This study is to compare the tolerability of different methods for switching from another medication to duloxetine for the management of diabetic nerve pain. The primary objective is to compare the most gradual method with the most abrupt method, to see if they have different tolerability.

Inclusion Criteria:

• You must have been diagnosed with Diabetic Peripheral Neuropathic Pain.
• You must have been taking the same dose of amitriptyline once daily at bedtime for at least four (4) weeks.
• You must have stable glycemic control.
• You must be able to visit the doctor's office once a week for ten (10) weeks.

Exclusion Criteria:

• You are in the acute recovery phase following myocardial infarction.
• You have Major Depressive Disorder, an Anxiety Disorder, or some other psychiatric illnesses that the doctor will ask you about.
• You are allergic to amitriptyline or duloxetine.
• You are currently taking an anticonvulsant, cisapride (Propulsid), or if you have taken an opioid for three or more consecutive days during the 14 days prior to Visit 2.
• You have uncontrolled narrow angle glaucoma.