Fentanyl powder for sale online. Fentanyl, also spelled fentanil, is an opioid used as a pain medication and together with other medications for anesthesia. Fentanyl is also used as a recreational drug, often mixed with heroin or cocaine. It has a rapid onset and its effects generally last less than two hours. Medically, fentanyl is used by injection, as a patch on the skin, as a nasal spray, or in the mouth. Fentanyl comes in several forms: patches and lollipops (Actiq) for example, and has numerous manufacturers. It is available in generic and brand versions. Generic fentanyl is covered by some Medicare and insurance plans, but some pharmacy coupons or cash prices may be lower.