Once-Daily Opioid Therapy Effective Option for Back Pain

San Antonio—Once-daily morphine sulfate (Kadim, Avinza) extended release is as effective as a twice-daily regimen for reducing pain and improving sleep scores in patients with chronic, moderate-to-severe low back pain, data presented at the American Pain Society’s 25th Annual Scientific Meeting show.

“The once-daily morphine sulfate dose provides a more convenient dosing schedule and improved drug accountability that may improve patient compliance,” said Richard L. Rauck, MD, of the Carolinas Pain Institute, Winston-Salem, NC.

Dr Rauck presented the results of a study comparing the once-daily opioid with twice-daily oxycodone (OxyContin) controlled release in 392 patients (aged 30-70) with mechanical or nonmechanical low back pain.

On a 10-point pain scale, all patients had a score of at least 4 and all had suffered back pain for at least 6 months before the study began. Patients who had undergone but did not respond to >2 surgical procedures for back pain were excluded, as were those who had received corticosteroid injections within 2 months before study entry and those who had used any controlled-release opioid during the 6 months preceding the study.

Once-daily morphine sulfate was given to 203 patients and twice-daily oxycodone to 189 patients. Dosages were uptitrated for the first 3 to 6 weeks, followed by an 8-week treatment evaluation. The mean daily doses used in the evaluation phase were 63.7 mg morphine sulfate and 53.3 mg oxycodone.

At the end of the evaluation period, patients treated with morphine sulfate had a mean 3.1 point pain score improvement compared with 2.5 points for those taking oxycodone (P <.05).

A 16-week extension phase included 79 patients receiving morphine sulfate and 95 patients taking oxycodone. The mean daily doses were 86 mg for morphine sulfate and 79.5 mg for oxycodone. The difference in pain scores between the 2 groups continued to favor once-daily morphine sulfate after 2 (P = .029), 3 (P = .023), and 4 (P = .055) months of treatment.

A significant difference was seen in mean sleep scores between the 2 treatments after the 8-week evaluation phase, with a 33% improvement in the morphine sulfate group versus a 17% improvement in the oxycodone group (P = .006). After the extension phase, overall sleep scores improved significantly and similarly from baseline in both treatment groups.

Opioid-related side effects were similar in the 2 groups and included constipation, drowsiness, dizziness, dry mouth, pruritus, nausea, and vomiting. The incidence and severity of side effects decreased in patients who participated in the extension phase.

Dr Rauck said that morphine sulfate has been previously shown to produce less opioid plasma level fluctuation during treatment compared with oxycodone, which may contribute to the better pain relief and sleep scores seen in this study.

He added that while both agents were effective for chronic low back pain, the once-daily morphine sulfate achieved better pain relief with a lower morphine-equivalent dose. The daily morphine-equivalent dose was 63.7 mg for morphine sulfate and 80 mg for oxycodone during the 8-week evaluation phase and 86 mg for morphine sulfate versus 119 mg for oxycodone during the 16-week extension.