The citalopram challenge test in patients with major depression and in healthy controls

Neuroendocrine challenge tests in depressed patients have revealed a blunted hormonal reaction to serotonergic stimuli. In the present study, citalopram was chosen as the serotonergic agent for neuroendocrine stimulation. Compared to earlier challenge agents, citalopram has the advantage of serotonergic selectivity, its application is well tolerated and the possibility of intravenous application reduces pharmacokinetic interference. Sixteen patients suffering from an acute episode of major depression and 16 healthy controls underwent the stimulation procedure with 20 mg of citalopram and placebo. Whereas significant differences in the secretion of prolactin and cortisol between citalopram and placebo challenge were observed in the control group, no differences were found in the group of depressed patients. Comparison of depressed patients and controls showed a significantly blunted prolactin secretion in patients. Differences in cortisol secretion following serotonergic stimulation with citalopram did not become significant. The stimulation procedure was well tolerated in all subjects, although a higher number of side effects was observed in the control group. The amount of side effects did not correlate with the hormone responses. These results are in line with the hypothesis of serotonergic hypofunction in depressed patients. In conclusion, the 20-mg citalopram challenge test is thought to be a promising tool for further investigation of serotonergic function in psychiatric illness.