What is 3-MMC? 3-MMC, or mephedrone, is a synthetic cathinone that first appeared on the ‘legal high’ market. Let’s take a closer look… 3-MMC is short for 3-Methylmethcathinone, and it’s also known as mephedrone. It’s part of the synthetic cathinone family and is an analog of mephedrone. That means it was designed to mimic the …