Acetylfentanyl (acetyl fentanyl) is an opioid analgesic drug that is an analog of fentanyl. Studies have estimated acetylfentanyl to be fifteen times more potent than morphine. It has never been licensed for medical use and instead only been sold as a designer drug.
Side effects of fentanyl analogs are similar to those of fentanyl itself, which include itching, nausea and potentially serious respiratory depression, which can be life-threatening.