Decreased R-R variation: a criterium for overdosage of tricyclic psychotropic drugs

Intensive Care Med. 1995 Jul;21(7):598-601. doi: 10.1007/BF01700167.


Objective: Since intoxication with tricyclic antidepressants is common, a supplementary screening method for differentiation between therapeutic and supratherapeutic ranges would be a valuable diagnostic tool, particularly in delirious and unconscious patients.

Setting: 108 patients treated with amitriptyline, 8 patients treated with doxepin, 10 patients treated with clozapine, and 72 normal control subjects matched for age and sex were tested for heart rate variability while resting.

Results: Considering time and frequency derived measures, which are rather independent of heart rate, the patients showed significantly decreased heart rate variability parameters (p < 0.0001), as compared with the normal subjects. Of the patients presenting delirious symptoms 6 showed coefficients of variation more than 4 standard deviations below the mean control value.

Conclusions: As heart rate variability can be easily calculated, this measurement is suggested as a useful tool to quickly exclude or support the diagnosis of chronic intoxication with tricyclic antidepressants or clozapine.

MeSH terms

  • Adult
  • Aged
  • Amitriptyline / poisoning*
  • Antidepressive Agents, Tricyclic / poisoning*
  • Antipsychotic Agents / poisoning*
  • Arrhythmias, Cardiac / chemically induced*
  • Arrhythmias, Cardiac / diagnosis
  • Case-Control Studies
  • Clozapine / poisoning*
  • Doxepin / poisoning*
  • Drug Monitoring / methods
  • Electrocardiography
  • Female
  • Heart Rate
  • Humans
  • Male
  • Middle Aged
  • Substance Abuse Detection


  • Antidepressive Agents, Tricyclic
  • Antipsychotic Agents
  • Doxepin
  • Amitriptyline
  • Clozapine