The effectiveness of fluoxetine hydrochloride for the treatment of PMDD was established in 3 placebo-controlled trials (1 intermittent and 2 continuous dosing). In an intermittent dosing trial described below, patients met Diagnostic and Statistical Manual-4th edition (DSM-IV) criteria for PMDD. In the continuous dosing trials described below, patients met Diagnostic and Statistical Manual-3rd edition revised (DSM-IIIR) criteria for Late Luteal Phase Dysphoric Disorder (LLPDD), the clinical entity now referred to as PMDD in the DSM-IV. Patients on oral contraceptives were excluded from these trials; therefore, the efficacy of fluoxetine in combination with oral contraceptives for the treatment of PMDD is unknown.

In an intermittent dosing double-blind, parallel group study of 3 months duration, patients (N = 260 randomized) were treated with fluoxetine 10 mg/day, fluoxetine 20 mg/day, or placebo. Fluoxetine or placebo was started 14 days prior to the anticipated onset of menstruation and was continued through the first full day of menses. Efficacy was assessed with the Daily Record of Severity of Problems (DRSP), a patient-rated instrument that mirrors the diagnostic criteria for PMDD as identified in the DSM-IV, and includes assessments for mood, physical symptoms, and other symptoms. Fluoxetine 20 mg/day was shown to be significantly more effective than placebo as measured by the DRSP total score. Fluoxetine 10 mg/day was not shown to be significantly more effective than placebo on this outcome. The average DRSP total score decreased 38% on fluoxetine 20 mg/day, 35% on fluoxetine 10 mg/day, and 30% on placebo.

In the first continuous dosing double-blind, parallel group study of 6 months duration involving N = 320 patients, fixed doses of fluoxetine 20 and 60 mg/day given daily throughout the menstrual cycle were shown to be significantly more effective than placebo as measured by a Visual Analogue Scale (VAS) total score (including mood and physical symptoms). The average total VAS score decreased 7% on placebo treatment, 36% on 20 mg, and 39% on 60 mg fluoxetine. The difference between the 20 and 60 mg doses was not statistically significant. The following table shows the percentage of patients meeting criteria for either moderate or marked improvement on the VAS total score:

In a second continuous dosing double-blind, cross-over study, patients (N = 19) were treated with fluoxetine 20 to 60 mg/day (mean dose = 27 mg/day) and placebo daily throughout the menstrual cycle for a period of 3 months each. Fluoxetine was significantly more effective than placebo as measured by within cycle follicular to luteal phase changes in the VAS total score (mood, physical, and social impairment symptoms). The average VAS total score (follicular to luteal phase increase) was 3.8 times higher during placebo treatment than what was observed during fluoxetine treatment.

In another continuous dosing double-blind, parallel group study, patients with LLPDD (N = 42) were treated daily with fluoxetine 20 mg/day, bupropion 300 mg/day, or placebo for 2 months. Neither fluoxetine nor bupropion was shown to be superior to placebo on the primary endpoint, that is, response rate [defined as a rating of 1 (very much improved) or 2 (much improved) on the CGI], possibly due to sample size.