Abstract
Nine previously depressed patients who had responded either to amitriptyline, nortriptyline, or ECT, according to defined criteria, were followed for six months on either 150 mg. or 75 mg. amitriptyline daily, double blind. Blood amitriptyline and nortriptyline levels were measured by gas chromatography over six months, and clinical measures were performed. The range of blood concentration of amitriptyline and nortriptyline was as would be expected from the literature.
Two patients relapsed within six months and both were in the 150 mg. dose group. Of the two relapsed patients one showed the highest blood levels of the group, often beyond the range which could be calculated, and the other showed very low blood levels. Analysis of the clinical scores and blood levels for the whole group did not reveal any relationship between variations in blood level and depression ratings from month to month, or any other information as to what dose or blood level produced optimal results for the patients who did not relapse.
This study tends to support the view that lack of effectiveness may be associated with too high or too low blood levels; that relapse may also be associated with very high or very low blood levels; and that the use of even rough measuring of blood levels could indicate which alternative was more likely in a given individual. In this study the group on 75 mg. amitriptyline daily did better than the group on 150 mg. daily in terms of relapse.
Most studies of the significance of tricyclic antidepressant blood levels have focused on the acute response over short intervals, usually six weeks, and used nortriptyline; this study focuses on relapse over six months and measures blood levels of amitriptyline and nortriptyline resulting from oral amitriptyline.