Tricyclic antidepressants: plasma levels and clinical findings in overdose

Am J Psychiatry. 1978 Nov;135(11):1325-8. doi: 10.1176/ajp.135.11.1325.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Amitriptyline / blood
  • Amitriptyline / poisoning
  • Antidepressive Agents, Tricyclic / blood
  • Antidepressive Agents, Tricyclic / poisoning*
  • Desipramine / blood
  • Electrocardiography
  • Female
  • Humans
  • Imipramine / blood
  • Imipramine / poisoning
  • Male
  • Middle Aged
  • Nortriptyline / blood


  • Antidepressive Agents, Tricyclic
  • Amitriptyline
  • Nortriptyline
  • Imipramine
  • Desipramine