PALM SPRINGS, CA — In a study evaluating combination morphine/oxycodone, researchers found the drug to produce less oxygen desaturation in patients with acute postoperative pain than either single component alone when administered in equianalgesic doses. The results of the randomized, double-blind study were presented at the 2012 American Academy of Pain Medicine Annual Meeting.

Patricia Richards, MD, PhD, of QRx Pharma in Bedminster, NJ, and colleagues from the Advanced Clinical Research Institute in Anaheim, CA, sought to determine the effect of combination morphine/oxycodone vs. morphine and oxycodone on oxygen desaturations (SpO2 <90%) in equianalgesic doses. The study compared morphine/oxycodone 12mg/8mg every 6 hours vs. morphine 24mg and oxycodone 16mg every 6 hours following bunionectomy surgery. Patients (n=375) were ≥18 years of age, American Society of Anesthesiologists (ASA) class I–III, and had moderate to severe pain. SpO2% was measured every two seconds over 48 hours with a pulse oximeter. The primary outcome was the AUC of the desaturation events over 48 hours (duration x magnitude of <90% SpO2). The study researchers assessed the change from baseline in pain intensity.

The AUC was lower with morphine/oxycodone vs. morphine and oxycodone for total and most severe desaturations. The median AUC of individual desaturations was 0.012 with morphine/oxycodone, 0.015 with morphine, and 0.022 with oxycodone (P =0.018, ANCOVA). Among patients with the worst observed desaturations, the risk was significantly greater with morphine (P <0.009) or oxycodone (P<0.002) vs. morphine/oxycodone (4:1 or 5:1 for morphine or oxycodone vs. morphine/oxycodone). The intensity of severe oxygen desaturation was significantly less (P <0.05) with morphine/oxycodone vs. morphine or oxycodone. For the worst desaturations, the mean SpO2 value was 53% with oxycodone, 68% with morphine, and 74% with morphine/oxycodone. Mean sum of pain-intensity difference over 48 hours (SPID48) scores were comparable among treatment groups.

Dr. Richards et al. found that at equianalgesic doses, oxygen desaturations were shorter and less intense with morphine/oxycodone vs. morphine or oxycodone. The respiratory benefits of morphine/oxycodone were demonstrated in a broad population needing opioids for moderate to severe acute pain.