Outpatients aged > or = 18 years ( placebo , n = 157 ; venlafaxine ER 75 mg , n = 156 ; venlafaxine ER 225 mg , n = 160 ; paroxetine , n = 151 ) , with a primary diagnosis of panic disorder ( + / - agoraphobia ) based on the Diagnostic and Statistical Manual of Mental Disorders ( Fourth Edition ) criteria for > or = 3 months were randomly assigned to receive venlafaxine ER ( titrated to 75 mg/day or 225 mg/day ) , paroxetine ( titrated to 40 mg/day ) , or placebo for 12 weeks .
