Inclusion Criteria:

• Age 18 - 75 yrs
• Male; or non-pregnant/non-lactating female
• Use of adequate birth-control measures as determined by investigator for females of child-bearing potential
• Diagnosis of TN using IHS criteria (see appendix A)
• Able to cooperate with and understand study instructions
• Signed informed consent prior to entering study
• Patients must be on a stable dose of concomitant medications for treatment of TN for at least 4 weeks (see below)
• If subject is currently receiving a tricyclic antidepressant, anticonvulsant, and/or Class I antiarrhythmic (e.g., amitriptyline, mexiletine, phenytoin, gabapentin or carbamazepine) for treatment of pain or any other condition, subject must be willing and able to maintain stable doses of these agents within 4 weeks prior to randomization and throughout the study (i.e., doses cannot be increased or decreased during this period).
• Subjects who require "rescue" analgesic medication during the study will be allowed to use increased doses of their current (pre-study) opioid and/or non opioid analgesics as clinically indicated (e.g., NSAIDs, acetaminophen, COX-2 inhibitors, topical analgesics). Subjects will be allowed to use a new analgesic for a limited time for non-neuropathic pain (e.g., headache, sinusitis, strained muscle, minor ache and pain), but will be prohibited from initiating therapy with a new analgesic agent and use it continuously throughout the remainder of the study.
• If subject is not currently receiving a tricyclic antidepressant, anticonvulsant, and/or Class I antiarrhythmic (e.g., amitriptyline, mexiletine, phenytoin, gabapentin or carbamazepine) for treatment of pain or any other condition, subject must be willing and able to abstain from initiation of these agents within 4 weeks prior to randomization and throughout the study.
• Subject must be willing and able to abstain from initiating an alternative therapy (e.g., acupuncture, massage or physical therapy) for pain relief during the study. (NOTE: subjects who are currently using alternative therapy for pain relief can be enrolled if they are willing and able to maintain such therapy stable throughout the study.)

Exclusion Criteria:

• Serious hepatic, respiratory, hematologic, cardiovascular or renal condition
• Neurologic pain other than TN, with the exception of occasional migranous/ tension-type headaches. (<4 headaches per month)
• Psychiatric or medical condition that might compromise participation in study, as determined by the investigator
• Use of opioid analgesic as treatment of neuralgia (>2 days per week)
• Administration of any investigational drug within 30 days prior to screening
• Concurrent use of sodium valproate
• Current diagnosis of active epilepsy or any active seizure disorder requiring chronic therapy with antiepileptic drug(s)
• Pregnant or breastfeeding women
• History of substance abuse/ alcoholism