Inclusion Criteria:

1. Signed written informed consent
2. Male or female aged 18 - 75
3. Diagnosis of diabetes mellitus
4. No change in diabetes medications within 4 weeks before screening
5. Daily pain attributed to diabetic neuropathy present for at least 6 months immediately prior to study entry
6. Presents with pain due to bilateral peripheral neuropathy caused by Type I or Type II diabetes mellitus. Pain must have begun in the feet, with relatively symmetrical onset. Diagnosis confirmed by a score of at least 2 on Section B of the MNSI
7. Judged to be reliable and agree to keep all appointments required by the protocol

8. Females should be of non child-bearing potential

   Additionally, at the baseline visit:

9. A mean average pain intensity of at least 4, but less than or equal to 9, on an 11 point Likert NPRS recorded twice daily during the two week placebo run-in; any patient who experiences a >30% decrease in the mean pain score compared to Day -14 during placebo run-in will be excluded, regardless of whether their final score is >4
10. Full completion of daily diaries for at least 11 of the days up to Day -1
11. Compliance in taking placebo run-in medication twice daily for at least 11 of the days up to Day -1

Exclusion Criteria:

1. Any clinically significant neurologic disorders (except DPNP)
2. Any clinically significant or unstable medical or psychiatric condition that would affect the patient's ability to participate in the study
3. Prior renal transplant, current renal dialysis
4. Pernicious anemia
5. Untreated hypothyroidism
6. Amputations or persistent ulceration due to diabetes mellitus
7. Any cardiovascular condition that would contraindicate the use of sympathomimetic amines
8. Uncontrolled hypertension
9. Known or at high risk of HIV infection
10. Any anticipated need for surgery during the study
11. Increased risk of seizures (defined as a history of seizure disorder (including alcoholic seizures), family history of seizures and history of head trauma that resulted in loss of consciousness or concussion).
12. Any malignancy in the past 2 years (except basal cell carcinoma)
13. Pain that cannot be clearly differentiated from, or conditions that interfere with, the assessment of diabetic neuropathic pain
14. Use of anticonvulsants, antidepressants (particularly MAO inhibitors), or prescription membrane-stabilizing agents, including topical therapies. Patients currently taking drugs in these classes may have them discontinued prior to entry into the placebo run-in period.
15. Use of opioids, especially meperidine (pethidine)