U-47700, goes by the street name U-4

[Lucinda F. Boyd]

The drug, U-47700, is a synthetic opioid analgesic eight times more powerful than morphine. It causes sedation and respiratory depression, which can be fatal. The shipments usually come from overseas, particularly China. It is sold in vials or plastic baggies that are labeled “Not for Human Consumption” or “For Research Purposes Only.”

It has been known to be sold as "oxycodone" on the streets. The synthetic opioid U-47700 has largely been limited to laboratories in the last several decades, but is now being "recycled" as a recreational drug.
The synthetic opioid can be snorted in powder form, and there have also been reports of it being taken orally, intravenously and even rectally. U-47700, which goes by the street name U-4, is a synthetic opioid that acts much like fentanyl, can cost as low as $40 per gram.

This drug, especially when mixed with other drugs can be deadly with one dose. There have been many recent overdoses noted in many states.