Effect of peRiopErative duLoxetIne Administration on Opioid Consumption Following Total kneE Arthroplasty (RELIFE)

Inclusion Criteria: 1. Age \>=50 2. Presence of knee osteoarthritis 3. Planned for elective unilateral total knee arthroplasty 4. ASA I - III 5. Baseline creatinine clearance (CrCl) ≥ 30 mL/min within 60 days prior to enrolment, if available. If not available, verbal report from patient of no known renal disease. Exclusion Criteria: 1. Lack of patient consent; unlikely to comply with follow-up 2. Presence of contraindications to study drug use: * Known hypersensitivity to the drug or components of the product * Known liver disease - history of cirrhosis, non-alcoholic steatohepatitis * Uncontrolled narrow - angle glaucoma * Severe renal impairment (CrCl\<30mL/min) * Concurrent use of thioridazine * Concurrent use of potent CYP1A2 inhibitors (e.g. fluvoxamine) and some quinolone antibiotics (e.g. ciprofloxacin or enoxacin) * Concurrent use of antidepressants (e.g. MAOI, SSRI, SNRI, TCA, St. John's Wort, buspirone) * Concurrent use of triptan or lithium 3. Chronic and high dose opioid use (\&gt;30mg oral morphine equivalent per day) 4. Substance use disorder (cannabis and related products, alcohol use disorder, opioid used disorder, illicit drugs) 5. Uncontrolled hypertension (systolic BP \&gt; 180mmHg) 6. Untreated psychiatric illness (e.g. depression, suicidal ideation, bipolar disorder) 7. Involved in worker's compensation case/law suit (verbally declared by patient)