oxicology & Pharmacology, Newcastle Mater Misericordiae Hospital Poisoning with newer Poisoning with newer antidepressants, antidepressants, diagnosis and diagnosis and management. management. AH Dawson, IM Whyte, GK Isbister Department of Clinical Toxicology, Newcastle Mater Hospital, Australia
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Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital Poisoning with newer antidepressants, diagnosis and management. AH Dawson, IM.
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Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Poisoning with newer Poisoning with newer antidepressants, diagnosis antidepressants, diagnosis
and management. and management. AH Dawson, IM Whyte, GK IsbisterDepartment of Clinical Toxicology, Newcastle Mater Hospital, Australia
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
The new antidepressantsThe new antidepressants
Classes– SSRI– Selective MAOI– NSSRI– Nefazodone
Patterns of Use
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
ToxicityToxicity
Direct extension of therapeutic effect– Serotonin Toxicity
Non-therapeutic effects – CNS, Cardiac, other
Differences– between drug class– within drug class
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
ADRADR
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
PharmacologyPharmacology
High lipid solubility P450 drug metabolism
– Saturable metabolism– Drug interactions
High volume of distribution
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Reports of fatal cases and severe cases with survival
Grundemar L, Wohlfart B, Lagerstedt C, et al Symptoms and signs of severe citalopram overdose. Lancet 1997; 349:1602-1602
Case series suggesting reasonable safety in overdose, with no deaths in the study, but a risk of seizures & ECG abnormalities 1,4
Hale AS. Citalopram is safe. BMJ 1998; 316:1825-1825. Personne M, Sjöberg G, Persson H. Citalopram overdose - review of
cases treated in Swedish hospitals. J.Toxicol.Clin.Toxicol. 1997; 35:237-240
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Cardiac toxicity of citalopram & Cardiac toxicity of citalopram & other selective serotonin other selective serotonin
reuptake inhibitors in overdosereuptake inhibitors in overdoseGK Isbister 1,2, IM Whyte 1,3, AH Dawson 1,3
1Department of Clinical Toxicology, Newcastle Mater Hospital, 2Emergency Department, Royal Prince Alfred Hospital, Sydney 3Discipline of Clinical Pharmacology, University of Newcastle
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
MethodsMethods Prospective data from the Hunter Area Toxicology Service
(HATS) was used.
Cases included were :– single SSRI overdoses (SSRI dose > max. daily dose)
– SSRI and co-ingestant with no known effect on the QT or QRS intervals
Control group :– overdoses with medications not known to cause cardiac
toxicity, or effect the QT or QRS interval
– paracetamol, paracetamol/codeine, diazepam and temazepam
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
AnalysisAnalysis Electrocardiograph analysis :
– R-R, QT and QRS were measured manually on ECGs by independent trained persons
– QTc was calculated using Bazett’s formula– QTc > 440 msec was defined as abnormal– An alternate HR correction for QT was used 5 = QT37
QTc =(RR)0.5
QT
QT37 = (RR)0.37
QT Statistical analysis :
– Comparisons were made of QT, QTc, QT37 and QRS– The means of the five groups of SSRIs and controls were
compared using ANOVA– Citalopram was compared to all other SSRIs using either
Welch’s t test or Mann-Whitney for non-parametric data.– Comparison of the proportion of abnormal measurements was
made using Fisher’s Exact Test
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Admission 6 hours after overdose
Discharge 38 hours after overdose
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Mean (+/-SD) QT(msec)
QTc(msec)
QT37
(msec)QRS
(msec)Citalopram (22) 396 49 455 31 439 32 89 17
Sertraline (69) 372 45 429 34 412 29 86 10
Paroxetine (57) 369 43 422 39 407 36 87 14
Fluoxetine (35) 366 40 435 54 418 48 87 9
Fluvoxamine (8) 363 19 425 12 408 9 88 8
SSRI (169) 368 41 428 40 - 87 11
Control (317) 366 41 425 38 409 34 88 14
ResultsResults
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
QT IntervalQT Interval The QT interval in citalopram overdoses was
396 msec (SD 49), significantly different to the 368 msec (SD 41) of all other SSRI overdoses (p=0.02), and to the 366 msec (SD 41) of controls (p= 0.001)
ANOVA comparison of SSRIs and control– 5 SSRIs + control (6 groups) p = 0.06– 3 SSRIs (C,P,S) p = 0.0144 with citalopram
significantly different to paroxetine and sertraline
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
QTc IntervalQTc Interval The QTc interval in citalopram overdoses was 455
msec (SD 31), significantly different to the 428 msec (SD 40) of all other SSRI overdoses (p=0.0008), and to the 425 msec (SD 38) of controls (p= 0.0002)
ANOVA comparison of SSRIs and control– 5 SSRIs + control (6 groups) p = 0.006 : C vs P; and C
vs. controls significantly different– 3 SSRIs (C,P,S) p = 0.003 with citalopram significantly
different to paroxetine, sertraline and controls
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
QTc > 440 msecQTc > 440 msec Proportion of overdoses with QTc > 440 msec was
significantly more for citalopram compared to controls, all other SSRIs, and each group of SSRIs individually.
No significant different between all 5 SSRIs and controls
QTQT3737 Interval IntervalANOVA comparison of SSRIs and control
– 5 SSRIs + control (6 groups) p = 0.004 : Citalopram significantly different to paroxetine, sertraline and controls
QRS IntervalQRS Interval
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
DiscussionDiscussionThis study has demonstrated a significant increase in QT, QTc and QT37 with citalopram overdose compared to overdose of other SSRIs as a group, paroxetine and sertraline overdoses individually, and control overdoses. This supports a previous cases series of citalopram overdoses 2,4 and shows the effect is for citalopram alone and not other SSRIs. There was no significant difference between controls and other SSRIs. There have been previous reports of severe symptomatic sinus bradycardia, with normal QT/QTc, in patients recently started on therapeutic doses of citalopram 6.
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
LimitationsLimitationsThe major limitation in this study was the size of the citalopram group which meant that ANOVA comparisons including controls and SSRIs were limited because nonparametric methods were required. Lengthening of the QT or corrected QT interval is only a surrogate measure for cardiac toxicity, and in some cases may be benign. However until larger data sets are available to demonstrate no cases of torsades de pointes, QT prolongation should be considered an indicator of cardiac toxicity.
RecommendationsRecommendationsAll patients with citalopram overdoses > 60 mg should have serial 12 lead ECGs and be monitored until the QTc < 440 msec. Citalopram should be used with care in patients with a history of cardiac disease or arrhythmias, in particular patients with bradycardia or known long QT syndrome.
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
Clinical Toxicology & Pharmacology, Newcastle Mater Misericordiae Hospital
TakehomeTakehome
Be aware of synergistic combinations Increased seizure rate of venlaxine Potential cardiotoxicity of cipramil