Diminution des concentrations plasmatiques de fentanyl par augmentation de son métabolisme hépatique par la rifampicine.Re: Genuinely Freaked Out!! Fentanyl OD or W/D, Unsure! Want Assistance!! I am a bit worried to suit your needs. To me it feels like you might not be that opiod tolerant and you also are experiecing some side effects that the ma