I was wondering if any of you have experienced any reactions while taking fentanyl? Or maybe an interaction with another drug you are taking. I recently had an appendectomy performed and while in the hospital they gave me fentanyl. Almost 1/2 hour later of given the drug I went into deep hallucinations. The surgeon who performed the surgery said he heard I was having a few problems but didn't seem it necessary to add fentanyl to my chart as an allergic reaction. I feel it needs to be added to my chart as I never want to go thru that mess again.