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Population pharmacokinetics and pharmacodynamics of escitalopram in overdose and the effect of activated charcoal
Author(s) -
van Gorp Freek,
Duffull Stephen,
Hackett L. Peter,
Isbister Geoffrey K.
Publication year - 2012
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.2011.04091.x
Subject(s) - escitalopram , population , medicine , pharmacology , pharmacokinetics , qt interval , pharmacodynamics , anesthesia , antidepressant , environmental health , hippocampus
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Escitalopram is a selective serotonin re‐uptake inhibitor and the S‐enantiomer of racemic citalopram. Previous studies have shown that the most clinically important effect of escitalopram overdose is QT prolongation with the associated risk of torsade de pointes. It remains unclear at what dose the risk of QT prolongation is important and whether decontamination will reduce this risk. WHAT THIS STUDY ADDS • Escitalopram overdose causes a dose‐related increase in the QT interval that lags the increase in drug concentration. In escitalopram overdose, single dose activated charcoal reduces the fraction absorbed and reduces the risk of QT interval prolongation. AIMS To describe the pharmacokinetics and pharmacodynamics (PKPD) of escitalopram in overdose and its effect on QT prolongation, including the effectiveness of single dose activated charcoal (SDAC). METHODS The data set included 78 escitalopram overdose events (median dose, 140 mg [10–560 mg]). SDAC was administered 1.0 to 2.6 h after 12 overdoses (15%). A fully Bayesian analysis was undertaken in WinBUGS 1.4.3, first for a population pharmacokinetic (PK) analysis followed by a PKPD analysis. The developed PKPD model was used to predict the probability of having an abnormal QT as a surrogate for torsade de pointes. RESULTS A one compartment model with first order input and first‐order elimination described the PK data, including uncertainty in dose and a baseline concentration for patients taking escitalopram therapeutically. SDAC reduced the fraction absorbed by 31% and reduced the individual predicted area under the curve adjusted for dose (AUC i /dose). The absolute QT interval was related to the observed heart rate with an estimated individual heart rate correction factor (α= 0.35). The heart rate corrected QT interval (QT c ) was linearly dependent on predicted escitalopram concentration [slope = 87 ms/(mg l –1 )], using a hypothetical effect‐compartment (half‐life of effect‐delay, 1.0h). Administration of SDAC significantly reduced QT prolongation and was shown to reduce the risk of having an abnormal QT by approximately 35% for escitalopram doses above 200 mg. CONCLUSIONS There was a dose‐related lengthening of the QT interval that lagged the increase in drug concentration. SDAC resulted in a moderate reduction in fraction of escitalopram absorbed and reduced the risk of the QT interval being abnormal.