Lemborexant for Sleep and Delirium Prevention in Elderly ICU Patients

Inclusion Criteria: * Age 65 years or older. * Admission to the Surgical Intensive Care Unit (SICU). * Anticipated ICU stay of at least 48 hours, as assessed by the ICU consultant and responsible surgeon. * Able to receive enteral medication via oral or nasogastric route. Exclusion Criteria: * Requirement for frequent neurological checks or scheduled awakening (e.g., acute stroke or neurosurgery). * Deep sedation defined as Richmond Agitation-Sedation Scale (RASS) ≤ -3. * Positive Confusion Assessment Method for the ICU (CAM-ICU) within 12 hours prior to randomization. * Severe hemodynamic or respiratory instability requiring neuromuscular blockers or high-dose vasopressors (e.g., norepinephrine ≥ 0.1 µg/kg/min and titrating upward). * High risk of aspiration, including ongoing vomiting, gastric residual volume \>250 mL, or intolerance to oral or enteral medications. * Concomitant use of strong CYP3A inhibitors or inducers (e.g., ketoconazole, itraconazole, clarithromycin, ritonavir, rifampicin, carbamazepine, phenytoin, or St. John's wort). * Severe hepatic impairment (Child-Pugh class C). * End-stage kidney disease or chronic kidney disease stage 5. * Concomitant use of sedative-hypnotic medications, including benzodiazepines, Z-drugs, trazodone, tricyclic antidepressants, melatonin, or other sleep-inducing agents. * Known hypersensitivity to lemborexant or other dual orexin receptor antagonists. * History of cataplexy-like symptoms or severe depression with suicidal ideation.