Pretreatment dexamethasone suppression test as a predictor of response to phenelzine

Twenty inpatients who met Research Diagnostic Criteria and DSM-III criteria for depression underwent a 2-week washout period before the administration of a pretreatment dexamethasone suppression test (DST); the patients then received the monoamine oxidase inhibitor (MAOI) phenelzine. The mean MAO inhibition level achieved during treatment was greater than 80%. On the basis of clinical global evaluation and changes in Hamilton Rating Scale for Depression scores, 7 of the 9 baseline DST suppressors were classified as responders, 1 as a partial responder, and 1 as a nonresponder; of the 11 baseline DST nonsuppressors, 3 were responders, 1 a partial responder, and 7 nonresponders. The Mann-Whitney U test yielded p less than .02, indicating that an abnormally high pretreatment level of cortisol in response to the DST appeared to be predictive of nonresponse to phenelzine.