MAO inhibition and clinical response in depressed patients treated with phenelzine

The authors studied clinical response in 47 depressed inpatients treated with the monoamine oxidase (MAO) inhibitor phenelzine. Improvement on ratings for depression at Week 2 of treatment was correlated with percent MAO inhibition at Week 2 (r = .35, p less than .03), and the modest positive correlation that was found remained after the authors adjusted for the effects of baseline scores on the Hamilton Rating Scale for Depression, dose (mg/kg), and psychosis (partial correlation = .49, p less than .002). Further, the 23 patients ultimately classified as responders had a significantly greater percent MAO inhibition at Week 2 than did the 24 nonresponders (t = 3.02, p less than .005). Thus, the rate of MAO inhibition at Week 2 was significantly correlated with clinical improvement at Week 2 and final response status. These findings could not be explained by other potentially moderating variables such as sex, age, endogenicity, recurrence, and incapacitation.