Key result
Higher amitriptyline and venlafaxine serum levels strongly link to prolonged QTc in elderly psychiatric inpatients.
Why the study?
The cardiac risk classification of antidepressants causing QT prolongation varies markedly and requires correlation with serum drug levels in elderly patients.
Do amitriptyline and venlafaxine serum levels correlate with QTc prolongation in elderly psychiatric inpatients?
Observational (n=38)
Do amitriptyline and venlafaxine serum levels correlate with QTc prolongation in elderly psychiatric inpatients?
Amitriptyline and venlafaxine serum levels correlate with QTc prolongation in elderly patients, though the extent is low within therapeutic ranges.
May warrant QTc monitoring in elderly inpatients on these agents; hypothesis-generating for serum level-guided dosing to reduce risk.
INTRODUCTION: Many antidepressants cause QT prolongation but the classification of cardiac risk of these drugs varies markedly in different published lists. This retrospective study analyzed the correlation of QTc time with amitriptyline and venlafaxine serum level in elderly psychiatric inpatients. METHODS: Elderly inpatients aged≥65 years for whom venlafaxine or amitriptyline serum level had been measured were selected retrospectively from a therapeutic drug monitoring database and screened for an electrocardiogram measurement at the time of blood withdrawal. The correlation of amitriptyline or venlafaxine serum levels with QTc time was examined by using Pearson's correlation analysis. RESULTS: Amitriptyline serum levels (n=11) correlated significantly with QTc time (r=0.918, p<0.001, CI 95%). Venlafaxine serum levels (n=27) also correlated significantly with QTc time (r=0.382, p<0.05, CI 95%). DISCUSSION: Amitriptyline and venlafaxine induce QT prolongation depending on drug concentrations in blood. Its extent, however, is very low when drug serum levels are within the therapeutic range. Future pharmacokinetic studies that correlate drug serum level and QT time should classify the cardiac risk of drugs based on the grade of the regression line in relation to the therapeutic range.
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Hefner et al. (2018) conducted an observational in Psychiatric conditions (n=38). Amitriptyline and venlafaxine serum levels was evaluated on Correlation of QTc time with amitriptyline and venlafaxine serum level (r=0.918 for amitriptyline, r=0.382 for venlafaxine, p=<0.001 for amitriptyline, <0.05 for venlafaxine). Amitriptyline and venlafaxine serum levels significantly correlated with QTc time in elderly psychiatric inpatients (r=0.918, p<0.001 and r=0.382, p<0.05, respectively).
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