Phenazepam

IUPAC Name

7-bromo-5-(2-chlorophenyl)-1,3-dihydro-1,4-benzodiazepin-2-one

Year(s) and type of review / ECDD meetings
Drug Class
ECDD Recommendation
Inclusion in Schedule IV of the 1971 Convention on Psychotropic Substances
Recommendation (from TRS)
Substance identification
Chemically, phenazepam is 7-bromo-5-(2-chlorophenyl)-1,3-dihydro-2H-1,4- benzodiazepin-2-one.

Previous review
Phenazepam has not been previously reviewed by the Committee.

Similarity to known substances and effects on the central nervous system
Phenazepam belongs to the 1,4-benzodiazepines, the same family to which diazepam, oxazepam and temazepam belong, and it has a structural resemblance to diazepam, which is in Schedule IV of the Convention on Psychotropic Substances of 1971. Phenazepam and its metabolite, 3-hydroxyphenazepam, bind to the benzodiazepine binding site on the GABAA receptor. In laboratory animals, phenazepam shows many in vivo effects typical of benzodiazepines, including suppression of locomotor activity at moderate to high doses, induction of myorelaxation and anticonvulsant activity, and it can induce sleep. In humans, phenazepam exhibits many of the effects of a sedative.

Dependence potential
In laboratory animals, phenazepam can induce tolerance, and discontinuation of its administration can result in withdrawal effects indicative of physical dependence. Withdrawal signs, measured as an increase in the score of the Hamilton Anxiety Scale following discontinued administration of phenazepam, have been reported in one study.

Actual abuse and/or evidence of likelihood of abuse
User reports from Internet websites indicate that phenazepam may be used to enhance the euphoric effects of opioids (for example, to "boost" methadone doses), to alleviate withdrawal or abstinence syndromes (such as between heroin doses), to temper cocaine highs, and to augment the effects of alcohol. Unauthorized use of phenazepam has been reported over the past few years in Finland, New Zealand, Norway, Turkey, Russian Federation, Sweden, the United Kingdom and the USA. Effects such as psychomotor impairment, respiratory arrest, psychotic experiences, delirium, overdose and deaths have been reported, as well as driving under its influence. Phenazepam can be directly purchased from the Internet and has been sold as a powder, as tablets, and spiked in blotters similar to lysergic acid diethylamide (LSD).

Therapeutic usefulness
Phenazepam has been in clinical use since 1978, primarily in the Russian Federation, to treat epilepsy, insomnia and alcohol withdrawal syndrome, for short-term treatment of anxiety disorders (panic attacks), and as premedication prior to surgery, as it enhances the effects of anaesthetics while reducing anxiety.

Recommendation
The Committee undertook a pre-review of the substance and considered that the information provided in the pre-review report was sufficient and indicated that dependence and harm caused by phenazepam was of such magnitude that proceeding directly into critical review within the meeting was warranted. All procedural requirements for a critical review, including two peer reviews, were fulfilled. Phenazepam has been shown to have effects similar to diazepam that is in Schedule IV of the Convention on Psychotropic Substances of 1971. The Committee considered that the degree of risk to public health and society associated with the abuse of phenazepam is smaller but is still a significant risk to public health compared to substances in Schedules I–III and has a therapeutic usefulness from little to great. The Committee considered that the evidence of its abuse warranted its placement under international control. The Committee further recommended that phenazepam be placed in Schedule IV of the 1971 Convention.