Tricyclic-resistant depression: treatment resistance or inadequate treatment?

The apparent resistance to tricyclic antidepressant treatment of many depressed patients often may be a result of an inadequate therapeutic trial. Several potentially important variables which may contribute to apparent treatment resistance are discussed, including interpatient pharmacokinetic variability, noncompliance, and inadequate duration of treatment. The current status of the relationship of clinical response and plasma levels of tricyclics and the use of therapeutic blood monitoring to reduce the failure rate in tricyclic antidepressant treatment are also discussed.