You know, that could have some seriously interesting uses, I would find it absolutely fascinating to try incorporating loperamide (immodium, heh) into one of those molecules, to try and make it cross the blood-brain barrier, as if it could be made to, it would be around the same potency as fentanyl.
That would certainly bee a sweet way to turn an OTC diarrhea medication into an high potency, unscheduled opioid