The value of assays in tricyclic antidepressant therapy

Studies are reviewed showing that neurotoxicity can be associated with plasma tricyclic antidepressant (TCA) assays above 350 ng/ml. The objective of this study was to develop guidelines in the use of plasma TCA assays from analysis of data of the treatment of patients with endogenous depressions and panic disorders with TCA dosages of 100-300 mgm per day. A total of 38.5% of a small group of patients treated with TCAs and concomitant neuroleptic therapy had plasma assays above 350 ng/ml; 16.7% of a larger group of patients treated with TCAs alone had assays above that level. Guidelines discussed for the use of plasma TCA assays come from analysis of the data and case vignettes.