TRICYCLIC ANTIDEPRESSANTS IN RED-CELLS AND PLASMA - CORRELATION WITH IMPAIRED INTRAVENTRICULAR-CONDUCTION IN ACUTE OVERDOSE

Objective: Tricyclic antidepressant levels in red blood cells and plas ma in acute overdose and their association with cardiotoxicity were st udied. Methods: This was a prospective study in 15 patients with acute tricyclic antidepressant overdose. Tricyclic antidepressant parent co mpounds and metabolites were measured in red blood cells and plasma, a nd tricyclic antidepressant levels were correlated with ECG indexes of toxicity. Results: Plasma levels of the parent compounds were higher than their red blood cell levels on admission (mean +/- SD, 691 +/- 40 9 and 337 +/- 220 ng/ml, respectively). Admission metabolite levels we re higher in red blood cells than in plasma (264 +/- 180 and 190 +/- 1 64 ng/ml, respectively). QRS duration and the red blood cell levels of the metabolites were significantly correlated at the time of admissio n (r = 0.77, p < 0.01), as well as at 6 to 10 hours (r = 0.74, p < 0.0 1). Conclusions. In acute overdose, a shift of tricyclic antidepressan ts from plasma to red blood cells and increased levels of red blood ce ll metabolites reflect tissue redistribution of the drug. Tricyclic an tidepressant red blood cell metabolites are the best markers for impai red intraventricular conduction.