Am J Psychiatry 1978; 135:1325-1328
Copyright © 1978 by American Psychiatric Association
Tricyclic antidepressants: plasma levels and clinical findings in overdose
DN Bailey, C Van Dyke, RA Langou and PI Jatlow
Following amitriptyline or imipramine overdose by 30 patients, total plasma
concentrations ranged from 29 to 1732 ng/ml but did not correlate well with
physical findings or most electrocardiographic changes. Only those patients
with a QRS interval greater than 0.1 second had significantly elevated
plasma levels. However, a plasma level ratio of the parent drug
(amitriptyline, imipramine) to its respective N-desmethyl metabolite
(nortriptyline, desmethylimipramine) greater than or equal to 2.0 was
associated with an acute overdose. This ratio was more useful than total
plasma levels in differentiating an overdose from a therapeutic dose with
associated toxicity and an elevated steady-state plasma level.
