Milnacipran for Lumbosacral Radicular Pain

The current study evaluates the potential efficacy of milnacipran in reducing lower extremity radicular pain associated with lumbar disk disease. Milnacipran will be titrated based on efficacy and tolerability aimed at the higher end of the therapeutic range; a recent study of a serotonin norepinephrine reuptake inhibitor in patients with osteoarthritis pain suggests efficacy may be dose related. Patients are likely to have concomitant nociceptive lower back pain, and cotreatment with opioids, muscle relaxants, benzodiazepines, or nonsteroidal anti-inflammatory drugs at stable doses will be permitted. Patients participating in stable regimen of physical therapy or biofeedback will be eligible. Procedural interventions (e.g. epidural steroid injection, nerve block, facet radioablation, acupuncture) during the study and 3 months prior will be exclusionary. Anticonvulsants, tramadol, and other antidepressant drugs will be excluded.

The study is a ten-week randomized, double-blind, placebo-controlled trial (RCT) of milnacipran (100-200 mg/day dosed twice a day) for radicular pain associated with lumbosacral disk disease.

Outcome measures and safety assessments will be obtained at weeks 1, 2, 4, 6, 8, and 10 according to the protocol schedule of assessments.

Inclusion criteria

• Subject is a male or female adult outpatient age 18 or older at the time of consent.
• Subject experiences chronic (> 6 months) radicular pain at least 5 days a week described as sharp or shooting below the level of the knee associated with lumbar or sacral disk disease without suspicion of recent injury; remote (>1 year ago) history of surgical intervention (e.g. "failed back syndrome") is allowed provided current symptoms meet severity criterion.
• Subject-rated VAS specifically related to radicular pain > or = 40 mm at screen and baseline visits
• Subject has an understanding, ability and willingness to fully comply with study procedures and restrictions.
• Subject has the ability to provide written, personally signed and dated informed consent to participate in the study, in accordance with the International Conference on Harmonisation (ICH) Good Clinical Practice (GCP) Guideline E6 and applicable regulations, before completing any study-related procedures.

Exclusion criteria

• Subjects unable to complete assessments due to language or cognitive impairment
• Subjects treated with antidepressant or anticonvulsant medication within 4 weeks of screening visit (6 weeks for fluoxetine).
• Subjects taking monoamine oxidase inhibitors
• Subjects who have received procedural intervention within 3 months of screen.
• Subjects with known sensitivity to milnacipran.
• Subjects unable to complete the questionnaires due to language or cognitive impairment.
• Subjects with a history of bipolar disorder or psychosis as confirmed by the Mini International Neuropsychiatric Interview (MINI).
• Subject currently has (or had a history within the last 6 months of) a drug dependence or substance abuse disorder according to Diagnostic and Statistical Manual for Mental Disorders, Text Revision criteria (excluding nicotine).
• Subjects who are currently considered a suicide risk, any subject who has previously made a suicide attempt or who has a prior history of or are currently demonstrating active suicidal ideation.
• Subject has any clinically significant electrocardiogram (ECG) or clinically significant laboratory abnormality (including a positive urine drug screen) at Screening.
• Subject has a concurrent chronic or acute illness, disability, or other condition that might confound the results of safety assessments administered in the study or that might increase risk to the subject. Similarly, the subject will be excluded if he or she has any additional condition(s) that in the Investigator's opinion would prohibit the subject from completing the study or would not be in the best interest of the subject. This would include any significant illness or unstable medical condition that could lead to difficulty complying with the protocol.
• Subjects who are pregnant or who are nursing
• Subjects who do not agree to use adequate and reliable contraception throughout the study.
• Subject previously completed, discontinued or was withdrawn from this study.
• Subject has taken an investigational drug or taken part in a clinical trial within 30 days prior to Screening.
• Subjects with liver disease or reduced liver function
• Subjects with obstructive uropathies
• Subjects who consume alcohol in amounts viewed by the Investigator to be contraindicated
• Subjects with uncontrolled narrow angle glaucoma
• Subjects with seizure disorders
• Subjects with bleeding disorders or use of other medications that may cause bleeding