The primary objective is to determine the efficacy, safety, and tolerability of venlafaxine extended release (ER) capsules in the treatment of outpatients with panic disorder (PD) in comparison to those of placebo.

Inclusion Criteria:

• Meet DSM-IV criteria for PD (with or without agoraphobia) for at least 3 months before study day 1
• Have sufficient symptoms to require anxiolytic drug therapy
• Have a score ≥4 on the Clinical Global Impressions Scale (CGI) severity of illness item at screening and baseline

Exclusion Criteria:

• Known hypersensitivity to venlafaxine (IR or ER), related compounds, or paroxetine
• History or presence of any clinically important hepatic, renal, or other medical disease that might compromise the study or be detrimental to the patient (eg, clinically important cardiac arrhythmia, unstable diabetes, carcinoma [except basal cell epithelioma], uncontrolled hypertension)
• Clinically important abnormality on screening physical examination, vital signs, electrocardiogram (ECG), laboratory tests or urine drug screen