Pain, PostoperativePhase 4NCT07720791
Acetaminophen vs Placebo for Postoperative Analgesia After Abdominal Surgery
A Phase 4 study testing Acetaminophen in people with Pain, Postoperative, run by Konya City Hospital.
Trial summary
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). Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Pain, Postoperative
- What is being tested?
- Acetaminophen
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 1,504 participants
- Where
- No sites listed yet
- Study dates
- 5 Sep 2026to 1 Aug 2027
- Phase
- Phase 4
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- Pregnant or nursing (breastfeeding) women
- Neurologic deficit or chronic pain disease
- Planned use of regional anesthesia techniques for postoperative pain
- Emergency surgery
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
Ayşenur Dostbil contact
About this study
Official title: Comparison of Placebo and Acetaminophen on Postoperative Opioid Consumption in Non-Cardiac Abdominal Surgery
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.
Read the 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.
- Conditions
- Pain, Postoperative
- Being tested
- Acetaminophen
- Medical subject headings
- Pain, Postoperative
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
AcetaminophenDrug
Also called Placebo
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).
| Study group | Role | What they receive |
|---|---|---|
| Acetaminophen | Active comparator | 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. Receives: Drug: Acetaminophen |
| Placebo | Placebo comparator | Participants will receive a matching placebo tablet, administered 30 minutes before surgery and every 6 hours postoperatively for 48 hours. Receives: Drug: Acetaminophen |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: 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.
Measured: 48 hours after surgery
Secondary outcomes (1)
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.
Measured: 24 and 48 hours after surgery
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Jul 2026
- Study start5 Sep 2026 (estimated)
- Primary completion15 Jul 2027 (estimated)
- Study completion1 Aug 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Pain, PostoperativeStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Participants will be randomized in a 1:1 ratio using a web-based randomization system (REDCap) with random-sized blocks to one of two parallel arms: oral acetaminophen 1000 mg or matching placebo tablet. The first dose will be administered 30 minutes before surgery, with repeat dosing every 6 hours for 48 hours postoperatively. Both groups will receive an identical standardized multimodal analgesic protocol, including intraoperative fentanyl, intraoperative/postoperative tramadol, and patient-controlled and per-request rescue analgesia. The two groups will be followed concurrently over the same 48-hour postoperative period, with no crossover between arms.
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Outcomes assessor
- Enrolment
- 1,504 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Konya City Hospital
- Sponsor type
- University, hospital or other
- Collaborators
- Erzurum Regional Training & Research Hospital
- Responsible party
- Principal investigator, Yasin Tire, MD, Konya City Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07720791
- Sponsor's protocol ID
- Study Aceta
- Status last verified
- Aug 2026
- First submitted
- 27 Jun 2026
- Last updated
- 25 Aug 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 25 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Comparison of Placebo and Acetaminophen on Postoperative Opioid Consumption in Non-Cardiac Abdominal Surgery
- ClinicalTrials.gov ID
- NCT07720791
- Acronym / sponsor ID
- Study Aceta
- Conditions
- Pain, Postoperative
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 1,504 participants (estimated)
- Lead sponsor
- Konya City HospitalUniversity, hospital or other
- Collaborators
- Erzurum Regional Training & Research Hospital
- Study start
- 5 Sep 2026 (estimated)
- Primary completion
- 15 Jul 2027 (estimated)
- Study completion
- 1 Aug 2027 (estimated)
- First posted
- 22 Jul 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, care provider, outcomes assessor)
- Number of arms
- 2
- Model description
- Participants will be randomized in a 1:1 ratio using a web-based randomization system (REDCap) with random-sized blocks to one of two parallel arms: oral acetaminophen 1000 mg or matching placebo tablet. The first dose will be administered 30 minutes before surgery, with repeat dosing every 6 hours for 48 hours postoperatively. Both groups will receive an identical standardized multimodal analgesic protocol, including intraoperative fentanyl, intraoperative/postoperative tramadol, and patient-controlled and per-request rescue analgesia. The two groups will be followed concurrently over the same 48-hour postoperative period, with no crossover between arms.
| Arm | Type | Receives |
|---|---|---|
| Acetaminophen | Active comparator | Drug: AcetaminophenArm 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. |
| Placebo | Placebo comparator | Drug: AcetaminophenParticipants will receive a matching placebo tablet, administered 30 minutes before surgery and every 6 hours postoperatively for 48 hours. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (4 listed)
- Pregnant or nursing (breastfeeding) women
- Neurologic deficit or chronic pain disease
- Planned use of regional anesthesia techniques for postoperative pain
- Emergency surgery
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| AcetaminophenAlso: PlaceboIntervention 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). | Drug | Acetaminophen, Placebo |
Primary outcome
Total Postoperative Opioid Consumption
Time frame: 48 hours after surgery
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.
Average Postoperative Pain Score
Time frame: 48 hours after surgery
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.
1 secondary outcome
Patient Satisfaction with Postoperative Pain Management
Time frame: 24 and 48 hours after surgery
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 25 Aug 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Ayşenur Dostbil contact
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing Acetaminophen in people with Pain, Postoperative, run by Konya City Hospital.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 25 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Yasin Tire (+905055367970, dryasintire@hotmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Total Postoperative Opioid Consumption (time frame: 48 hours after surgery). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 25 Aug 2026.