Why ? Do you want to do a series about the death penalty and associated drugs? I think it's interesting that the stuff is banned for Vet use as it might hide pain (associated with suffocation etc...) but it's okay to use it for the death penalty. Humanity or more precisely the lack thereof always amazes me.
I doubt that it has any photographic use maybe as a substitute for other bromides but I don't know anything about pancuronium and its effect on photographic emulsions. You could try to make a small batch of emulsion and substitute the potassium bromide with pancuronium bromide. Or alternatively mix a film/paper developer and use pancuronium bromide instead of other bromides.
If you do death penalty stuff the final chemical that is being administered is often used in photography potassium chloride.
The medical use of pancuronium bromide is as a muscle relaxant which permits a lighter degree of anesthesia and hence less risk during surgery. Without it more anesthetic would be needed to produce the required degree of relaxation. Particularly used in abdominal and thoracic surgeries.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.