This causes feelings of well-being (euphoria) and relaxation and relieves pain. Street names for fentanyl include Apache, China Girl, Goodfellas, Great Bear, and Tango & Cash. Side effects include drowsiness, weakness, and dry mouth. Fentanyl is up to 100 times more potent than morphine and 50 times more potent than heroin.
The Invisible Majority: People Whose Drug Use Is Not Problematic

In fact, most fentanyl-related deaths are from fentanyl made in illegal laboratories. Naloxone is used to reverse the life-threatening effects of an overdose. In case of overdose, remove the fentanyl from the victim's mouth and call local emergency services at 911.
Fentanyl’s strength increases this risk of overdose substantially. In high enough doses, opioids can cause breathing to stop completely. Fentanyl carries a high risk of overdose and fatality. Fentanyl is a powerful synthetic opioid.
Though this is dwarfed by the direct export trade – which exceeds $32 million in crypto – there nevertheless remains some key implications for countering the trade in fentanyl. Our analysis has revealed that dark web vendors have purchased fentanyl to the tune of $0.5 million from dealers. Vendor clusters with Bitcoin payments to fentanyl suppliers have also been identified interacting with dark web marketplaces that have since gone offline, such as Silk Road and Hydra. This cluster of vendors receives fentanyl from a supplier based in Shanghai, China.