A long-term, open-label safety study of single-entity hydrocodone bitartrate extended release for the treatment of moderate to severe chronic pain

Srinivas Nalamachu,1,2 Richard L Rauck,3 Martin E Hale,4 Orlando G Florete Jr,5 Cynthia Y Robinson,6 Stephen J Farr,6 1International Clinical Research Institute, Overland Park, KS, USA; 2Kansas University Medical Center, Kansas City, KS, USA; 3Carolinas Pain Institute, Center for Clinical Research, Wake Forest University School of Medicine, Winston-Salem, NC, USA; 4Gold Coast Research, LLC, Weston, FL, USA; 5Institute of Pain Management, Jacksonville, FL, USA; 6Zogenix, Inc., Emeryville, CA, USA Objective: To evaluate the long-term safety, tolerability, and effectiveness of single-entity extended-release hydrocodone in opioid-experienced subjects with moderate to severe chronic pain not receiving adequate pain relief or experiencing intolerable side effects from their current opioid. Methods: This multicenter, open-label study started with a conversion/titration phase (≤6 weeks) where subjects (n=638) were converted to individualized doses (range 20–300 mg) of extended-release hydrocodone dosed every 12 hours, followed by a 48-week maintenance phase (n=424). The primary objective (safety and tolerability) and the secondary objective (long-term efficacy as measured by change in average pain score; 0= no pain, 10= worst imaginable pain) were monitored throughout the study. Results: Subjects were treated for a range of chronic pain etiologies, including osteoarthritis, low back pain, and neuropathic and musculoskeletal conditions. The mean hydrocodone equivalent dose at screening was 68.9±62.2 mg/day and increased to 139.5±81.7 mg/day at the start of the maintenance phase. Unlimited dose adjustments were permitted at the investigator's discretion during the maintenance phase, reflecting typical clinical practice. No unexpected safety issues were reported. Common adverse events during the conversion/titration and maintenance phases, respectively, were constipation (11.3% and 12.5%), nausea (10.7% and 9.9%), vomiting (4.1% and 9.7%), and somnolence (7.7% and 4.2%). Four deaths occurred during the study; all were considered unrelated to treatment. One subject died 13 months after the study ended. From the start to end of the conversion/titration phase, 84% of subjects had a clinically meaningful improvement in average pain score (≥30% improvement), and the mean average pain scores remained stable through the maintenance phase. Conclusion: This single-entity, extended-release formulation of hydrocodone was generally safe, well tolerated, and effective in reducing chronic pain for 48 weeks. This formulation provides a new option for patients experiencing chronic pain, especially those who are taking immediate-release hydrocodone and have concerns about liver toxicity due to acetaminophen. Keywords: opioids, long-term, chronic pain, hydrocodone, extended-release, single-entity