Safety and Efficacy Study in Subjects With Diabetic Neuropathic Pain

* If female, subject is either postmenopausal for at least two (2) years or surgically sterile or is practicing at least one (1) method of birth control. * If female, subject must have negative results for pregnancy tests. * The subject must have a diagnosis of diabetes mellitus (Type 1 or Type 2) and a diagnosis of DNP. * Subject's DNP must be present for a minimum of six (6) months and should have begun in the feet with relative symmetrical onset. * Subject has an HgbA1c \<= 9. Subjects who have an HgbA1c \> 9 and \<= 11 may be included in the study. * If male, the subject is surgically sterile (vasectomy), is sexually inactive, or is using a barrier method (condom) of birth control for the duration of the study and for 7 days following the last dose of study drug.

* The subject has failed previous treatment with duloxetine for DNP. * Subject has a diagnosis of narrow-angle glaucoma. * Subject has a history of an allergic reaction or intolerance to duloxetine, acetaminophen, or any other NNR agonist. * Subject has a diagnosis of fibromyalgia that requires treatment. * Subject has a functioning implanted medical device (spinal cord stimulator, intrathecal pump or peripheral nerve stimulator) for the treatment of neuropathic pain. * Subject has a history of seizures (febrile may be ok) or major depressive episode within the past two (2) years or major psychiatric disorder including bipolar disorder, schizophrenia or borderline personality disorder. * Subject has a history of myocardial infarction (MI) within six (6) months of the Screening Visit. * Subject has unstable angina. * Subject has ventricular arrhythmia requiring anti-arrhythmic therapy. * Subject has undergone a cardiac revascularization procedure within 30 days of Screening. * Subject has uncontrolled hypertension (HTN) defined as a systolic blood pressure (BP) \>= 160 and/or a diastolic blood pressure (BP) \>= 100 at Screening and/or Baseline. * Subject has a clinically significant abnormal ECG at Screening * Subject has an active malignancy of any type or has been diagnosed with or treated for cancer within the past 5 years. * Subject has a positive result for drugs of abuse at Screening with the exception of a positive result for a known prescribed medication. * Subject's screening laboratory results show hepatitis A, B or C. * Subject has a known or suspected history of Human Immunodeficiency Virus (HIV).