Use of low-dose fluoxetine in major depression and panic disorder

Recent reports suggest that fluoxetine in doses less than the standard 20 mg/day may be effective in the treatment of depression and that some patients, particularly those with panic disorder, may be intolerant of the 20 mg/day dose. We examined the utility of starting fluoxetine at a low daily dose (5 mg) and increasing to the standard daily dose (20 mg) in depressed outpatients with and without concurrent panic disorder.

One hundred thirty-three consecutive outpatients meeting DSM-III-R criteria for major depression were studied. Patients were started on fluoxetine 5 mg/day and were gradually increased to 20 mg/day over a 1-week period. Patients who were unable to reach the 20 mg/day dose were instructed to take the highest tolerable dose for the duration of the study. After a month of fluoxetine treatment, patients were evaluated for compliance with treatment and improvement on the Clinical Global Improvement scale.

Twenty-eight percent of the patients were unable to increase the dose to the full 20 mg. Of these patients, half could not tolerate doses lower than 20 mg and discontinued the drug, while the other half did well clinically on the lower doses. Patients who discontinued fluoxetine tended to have panic disorder in addition to depression.

We conclude that starting fluoxetine at doses lower than 20 mg is a useful strategy because of the substantial fraction of patients who cannot tolerate a 20-mg dose but appear to benefit from lower doses. This dosing strategy may be of particular benefit for patients with panic disorder.