Furanyl Fentanyl FuF Powder is more potent than fentanyl. It is available in the market now as a designer substance. It falls in a class of medications called opioids together with others like OxyContin, Vicodin, Percocet, and oxycodone. These opiates work by acting on opioid receptors to cause morphine-like effects. Furanyl Fentanyl Powder is classified under the class of sedatives too. Sedatives are substances or medications used for relaxation of the CNS.