modified on 2 January 2019 at 13:31 ••• 8,250 views


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Nimetazepam 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.

Systematic (IUPAC) name
CAS number 2011-67-8
ATC code N05
PubChem 4496
DrugBank ?
Chemical data
Formula C16H13N3O3 
Mol. mass 295.3
Pharmacokinetic data
Bioavailability 95%
Metabolism Hepatic
Half life 14-30 hours
Excretion Renal
Therapeutic considerations
Pregnancy cat.


Legal status

Prohibited (S9)(AU) Schedule IV(US) III (International)

Routes Oral


Half life of Nimetazepam

Ranging from 0.5-0.7 hours and the terminal half-life from 8–26.5 hours.

Recreational use of Nimetazepam

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. Together with temazepam abusers, they accounted for 47% of the abusers arrested in 2005. 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.

Darke, Ross & Hall found that nimetazepam was rated extremely high by drug abusers, rating second only to temazepam among benzodiazepines. The two most common reasons for this preference were that it was the ‘strongest’ and that it gave a good ‘high’.

Legal status

Nimetazepam is currently a Schedule III drug under the international Convention on Psychotropic Substances of 1971.

In Singapore, nimetazepam is a Class A controlled drug under the Misuse of Drugs Act along with one other benzodiazepine, temazepam. As a Class C controlled drug, it is a Schedule I drug available only by private prescription from a registered doctor. Nimetazepam is only used as a last resort hypnotic to treat severe or debilitating insomnia that has not responded to other treatments. 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.

Brand names for Nimetazepam

  • Erimin