The Use of Venlafaxine in Reducing Pain in Primary Total Knee Replacement

Patients meeting the inclusion criteria will be randomized to receive either Venlafaxine extended release (ER) 37.5 mg/d or a placebo on the day of surgery and continue the treatment for 7 days after surgery. The primary outcomes include pain severity score (numeric rating scale, NRS) and consumption of morphine miligram equivalent (MME) at 24 hours. The secondary outcome will measure MME and NRS at postoperative day 7. In addition, the disability scale and perceived function 3 months after surgery will be compared to the baseline level by using PROMIS (Patient-Reported Outcomes Measurement Information System)10 Global Health, KOOS, JR. (Knee injury and Osteoarthritis Outcome Score Short Form), and VR-12 (Veterans RAND 12 Item Health Survey) Scale.

Subjects in placebo arm will receive inactive placebo capsule daily for 7 consecutive days starting on day of primary arthroplasty surgery.

Drug: Placebo

Subjects in venlafaxine arm will receive venlafaxine 37.5mg daily for 7 consecutive days starting on day of primary arthroplasty surgery.

Drug: Venlafaxine 37.5 MG

venlafaxine 37.5mg daily for 7 consecutive days.

placebo filled pill daily for 7 consecutive days.

Plazo: Postoperative Day 1

Total opioid consumption measured in morphine milligram equivalents (MME) on postoperative day 1.

Plazo: Postoperative Day 1

Pain Scores will be measured on the Numerical Rating Scale (NRS), the score ranges from 0-10, zero indicating no pain and 10 indicating the worst pain.

Plazo: Postoperative Day 7

The Brief Pain Inventory (BPI) assesses the severity of pain and its impact on functioning.The BPI scale defines pain as follows:1 - 4 = Mild Pain. Worst Pain Score: 5 - 6 = Moderate Pain. Worst Pain Score: 7 - 10 = Severe Pain.

Plazo: 3 months

The Brief Pain Inventory (BPI) assesses the severity of pain and its impact on functioning.The BPI scale defines pain as follows:1 - 4 = Mild Pain. Worst Pain Score: 5 - 6 = Moderate Pain. Worst Pain Score: 7 - 10 = Severe Pain.

Plazo: 7 days

morphine miligram equivalent

Plazo: 3 months

Knee Injury and Osteoarthritis Outcome Score Short Form (KOOS-12), a 12-item patient-reported questionnaire assessing knee-related quality of life. Scored 0-100 where 0 = extreme knee problems and 100 = no knee problems. Higher scores represent better knee function. Values reported as change from baseline to 3 months postoperatively (3-month score minus baseline score); higher change scores indicate greater improvement. Assessed at baseline and 3 months postoperatively.

Plazo: 3 months

number of participants who reported consuming opioids at the 3-month follow-up.

Plazo: Postoperative Days 1, 2, 7, and 3 months

Patient satisfaction with pain control measured on a 0-100 visual analog scale, where 0 = completely dissatisfied and 100 = completely satisfied. Assessed at POD1, POD2, POD7, and 3 months postoperatively. Values represent model-predicted means from mixed-effects repeated measures analysis.

Plazo: 3 months

PROMIS Global-10 (Patient-Reported Outcomes Measurement Information System), reported as T-scores standardized to the US general population (mean=50, SD=10). Four subscores reported separately: Global Mental Health (GMH), Global Physical Health (GPH), Mental Component Score (MCS), and Physical Component Score (PCS). For all subscores, higher T-scores represent better health outcomes. Values reported as change from baseline to 3 months postoperatively (3-month score minus baseline score); higher change scores indicate greater improvement. Assessed at baseline and 3 months postoperatively.

The Use of Venlafaxine in Reducing Acute Post-Surgical Pain and Opioid Consumption in Primary Total Knee Replacement