Serum cortisol concentration in patients with major depression after treatment with fluoxetine

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis and elevated cortisol levels is characteristic of the pathophysiology of major depressive disorder (MDD). The aim of this study was to determine whether increased plasma cortisol levels appear in patients with major depression and if effective antidepressant treatment by fluoxetine leads to regulation of cortisol level. This aim was realized by describing and validation of methods of determining fluoxetine and cortisol in serum and searching for correlation between their concentrations in patients with endogenous depression, the therapeutic effect as assessed in Hamilton Depression Rating Scale (HDRS), age and sex of patients. Plasma cortisol and fluoxetine levels were measured using high performance liquid chromatography (HPLC) methods with applying Shimadzu chromatograph with UV detection. Plasma cortisol and fluoxetine levels were measured at time zero (before therapy) and after 6 h, 24 h, 2, 4, 6 and 8 weeks of fluoxetine administration in patients with major depression qualified for therapeutic drug monitoring (TDM). The study included 21 patients (14 women, 7 men; mean age 29-75 years) and 24 healthy comparison subjects. The patients had a mean score on the 21-item HDRS. As the effect of fluoxetine administration the decrease of the level of cortisol was observed in patients who responded to the therapy (the reduction of points in HDRS scale in at least 50%). The validation parameters of HPLC method of fluoxetine and cortisol determination indicate the possibility of applying them for determination of both: the level of concentration of the drug in therapeutic drug monitoring and the level of cortisol in serum of patients with endogenous depression.