The molecule above is oxycodone, the molecule that very likely killed Prince.
The shape and chemistry of oxycodone are very similar to morphine and heroin.
Although oxycodone blocks pain and produces euphoria it is very addictive. It is hard to stop taking oxycodone because of the painful withdrawal symptoms that lack of the drug produces.
Like morphine and heroin, oxycodone binds to receptors which are normally the home of peptide hormones. The peptide hormones are the neurotransmitters which make humans feel good, scared, hungry, or satisfied. Such receptors have a hard time dealing with generally rigid molecules like oxycodone. Such molecules are not broken down like flexible peptide neurotransmitters and exert their influence on the receptor for extended periods of time.