A Study to Assess the Effect of AZD4041 on Respiratory Drive in Recreational Opioid Users.

This is a Phase 1, single-centre, randomized, double-blind, placebo-controlled, 2 fixed sequences, multiple dose study in healthy male and/or female recreational opioid users. This study is being primarily conducted to assess the effect on respiratory drive of morphine administered after multiple doses of AZD4041 compared to morphine administered alone in healthy recreational opioid users. The study will include up to 44 participants who will be randomized to either AZD4041 and morphine (28 participants) or placebo and morphine (16 participants). This is to ensure completion of at least 36 participants (24 AZD4041 + morphine, and 12 Placebo + morphine on Day 15). The total study duration will be up to 54 days (including screening) per participant.