Call: 888-217-2719. Fentanyl is an extremely potent synthetic opioid that poses life-threatening risks even in tiny doses. Even microgram amounts equivalent to a few grains of salt can trigger dangerous or fatal overdoses. Fentanyl has a rapid pharmacological potency up to 100 times stronger than morphine. When fentanyl is misused or accidentally released in buildings or vehicles, residues can remain behind even after the substance is no longer visible.