Trefentanil is most similar to short-acting fentanyl analogues such as alfentanil. In comparative studies, trefentanil was slightly more potent and shorter acting than alfentanil as an analgesic, but induced significantly more severe respiratory depression. For this reason trefentanil has not been adopted for clinical use, although it is still used in research.
Valerylfentanyl POWDER Valerylfentanyl is an opioid analgesic that is an analog of fentanyl and has been sold online as a designer drug. It has been seldom reported on illicit markets and there is little information about it, though it is believed to be less potent than butyrfentanyl but more potent than benzylfentanyl.