A Phase 4 interventional study of Acetaminophen in Pain, Postoperative, sponsored by Konya City Hospital. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-25.
Sponsored by Konya City Hospital · Phase 4, Interventional, and Treatment
This study investigates whether oral acetaminophen, when added to standard pain management, reduces opioid use and pain after major abdominal surgery, compared to a placebo (inactive pill). Patients undergoing planned abdominal surgery under general anesthesia will be randomly assigned to receive either acetaminophen or a placebo tablet before surgery and every 6 hours afterward for 48 hours, in addition to their usual pain medication. Researchers will measure how much opioid pain medication patients need, how much pain they report, and how satisfied they are with their pain control during the first two days after surgery. The goal is to determine whether oral acetaminophen provides a genuine benefit beyond placebo in reducing opioid use while maintaining adequate pain control.
Detailed Description:
Postoperative pain remains a major clinical challenge despite advances in analgesic pharmacology and surgical technique, contributing to delayed mobilization, prolonged hospital stay, and increased morbidity. Oral acetaminophen is widely used as part of multimodal analgesia regimens, but high-quality evidence supporting its independent analgesic effect - as distinct from placebo response - remains limited, particularly after major abdominal surgery.
This is a prospective, multicenter, randomized, double-blind, placebo-controlled trial enrolling adults undergoing elective non-cardiac abdominal surgery under general anesthesia, with an expected surgical duration of at least 2 hours and a planned hospital stay of at least 48 hours. Prior to the main trial, each participating site will enroll a minimum of 10 pilot patients to confirm proper implementation of the analgesic protocol.
Eligible patients will be randomized 1:1 using a web-based system (REDCap) with random-sized blocks to receive either oral acetaminophen 1000 mg or matching placebo tablets. The first dose will be administered 30 minutes before surgery, followed by repeat dosing every 6 hours for 48 hours postoperatively. All patients will receive a standardized intraoperative analgesic protocol (fentanyl 1.5 mcg/kg at induction; tramadol 2 mg/kg approximately 30 minutes before anticipated completion of surgery), with postoperative rescue analgesia provided via patient-controlled analgesia (tramadol; demand dose 10 mg, lockout 6 minutes, continuous baseline 10 mg/h) and per-patient-request dosing (tramadol 1 mg/kg for pain score >4).
The joint primary outcomes are (1) total opioid consumption (expressed as IV morphine milligram equivalents) and (2) average postoperative pain score (0-10 visual analog scale), both assessed over the first 48 postoperative hours. Acetaminophen will be considered superior to placebo only if it demonstrates both statistical superiority on opioid consumption and statistical noninferiority on pain score (noninferiority margin of 1 point), tested jointly at an overall one-sided alpha of 0.025. Opioid consumption will be analyzed using a linear regression model on log-transformed values; pain score will be analyzed using a repeated-measures linear regression model with an autoregressive correlation structure.
Secondary outcomes include patient-reported satisfaction with postoperative pain management at 24 and 48 hours. Exploratory outcomes include a composite measure of opioid-related side effects (Opioid-Related Symptom Distress Scale, ORSDS), capturing nausea, vomiting, constipation, sedation, dizziness, and related symptoms.
Based on a sample size calculation incorporating group sequential interim analyses (planned at each 25% of enrollment), a maximum of 1504 patients (752 per group) will be enrolled to achieve approximately 90% overall power at the 0.025 significance level. An internal pilot analysis at 25% enrollment will re-evaluate sample size assumptions based on observed variability in opioid consumption.
Data will be collected from electronic medical records at each participating site and centrally coordinated and analyzed at the trial coordinating center.
5,640 studies on the registry are indexed under Pain, Postoperative; 1,230 are open to participants now.
This study's planned enrollment of 1,504 is above the median of 75 across 4,821 interventional studies indexed under Pain, Postoperative.
Browse Pain, Postoperative studies →Konya City Hospital is the lead sponsor of 81 studies on the registry; 23 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Arm 1: Acetaminophen (Arm Type: Experimental) Participants will receive oral acetaminophen 1000 mg, administered 30 minutes before surgery and every 6 hours postoperatively for 48 hours.
Drug: Acetaminophen
Participants will receive a matching placebo tablet, administered 30 minutes before surgery and every 6 hours postoperatively for 48 hours.
Drug: Acetaminophen
Intervention 1: Acetaminophen (Type: Drug) Oral acetaminophen 1000 mg tablet, administered 30 minutes before surgery and every 6 hours postoperatively until 48 hours after surgery. Other Name(s): Paracetamol Intervention 2: Placebo (Type: Other / Drug) Oral placebo tablet, visually identical to the acetaminophen tablet, administered on the same schedule (30 minutes before surgery and every 6 hours postoperatively until 48 hours after surgery).
Also known as: Placebo
Total Postoperative Opioid Consumption
Cumulative opioid consumption during the first 48 postoperative hours, expressed as intravenous morphine milligram equivalents (MME). Tramadol consumption will be converted using a potency equivalence factor of 0.15 relative to morphine.
Time frame: 48 hours after surgery
Average Postoperative Pain Score
Average postoperative pain intensity assessed using a 0-10 Visual Analog Scale (VAS), with 0 indicating no pain and 10 indicating the worst pain. Pain will be assessed every 30 minutes during the first 2 hours in the recovery area, then approximately every 6 hours thereafter until 48 hours postoperatively.
Time frame: 48 hours after surgery
Patient Satisfaction with Postoperative Pain Management
Patient-reported satisfaction with postoperative pain management, assessed at 24 and 48 hours postoperatively using the question: "How do you rate your pain management?" on a 0-10 scale, where 0 = very bad and 10 = excellent.
Time frame: 24 and 48 hours after surgery
Composite Opioid-Related Symptom Distress
Composite score of opioid-related side effects assessed using the Opioid-Related Symptom Distress Scale (ORSDS), evaluating 12 symptoms (nausea, vomiting, constipation, difficulty passing urine, difficulty concentrating, drowsiness, dizziness, confusion, fatigue, itchiness, dry mouth, and headache) across three dimensions (frequency, severity, bothersomeness), each scored 0-4. The composite ORSDS is the mean of all 12 symptom-specific scores, with possible scores ranging from 0 to 4.
Time frame: 48 hours after surgery
No study locations are listed for this record.
Plan to share: No
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This study is not yet recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Acetaminophen
Konya City Hospital