Meclonazepam, also known as (S)-3-methylclonazepam, was unearthed in the 1970s by a research team at Hoffmann-La Roche. This compound falls into the category of benzodiazepine derivatives, sharing structural similarities with clonazepam. Meclonazepam exhibits sedative and anxiolytic properties, mirroring the characteristics of other benzodiazepines. Additionally, it displays anti-parasitic effects against the parasitic worm Schistosoma mansoni.

It’s important to note that Meclonazepam was never utilized as a pharmaceutical medication. Instead, it emerged online as a designer drug.

IUPAC name
CAS Number58662-84-3 
PubChem CID3033985
CompTox Dashboard (EPA)DTXSID10207366
Chemical and physical data
Molar mass329.74 g·mol−1

Legal Issues

In the United Kingdom, meclonazepam received classification as a Class C drug through the May 2017 amendment to The Misuse of Drugs Act 1971, a change that also encompassed numerous other designer benzodiazepine substances.


1. What is Meclonazepam?

Meclonazepam is a chemical compound that falls within the benzodiazepine class. It is related to clonazepam and is known for its sedative and anxiolytic (anxiety-reducing) properties.

2. Is Meclonazepam a legal drug?

The legal status of Meclonazepam varies by country. In some regions, it is classified as a controlled or illegal substance, while in others, it may be unregulated or considered a prescription medication.

3. How does Meclonazepam work?

Meclonazepam works by affecting the central nervous system. It enhances the activity of a neurotransmitter called gamma-aminobutyric acid (GABA), which has a calming and inhibitory effect on the brain, resulting in reduced anxiety and sedation.

4. What are the potential effects of Meclonazepam use?

Meclonazepam use may induce relaxation drowsiness, and alleviate symptoms of anxiety. It is important to note that it can also impair coordination, memory, and judgment. The effects can vary from person to person.

5. Is Meclonazepam safe to use?

The safety of Meclonazepam is a matter of concern. It is not approved for medical use in many countries and is often considered a designer drug. The misuse of benzodiazepines, including Meclonazepam, can lead to various health risks, including addiction and withdrawal symptoms.

6. Can Meclonazepam be detected in drug tests?

Meclonazepam can be detected in specific drug tests, particularly those designed to identify benzodiazepines. However, its inclusion in standard drug panels may vary.

7. Is Meclonazepam prescribed by medical professionals?

Meclonazepam is typically not prescribed by medical professionals. It is more commonly found as a research chemical or a designer drug and is not intended for legitimate medical use.

8. What should I do if I or someone I know is experiencing issues related to Meclonazepam use?

If you or someone you know is struggling with Meclonazepam use or facing adverse effects, seek help from a healthcare professional or an addiction treatment centre. Prompt intervention is essential for your well-being and safety.

9. Can I purchase Meclonazepam legally online?

The legality of purchasing Meclonazepam online depends on your location. It may be available through specific online sources, but it’s crucial to understand the laws and regulations regarding its purchase in your country.

10. Where can I find more information about Meclonazepam?

For reliable information about Meclonazepam, refer to scientific literature, government health agencies, and educational resources related to substance use and addiction. Always prioritize your health and safety when seeking information about psychoactive substances.


  1. US 4031078, a patent granted to Szente A for “Benzodiazepine Derivatives” on 21 June 1977, with the assignment to Hoffmann La Roche Inc.
  2. The Lundbeck Institute, a reputable source providing information about “Meclonazepam” as part of their “Psychotropics” resources.
  3. Ansseau M, Doumont A, Thiry D, von Frenckell R, and Collard J (1985). In their “Initial Study of Methylclonazepam in Generalized Anxiety Disorder: Evidence for Greater Efficacy in a Cross-Over Design” (PDF), published in Psychopharmacology. Volume 87, Issue 2, Pages 130–135. doi: 10.1007/bf00431795. PMID 3931136. S2CID 9776700.
  4. O’Boyle C, Lambe R, and Darragh A (1985). “Central Effects in Humans of the Novel Schistosomicidal Benzodiazepine Meclonazepam,” featured in the European Journal of Clinical Pharmacology. Volume 29, Issue 1, Pages 105–108. doi: 10.1007/bf00547377. PMID 4054198. S2CID 1150292.
  5. Meyer MR, Bergstrand MP, Helander A, and Beck O (May 2016). “Identification of Main Human Urinary Metabolites of Designer Nitrobenzodiazepines Clonazolam, Meclonazepam, and Nifoxipam by Nano-Liquid Chromatography-High-Resolution Mass Spectrometry for Drug Testing Purposes,” a study published in Analytical and Bioanalytical Chemistry. Volume 408, Issue 13, Pages 3571–3591. doi: 10.1007/s00216-016-9439-6. PMID 27071765. S2CID 25831532.
  6. Pettersson Bergstrand M, Helander A, Hansson T, and Beck O (April 2017). “Detectability of Designer Benzodiazepines in CEDIA, EMIT II Plus, HEIA, and KIMS II Immunochemical Screening Assays,” published in Drug Testing and Analysis. Volume 9, Issue 4, Pages 640–645. doi: 10.1002/dta.2003. PMID 27366870.
  7. Manchester KR, Maskell PD, and Waters L (March 2018). “Experimental Versus Theoretical Log D7.4, pKa, and Plasma Protein Binding Values for Benzodiazepines Appearing as New Psychoactive Substances,” published in Drug Testing and Analysis. Volume 10, Issue 8, Pages 1258–1269. doi: 10.1002/dta.2387. PMID 29582576.
  8. Manchester KR, Waters L, Haider S, and Maskell PD (July 2022). “The Blood-to-Plasma Ratio and Predicted GABAA-Binding Affinity of Designer Benzodiazepines,” featured in Forensic Toxicology. Volume 40, Issue 2, Pages 349–356. doi: 10.1007/s11419-022-00616-y. PMC 9715504. PMID 36454409.
  9. “The Misuse of Drugs Act 1971 (Amendment) Order 2017,” an official legislative document.

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