Efficacy and Safety of Bicifadine in the Treatment of Chronic Low Back Pain

Main Inclusion Criteria: * Patients with low back pain assessed as Class 1, Class 2 or Class 3 according to the Quebec Task Force Classification for Spinal Disorders and without detectable leg weakness on neurological examination. * Patients with pain categorized as Class 1 according to the Quebec Task Force Classification must have a Roland-Morris Disability Rating of \>17 at baseline to qualify. Patients with pain categorized as Class 2 or Class 3 according to the Quebec Task Force Classification must have a Roland-Morris Disability Rating of at least 10 at baseline to qualify. * Patients must have required daily analgesics for the treatment of low back pain for at least 3 months prior dosing. Main Exclusion Criteria: * Patients may not have persistent moderate or severe pain in a location other than the lower back (with the exception of radiation to the lower extremity). * Patients must not have had lower back surgery within 6 months prior to baseline, nor epidural corticosteroid injections within 3 months prior to baseline. * Patients may not have an unstable medical condition.