The original author is Kavita Babu, MD.
Back in the 1990’s “designer” drugs were hitting the street. They were drugs modified from fentanyl’s chemical composition that, since it wasn’t exactly fentanyl, wasn’t illegal. One of the fentanyl based designer drugs lead to a Parkinson’s like condition that rapidly progressed to death. I haven’t heard much about designer drugs in a while. The thing with fentanyl is that you rapidly build a tolerance. With large doses the drug sequesters in the lungs. After several hours it leeches out of lung tissue and can lead to respiratory depression and death.