Higher plasma 5-hydroxyindoleacetic acid levels are associated with SSRI-induced nausea.

We investigated the association between selective serotonin reuptake inhibitors (SSRIs; paroxetine or fluvoxamine) and nausea with regard to plasma 5-hydroxyindoleacetic acid (p5-HIAA) levels. Forty-eight patients meeting the DSM-IV criteria for major depressive disorder and treated with paroxetine or fluvoxamine participated in this study. p5-HIAA levels after SSRI administration were significantly higher in the nausea group than those in the nonnausea group (nausea group: 8.0 +/- 4.6 ng/ml; nonnausea group: 3.6 +/- 2.2 ng/ml; p < 0.01). On the other hand, no significant difference was found between the nausea and nonnausea group in terms of p5-HIAA levels before each drug administration. These results suggest that SSRI-induced nausea is associated with serotonergic hyperactivity in the gastrointestinal tract.