Therapeutic monitoring of tricyclic antidepressants: quality-control considerations.

While the correlation between plasma levels of some tricyclic antidepressants and therapeutic efficacy is well documented and the value of tricyclic antidepressant plasma level measurements is reasonably well established, the sources of error in the collection and analysis of specimens are not generally known and understood. An outline of the factors affecting the interpretation and utilization of plasma level measurements and the procedures needed to insure the accuracy and precision of tricyclic antidepressant plasma level determinations is presented. Problems facing the clinical laboratory attempting to set up a quality-control program for its tricyclic antidepressant analyses are also discussed.