Buprenorphine-Fentanyl Interaction Study

"Buprenorphine intravenous (IV) injection given as a primed-continuous infusion.~Low Dose: initial bolus (0.05 mg/70 kg) administered over 15 minutes and infusion continued (0.02 mg/70 kg/hour infusion rate) to complete 360 minutes of administration targeting 0.2 ng/ml.~High Dose: initial bolus (0.125 mg/70 kg) administered over 15 minutes and infusion continued (0.05 mg/70 kg/hour infusion rate) to complete 360 minutes of administration targeting 0.5 ng/ml.~Administration of buprenorphine was flexible and infusion rates were selected to target approximately 25 to 50% respiratory depression."

0.9% normal saline for IV administration was used as placebo matching the buprenorphine formulation and administration.

Participant received up to four fentanyl doses: 0.075, 0.15, 0.25, and 0.35 mg/70 kg in Periods 1 and 2. Fentanyl boluses were administered over 90 seconds by dose escalation +2hr, +3hr, +4hr and +5hr after starting administration of buprenorphine/ placebo. Administration of fentanyl was flexible and bolus doses were selected to elicit moderate to more severe respiratory depression with apnoea ≥20 seconds.

A non-investigational intervention administered as an infusion prior to investigation intervention. 4 mg of ondansetron was administered to manage the expected gastrointestinal side effect (nausea, vomiting) to buprenorphine.

"Buprenorphine intravenous (IV) injection given as a primed-continuous infusion.~Low Dose: initial bolus (0.25 mg/70 kg) administered over 15 minutes and infusion continued (0.1 mg/70 kg/hour infusion rate) to complete 360 minutes of administration targeting 1 ng/ml.~Mid Dose: initial bolus (0.5 mg/70 kg) administered over 15 minutes and infusion continued (0.2 mg/70 kg/hour infusion rate) to complete 360 minutes of administration targeting 2 ng/ml.~High Dose: initial bolus (1.25 mg/70 kg) administered over 15 minutes and infusion continued (0.5 mg/70 kg/hour infusion rate) to complete 360 minutes of administration targeting 5 ng/ml."

"Participant received up to four fentanyl doses: 0.25, 0.35, 0.5, and 0.7 mg/70 kg in Periods 1 and 2.~Fentanyl boluses were administered over 90 seconds by dose escalation +2hr, +3hr, +4hr and +5hr after starting administration of buprenorphine/ placebo."

All opioid-tolerant participants in Part B were transitioned to oral oxycodone at least 48 hours before Period 1 to ensure washout of the participants' regular opioids and a stable dose of oxycodone with an adequate bridging schedule reached. Oxycodone is a non-investigational intervention.