Acetaminophen vs Placebo for Postoperative Analgesia After Abdominal Surgery
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Acetaminophen.
- Who it may be relevant to
- Registry conditions: Pain, Postoperative. Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Center list to be confirmed — check the primary protocol.
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Official title
Comparison of Placebo and Acetaminophen on Postoperative Opioid Consumption in Non-Cardiac Abdominal Surgery
Overview
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
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.
Interventions
- 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).
Primary outcome measures
- Total Postoperative Opioid Consumption [Time frame: 48 hours after surgery]
- Average Postoperative Pain Score [Time frame: 48 hours after surgery]
Secondary outcome measures (1)
- Patient Satisfaction with Postoperative Pain Management [Time frame: 24 and 48 hours after surgery]
Eligibility criteria
Inclusion criteria
- Written informed consent
- Age ≥ 18 years
- ASA physical status I, II, or III
- Scheduled for elective non-cardiac abdominal surgery with expected surgery duration ≥ 2 h-hours
- General anesthesia
- Planned hospital stay of at least 48 hours
Exclusion criteria
- Pregnant or nursing (breastfeeding) women
- Neurologic deficit or chronic pain disease
- Planned use of regional anesthesia techniques for postoperative pain
- Emergency surgery
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Allocation
- Randomized
- Model
- Parallel assignment
- Masking
- Triple blind
- Primary purpose
- Treatment
Study locations
Center list to be confirmed — check the primary protocol.
Identifiers
NCT: NCT07720791 · Study Aceta