3-methylfentanyl(redirected from Mefentanyl)
a potent heroin substitute and so-called designer drug. It is an analog of fentanyl and reportedly 3000 times as potent as morphine. One ounce represents 25 million doses of a drug with effects equivalent to that of high-grade heroin. A related designer drug is p-fluoro fentanyl. See also designer drugs.