Lack of association between platelet tritiated imipramine binding and clinical status of depressed patients on chronic antidepressant treatment.

Platelet tritiated imipramine binding (Bmax) was studied in 33 depressed patients, before and after 1 and 4 weeks of antidepressant treatment, and in 34 healthy volunteers. The Bmax was significantly lower (-21%) in drug-free depressed patients than in controls and increased significantly as early as the first week of treatment to reach the control value, in parallel with a 38% decrease in the Hamilton depression rating scale (HDRS) score. After 4 weeks of treatment, the Bmax was still normal and remained significantly higher than the baseline value, while the clinical state of the patients had greatly improved (a 63% decrease in the HDRS score). However, an increase in the Bmax also occurred in non-responders to treatment. In addition, we observed that the ability of the treatment to increase the Bmax depended on the pharmacological profile of the drug used. The present results show that, in patients on antidepressant medication, platelet tritiated imipramine binding normalization cannot be considered as a marker of clinical remission.