Pain relief can come at a price—physical dependence—when opioid therapy is prolonged. Researchers from Lifetree Clinical Research in Salt Lake City, Utah, and Pain Therapeutics in San Francisco, California, suggest adding a little naltrexone.
Oxytrex (Pain Therapeutics), an investigational drug combining oxycodone (OxyContin, Purdue Pharma) and ultra-low-dose naltrexone, provided strong analgesia while minimizing physical dependence.
In a phase 3 clinical trial, 719 patients were randomly assigned to placebo, oxycodone four times daily, or Oxytrex four times daily or twice daily. Each Oxytrex tablet contained naltrexone 1 mcg. The twice-daily and four-times-daily Oxytrex treatments provided naltrexone 2 mcg/ day and 4 mcg/day.
Opioid-related adverse events did not differ significantly among the three treatment groups; however, the Oxytrex patients needed a significantly lower amount of medication to achieve compaable analgesia. Patients taking Oxytrex twice a day reported 55% less physical dependence than did patients receiving oxycodone 24 hours after stopping treatment; they also reported less moderate-to-severe constipation (44%), less somnolence (33%), and less pruritus (51%).
Oxytrex twice daily also provided a better safety profile, compared with four-times-daily oxycodone, by significantly reducing the number of moderate-to-severe events. A subgroup analysis showed a slightly stronger effect in reducing dependence on the medication in patients older than 50 years of age.
Although the researchers acknowledged that lowering the oxycodone dose might have contributed to the reduction in dependence, they suggest that it is unlikely that the difference of 4.3 mg would have caused such a profound decrease.
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One major limitation of the study was the large number of patients who dropped out—more than 50%—in all treatment groups. The percentage of dropouts attributable to adverse events during titration was somewhat higher in those receiving twice-daily Oxytrex (14% versus 22%). The difference was most likely a result of the higher individual doses of oxycodone in twice-daily versus four-times-daily administration, the researchers say. They advised titrating the twice-daily Oxytrex dose more slowly and starting with a lower dose.