Diminution des concentrations plasmatiques de fentanyl par augmentation de son métabolisme hépatique par la rifampicine.Re: Genuinely Freaked Out!! Fentanyl OD or W/D, Undecided! Need Guidance!! I am just a little worried in your case. To me it appears like you may not be that opiod tolerant therefore you are experiecing some side effects that pl