Prolonged coma due to amitriptyline overdose and genetic polymorphism: a case report

Abstract

Background: Reduced consciousness has a wide variety of possible causes, not infrequently being toxic in nature. An intoxication might be obvious, but in this paper an unexpected case with a tricyclic antidepressant is presented.

Case presentation: A 76-year-old caucasian female was found unconscious. Primary diagnostic evaluation, including a negative drugs of abuse test, did not give direction to any clear cause. Yet an intraventricular conductive disorder with widening of the QRS complex and electroencephalogram abnormalities did suggest a possible drug effect. Heteroanamnestic information led to the suspicion of an amitriptyline intoxication, which was confirmed by further laboratory analysis. The patient remained comatose for several days. High concentrations of amitriptyline indicated a large overdose of amitriptyline and, in combination with a cytochrome P450 2D6 poor metabolizer status, could explain the long persistence of her comatose state.

Conclusion: We present a tricyclic antidepressant intoxication, where the patient is thought to have taken a large amount of amitriptyline at once, which, in combination with a cytochrome P450 2D6 poor metabolizer status, led to an unusual long persistence of her coma.

Keywords: Amitriptyline; Case report; Coma; Intoxication; Metabolizer status; Tricyclic antidepressant.

Fig. 1

The electrocardiogram on admission showed an intraventricular conductive disorder with QRS of 150 ms

Fig. 2

Electroencephalogram on admission. Symmetrical pattern with excess of slow activity with generalized predominant synchronous frequencies of theta (4–7 Hz) and delta (1–3 Hz) throughout the background, most likely appropriate to the diagnosis of metabolic or toxic encephalopathy

Fig. 3

Plasma concentrations of amitriptyline and active metabolite nortriptyline

Fig. 4

Electrocardiogram 3 days after admission. Normalization of intraventricular conductance and QRS duration