Indications and guidelines for plasma tricyclic antidepressant concentration monitoring

Some tricyclic antidepressants appear to have critical ranges of plasma tricyclic antidepressant concentrations necessary for optimal clinical efficacy. For any given dose of tricyclic medication, there are marked interindividual variations in steady-state tricyclic concentrations. Furthermore, plasma tricyclic concentrations may be influenced by factors such as weight, diet, smoking status, differences in bioequivalence among manufacturers, and the addition or withdrawal of concurrent medications. There has been considerable controversy in the literature about the clinical utility of plasma tricyclic level monitoring. These authors believe that, at present, routine plasma level monitoring probably is not warranted, but that there are a variety of instances where plasma tricyclic concentration determinations may be clinically useful. The authors review methodological issues in plasma tricyclic concentration determinations and suggest guidelines for when such determinations may be clinically appropriate.