synthetic opioid

An opioid is a drug that acts on the brain's opioid receptors. Some are extracted from the poppy plant, such as morphine and codeine, and some are semisynthetic, such as heroin. A synthetic opioid is the third kind: the US National Institute on Drug Abuse describes fentanyl as synthetic, meaning it is made entirely in laboratories and has no natural ingredients. Methadone, tramadol and buprenorphine are synthetic opioids too, and all four are used as medicines as well as taken illicitly.

Potency is what separates this group in practice. NIDA states that fentanyl is much more potent than morphine or heroin and that its effects can start more quickly, and that as little as 2 mg, about the amount of a few grains of salt, can be fatal. Because the doses involved are so small, a supply can vary in strength without anyone being able to tell by looking.

In US mortality data, deaths involving synthetic opioids other than methadone are reported as their own line, and that line is dominated by illegally manufactured fentanyl and its close chemical relatives. It is the category that rose fastest through the crisis and, since 2023, the one that has fallen fastest.