Fluoxetine: relationships among dose, response, adverse events, and plasma concentrations in the treatment of depression

Data from two large, fixed-dose trials support the efficacy of a fixed 20 mg/day dose of fluoxetine in the treatment of depression. Data pooled from these two studies suggest a dose relationship for adverse events during fluoxetine therapy. At a fixed 20 mg/day dose, only nausea and insomnia were reported by a significantly greater percentage of patients (p less than .05) than those treated with placebo. However, at 60 mg/day, nausea, anxiety, dizziness, and insomnia were reported by a significantly greater percentage of patients (p less than .05) than those treated with placebo. The potential relationship of response rate [Hamilton Rating Scale for Depression (HAM-D) total decrease greater than or equal to 50%] to plasma concentrations of fluoxetine, norfluoxetine, and fluoxetine plus norfluoxetine was evaluated in one study which excluded early responders (less than or equal to 3 weeks of therapy). No significant relationship was found. Furthermore, adverse events were not related to plasma concentrations.