Dexamethasone suppression test and selection of antidepressant medications

Endogenous depressives with abnormal dexamethasone suppression tests (DSTs) respond better to somatic antidepressant treatments than those with normal DSTs. Whether the DST also aids in the selection of specific antidepressants has not been determined. A pilot report suggested that patients with abnormal DSTs might be noradrenaline-deficient and respond preferentially to imipramine or desipramine, whereas those with normal DSTs might be serotonin-deficient and respond best to amitriptyline or clomipramine. Attempting to replicate this observation, we studied 26 patients diagnosed with Research Diagnostic Criteria as major depressive disorder, endogenous subtype, and with DSM-III as having melancholia. All were drug-free during baseline evaluation. All had abnormal DST results, with post-dexamethasone plasma cortisol levels exceeding 5 microgram/dl. We treated subjects with either imipramine or amitriptyline and compared clinical response with weekly Hamilton Depression Rating Scales, completed by raters blind to both DST results and the research question. Thereapeutic plasma levels were documented. We found no significant differences in treatment response between the subgroups. Twenty of the 26 subjects did well. The imipramine-treatment group failed to have either earlier response or better final outcome. These data fail to replicate suggestions that DST results assist in the selection of either imipramine or amitriptyline.