I know this is off topic but I don't find the answer anywhere else.

Today's news has Pres. Trump accusing the Chinese of continuing to
sell fentanyl to the United States -- "and many Americans continue to
die!"

But my research shows that fentanyl is a medical drug for the
alleviation of severe pain and as such I would assume to be a
controlled substance. How than, "many Americans continue to die!" ?
--
cheers,

John B.