The primary objective of this study is to evaluate the pharmacokinetic (PK) profile of naldemedine and nor-naldemedine after a single oral dose of naldemedine in pediatric participants who are receiving or about to receive opioids.
Participants with cancer or non-cancer pain who are receiving (or who are about to receive) acute or chronic treatment with opioids.
Participants with either newly diagnosed constipation, a history of constipation treated with laxatives, or are expected to develop constipation after opioid treatment.
Able to remain in the clinic for blood sampling for at least 12 hours following the first study intervention dose and are able to return for blood sampling at the 24-hour time point.
Body mass index within approximately the 3rd to 97th percentile for their age according to the World Health Organization Child Growth Standards.
History of a gastrointestinal (GI) neoplasm or an ongoing GI-related issue or any recent (within last 1 year) or planned GI tract surgery.
Signs or symptoms of GI obstruction or participants with recurrent obstruction who may be at increased risk of GI perforation.
Inability to eat/swallow or have need of a nasogastric tube.
No bowel movements reported for 7 consecutive days at the time of obtaining informed consent or on the initial day of study intervention administration (Study Day 1).