a class c drug by the may 2017 amendment to the misuse of drugs act 1971 along with several other designer benzodiazepine drugs.