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

Inclusion Criteria

• Recreational opioid user, not currently considered to have moderate or severe substance use disorder for opioids (based on the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition [DSM-5] criteria) and has experience with opioid use for non-therapeutic purposes (ie, for psychoactive effects) on at least 10 occasions in their lifetime and at least 1 occasion in the last 12 weeks prior to screening.
• Provision of signed and dated informed consent form (ICF) prior to the initiation of any protocol-specific procedures.
• Stated willingness to comply with all study procedures and availability for the duration of the study.
• Healthy adult male or female, 18 to 55 years of age, inclusive, prior to the first study drug administration.
• Body mass index (BMI) within 18.0 kg/m^2 to 35.0 kg/m^2, inclusive, and body weight at least 50 kg at screening.
• A female study participant of non-childbearing potential must meet 1 of the following criteria:

(1) Physiological postmenopausal status, defined as the following:

• absence of menses for at least 1 year prior to the first study drug administration (without an alternative medical condition); and
• Follicle stimulating hormone (FSH) levels ≥ 40 mIU/mL at screening

AND/OR

(2) Surgical sterile, defined as those who have had hysterectomy, bilateral oophorectomy and/or bilateral salpingectomy, or bilateral tubal ligation. Women who are surgically sterile must provide documentation of the procedure by an operative report, ultrasound, or other verifiable documentation.

• If male, must agree to use a highly effective method of contraception when engaging in sexual activity and must not donate sperm during the study and for at least 4 months (120 days) after the last dose of study medication.
• Healthy in the opinion of an Investigator, as determined by no clinically significant findings from medical history, physical examination, 12-lead ECG, vital signs, SpO2, respiratory rate, or clinical laboratory (including hematology, coagulation, clinical chemistry, urinalysis, and serology [screening visit only]) at screening visit and/or prior to the first study drug administration.

Exclusion Criteria

• Female who is pregnant according to the pregnancy test at screening or prior to the first study drug administration.
• Male participants with a history of oligospermia or azoospermia or any other disorder of the reproductive system.
• Male participants who are undergoing treatment or investigation for infertility.
• History of moderate or severe substance or alcohol use disorder (excluding nicotine and caffeine) within the past 2 years, as defined by the DSM-5.
• History of any significant psychiatric disorder according to the criteria of the DSM-5 which, in the opinion of the Investigator, could be detrimental to participant safety or could compromise study data interpretation.
• History of significant hypersensitivity to AZD4041, morphine and/or other opioids, naloxone, or any related products (including excipients of the study formulations) as well as severe hypersensitivity reactions (like angioedema) to any drugs.
• History of any significant disease, including [but not necessarily limited to] significant hepatic, renal, cardiovascular, pulmonary, hematologic, neurological, psychiatric, gastrointestinal, endocrine, immunologic, ophthalmologic, or dermatologic disease of any etiology (including infections) identified at screening.
• Presence or history of significant gastrointestinal, liver or kidney disease, or any other condition [including those that may result from surgery] that is known to interfere with drug absorption, distribution, metabolism, or excretion, or known to potentiate or predispose to undesired effects.
• SpO2 below 95% at screening or prior to first study drug administration.
• Any abnormal vital signs, after no less than 5 minutes rest (supine position), as defined in the list below, at screening and/or prior to th