Inclusion criteria:

• Primary diagnosis of Major Depressive Disorder (MDD)
• must have met DSM-IV criteria for current major depressive episode for at least 8 weeks but no long than 2 years.
• HAM-D17 total score of >17 at screening and baseline.
• Severity of illness score of >4 at screening and baseline.
• Willing to discuss sexual functioning with investigator or designee.
• Sexual activity that leads to orgasm at least every 2 weeks.

Exclusion Criteria:

• Past or current DSM-IV diagnosis of Bipolar Disorder I or II, schizophrenia or another psychotic disorder(s).
• Primary DSM-IV diagnosis or received treatment for Panic Disorder, Obsessive Compulsive Disorder or Post Stress Disorder within previous 12 months.
• Poses a homicidal or serious suicidal risk, have made an attempt within months prior to screening or who has ever been homicidal.
• Myocardial infarction with 1 year of screening.
• Taken ibupropion hydrochloride or venlafaxine in the last 6 months.
• Positive urine test for illicit drug use or alcohol or substance abuse within the past 12 months.
• Psychotherapy within 3 months.
• Pregnant.
• Electroconvulsive therapy or transcranial magnetic stimulation within 6 months prior of screening.
• ECG or clinical evidence of atrial or ventricular hypertrophy.