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Formula | C16H12ClN3O3 |
Molar mass | 329.74 g·mol−1 |
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Meclonazepam [1] ((S)-3-methylclonazepam) was discovered by a team at Hoffmann-La Roche in the 1970s and is a drug which is a benzodiazepine derivative similar in structure to clonazepam. [2] It has sedative and anxiolytic actions like those of other benzodiazepines, [3] and also has anti-parasitic effects against the parasitic worm Schistosoma mansoni . [4]
Meclonazepam was never used as medicine and instead appeared online as a designer drug. [5] [6] [7] [8]
Its sedative and anxiolytic abilities are attributed to the same mechanism used by other benzodiazepine drugs: modulation of the GABAA receptor in the brain. This psychoactive activity makes it useful for recreational use. [7] The sedating side effect would also make it unsuitable for routine use as an antiparasitical. [9]
Schistosomal parasites do not have an ortholog of the GABAA receptor. Instead, meclonazepam seems to cause a rapid calcium influx, leading to muscle contraction and tegument damage. In 2023, meclonazepam is shown to activate a calcium-permeable schistosome TRP (transient receptor potential), making this TRP a very likely candidate for its parasite receptor. [9]
Some work has been done to produce two meclonazepam derivatives that show less sedation and more anti-parasite activity in mice. They seem to do this by crossing the blood-brain barrier less readily. [9]
In the UK, meclonazepam has been classified as a Class C drug by the May 2017 amendment to The Misuse of Drugs Act 1971 along with several other designer benzodiazepine drugs. [10]
Etizolam is a thienodiazepine derivative which is a benzodiazepine analog. The etizolam molecule differs from a benzodiazepine in that the benzene ring has been replaced by a thiophene ring and triazole ring has been fused, making the drug a thienotriazolodiazepine.
Gaboxadol, also known as 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP), is a conformationally constrained derivative of the alkaloid muscimol that was first synthesized in 1977 by the Danish chemist Poul Krogsgaard-Larsen. In the early 1980s gaboxadol was the subject of a series of pilot studies that tested its efficacy as an analgesic and anxiolytic, as well as a treatment for tardive dyskinesia, Huntington's disease, Alzheimer's disease, and spasticity. It was not until 1996 that researchers attempted to harness gaboxadol's frequently reported sedative "adverse effect" for the treatment of insomnia, resulting in a series of clinical trials sponsored by Lundbeck and Merck. In March, 2007, Merck and Lundbeck cancelled work on the drug, citing safety concerns and the failure of an efficacy trial. It acts on the GABA system, but in a different way from benzodiazepines, Z-Drugs, and barbiturates. Lundbeck states that gaboxadol also increases deep sleep. Unlike benzodiazepines, gaboxadol does not demonstrate reinforcement in mice or baboons despite activation of dopaminergic neurons in the ventral tegmental area.
Suriclone (Suril) is a sedative and anxiolytic drug in the cyclopyrrolone family of drugs. Other cyclopyrrolone drugs include zopiclone and pagoclone.
Pazinaclone (DN-2327) is a sedative and anxiolytic drug in the cyclopyrrolone family of drugs. Some other cyclopyrrolone drugs include zopiclone and eszopiclone.
Imidazenil is an experimental anxiolytic drug which is derived from the benzodiazepine family, and is most closely related to other imidazobenzodiazepines such as midazolam, flumazenil, and bretazenil.
Pipequaline (INN) is an anxiolytic drug that was never marketed. It possesses a novel chemical structure that is not closely related to other drugs of this type. The drug has a similar pharmacological profile to the benzodiazepine family of drugs, but with mainly anxiolytic properties and very little sedative, amnestic or anticonvulsant effects, and so is classified as a nonbenzodiazepine anxiolytic.
L-838,417 is an anxiolytic drug used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. The compound was developed by Merck, Sharp and Dohme.
CL-218,872 is a sedative and hypnotic drug used in scientific research. It has similar effects to sedative-hypnotic benzodiazepine drugs such as triazolam, but is structurally distinct and so is classed as a nonbenzodiazepine hypnotic.
ELB-139 (LS-191,811) is an anxiolytic drug with a novel chemical structure, which is used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
N-Desalkylflurazepam is a benzodiazepine analog and an active metabolite of several other benzodiazepine drugs including flurazepam, flutoprazepam, fludiazepam, midazolam, flutazolam, quazepam, and ethyl loflazepate. It is long-acting, prone to accumulation, and binds unselectively to the various benzodiazepine receptor subtypes. It has been sold as a designer drug from 2016 onward.
Pyrazolam (SH-I-04) is a benzodiazepine derivative originally developed by a team led by Leo Sternbach at Hoffman-La Roche in the 1970s. It has since been "rediscovered" and sold as a designer drug since 2012.
Diclazepam (Ro5-3448), also known as chlorodiazepam and 2'-chloro-diazepam, is a benzodiazepine and functional analog of diazepam. It was first synthesized by Leo Sternbach and his team at Hoffman-La Roche in 1960. It is not currently approved for use as a medication, but rather sold as an unscheduled substance. Efficacy and safety have not been tested in humans.
Flubromazepam is a benzodiazepine derivative which was first synthesized in 1960, but was never marketed and did not receive any further attention or study until late 2012 when it appeared on the grey market as a novel designer drug.
3-Hydroxyphenazepam is a benzodiazepine with hypnotic, sedative, anxiolytic, and anticonvulsant properties. It is an active metabolite of phenazepam, as well as the active metabolite of the benzodiazepine prodrug cinazepam. Relative to phenazepam, 3-hydroxyphenazepam has diminished myorelaxant properties, but is about equivalent in most other regards. Like other benzodiazepines, 3-hydroxyphenazepam behaves as a positive allosteric modulator of the benzodiazepine site of the GABAA receptor with an EC50 value of 10.3 nM. It has been sold as a designer drug.
Flubromazolam (JYI-73) is a triazolobenzodiazepine (TBZD), which are benzodiazepine (BZD) derivatives. Flubromazolam is reputed to be highly potent, and concerns have been raised that clonazolam and flubromazolam in particular may pose comparatively higher risks than other designer benzodiazepines, due to their ability to produce strong sedation and amnesia at oral doses of as little as 0.5 mg. Life-threatening adverse reactions have been observed at doses of only 3 mg of flubromazolam.
Deschloroetizolam is a thienotriazolodiazepine that is the dechlorinated analog of the closely related etizolam. The compound has been sold as a designer drug.
Nifoxipam is a benzodiazepine that is a minor metabolite of flunitrazepam and has been sold online as a designer drug.
Bromazolam (XLI-268) is a triazolobenzodiazepine (TBZD) which was first synthesised in 1976, but was never marketed. It has subsequently been sold as a designer drug, first being definitively identified by the EMCDDA in Sweden in 2016. It is the bromo instead of chloro analogue of alprazolam and has similar sedative and anxiolytic effects to it and other benzodiazepines. Bromazolam is a non subtype selective agonist at the benzodiazepine site of GABAA receptors, with a binding affinity of 2.81 nM at the α1 subtype, 0.69 nM at α2 and 0.62 nM at α5. The "common" dosage range for users of bromazolam was reported to be 1–2 mg, suggesting its potency is similar to alprazolam.
Difludiazepam (Ro07-4065) is a benzodiazepine derivative which is the 2',6'-difluoro derivative of fludiazepam. It was invented in the 1970s but was never marketed, and has been used as a research tool to help determine the shape and function of the GABAA receptors, at which it has an IC50 of 4.1nM. Difludiazepam has subsequently been sold as a designer drug, and was first notified to the EMCDDA by Swedish authorities in 2017.