Effect of Preoperative Melatonin on Quality of Recovery After Elective Laparoscopic Cholecystectomy

Inclusion Criteria: * Age 18-60 years * American Society of Anesthesiologists (ASA) physical status I-II * Scheduled for elective laparoscopic cholecystectomy under general anesthesia * Able to understand and provide informed consent * Willing to participate in the study and complete follow-up assessments * Body mass index (BMI) 18-35 kg/m2 Exclusion Criteria: * Known allergy or hypersensitivity to melatonin or placebo component * Chronic use of opioids, sedatives, or hypnotics (regular use for ≥4 weeks prior to surgery) * Current use of beta-adrenergic receptor antagonists (beta-blockers) (suppress endogenous melatonin secretion via inhibition of pineal β₁-adrenergic receptors) * History of psychiatric disorders requiring ongoing pharmacological treatment * Pregnancy or lactation * Severe hepatic impairment (Child-Pugh class B or C), as melatonin undergoes extensive first-pass hepatic metabolism via CYP1A2 * Diagnosed obstructive sleep apnoea requiring continuous positive airway pressure * Diagnosed circadian rhythm disorder (e.g., delayed sleep phase disorder, advanced sleep phase disorder) requiring medical management * Use of exogenous melatonin supplements within 30 days prior to surgery * Inability to complete study questionnaires due to language barrier or cognitive impairment * History of substance abuse or dependence