Oxytrex^®: an oxycodone and ultra-low-dose naltrexone formulation

Abstract

Oxytrex^® (Pain Therapeutics, Inc.) is an oral opioid that combines a therapeutic amount of oxycodone with an ultra-low dose of the antagonist naltrexone. Animal data indicate that this combination minimizes the development of physical dependence and analgesic tolerance while prolonging analgesia. Oxytrex is in late-stage clinical development by Pain Therapeutics for the treatment of moderate-to-severe chronic pain. To evaluate the safety and efficacy of the oxycodone/naltrexone combination, three clinical studies have been conducted, one in healthy volunteers and the other two in patients with chronic pain. The putative mechanism of ultra-low-dose naltrexone is to prevent an alteration in G-protein coupling by opioid receptors that is associated with opioid tolerance and dependence. Opioid agonists are initially inhibitory but become excitatory through constant opioid receptor activity. The agonist/antagonist combination of Oxytrex may reduce the conversion from an inhibitory to an excitatory receptor, thereby decreasing the development of tolerance and physical dependence.

Keywords::

• analgesia
• chronic pain
• naltrexone
• opioids
• oxycodone
• physical dependence
• tolerance
• ultra-low-dose antagonist

Disclosure

As of June 2007, LR Webster has been a Consultant and conducted research for Medtronic. LR Webster has been a Consultant and received an honorarium from Cephalon, Elan Corp. (and conducted research), King Pharmaceuticals, Advanced Bionics (and conducted research for). LR Webster has also conducted research for Torreypines Therapeutics, Takeda Pharmaceuticals, Jazz Pharmaceutical, Zars, Inc., Forest Laboratories, Merck, Inc., Purdue Pharma, Durect Corp., Mallinckrodt Pharmaceuticals, GlaxoSmithKline, Neurogesx, Inc., Predix Pharmaceuticals, Elite Pharmaceuticals and CoMentis.

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