Clinical Neuropharmacology of Pain in Spinal Cord Injury- Dextromethorphan Dose Response Clinical Trial

Inclusion criteria

• Healthy male or female adults, age 18 to 70 with central neuropathic pain for a minimum of 3 months following SCI as confirmed by neurologic evaluation, with an average pain intensity score of at least moderate over at least 50% of the day for the 7 days prior to the screening visit and over the 7 days prior to starting study medication.
• Subjects used no medication or a stabilized medication regimen for chronic and well-controlled medical conditions
• Serum laboratory examination obtained at study entry:

• Liver function tests (albumin within 20% of normal, SGOT/SGPT within 50% of normal).
• For women of childbearing age: negative serum beta HCG.
• Postmenopausal women, or be physically incapable of childbearing, or be practicing an acceptable method of birth control.
• Normal cognitive function.
• Normal communicative ability (English).
• Ability to demonstrate competence in recording five times daily in pain diary for 1 week (with 100% compliance), and in completing required questionnaires.
• Signed informed consent.

Exclusion criteria

• Pregnancy or breast-feeding.
• Renal or hepatic dysfunction.
• Significant cardiac disease (e.g. MI within 1 year).
• Signs or symptoms of central neurological disorder, excluding SCI.
• Severe psychological disorder requiring treatment.
• Concurrent use of monoamine oxidase inhibitors within 2 weeks prior to study entry.
• Use of known CYP2D6 (but not CYP3A4) inhibitors or inducers.
• History of hypersensitivity or intolerance to dextromethorphan or lidocaine.
• Chronic substance abuse, including alcohol.
• Participation in a study of an investigational drug or device within 30 days prior to screening for this study.
• Poor metabolizer of P450 2D6 substrates.