Prince

Two former employees of Insys Therapeutics, Jonathan Roper and Fernando Serrano, were arrested on Thursday for allegedly participating in kickback schemes involving doctors who prescribed the company's main drug, Subsys, a pain medication containing fentanyl.

Headlines linking Prince's death to a fentanyl overdose have raised the profile of the opioid; however, CNBC has previously reported on the dangers of these highly addictive drugs and the alleged illegal tactics some pharmaceutical companies have employed to drive sales.