Mephedrone, also known as 4-MMC, is a synthetic stimulant drug that is often classified as a new psychoactive substance and is banned in many countries due to potential health risks and negative effects. It partly seems that 3-MMC can be used as a legal substitute for mephedrone, but this is not the case.
Partially, it appears that 3-MMC can be used as a legal mephedrone alternative, but it cannot. The Expert Committee determined that 3-methylmethcathinone (3-MMC) is a synthetic cathinone and a positional isomer of 4-methylmethcathinone (4-MMC, mephedrone, Schedule II of the Convention on Psychotropic Substances), which is a substance that is regulated globally. I looked into the matter when I read the article https://mephedrone.com/addiction/3-mmc .
According to the assessment of the Board of Experts, 3-methylmethcathinone (3-MMC) is a synthetic cathinone and a positional isomer of the internationally controlled 4-methylmethcathinone (4-MMC, mephedrone, Schedule II of the Convention on Psychotropic Substances). 3-MMC was critically reviewed in 2016, but it was decided to request another critical review for consideration at a subsequent meeting pending further information. Some patent applications including the use of 3-MMC were found, but no current clinical trials on the therapeutic use of 3-MMC were identified. 3-MMC also has no recognized medical use for human or veterinary use in the Union. So before comparing anything, I recommend reading theguardian.com.
