Objective: Although opioid analgesics are used in the management of neuropathic pain syndromes, evidence of their efficacy remains to be established. We evaluated the clinical efficacy and safety of oxycodone in neuropathic pain using postherpetic neuralgia as a model.
Methods: Patients with postherpetic neuralgia of at least moderate intensity were randomized to controlled-release oxycodone 10 mg or placebo every 12 hours, each for 4 weeks, using a double-blind, crossover design. The dose was increased weekly up to a possible maximum of 30 mg every 12 hours. Pain intensity and pain relief were assessed daily, and steady (ongoing) pain, brief (paroxysmal) pain, skin pain (allodynia), and pain relief were recorded at weekly visits. Clinical effectiveness, disability, and treatment preference were also assessed.
Results: Fifty patients were enrolled and 38 completed the study (16 men, 22 women, age 70+/-11 years, onset of postherpetic neuralgia 31+/-29 months, duration of pain 18+/-5 hours per day). The oxycodone dose during the final week was 45+/-17 mg per day. Compared with placebo, oxycodone resulted in pain relief (2.9+/-1.2 versus 1.8+/-1.1, p=0.0001) and reductions in steady pain (34+/-26 versus 55+/-27 mm, p=0.0001), allodynia (32+/-26 versus 50+/-30 mm, p=0.0004), and paroxysmal spontaneous pain (22+/-24 versus 42+/-32 mm, p=0.0001). Global effectiveness, disability, and masked patient preference all showed superior scores with oxycodone relative to placebo (1.8+/-1.1 versus 0.7+/-1.0, p=0.0001; 0.3+/-0.8 versus 0.7+/-1.0, p=0.041; 67% versus 11%, p=0.001, respectively).
Conclusions: Controlled-release oxycodone is an effective analgesic for the management of steady pain, paroxysmal spontaneous pain, and allodynia, which frequently characterize postherpetic neuralgia.