The Effect of Naldemedine on Opioid-induced Bowel Dysfunction

Inclusion Criteria: * Healthy (assessed by a study-affiliated medical doctor) * Signed informed consent * Able to read and understand Danish. * Male (to avoid influence of menstrual cycles). * Northern European descent (to minimize genetic variance influences on drug metabolism). * The researcher believes that the participant understands the study details, is compliant and is expected to complete the study. * Opioid naïve (no history of opioid use/addiction. Opioid use more than a year ago to treat pain post-surgery is accepted. Opioid use in connection with participation in a clinical trial more than a year ago is accepted) * Between 20 and 40 years of age. * A STAI (Spielberger State-Trait Anxiety Inventory) score in the range of 20-37 i.e., classified as "no or low anxiety" at inclusion. Exclusion Criteria: Known hypersensitivity or allergy towards the used pharmaceutical compounds or pharmaceutical compounds similar to those used in the study. * Less than three spontaneous bowel movements per week. * Participation in other studies within 14 days prior to first visit. * Expected need of medical/surgical treatment during the study. * Any diagnosed disease, which investigator concludes will affect the trial (including all contraindicated complications: severe chronic obstructive pulmonary disease, pulmonary heart disease, severe bronchial asthma, paralytic ileus, hypercapnia, serious respiratory depression with hypoxia, moderate to severe decreased liver function, gastro…