<qa>  What is the secondary objective of the study?The secondary objectives are to investigate the dose-response relationship of three dose levels of bicifadine, to evaluate the clinical meaningfulness of bicifadine efficacy, to evaluate the effect of bicifadine on function and general quality of life, to describe the population pharmacokinetics of bicifadine in patients with chronic low back pain, and to evaluate safety following discontinuation of bicifadine treatment. 