Use of Tapentadol Oral Solution for Pain After Surgery in Children From Newborn to Less Than 2 Years Old

Inclusion Criteria: * The participant's parent(s) or legal guardian(s) have given written informed consent to participate. * Participant is not obese (e.g., a body weight above the 97th percentile for children based on the World Health Organization weight charts) with a minimum body weight of 2.5 kg. * Physical status rated not higher than P3 on the American Society of Anesthesiologists physical status classification in participants aged from 1 month to less than 2 years. * Participant has undergone surgery that, in the investigator's opinion, would reliably produce moderate to severe pain requiring opioid treatment. * At the time of allocation to IMP, participant has a sedation score that is not higher than 2 (moderately sedated) on the University of Michigan Sedation Scale with the exception of participants who are mechanically ventilated in age subgroup 3, has a functioning gastrointestinal tract after surgery, and can tolerate medication administered orally or via a feeding tube at the time of allocation to IMP. * Participant has a reliable venous vascular access for pharmacokinetic blood sampling. Exclusion Criteria: * The participant's parent(s) or legal guardian(s) is an employee of the investigator or trial site, with direct involvement in this trial or other trials under the direction of that investigator or trial site, or the participant, or participant's parent(s), or legal guardian(s) is a family member of the employees or the investigator. * Participant has be…