Title: Clonazepam
CAS Registry Number: 1622-61-3
CAS Name: 5-(2-Chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one
Additional Names: 7-nitro-5-(2-chlorophenyl)-3H-1,4-benzodiazepin-2(1H)-one
Manufacturers' Codes: Ro-5-4023
Trademarks: Clonopin (Roche); Iktorivil (Roche); Klonopin (Roche); Landsen (Sumitomo); Rivotril (Roche)
Molecular Formula: C15H10ClN3O3
Molecular Weight: 315.71
Percent Composition: C 57.07%, H 3.19%, Cl 11.23%, N 13.31%, O 15.20%
Literature References: Antiepileptic agent with anxiolytic and antimanic properties. Prepn: L. H. Sternbach et al., J. Med. Chem. 6, 261 (1963); O. Keller et al., US 3121076 (1964 to Hoffmann-La Roche). Prepd but not claimed: J. Kariss, H. L. Newmark, US 3116203 (1963 to Hoffmann-La Roche). Alternate process: A. Focella, A. I. Rachlin, US 3335181 (1967 to Hoffmann-La Roche). Pharmacology: Guerrero-Figueroa et al., Curr. Ther. Res. 11, 40 (1969); Lechat et al., Therapie 25, 893 (1970); D'Armagnac et al., ibid. 26, 439 (1971). Toxicology: Blum et al., Arzneim.-Forsch. 23, 377 (1973). Determn of clonazepam and its main metabolites: S. Ebel, H. Schütz, ibid. 27, 325 (1977). Clinical efficacy in acute mania: G. Chouinard, Psychosomatics 26(12), Suppl., 7 (1985); in panic disorders and agitation: R. Fontaine, ibid. 13. Comprehensive description: W. C. Winslow, Anal. Profiles Drug Subs. 6, 61-81 (1977).
Properties: White crystals from ethanol-methylene chloride, mp 236.5-238.5°. uv max (7.5% methanol in isopropanol): 248, 310 nm (e 14500, 11600). Soly in mg/ml at 25°: acetone 31; chloroform 15; methanol 8.6; ether 0.7; benzene 0.5; water <0.1. pK1 1.5, pK2 10.5. LD50 orally in mice: >4000 mg/kg (Blum).
Melting point: mp 236.5-238.5°
pKa: pK1 1.5, pK2 10.5
Absorption maximum: uv max (7.5% methanol in isopropanol): 248, 310 nm (e 14500, 11600)
Toxicity data: LD50 orally in mice: >4000 mg/kg (Blum)
NOTE: This is a controlled substance (depressant): 21 CFR, 1308.14.
Therap-Cat: Anticonvulsant.
Keywords: Anticonvulsant.
Clonidine Clonitazene Clonitrate Clonixin Clopamide

Clonazepam structure.svg
Clonazepam 3D animated.gif
Systematic (IUPAC) name
Clinical data
Trade names Klonopin
AHFS/ monograph
MedlinePlus a682279
Pregnancy cat. C (AU) D (US)
Legal status Prescription Only (S4) (AU) Schedule IV (CA) schedule Q (UK) Schedule IV (US)
Dependence liability High
Routes Oral, I.M., I.V, sublingual
Pharmacokinetic data
Bioavailability 90%
Protein binding ~85%
Metabolism Hepatic CYP3A4
Half-life 18-50 hours
Excretion Renal
CAS number 1622-61-3 YesY
ATC code N03AE01
PubChem CID 2802
DrugBank DB01068
ChemSpider 2700 YesY
KEGG D00280 YesY
Chemical data
Formula C15H10ClN3O3 
Mol. mass 315.715
 YesY (what is this?)  (verify)

Clonazepam[1] is a benzodiazepine drug having anxiolytic, anticonvulsant,[2] muscle relaxant, sedative, and hypnotic properties.[3] It is marketed under the trade name Rivotril by Roche in Argentina, Australia, Brazil, Bulgaria, Canada, Colombia, Costa Rica, Denmark, Germany, Ireland, Italy, Mexico, Portugal, South Africa and Spain; Linotril and Clonotril in India, South Korea, and other parts of Europe; and under the trade name Klonopin by Roche in the United States. Other names, such as Ravotril, Rivatril, Iktorivil, Clonex, Paxam, Petril, Naze and Kriadex, are known throughout the world.[citation needed] Clonazepam has an unusually long elimination half-life of 18–50 hours, making it generally considered to be among the longest-acting benzodiazepines.[4] Clonazepam is a chlorinated derivative of nitrazepam[5] and therefore a chloro-nitrobenzodiazepine.[6]

Clonazepam has an intermediate onset of action, with a peak blood level occurring one to four hours after oral administration. Long-term effects of benzodiazepines include tolerance, benzodiazepine dependence, and benzodiazepine withdrawal syndrome, which occurs in one third of patients treated with clonazepam for longer than four weeks.[7]

Benzodiazepines such as clonazepam have a fast onset of action, high effectivity rate, and low toxicity in overdose; however, as with most medications, it may have drawbacks due to adverse or paradoxical effects. The benzodiazepine clorazepate may be an alternative to clonazepam due to a slow onset of tolerance and its availability in a slow-release formula to counter fluctuations in blood levels. The pharmacological property of clonazepam, as with other benzodiazepines, is the enhancement of the neurotransmitter GABA via modulation of the GABAA receptor.[7]