Comparison of the Efficacy of Duloxetine With Placebo in Patients With Chronic Low Back Pain With a Radicular Component

Inclusion Criteria: * Low back pain ( below L1) * Chronic pain, \>6 months * Visual Analogue Scale (VAS) ≥ 5 * Back pain with radicular component defined as pain with a burning, tingling sensation within the anatomic distribution of the nerve root and diagnosed by painDETECT questionnaire * Failed back surgery Exclusion Criteria: * Current mood disorder (dysthymia, bipolar mood disorder) * Major Depression \> 12 months (Beck Depression Inventory Score ≥ 18) * History of a psychoactive substance use disorder within the preceding 12 months * Major coexisting medical illness (e.g. severe heart failure, pulmonary hypertension, renal insufficiency) * Glaucoma * Acute myocardial infarction * uncontrolled hypertension * Prostate hyperplasia * History of convulsion * Pregnancy; women of childbearing age will be required to use contraceptives during the duration of the study. Furthermore a pregnancy test will be performed prior to the beginning of the study and once a month during the study period. * Participation in a clinical trial in the 3 weeks preceding the study * Allergy to study medication * Use of the following medication: * opioids except for tramadol, * benzodiazepines other than indicated at low doses for sleep disorders * antineuropathic medication including except for that specified in the study protocol * muscle relaxants * antidepressants other than indicated at low doses for sleep disorders * NSAID, Paracetamol * non-selective MAO-Inhibitors * Fluvoxamine, Ciprofloxacin, Enoxacin * Selective Serotonin-reuptake Inhibitors (SSRI) if tapering of these drugs is impossible before inclusion. * Impaired kidney function (Creatinine \> 1.5mg/dl) * Impaired hepatic function (GOT, GPT \>2 fold standard levels) * Patients who are not able to understand the study measures and are not able to complete pain assessment forms.