The purpose of this is to determine the efficacy, safety, and tolerability of sertraline in patients with major depressive disorder (MDD) who have shown inadequate response ot escitalopram.

Eight week open-label flexible dose trial in adult outpatients diagnosed with Major Depressive Disorder (MDD) who have had a prior failure with escitalopram. Failure is operationally defined as either premature discontinuation because of side effects or the report of an incomplete response to escitalopram, minimum dose 10mg/day, maintain for 3 weeks or more. 10mg/day was chosen because 1) it is the most commonly prescribed single dose of escitalopram in clinical practice, 2) it is equivalent to approx. 30mg/day of arcemic citalopram and 3) escitalopram has very high potency at the serotonin transporter (Ki=1.1); this means that escitalopram would be expected to saturate the transporter at relatively low doses. A total of twenty patients will be treated.

Inclusion Criteria:

• Primary DSM-IV diagnosis of Major Depressive episode of MDD without psychotic symptoms. Additional axis I diagnoses will be permitted only if they are identified as secondary diagnoses
• Ham-D 21 item score of greater than or equal to 18
• Age 18 and above
• Ability and willingness to provide consent for participation
• Failure to respond to escitalopram

Exclusion Criteria:

• Diagnosis of Bipolar Disorder or any psychotic disorder
• Alcohol or drug abuse or dependence currently or in the last 6 months
• A history of non-response or intolerance to sertraline at least 50 mg. for at least 4 weeks or more
• Concomitant use of another antidepressant or use of an antidepressant within 2 weeks of baseline (4 weeks for fluoxetine)
• Use within 1 week of baseline, or concomitant use of any psychotropics with the exception of zolpidem for sleep
• Use within 4 weeks of baseline or concomitant use of benzodiazepines with the exception of PRN use of diazepam 10 mg/day or its equivalent
• Presence of serious and/or unstable medical condition
• Score of 3 or 4 on the suicide item (item 3) of the Ham-D scale
• Known sensitivity of sertraline