Question for you all.....I recently was switched from Morphine pills to a Fentanyl patch. In that time I have begun to have horrible leg pain radiating from my groin down my left thigh. I seem to remember having this previously while on Percocet. Today I did NOT replace my patch and took a leftover morphine pill that I had a VOILA....the leg pain seems to have subsided! Does this mean I may be allergic? Has anyone ever heard of this before?