Plasma Oxytocin Level and Sexual Dysfunction in Depressed Women Treated by Either Fluoxetine or Citalopram: a Pilot Clinical Trial

Sexual dysfunction is a common cause of selective serotonin reuptake inhibitor (SSRI) withdrawal. Various studies indicate that decreased oxytocin is involved as a mechanism of delayed ejaculation induced by SSRIs. The aim of the present pilot study was to evaluate and compare sexual dysfunction and oxytocin levels in women being treated with either fluoxetine or citalopram. Thirty-nine women with the diagnosis of major depressive disorder were enrolled in the study. A baseline blood sample was collected and each participant was given either fluoxetine 20 mg/d or citalopram 20 mg/d. After 1 month, a second blood sample was collected and sexual dysfunction was evaluated via the Female Sexual Function Index (FSFI) questionnaire. Twenty-three women completed the study (12 and 11 in the fluoxetine and citalopram groups, respectively). After 1 month, the FSFI scores were 22.8 ± 7.8 and 22.5 ± 4.8 in the fluoxetine and citalopram groups, respectively. The oxytocin levels were 187.8 ± 38.8 pg/mL and 214.6 ± 23.1 pg/mL in the fluoxetine and citalopram groups, respectively. Statistical analysis did not reveal any difference in the FSFI score between the two groups after 1 month (p = 0.89). However, the oxytocin levels were significantly lower in the fluoxetine group than in the citalopram group (p = 0.05). We also observed a positive relationship between the FSFI score and oxytocin level at 1 month after starting fluoxetine or citalopram (r = 0.43, p = 0.04).A positive relationship between the oxytocin level and FSFI score supports the hypothesis that the oxytocin level plays a role in sexual dysfunction induced by SSRIs.