It is a very powerful narcotic but very short acting. It is used in general anesthesia and for severe pain. People abuse it like any other opioid. I have seen people eat the transdermal patches or brew them in hot water like tea. It is not available in pill form, the only other way to get it outside of a hospital is in the form of a small lollipop that is held against the cheek until absorbed. This makes it very useful for wilderness trips where one might have to treat major trauma with limited space to carry supplies
Like any other drug, it is a blessing or curse depending how used. I’m surprised it is used to cut street drugs - its very expensive. It is not available in a gas form so I doubt it was used in Moscow.
It is/was available from Russian munitions stores in gaseous form. No reason civilian medical staff would have any knowledge of or access to it.
If my memory serves me correctly it was not fentanyl but an molecular analog of fentanyl that could be vaporized and used as a gas.
Folly the link below to the suspected analog of fentanyl that is what was probably used.
https://en.wikipedia.org/wiki/3-Methylfentanyl