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Systematic (IUPAC) name
Clinical data
  • X
Routes of
Legal status
Legal status
Pharmacokinetic data
Bioavailability 95%
Metabolism Hepatic
Biological half-life 14-30 hours
Excretion Renal
CAS Number 2011-67-8
ATC code N05
PubChem CID 4496
DrugBank ?
Chemical data
Formula C16H13N3O3
Molar mass 295.3[[Script error: No such module "String".]]
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Nimetazepam (marketed under brand name Erimin) is an intermediate-acting hypnotic drug which is a benzodiazepine derivative. It was first synthesized in Japan in 1964. It possesses hypnotic, anxiolytic, sedative, and skeletal muscle relaxant properties. Nimetazepam is also an anticonvulsant.[1] It is sold in 5 mg tablets known as Erimin. It is generally prescribed for the treatment of short-term severe or debilitating insomnia in patients who have difficulty falling asleep or maintaining sleep.


Taken orally, nimetazepam has very good bioavailability with nearly 100% being absorbed from the gut. It is among the most rapidly absorbed and quickest acting oral benzodiazepines, and hypnotic effects are typically felt within 15-30 minutes after oral ingestion. The blood level decline of the parent drug was biphasic with the short half-life ranging from 0.5-0.7 hours and the terminal half-life from 8–26.5 hours (mean 17.25 hours).[citation needed]

Drug misuse

Nimetazepam has a reputation for being particularly subject to abuse (known as 'Happy 5', sold as an Ecstasy replacement without a hangover), especially by persons addicted to amphetamines or opiates.[2] For this reason it is no longer sold in most Western nations, but is still a significant drug of abuse in some Asian countries such as Japan and Malaysia. Nimetazepam is subject to legal restrictions in Malaysia, and due to its scarcity, many tablets sold on the black market are in fact counterfeits containing other benzodiazepines such as diazepam or nitrazepam instead. The Central Narcotics Bureau of Singapore seized 94,200 nimetazepam tablets in 2003. This is the largest nimetazepam seizure recorded since nimetazepam became a controlled drug under the Misuse of Drugs Act in 1992.[3] Together with temazepam abusers, they accounted for 47% of the abusers arrested in 2005.[4] In Japan, where seizures of diverted nimetazepam are mostly concentrated, it remains as a major drug of abuse. Seizures of the drug in Thailand, Malaysia, Singapore, Laos, Hong Kong, and Indonesia are also common. The drug is usually exported from Japan, where the drug is legal by prescription for insomnia. Japanese organized crime syndicates control the distribution of nimetazepam and to a lesser extent, flutoprazepam, temazepam, midazolam, and triazolam, all of which are the most heavily controlled and most in demand benzodiazepines throughout East Asia and Southeast Asia.[5]

Darke, Ross & Hall found that benzodiazepines were rated extremely high by drug abusers, rating, in descending order; flunitrazepam, diazepam, temazepam, and nimetazepam. The two most common reasons for these preferences were that they were the ‘strongest’ and that it gave a good ‘high’.[6]

Legal status

Nimetazepam is currently a Schedule III drug under the international Convention on Psychotropic Substances of 1971.[7][8][9]

In Thailand, nimetazepam is a banned substance and it's not available on prescription. It is a Schedule II controlled drug under the Psychotropic Substances Act. Possession and distribution of the drug is illegal.

In Singapore, nimetazepam is banned under the Misuse of Drugs Act. The illegal possession or consumption of nimetazepam is punishable by up to ten years of imprisonment, a fine of 20,000 Singapore dollars, or both; illegally importing or exporting nimetazepam is punishable by up to 20 years of imprisonment and caning.[10]

In Hong Kong, nimetazepam is regulated under Schedule 1 of Hong Kong's Chapter 134 Dangerous Drugs Ordinance. Nimetazepam can only be used legally by health professionals and for university research purposes. The substance can be given by pharmacists under a prescription. Anyone who supplies the substance without prescription can be fined $10000 (HKD). The penalty for trafficking or manufacturing the substance is a $5,000,000 (HKD) fine and life imprisonment. Possession of the substance for consumption without license from the Department of Health is illegal with a $1,000,000 (HKD) fine and/or 7 years of jail time.[11]


In a rat study Nimetazepam showed greater damage to the fetus, as did nitrazepam when compared against other benzodiazepines, all at a dosage of 100mg/kg. Diazepam however showed relatively weak fetal toxicities.[12] The same fetotoxicity of nitrazepam could not be observed in mice and is likely due to the particular metabolism of the drug in the rat. [13]

See also


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ja:ニメタゼパム sv:Nimetazepam
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  2. DEA Resources, Microgram Journal, Volume 2, Numbers 1-4, January-December 2004
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  4. Hong Kong Government. "Suppression of Illicit Trafficking and Manufacturing" (PDF). Hong Kong: Retrieved 13 February 2009. 
  5. Devaney, M., Reid, G. and Baldwin, S., 2006. Situational analysis of illicit drug issues and responses in the Asia-Pacific region, Research Paper 12. Australian National Council on Drugs, Canberra.
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  7. Annual Estimates Of Requirements Of Narcotic Drugs, Manufacture Of Synthetic Drugs, Opium Production And Cultivation Of The
  8. [Central Narcotics Bureau, Singapore]
  9. "Green List—List of psychotropic substances under international control" (PDF). International Narcotics Control Board. 23rd edition, August 2003. Retrieved 2007-11-25.  Check date values in: |date= (help)
  10. "Nimetazepam". Central Narcotics Bureau. December 6, 2006. Retrieved 2009-09-29. 
  11. "Bilingual Laws Information System" (English). The Government of the Hong Kong Special Administrative Region of the People's Republic of China. 
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