Tritiated platelet imipramine binding and treatment response in depressed outpatients

Mirtazapine was administered to 35 outpatients who participated in a clinical drug trial. This new antidepressant is structurally and pharmacologically similar to mianserin. Blood was obtained for the measurement of platelet [³H]‐imipramine binding before and after drug treatment. The treatment outcome groups were divided into three groups: those with the most rapid response, nonresponders, and slow responders. The rapid response group had the highest mean pretreatment binding and was presumably the placebo responders. Patients were classified as rapid responders if they showed a 50% reduction in Hamilton Depression Rating Scale (HDRS) after 2 weeks of treatment. Slow responders had the lowest mean B_max and were felt to be the medication responders. Differences between the three groups were statistically significant. These differences in pretreatment B_max values were sustained after controlling for the effects of age, protein concentration, maximum drug dosage, and HDRS scores. Only the slow treatment responder group, the presumed medication responders, showed significant change from pretreatment to post treatment B_max. This study represents one of the first, which uses pretreatment density of platelet imipramine binding sites to predict antidepressant response. Moreover, drug treatment and concomitant recovery was associated with increased [³H]‐imipramine binding density. Depression 1:20–23 (1993). © 1993 Wiley‐Liss, Inc.