A Study to Look at Tapentadol Oral Solution in Children and Adolescents in Pain

Inclusion Criteria

• Informed consent, and if applicable assent, given according to local regulations.
• Male or female participant aged from birth (at least 37 weeks gestational age) to less than 18 years.
• A female participant must be pre-menarchal, or surgically incapable of childbearing, or sexually abstinent, or if a female participant is sexually active, then she must be practicing an effective method of birth control (e.g., prescription hormonal contraceptives, intra-uterine devices used according to the product's instruction, double-barrier methods) before trial entry and throughout the trial.
• A female participant must have a negative pregnancy test if aged 12 years or older, or is post-menarchal, or is sexually active.
• Participant has undergone surgery (other than brain surgery or gastrointestinal surgery expected to affect the absorption of tapentadol [in the investigator's judgment]) that, in the investigator's opinion, would reliably produce moderate to severe pain requiring opioid treatment for at least 24 hours after first dose of IMP. Participants must remain hospitalized until the End of Treatment Visit.
• Participant has received post-operative morphine or hydromorphone by NCA/PCA, with or without a background infusion of the same opioid, according to standard of care prior to allocation/randomization to IMP and participant is expected to require this morphine or hydromorphone by NCA/PCA after starting IMP.
• Participant is able to tolerate liquids at the time of allocation/randomization to IMP.

Exclusion Criteria

• Participant, parent or the legal representative is an employee of the investigator or trial site, with direct involvement in the proposed trial or other trials under the direction of that investigator or trial site, or family member of the employees or the investigator.
• Participant has been previously exposed to tapentadol.
• Participant has received an experimental drug or used an experimental medical device within 28 days before allocation/randomization to IMP, or within a period less than 10 times the drug's half-life, whichever is longer.
• Participant has a history or current condition of any one of the following:
• Non-febrile seizure disorder.
• Epilepsy.
• Serotonin syndrome.
• Traumatic or hypoxic brain injury, brain contusion, stroke, transient ischemic attack, intracranial hematoma, post-traumatic amnesia, brain neoplasm, or episode(s) of unconsciousness of more than 24 hours.
• Participant has a history or current condition of any one of the following:
• Moderate to severe renal or hepatic impairment.
• Abnormal pulmonary function or clinically relevant respiratory disease (e.g., acute or severe bronchial asthma, hypercapnia).
• Participant has a concomitant disease or disorder (e.g., endocrine, metabolic, neurological, psychiatric, infection, febrile seizure, paralytic ileus) that in the opinion of the investigator may affect or compromise participant safety during the study participation.
• Participant has history of suicidal ideation or behavior.
• Participant is obese in the investigator's judgment. Obesity can be determined based on appropriate body mass index (BMI) charts or tables; e.g., a BMI above the 97th percentile for children based on the World Health Organization growth charts or the participant's weight is less than 2500 grams.
• Participant has a clinically relevant history of hypersensitivity, allergy, or contraindication to the supplemental opioid analgesic medication or tapentadol, or the excipients, or naloxone.
• Participant is not able to understand and comply with the protocol as appropriate for the age of the participant or participant is cognitively impaired in the investigator's judgment such that they cannot comply with the protocol
• Participant has a history of alcohol and/or substance abuse in the investigator's judgment based on participant's history and physical examination.
• Participant is taking prohibited concomitan