Flexible Dose Superior to Low-Dose MoxDuo for Pain Relief in Total Knee Arthroplasty

AUSTIN,TX— Investigators at the American Pain Society's 30th Annual Scientific Meeting reported on a study of MoxDuo IR, a 3:2 fixed-dose capsule combination of morphine + oxycodone, in patients with moderate-to-severe pain following total knee arthroplasty (TKA).

The multicenter, double-blind, randomized, parallel-group study compared two doses of MoxDuo in142 patients administered every 4 to 6 hours for up to 48 hours: a flexible dose that ranged from 6mg/4mg up to 24mg/16mg or a fixed low dose of 3mg/2mg with a 6mg/4mg loading dose. Acetaminophen rescue medication (≤1000mg every 4-6 hours; ≤4000mg in any 24-hour period as needed) was permitted, noted study investigator Patricia T. Richards, MD, PhD, of QRxPharma Inc., Bedminster, NJ, and colleagues.

Following TKA surgery, patients received PCA morphine for up to 24 hours that was then discontinued. When pain intensity level was at least 4 on Numeric Pain Rating Scale (NPRS), patients were randomized to treatment at a 1:1 ratio. The primary efficacy variable was the time-weighted sum of pain intensity difference (SPID) from 0-48 hours after the first dose.

Median age of the patients was 66 years; 57% of patients were female. The median number of doses required during the 48-hour treatment period was 8.5 for flexible-dose MoxDuo and 10 for fixed low-dose MoxDuo. For the 0-24 hour interval, 37 patients (54.4%) in the flexible-dose group vs. 29 (39.2%) in the low-dose group were considered responders; for the 0-48 hour interval, this was 41 patients (60.3%) and 38 (51.4%), respectively. The proportion of patients who requested supplemental analgesia from 0-48 hours was 80.9% in the flexible dose arm and 85.1% in the low dose arm.

Most common opioid-related, treatment-emergent adverse events (moderate/severe) included nausea (33.8% in the flexible MoxDuo group and 10.8% in the MoxDuo low-dose group) and constipation (16.2% vs. 17.6%, respectively). No patients had a respiratory rate <10/min during 0-48 hours.

The investigators concluded that MoxDuo represents a valuable option for the treatment of moderate-severe acute postoperative pain. Previous studies have shown MoxDuo to produce substantial reductions in the rate of moderate/severe nausea, emesis, and dizziness relative to equianalgesic doses of morphine or of oxycodone.