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Nimetazepam chemical structure

IUPAC name
CAS number
ATC code


Chemical formula {{{chemical_formula}}}
Molecular weight 295.3
Bioavailability ?
Metabolism Hepatic
Elimination half-life ?
Excretion Renal
Pregnancy category X
Legal status Schedule IV(US)
Routes of administration Oral

Nimetazepam (marketed under brand name Erimin) is a powerful hypnotic drug which is a benzodiazepine derivative which was first synthesized in Japan in 1964. It possesses strong hypnotic, anxiolytic, sedative, and skeletal muscle relaxant properties. Nimetazepam is also a particularly potent 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.

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. 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. Diazepam and nitrazepam are among the most widely prescribed benzodiazepines in the region, and as a result, they're commonly diverted and encountered on the black market. They usually end up on the black market as a result of being passed off as nimetazepam, temazepam or triazolam.[2]

In Singapore, nimetazepam is a Class A-Schedule I controlled drug, along with another benzodiazepine, temazepam. The illegal distribution of nimetazepam may be punishable by death. Possession of the drug without a valid prescription from a registered medical doctor is illegal and punishable by extremely long prison terms.

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.[3]

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.[4]

In a rat study Nimetazepam showed greater damage to the fetus, as did nitrazepam when compared against other benzodiazepines. Diazepam however showed relatively weak fetal toxicities.[5]

See also


  1. Fukinaga M, Ishizawa K, Kamei C. (November 1998). Anticonvulsant properties of 1,4-benzodiazepine derivatives in amygdaloid-kindled seizures and their chemical structure-related anticonvulsant action.. Pharmacology 5 (57): 233–41.
  2. DEA Resources, Microgram Journal, Volume 2, Numbers 1-4, January-December 2004
  3. Bilingual Laws Information System. (English) The Government of the Hong Kong Special Administrative Region of the People's Republic of China.
  4. 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.
  5. Saito H, Kobayashi H, Takeno S, Sakai T. (1984). Fetal toxicity of benzodiazepines in rats.. Res Commun Chem Pathol Pharmacol. 46 (3): 437–47.

Anticonvulsants edit


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Barbiturates edit

{Phenobarbital} {Methylphenobarbital} {Metharbital} {Barbexaclone}

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