Tricyclic Antidepressant Cardiotoxicity

To the Editor.— The article by Robinson and Barker (236:2089, 1976) regarding tricyclic antidepressant (TCA) toxicity has its good and bad features. The good is that the Food and Drug Administration and its advisors are continuing to present their data and views in a general scientific forum. The bad is that this particular article, while providing very useful and timely information, could also mislead the physician on important scientific and regulatory points. In the scientific area, the authors state that "unfortunately, plasma TCA levels are too variable from patient to patient to be of value in defining a safe therapeutic range." Evidence suggests that, in fact, minimum and maximum therapeutic plasma levels for TCAs do exist and are useful guides to therapy. 1,2 In defining "resistant cases of depression" as adults failing to respond to 200 mg imipramine hydrochloride daily, the authors ignore evidence that at least 30% of patients