Effectiveness of pregabalin for treatment of chronic cervical radiculopathy with upper limb radiating pain: an 8-week, multicenter prospective observational study in Japanese primary care settings.

Background: Despite high prevalence of chronic neck pain in Japan and the negative impact pain has on patient's quality of life (QoL), the therapeutic value of pregabalin for chronic neck pain with a neuropathic pain (NeP) component has not been assessed in a typical Japanese health care setting. Methods: An 8-week, non-interventional, multicenter, observational study of Japanese adults (>= 20 years) with chronic refractory cervical pain including a NeP element (for >= 12 weeks) and sleep disturbance on the Pain-Related Sleep-Interference Scale (PRSIS) >= 1 (from 0 "does not interfere with sleep" to 10 "completely interferes"). Patients received either usual care with conventional analgesics or pregabalin (150-600 mg/day) for 8 weeks. "Usual care" with analgesics or other treatment(s) was determined based on physician's best clinical judgment. Primary endpoint was change from baseline to week 8 in PRSIS. Secondary endpoints included: change from baseline to week 4 in PRSIS, and to week 4 and 8 in pain Numerical Rating Scale (NRS; from 0 "no pain" to 10 "worst possible pain"), and on the Neck Disability Index (NDI). Other assessments of QoL were undertaken. Safety was monitored. Results: Overall, 369 patients received pregabalin (n=145) or usual care (n=224). The median (range) dose of pregabalin was 49.6 (25.0-251.5) mg/day. Least-squares mean change in PRSIS from baseline to week 8 favored pregabalin (-1.167 vs-0.269; treatment difference-0.898 [95% CI-1.262,-0.535], P<0.001). Similar observations were seen at week 4 in favor of pregabalin versus usual care (P<0.001). Pregabalin significantly improved pain NRS and NDI scores at weeks 4 and 8 (all P<0.001). Improvements in QoL versus usual care were also observed. Pregabalin was generally well tolerated. Conclusion: In this open-label study, pregabalin improved PRSIS and resulted in clinically meaningful reductions in pain in Japanese patients with NeP associated with chronic cervical pain.