Effect of Duloxetine 60 mg to 120 mg Once Daily in Patients With Chronic Low Back Pain

The primary purpose of your participation in this study is to help answer the following research question, and not to provide you treatment for your condition. Whether duloxetine once daily can help patients with Chronic Low Back Pain. Patients who do not have their pain reduced by at least 30% by week 7 will be given 120 mg dose for the duration of the study. After the 13 week double blind period, patients randomized to placebo will switch to duloxetine 60 mg or 120 mg in the 41-week extension period.