Efficacy and Tolerability of Controlled-Release and Immediate-Release Paroxetine in the Treatment of Depression

Background: Antidepressant efficacy may be compromised by early discontinuation of treatment secondary to common, treatment-emergent side effects, including nausea, agitation, and somnolence. Paroxetine controlled-release (CR) was developed to improve general tolerability and, in particular, gastrointestinal tolerability.

Objective: To determine the antidepressant efficacy and tolerability of paroxetine CR in adult patients 18 to 65 years of age with DSM-IV major depressive disorder.

Method: Paroxetine CR (25-62.5 mg/day; N = 212) and paroxetine immediate-release (IR; 20-50 mg/day; N = 217) were compared with placebo (N = 211) in the pooled dataset from 2 identical, double-blind, 12-week clinical trials.

Results: Both paroxetine CR and paroxetine IR exhibited efficacy in major depressive disorder as assessed by the reduction in 17-item Hamilton Rating Scale for Depression total score compared with placebo. Moreover, depressed mood and psychic anxiety symptoms improved as early as treatment week 1 in the paroxetine CR group compared with the placebo group. After 6 weeks of treatment, response and remission rates were 41.5% and 20.5% for placebo, 52.8% and 29.6% for paroxetine IR, and 58.9% and 34.4% for paroxetine CR, respectively. After 12 weeks of treatment, response and remission rates were 61.2% and 44.0% for placebo, 72.9% and 52.5% for paroxetine IR, and 73.7% and 56.2% for paroxetine CR, respectively. Rates of nausea were significantly lower for paroxetine CR (14%) than for paroxetine IR (23%; p <= .05) during week 1. Rates of dropout due to adverse events were comparable between paroxetine CR and placebo, while significantly (p = .0008) more patients treated with paroxetine IR withdrew from the study prematurely compared with those treated with placebo.

Conclusion: Paroxetine CR is an effective and well-tolerated antidepressant exhibiting symptomatic improvement as early as week 1. Paroxetine CR is associated with low rates of early-onset nausea and dropout rates due to adverse events comparable to those of placebo. The clinical improvement seen with paroxetine CR, coupled with its favorable adverse event profile, suggests a benefit for therapeutic outcome with paroxetine CR.