The official autopsy report has revealed that fentanyl killed Prince. (Originally it was thought that oxycodone was the culprit).
The structure of a fentanyl molecule is shown above. Like oxycodone, fentanyl is an opioid drug, and like oxycodone it operates on the receptors that transmit pain.
Although fentanyl is medically employed for pain relief it delivers a 'high' to people who take the drug.
Fentanyl is a flexible drug molecule (unlike oxycodone). It has more than five torsions or dihedral angles by which its conformation can be altered.
Hence, in some respects it resembles the peptide endorphins that are thought to be the natural equivalents of opioids.
Despite its flexibility, fentanyl is a powerful drug. It is approximately 100 times more active than morphine, for example. Given its activity, fentanyl is a dangerous drug - overdoses are unfortunately common because a small quantity of fentanyl can cause substantial respiratory depression and death.