To determine the dose of naltrexone hydrochloride (HCL) that will reduce the “liking” scale of the Drug Evaluation Questionnaire (DEQ) when administered with oxycodone HCL.

Methods:

Eighty-two males, 18 to 50 years, who had abused opioids on at least 5 occasions within 12 months but were not physically dependent on opioids, were randomized to receive a combined dose of oxycodone HCL and naltrexone HCL.

Four groups received 40 mg oxycodone with individual groups receiving 0, 1X, 5X, or 10X mg of naltrexone. One group received 20 mg oxycodone with 2.5X mg naltrexone; and two groups received 10 mg of oxycodone: 1 with 0 mg of naltrexone and one with 1.25X mg of naltrexone.

Subjects completed the following measures at selected times from pre-dose to 5 hours post treatment: The Drug Effects Questionnaire (DEQ), consisting of 9 items related to drug effects rated from 0 = None to 100 = Extremely; and the Morphine Benzedrine Group (ARCI-MBG) Scale, consisting of 16 items rated on a scale from 0 = False to 3 = True.

Results:

At 40 mg of oxycodone, 5X mg and 10X mg of naltrexone showed significantly lower DEQ and MBG scores compared to 0 mg naltrexone. The 1X mg dose showed lower scores for only a few test items.

At 20 mg of oxycodone, 2.5X mg of naltrexone showed significant decreases from 0 mg naltrexone for DEQ items 1, 2, 4, and 5 and the MBG total score. No discrimination was found between 0 and 1.25X mg of naltrexone at 10 mg of oxycodone.

Conclusion:

Naltrexone was found to reduce the euphoric (“liking”) effect of oxycodone, suggesting potential value in formulating naltrexone-oxycodone abuse-deterrent analgesics. The ratio of naltrexone to oxycodone is proprietary, but the euphoria-reducing ratio was similar at 40 and 20 mg oxycodone.