Since the killing dose for an adult person is the size of the head of a straight pin-— HOW could this be an “overdose”?
IOW it was an INTENTIONAL dose of a deadly likely illegally imported chemical agent. Anaesthesiologists can speak of the dosing of fentanyl for use in major surgery— and how dicey this can be.
This dude, getting high, killed himself.
Yep, poisoning.