The goal of this randomized, double-blind, placebo-controlled clinical trial is to assess whether the combination of N-acetylcysteine and simethicone improves mucosal visibility during upper gastrointestinal endoscopy in adults aged 18 to 99 years of both sexes, including both healthy individuals and those with non-bleeding gastrointestinal symptoms.

The main questions this study aims to answer are:

Does pre-endoscopy administration of N-acetylcysteine/simethicone improve mucosal visualization based on the Toronto Upper Gastrointestinal Cleanliness Score (TUGS)?

Is this combination safe and well tolerated in this patient population?

Researchers will compare patients receiving N-acetylcysteine (600 mg) and simethicone (100 mg) orally 20-60 minutes before the procedure with those receiving placebo (water) to determine if there is a significant improvement in TUGS scores.

Participants will:

Receive a single oral dose of either N-acetylcysteine/simethicone or placebo prior to endoscopy

Undergo a routine upper GI endoscopy

Have mucosal cleanliness evaluated using the TUGS scoring system

Be monitored for any adverse events or intolerance

This is a randomized, double-blind, placebo-controlled, multicenter clinical trial designed to evaluate the efficacy of N-acetylcysteine (NAC) combined with simethicone in improving mucosal visibility during upper gastrointestinal endoscopy (UGIE). The evaluation will be based on the Toronto Upper Gastrointestinal Cleanliness Score (TUGS), a validated tool to assess mucosal cleanliness.

Participants will include adult patients aged 18 to 99 years who are scheduled to undergo diagnostic UGIE for various indications and who do not present with active gastrointestinal bleeding. Eligible participants will be randomized to receive either a single dose of NAC (600 mg) plus simethicone (100 mg) or a placebo (water), administered orally 20 to 60 minutes prior to the procedure. The allocation will be blinded to both participants and endoscopists.

The main objective of the study is to determine whether this premedication protocol results in better mucosal visibility, as measured by the total TUGS score. Secondary objectives include documenting the presence of significant endoscopic findings and histopathological diagnoses, and evaluating the tolerability and safety profile of the premedication.

TUGS scores will be assigned by trained endoscopists blinded to the treatment allocation. Variables such as age, sex, BMI, duration of fasting, hospital site, and endoscope model will be recorded and controlled for in statistical analyses. The study will also assess any potential adverse events associated with the administration of NAC/simethicone.

This study is categorized as Phase 2 because it evaluates the preliminary efficacy and short-term safety of pre-procedural oral N-acetylcysteine (NAC) and simethicone to improve mucosal visibility during diagnostic upper gastrointestinal endoscopy, using the Toronto Upper Gastrointestinal Cleaning Score (TUGCS) as a validated surrogate endpoint. Both agents have established safety profiles for other indications, but their combined use for this indication is not an approved or established standard of care. The trial is randomized, double-blind, placebo-controlled with a moderate sample size designed to estimate effect size and variability rather than to deliver definitive, multi-center confirmatory evidence on hard clinical outcomes.

All procedures will adhere to ethical standards, and informed consent will be obtained from all participants. Data will be collected in a coded, anonymized format and analyzed using appropriate statistical methods, including ANCOVA and non-parametric tests where assumptions of normality are not met.

Inclusion Criteria:

• Men and women aged 18 to 70 years old.
• Patients who agree to participate in the clinical trial.
• Patients without active gastrointestinal bleeding.
• Signing of informed consent form.

Exclusion Criteria:

• Patients with a history of hypersensitivity to N-acetylcysteine
• Patients with a history of hypersensitivity to simethicone
• Patients with a previous endoscopic diagnosis
• Patients with a history of gastric or bariatric surgery
• Patients with a history of motor disorders (e.g., scleroderma, diabetic gastroparesis)
• Patients taking medications that delay gastric emptying (GLP-1 analogues)
• Pregnant or breastfeeding patients
• Patients who do not agree to participate in the clinical trial

De-identified individual participant data related to baseline demographics, Toronto Upper Gastrointestinal Cleaning Score (TUGS), endoscopic findings, and histopathological results.

IPD will be available beginning 6 months after publication of the main results and for up to 3 years thereafter.

Researchers whose proposed use of the data has been approved by the study's principal investigator.