Tricyclic wash-out and growth hormone response to clonidine

We have observed a significantly higher growth hormone (GH) response to clonidine administration (150 micrograms i.v.) in 14 patients with a major depressive disorder who had never received antidepressant therapy than in 14 matched depressive patients who had not received tricyclic drugs for at least 15 days. Compared with a control group of eight subjects, untreated depressed patients, as a group, had a normal response, while matched patients had markedly blunted response. Results for the group of untreated depressed patients showed that some patients had a blunted response while others had a response in the normal range. The results suggest that studies on the GH response to clonidine in psychiatric patients need to take into account the confounding and long-lasting effects of tricyclics.