The urinary excretion of the norepinephrine metabolite 3-methoxy4-hydroxyphenylglycol (MHPG) was measured in unipolar depressed patients before and during the fourth week of treatment with either imipramine hydrochloride or amitriptyline hydrochloride. On the basis of strict rating criteria, 24 patients were selected as either unequivocal responders or nonresponders.
In the imipramine group the mean pretreatment MHPG was significantly lower in the nine responders than in the seven nonresponders; the converse was found with the amitriptyline patients. Of particular interest is that there was no overlap in individual values between the responders and nonresponders to either drug.
Treatment with either imipramine or amitriptyline was associated with a significant decrease in MHPG excretion, which was independent of clinical response.