Study Evaluating the Long-Term Safety of Desvenlafaxine Succinate Sustained-Release (DVS SR) in Subjects With Pain Associated With Diabetic Peripheral Neuropathy

Inclusion Criteria: * Outpatients who have completed double-blind treatment in study 322 (NCT01050218) for DPN. Subjects must have completed all scheduled evaluations, with no major protocol violations and no events that, in the opinion of the investigator, would preclude the subject's entry into the long-term open-label study. * Women of childbearing potential must have a negative serum pregnancy test on day 91 of the short-term study. A woman of childbearing potential is one who is biologically capable of becoming pregnant. "Biologically capable" includes women who are using contraceptives or whose sexual partners are either sterile or using contraceptives. Sexually active women participating in the study who are biologically capable of becoming pregnant must use a medically acceptable form of contraception during the study and for at least 15 days after the last dose of test article. Medically acceptable forms of contraception include oral contraceptives, transdermal, injectable, or implantable methods, intrauterine devices, or properly used double-barrier contraception, eg, condom plus diaphragm. Exclusion Criteria: * Presence of any new and/or clinically important medical condition that might compromise subject safety (including, but not limited to, significant changes in glycemic control). * Pregnancy, lactation, or plans to become pregnant during the study. * Use of prohibited treatments. * Meets any of the exclusion criteria listed for study 322 (NCT01050218).