Serum Prolactin Levels Among Outpatients with Major Depressive Disorder During the Acute Phase of Treatment with Fluoxetine

Objective: To determine changes in serum prolactin levels in outpatients with DSM-IV-diagnosed major depressive disorder (MDD) following a 12-week open-label trial of fluoxetine.

Method: 87 outpatients enrolled in the trial had serum prolactin levels determined at baseline and during their final visit (week 12 or discontinuation visit). In addition, serum testosterone levels were measured in 44 of the 46 men during these 2 visits. Hyperprolactinemia was defined as a serum prolactin level greater than 16.5 ng/mL or 18.9 ng/mL for men and women, respectively. The study was conducted from September 1997 to March 2002.

Results: Of 80 patients with normal prolactin levels at baseline, 10 (12.5%) developed hyper-prolactinemia following fluoxetine treatment. Specifically, 2 (4.5%) of 44 men and 8 (22.2%) of 36 women with normal prolactin levels at baseline developed hyperprolactinemia following treatment with fluoxetine (p = .0174 for between-gender difference). In addition, there was a significant increase in mean +/- SD serum prolactin levels following treatment with fluoxetine in all patients with normal baseline prolactin levels (6.4 +/- 3.4 to 10.0 +/- 7.0 ng/mL, p = .002). There were no significant changes from baseline in testosterone levels in men following fluoxetine treatment (448.4 +/- 139.6 to 439.5 +/- 142.1 ng/dL, p > .05; normal above 245 ng/dL), while none of the 44 men developed low testosterone levels following fluoxetine treatment.

Conclusion: 4.5% of men and 22.2% of women with MDD developed new onset hyper-prolactinemia following fluoxetine treatment.