A Study of Duloxetine (LY248686) in Participants With Chronic Low Back Pain

Inclusion Criteria: * Participants with CLBP present for the preceding 6 months or longer * Participants used nonsteroidal anti-inflammatory drugs for CLBP for more than 14 days on average per month in the past 3 months and more than 14 days in one month prior to screening * Participants having a score of ≥4 on Brief Pain Inventory (BPI) average pain score before randomized * Female participants having child-bearing potential must test negative (-) on a pregnancy test Exclusion Criteria: * Participants have received treatment within the last 30 days with a drug that has not received regulatory approval for any indication * Participants having a history of low back surgery * Participants having received epidural steroids, facet block, nerve block or other invasive procedures aimed to reduce low back pain within one month prior to screening * Participants who have any difficulties to fulfill diary appropriately * Participants having any previous diagnosis of psychosis, bipolar disorder, or schizoaffective disorder * Participants having major depressive disorder as determined using depression module of the Mini-International Neuropsychiatric Interview * Participants having primary painful condition due to other than CLBP * Participants being anticipated by the investigator to require use of nonsteroidal anti-inflammatory drugs and includes acetaminophen, opioid analgesics, or other excluded medication for the duration of the study * Participants being considered as inappropriate for participation to the study for any medical or other reason as judged by the investigator * Participants answering "yes" to any of the questions about active suicidal ideation/intent/behaviors occurring within the past month (Columbia Suicide Severity Rating Scale, Suicide Ideation section - Questions 4 and 5; Suicidal Behavior section) * Participants having a positive urine drug screen for any substances of abuse or excluded medication * Participants having alanine aminotransferase or aspartate aminotransferase higher than 100 International Units per Liter (IU/L) or total bilirubin higher than 1.6 milligram per deciliter (mg/dL) * Participants having serum creatinine level higher than 2.0 mg/dL, or had renal transplantation or receiving renal dialysis * Participants having uncorrected thyroid disease, uncontrolled narrow-angle glaucoma, history of uncontrolled seizures, or uncontrolled or poorly controlled hypertension * Participants have had previous exposure to duloxetine or com…