title: Population pharmacokinetics and pharmacodynamics of escitalopram in overdose and the effect of activated charcoal.
abstract: OBJECTIVE
  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, 140mg [10-560mg]). 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 = 87ms/(mgl(-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 200mg.
  
  
  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.
authors: Department of Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
authors: Freek
authors: F
authors: van Gorp
authors: Stephen
authors: S
authors: Duffull
authors: L Peter
authors: LP
authors: Hackett
authors: Geoffrey K
authors: GK
authors: Isbister
mesh_terms: D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D001499:Bayes Theorem; D002606:Charcoal / Q000008:administration & dosage*; D002853:Chromatography, Liquid; D015283:Citalopram / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D062787:Drug Overdose / Q000188:drug therapy; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012307:Risk Factors; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology; D016171:Torsades de Pointes / Q000139:chemically induced* / Q000517:prevention & control; D055815:Young Adult
chemical_list: D002606:Charcoal; D015283:Citalopram; D017367:Selective Serotonin Reuptake Inhibitors