Application of pharmacokinetic-pharmacodynamic modelling in management of QT abnormalities after citalopram overdose

Prediction of Ventricular Arrhythmias by QRS/QTc - Ratio in Citalopram or Escitalopram Intoxication

Background

The U.S. Food and Drug Administration (FDA) has stated that citalopram and escitalopram should not be used at daily doses above 40 mg/20 mg due to risk for development of fatal ventricular arrhythmias like torsade de pointes (TdP). Yet, supratherapeutic serum concentrations of citalopram are common and predicting patients at risk for TdP is of high clinical value. Accordingly, we investigated whether QRS/QTc; developed for predicting TdP in hypothermic patients could be used in citalopram intoxication.

Methods

A total of 16 publications describing patients suffering from complications due to citalopram or escitalopram treatment, or intoxication with the same substances, were included after a systematic search. The main criterion for inclusion was admission ECG, either with given QRS and QTc values or with attached ECG-files that enabled calculation.

Results

QRS/QTc rather that QTc alone emerged as a marker of ventricular arrhythmia in the 16 included case reports, with highly significant (p < 0.0005) lower values in patients displaying ventricular arrhythmias.

Conclusion

Citalopram and escitalopram are extensively used in treatment of depressive disorders, and a large proportion of patients have supratherapeutic serum concentrations. Calculation of QRS/QTc in available case reports show that this novel ECG-marker has potential to predict patients at risk for developing ventricular arrhythmias.

Population pharmacokinetics of Pseudechis porphyriacus (red-bellied black snake) venom in snakebite patients

OBJECTIVES

Understanding the time course of venom exposure in snakebite patients is important for the optimisation of treatment including antivenom dose and timing. We aimed to investigate the pharmacokinetics of red-bellied black snake (RBBS; Pseudechis porphyriacus) venom in envenomed patients.

METHODS

Timed venom concentration data were obtained from patients with RBBS envenomation recruited to the Australian Snakebite Project (ASP), including demographics and antivenom treatment. Venom concentrations were measured using an enzyme immunoassay. Data were modelled using NONMEM version 7.3. Uncertainty in venom "dose" was accounted for by arbitrarily fixing the average amount to 1 mg and incorporating between-subject variability on relative bioavailability. A scale parameter for venom clearance was implemented to account for the rapid venom clearance following antivenom dosing. A sensitivity analysis was performed to determine the magnitude of venom clearance amplification.

RESULTS

There were 457 venom concentrations in 114 patients (median age 41, 2-90 y; 80 male). Antivenom was administered to 54 patients a median of 4.2 h post-bite (0.67 to 32 h). A one-compartment model with first-order absorption and elimination provided the best description of the data. The estimated clearance and volume of distribution were 5.21 L/h and 39.9 L, respectively. The calculated elimination half-life of P. porphyriacus venom from the final pharmacokinetic model was 5.35 ± 0.36 h. The variability in the relative dose of injected venom was 140%. Antivenom administration increased venom clearance by 40-fold. Ten patients showed evidence of a double peak in the absorption profile.

CONCLUSION

The information on the exposure time of venom in the body following envenomation will help improve treatment and the timing of antivenom.

Management of pharmaceutical and recreational drug poisoning

BACKGROUND

Poisoning is one of the leading causes of admission to the emergency department and intensive care unit. A large number of epidemiological changes have occurred over the last years such as the exponential growth of new synthetic psychoactive substances. Major progress has also been made in analytical screening and assays, enabling the clinicians to rapidly obtain a definite diagnosis.

METHODS

A committee composed of 30 experts from five scientific societies, the Société de Réanimation de Langue Française (SRLF), the Société Française de Médecine d'Urgence (SFMU), the Société de Toxicologie Clinique (STC), the Société Française de Toxicologie Analytique (SFTA) and the Groupe Francophone de Réanimation et d'Urgences Pédiatriques (GFRUP) evaluated eight fields: (1) severity assessment and initial triage; (2) diagnostic approach and role of toxicological analyses; (3) supportive care; (4) decontamination; (5) elimination enhancement; (6) place of antidotes; (7) specificities related to recreational drug poisoning; and (8) characteristics of cardiotoxicant poisoning. Population, Intervention, Comparison, and Outcome (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Analysis of the literature and formulation of recommendations were then conducted according to the GRADE® methodology.

RESULTS

The SRLF-SFMU guideline panel provided 41 statements concerning the management of pharmaceutical and recreational drug poisoning. Ethanol and chemical poisoning were excluded from the scope of these recommendations. After two rounds of discussion and various amendments, a strong consensus was reached for all recommendations. Six of these recommendations had a high level of evidence (GRADE 1±) and six had a low level of evidence (GRADE 2±). Twenty-nine recommendations were in the form of expert opinion recommendations due to the low evidences in the literature.

CONCLUSIONS

The experts reached a substantial consensus for several strong recommendations for optimal management of pharmaceutical and recreational drug poisoning, mainly regarding the conditions and effectiveness of naloxone and N-acetylcystein as antidotes to treat opioid and acetaminophen poisoning, respectively.

Risk of Ventricular Arrhythmia with Citalopram and Escitalopram: A Population-Based Study

Background

The risk of ventricular arrhythmia with citalopram and escitalopram is controversial. In this study we investigated the association between these two drugs and the risk of ventricular arrhythmia.

Methods

We conducted a population-based retrospective cohort study of older adults (mean age 76 years) from 2002 to 2012 in Ontario, Canada, newly prescribed citalopram (n = 137 701) or escitalopram (n = 38 436), compared to those prescribed referent antidepressants sertraline or paroxetine (n = 96 620). After inverse probability of treatment weighting using a propensity score, the baseline characteristics of the comparison groups were similar. The primary outcome was a hospital encounter with ventricular arrhythmia within 90 days of a new prescription, assessed using hospital diagnostic codes. The secondary outcome was all-cause mortality within 90 days.

Results

Citalopram was associated with a higher risk of a hospital encounter with ventricular arrhythmia compared with referent antidepressants (0.06% vs. 0.04%, relative risk [RR] 1.53, 95% confidence intervals [CI]1.03 to 2.29), and a higher risk of mortality (3.49% vs. 3.12%, RR 1.12, 95% CI 1.06 to 1.18). Escitalopram was not associated with a higher risk of ventricular arrhythmia compared with the referent antidepressants (0.03% vs. 0.04%, RR 0.84, 95% CI 0.42 to 1.68), but was associated with a higher risk of mortality (2.86% vs. 2.63%, RR 1.09, 95% CI 1.01 to 1.18).

Conclusion

Among older adults, initiation of citalopram compared to two referent antidepressants was associated with a small but statistically significant increase in the 90-day risk of a hospital encounter for ventricular arrhythmia.

Top-down, Bottom-up and Middle-out Strategies for Drug Cardiac Safety Assessment via Modeling and Simulations

Cardiac safety is an issue causing early terminations at various stages of drug development. Efforts are put into the elimination of false negatives as well as false positives resulting from the current testing paradigm. In silico approaches offer mathematical system and data description from the ion current, through cardiomyocytes level, up to incorporation of inter-individual variability at the population level. The article aims to review three main modelling and simulation approaches, i.e. "top-down" which refers to models built on the observed data, "bottom-up", which stands for a mechanistic description of human physiology, and "middle-out" which combines both strategies. Modelling and simulation is a well-established tool in the assessment of drug proarrhythmic potency with an impact on research and development as well as on regulatory decisions, and it is certainly here to stay. What is more, the shift to systems biology and physiology-based models makes the cardiac effect more predictable.

Model-based evaluation of drug-induced QTc prolongation for compounds in early development

AIMS

Significant differences between dogs and humans have been observed in the concentration-QTc effect relationship of compounds with known pro-arrhythmic properties. These findings suggest that interspecies differences must be considered when evaluating drug effects. The aim of this study was to evaluate the performance of a model-based approach to assess the risk of QTc prolongation for three investigational compounds (NCE01, NCE02 and NCE03).

METHODS

Pharmacokinetic and pharmacodynamic data from experiments in conscious dogs and healthy subjects were included in this analysis. Pharmacokinetic modelling and deconvolution methods were applied to derive drug concentrations at the time of each QT measurement. An integrated pharmacokinetic-pharmacodynamic (PKPD) model was then used to describe QT prolongation. A threshold of ≥10 ms was used to characterize the probability of QTc prolongation.

RESULTS

The PKPD relationships of all three compounds were successfully described in both species. A strong effect was observed after administration of NCE01 to dogs and humans, with a slope of 0.0061 and 0.0662 ms nm(-1), respectively, and maximal probability of QTc prolongation ≥10 ms at peak concentration. For NCE02 and NCE03, QTc-shortening and borderline QT effects were observed both in dogs and humans, as described by negative or very shallow slopes (NCE02, -0.00098 and -0.01 ms nm(-1); NCE03, 0.00064 and -0.0002 ms nm(-1)).

CONCLUSIONS

Whilst NEC01 shows clear pro-arrhythmic effects, the liability for QT/QTc prolongation for NCE02 and NCE03 can be deemed low at the expected therapeutic exposure. Moreover, our results show the advantages of an integrated PKPD approach as the basis for translating pro-arrhythmic effects from dogs to humans.

No effect on QT intervals of mipomersen, a 2'-O-methoxyethyl modified antisense oligonucleotide targeting ApoB-100 mRNA, in a phase I dose escalation placebo-controlled study, and confirmed by a thorough QT (tQT) study, in healthy subjects

PURPOSE

The aim of this study to evaluate the effect of mipomersen on QT intervals in a phase I dose escalation, placebo-controlled study, and a thorough QT (tQT) study in healthy subjects.

METHODS

In the initial phase I study, 29 healthy subjects received either single or multiple (for 4 weeks) ascending doses of mipomersen (50-400 mg) administered subcutaneously (SC) or via a 2-h intravenous (IV) infusion, and 7 subjects received placebo. In the confirmative tQT study, 58 healthy subjects received placebo, 400 mg IV moxifloxacin, 200 mg SC, or 200 mg IV of mipomersen in a double-blind, 4-way crossover design with a minimum 5-day washout between treatments. ECG measurements were performed at baseline and selected time points (including Tmax). The correlation between QTcF intervals corrected for baseline and time-matched placebo when available with PK plasma exposure was evaluated by linear regression analysis.

RESULTS

In the phase I study, no positive correlation between the PK exposure and ∆QTcF or ∆∆QTcF was observed within the wide dose or exposure range tested. Similar results were observed in the tQT study, where the predicted ΔΔQTcF and its upper bound of the 90% CI at Cmax of therapeutic and supratherapeutic dose were approximately -1.7 and 2.9 ms, respectively.

CONCLUSIONS

Mipomersen showed no effect on QT intervals in both the phase I dose escalation study and the tQT study. These results support the proposal that QT assessment can be made in a phase I dose escalation study, and no tQT study may be necessary if the phase I dose escalation study showed a negative QT effect.

Drug induced QT prolongation: the measurement and assessment of the QT interval in clinical practice

There has been an increasing focus on drug induced QT prolongation including research on drug development and QT prolongation, following the removal of drugs due to torsades de pointes (TdP). Although this has improved our understanding of drug-induced QT prolongation there has been much less research aimed at helping clinicians assess risk in individual patients with drug induced QT prolongation. This review will focus on assessment of drug-induced QT prolongation in clinical practice using a simple risk assessment approach. Accurate measurement of the QT interval is best done manually, and not using the measurement of standard ECG machines. Correction for heart rate (HR) using correction formulae such as Bazett's is often inaccurate. These formulae underestimate and overestimate the duration of cardiac repolarization at low and high heart rates, respectively. Numerous cut-offs have been suggested as an indicator of an abnormal QT, but are problematic in clinical practice. An alternative approach is the QT nomogram which is a plot of QT vs. HR. The nomogram has an 'at risk' line and QT-HR pairs above this line have been shown in a systematic study to be associated with TdP and the line is more sensitive and specific than Bazett's QTc of 440 ms or 500 ms. Plotting the QT-HR pair for patients on drugs suspected or known to cause QT prolongation allows assessment of the QT interval based on normal population QT variability. This risk assessment then allows the safer commencement of drugs therapeutically or management of drug induced effects in overdose.

Antidepressant and QT interval prolongation, how should we look at this issue? Focus on citalopram

INTRODUCTION

Evidence increasingly points to the potential development of harmful cardiac side effects concomitant with the use of a number of psychotropic drugs, primarily traditional antipsychotics and tricyclic antidepressants.

AREAS COVERED

The US Food and Drug Administration announced safety warnings associated with the use of citalopram with QT interval prolongation in 2011 and 2012. This paper explores the clinical background of QT interval prolongation, clinical data related to antidepressants and QT interval prolongation, the clinical implications of safety issues associated with the use of antidepressants and future research directions.

EXPERT OPINION

Currently available evidence proposes that citalopram may not be definitely associated with the increase of cardiac mortality, although it should be related with increase of QT prolongation. A firm consensus regarding the cardiac safety issues associated with antidepressants has to be established in near future. Hence, the choice of an individual antidepressant regarding cardiac safety issues should be based on multiple factors; clinicians may need to select the best available antidepressant for each individual based on that patient's vulnerability, the proven efficacy and safety of each agent and a reasonable benefit:risk ratio, based on currently available findings.

Predicting the requirement for N-acetylcysteine in paracetamol poisoning from reported dose

Context

There is contention over whether reported dose correlates with toxicity in paracetamol poisoning and risk assessment is currently based on serum paracetamol concentration compared to a nomogram, irrespective of reported dose.

Objective

To determine if reported dose predicts the need for N-acetylcysteine (NAC).

Methods

Data were taken from paracetamol overdoses presenting to a tertiary toxicology service. Age, sex, reported dose, ingestion time, timed paracetamol concentrations between 4 and 16 h, hepatotoxicity (peak alanine transaminase > 1000 U/L) and treatment (single dose-activated charcoal [SDAC] and NAC) were analysed. Data were analysed within a repeated measures logistic regression framework using NONMEM (ver 7.2). The primary outcome was administration of NAC, which was determined based on a serum paracetamol concentration greater than the nomogram line.

Result

There were 1571 admissions in 1303 patients, with a median age of 27 years (12–96 years) and 1140 (73%) were females. The median dose was 10 g (1–100 g). The paracetamol concentration was above the nomogram line in 337 of 1571 (22%) patients. Patients presenting later (first paracetamol concentration between 7 and 16 h post-overdose) compared to those presenting earlier (4–7 h post-overdose) were more likely to have hepatotoxicity (5.5% vs. 0.4%; p < 0.0001), have a toxic paracetamol concentration (34% vs. 18%; p < 0.0001) and receive NAC (48% vs. 23%; p < 0.0001). SDAC reduced the probability of the paracetamol concentration being above the nomogram. Based on SDAC not being administered there was a 5% probability of requiring NAC at a dose of 6–9 g, a 10% chance of requiring NAC at a dose of 13–16 g, a 50% chance of requiring NAC at a dose of 30–34 g and a 90% chance for needing NAC at 48–50 g.

Conclusion

Reported dose was a good predictor of a toxic paracetamol concentration and SDAC reduced the probability of the concentration being above the nomogram. These predictions may assist in determining which patients could be started on NAC immediately.

Population pharmacokinetics and pharmacodynamics of escitalopram in overdose and the effect of activated charcoal

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, 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.

Low-dose escitalopram for 2 days associated with corrected QT interval prolongation in a middle-aged woman: a case report and literature review

Prolongation of the corrected QT interval (QTc) on the electrocardiography is an important clinical condition because it increases the risk of torsade de pointes, a medical emergency that can cause sudden cardiac death. QTc prolongation can be induced by many drugs, including antipsychotics and tricyclic antidepressants (TCAs). Compared with TCAs, use of selective serotonin reuptake inhibitors (SSRIs) was less likely to cause severe cardiac adverse effects. Escitalopram, one of the SSRIs, has shown significant antidepressant efficacy and well tolerability. Here, we present one female patient showing QTc prolongation induced by low-dose (5 mg/day) treatment of escitalopram for 2 days. The QTc returned to normal soon after discontinuation of escitalopram. Clinicians should be cautious about cardiac effects when using a SSRI, even in a low dose.

Introduction to pharmacokinetics in clinical toxicology

In clinical toxicology, a better understanding of the pharmacokinetics of the drugs may be useful in both risk assessment and formulating treatment guidelines for patients. Pharmacokinetics describes the time course of drug concentrations and is a driver for the time course of drug effects. In this chapter pharmacokinetics is described from a mathematical modeling perspective as applied to clinical toxicology. The pharmacokinetics of drugs are described using a combination of input and disposition (distribution and elimination) phases. A description of the time course of the input and disposition of drugs in overdose provides a basis for understanding the time course of effects of drugs in overdose. Relevant clinical toxicology examples are provided to explain various pharmacokinetic principles. Throughout this chapter we have taken a pragmatic approach to understanding and interpreting the time course of drug effects.

Indications for single-dose activated charcoal administration in acute overdose

PURPOSE OF REVIEW

Gastrointestinal decontamination in overdose patients remains a controversial problem in emergency medicine. There has been a significant decrease in the use of single-dose activated charcoal (SDAC) in recent years based on little new evidence and possibly because the overall mortality in overdose patients is low.

RECENT FINDINGS

Human volunteer studies suggest SDAC is effective and this effect occurs for up to 4 h after ingestion, but the magnitude of the reduction in area under the curve (AUC) decreases over time. Two randomized controlled trials including one recent large study did not find SDAC to be beneficial. Pharmacokinetic and pharmacodynamic studies of specific drugs in overdose suggest that for most drugs SDAC decreases drug exposure, but this does not translate to clinical benefit in all cases. The administration of SDAC is a low-risk intervention.

SUMMARY

Although SDAC is unlikely to be beneficial in many overdose patients, for some subgroups with severe poisoning, the benefits will outweigh the low risk of administration. The use of SDAC should be based on the potential toxicity of the drug ingested and the potential benefit of SDAC balanced against the willingness of the patient to take SDAC and the low risk of administration.

A comparison of venlafaxine and SSRIs in deliberate self-poisoning

To compare the clinical features of deliberate self-poisoning with venlafaxine and selective serotonin reuptake inhibitors (SSRIs) presenting to the emergency department of an Australian tertiary referral hospital. A retrospective cohort study comparing all 36 patients who presented with venlafaxine self-poisoning with 44 randomly selected patients with SSRI self-poisoning between 1997 and 2006. Patients who had overdosed on venlafaxine were older (mean age 37.4 versus 28.8 years, p ≤ 0.001) and generally exhibited a higher degree of suicidal intent (p ≤ 0.017). Median venlafaxine dose taken was 35 defined daily doses (DDDs) compared with SSRIs 19.4 DDDs. Those who ingested venlafaxine were more likely to become confused (25% versus 0%; p = 0) and have mydriasis (19.4% versus 2%; p ≤ 0.02), than those who took SSRIs. One patient from the venlafaxine group died. Compared with SSRI self-poisoners, patients who deliberately ingested venlafaxine were more likely to exhibit serious suicide intent. They were also more likely to be older, take a higher DDD of the drug, and have confusion and mydriasis. This has implications for management of severely depressed and suicidal patients.

How do we use drug concentration data to improve the treatment of overdose patients?

The role of drug assays for screening, diagnosis, and guiding treatment decisions in overdose patients remains unclear. The use of drug concentration data in clinical toxicology research is more problematic, with studies using drug concentrations to simply confirm ingestion in observational studies or others report drug concentration time profiles with simplified pharmacokinetics. The reasons for the lack of more substantial pharmacokinetic and/or pharmacodynamic analysis in overdose patients include problems with uncertainty in dose, uncertainty in the time of ingestion, and limited sampling in the absorption phase. Many of these can be overcome by using population pharmacokinetic and pharmacokinetic-pharmacodynamic analysis in prospective studies of overdose patients to understand dose-concentration-effect relationships. Uncertainty in dose and dose time can be included using population analysis techniques, which may involve a clinical assessment of the veracity of the patient history. The pharmacokinetic-pharmacodynamic model can then be used as the basis for predicting toxicity and clinical outcomes from historical information such as dose and early clinical effects. Using such an approach means that the use of drug concentration data in research will improve the risk assessment in overdose patients, without requiring these assays to be rapidly available in the acute health setting.

Electrocardiographic effects of methylphenidate overdose

OBJECTIVES

Stimulants used in the management of attention-deficit hyperactivity disorder have been associated with an increased risk of sudden cardiac death. One mechanism could involve drug-induced repolarization delay, reflected as prolongation of the QT interval on the electrocardiogram, which has been described in some recipients of methylphenidate in therapeutic doses. Because QT prolongation is usually dose-related, this study was performed to investigate effects of methylphenidate overdose on the QT interval.

METHODS

Adults with methylphenidate overdose identified retrospectively were matched for sex and heart rate with a control subject with overdose of a noncardiotoxic substance, mainly acetaminophen. Notes were reviewed for clinical details and coingestants. Admission 12-lead electrocardiograms were individually calibrated and analyzed using a manual digitizer in a blinded manner by a single investigator. Mean QRS and QT intervals were calculated and differences between groups were analyzed.

RESULTS

Twenty-three cases of methylphenidate overdose (median reported dose 120 mg, range 40-1,500 mg) were identified (10 males, 13 females, mean age 27.8 years). There were multiple coingestants. Level of consciousness and mean hemodynamic variables were within normal limits for all cases. Symptoms recorded in cases included anxiety (32%), dilated pupils (20%), abdominal pain (16%), vomiting (12%), palpitations (12%), and chest pain (8%). No arrhythmias were recorded. Mean heart rate was 92.4/min in methylphenidate cases and 93.8/min in the heart rate-matched controls. There were no significant differences between the groups in mean QRS (cases 86.1, controls 86.2, mean difference 0.1, 95% confidence interval = -5.1 to 5.0 ms) or mean QT intervals (cases 354, controls 355, mean difference -0.8, 95% confidence interval = -10.7 to 9.2 ms).

CONCLUSIONS

Methylphenidate overdose is unlikely to have substantial effects on the QRS or QT intervals.

Electrophysiological changes of cardiac function during antidepressant treatment

Some antidepressant agents can cause electrophysiological changes of cardiac function leading to ventricular arrhythmias and sudden death. However, antidepressants have also protective effects on the heart through their capacity to modulate cardiac autonomic-mediated physiological responses. Heart rate variability and QTc length are two strictly linked parameters that allow us to appreciate the effects of different drugs on cardiac physiology. Heart rate variability reflects functioning of the autonomic nervous system and possibly also regulation by the limbic system. Autonomic regulation of cardiac activity influences also cardiac repolarization and QT length, both directly and via its effects on heart rate. In this review we present the methodologies adopted to study the effect of antidepressant drugs on QT length and heart rate variability and we summarize data on electrophysiological changes related to antidepressant treatment. Clinical implications for the choice of different antidepressants in different clinical populations are discussed.

Acute respiratory failure after aspiration of activated charcoal with recurrent deposition and release from an intrapulmonary cavern

OBJECTIVE

To report on the recurrent release of charcoal from an intrapulmonary cavern in a case of acute respiratory failure after charcoal aspiration.

DESIGN

Case report.

SETTING

Anaesthesiological ICU, university hospital.

PATIENT

An 18-year-old ethanol intoxicated comatose patient regurgitated and aspirated activated charcoal during orotracheal intubation.

TREATMENT

After 2 days of mechanical ventilation, the patient was transferred to a tertiary care university hospital. On admission, acute respiratory distress syndrome with bilateral pulmonary infiltrations was diagnosed. The patient's recovery was hampered by recurrent release of charcoal from an intrapulmonary cavern. Sophisticated ventilatory support, prone positioning, secretolytics, repetitive bronchoscopy, and antibiotic therapy may have facilitated bronchoalveolar clearance and weaning after 18 days.

CONCLUSION

Aspiration may be a dramatic complication if charcoal is administered in comatose patients without airway protection. In this case report, advanced intensive care measures were necessary to tackle the special feature of charcoal release from an intrapulmonary cavern.

Citalopram overdose: late presentation of torsades de pointes (TdP) with cardiac arrest

INTRODUCTION

Citalopram overdose may produce bradycardia, QT prolongation, and torsades de pointes (TdP). A cardiotoxic metabolite may be responsible for the delayed onset of cardiotoxicity. Although some authorities recommend a minimum of 24 hours of observation following citalopram overdose, a recent analysis suggested that dysrhythmias rarely occur beyond 13 hours post-ingestion. We present a case of citalopram overdose with a substantially delayed onset of cardiac toxicity.

CASE REPORT

A 36-year-old woman complained of shakiness, numbness in the arms, and palpitations that began approximately 32 hours after ingesting 50 (20-mg) tablets of citalopram. Her initial vital signs were: blood pressure, 84/44 mmHg; pulse, 102-150/minute; respirations, 17/min; temperature, 99.3 degrees F (37.3 degrees C). Her initial ECG showed sinus rhythm with a prolonged corrected QT interval (572 msec) with paroxysmal, self-limited runs of wide-complex tachycardia that appeared multifocal in nature. Approximately 20 minutes after presentation, she experienced self-terminating TdP, with transient hypotension and loss of consciousness. Her serum citalopram concentration (33 hours post-ingestion) was 477 ng/mL (therapeutic: 40-110 ng/mL); desmethylcitalopram concentration was 123.2 ng/mL (therapeutic: 14-40 ng/mL). She was treated with magnesium and lidocaine, and her corrected QT interval remained abnormal for 24 hours after presentation.

DISCUSSION

Citalopram overdose can produce life-threatening cardiac toxicity with a clinical onset that may be delayed beyond a routine observation period of 6 hours. Once the QT interval is prolonged, it seems prudent to prolong the observation period.

Corrected QT interval prolongation after an overdose of escitalopram, morphine, oxycodone, zopiclone and benzodiazepines

Escitalopram is the recently marketed S-enantiomer of the widely used antidepressant citalopram. Data from intentional overexposure to this medication are limited. Twelve-lead electrocardiogram (ECG) effects from racemic citalopram have been described; however, the present report is the first, to the best of the authors' knowledge, that describes all the reported abnormalities in a single patient receiving escitalopram. A 52-year-old man with a history of depression treated with escitalopram 10 mg/day, extended-release morphine 30 mg/day and zopiclone 15 mg/day was found unconscious at his home. He was known to have attempted suicide three weeks previously. Partially emptied bottles of escitalopram, morphine, oxycodone, zopiclone, lorazepam and diazepam were found close to the patient. He was transferred to the emergency department, where airway management and other supportive care were initiated. The patient was transferred to the intensive care unit. The initial 12-lead ECG demonstrated junctional rhythm at 48 beats/min, a wide complex escape (145 ms) with right bundle branch morphology and a prolonged corrected QT interval at 650 ms. Cardiac monitoring was undertaken. No ventricular arrhythmias or torsade de pointes were detected. No specific treatment for shortening the QT was implemented. Another 12-lead ECG performed 48 h later demonstrated sinus tachycardia with a normal corrected QT, normal PR interval and normal QRS duration. The effects of the overdose of escitalopram on the ECG and its interactions with other drugs are reviewed.

Activated Charcoal Decreases the Risk of QT Prolongation After Citalopram Overdose

STUDY OBJECTIVE

We determine whether single-dose activated charcoal (SDAC) administration after citalopram overdose reduces the proportion of patients developing abnormal QT prolongation.

METHODS

Data were collected retrospectively for citalopram overdose patients presenting to 8 emergency departments. Demographics, dose, coingested drugs, SDAC administration, and serial ECGs were extracted from medical records. The primary outcome was the proportion of patients who had an observed QT,RR combination at any time above an abnormal threshold, established as a predictor of torsade de pointes. We compared the proportion of patients with QT prolongation who received or did not receive SDAC. These data were analyzed within a Bayesian framework, using probabilities of abnormal QT,RR combinations with and without derived from a previous single-center study. WinBUGS was used to generate posterior estimates and credible intervals of the relative risk by combining the prior probabilities and the study data.

RESULTS

SDAC was administered on average 2.1 hours (range, 0.5 to 6.25 hours) after ingestion in 48 of 254 admissions, and abnormal QT,RR combinations occurred in 2 cases (4.2%), compared with 23 of 206 (11.2%) cases not receiving SDAC. There did not appear to be any clinically important difference in age, sex, dose, and cardiotoxic coingestants between the 2 groups. No cases of torsade de pointes occurred. The estimated relative risk of having an abnormal QT,RR combination for SDAC compared to no SDAC was 0.28 (0.06 to 0.70) (median with 2.5% and 97.5% credible limits). The probability that the relative risk was less than 1.0 was 0.99, which can be interpreted as very strong evidence in favor of a beneficial effect of SDAC. The absolute risk difference was estimated as 7.5% and the median number needed to treat as 13.3.

CONCLUSION

SDAC may be effective in reducing the risk of a prolonged QT in patients after citalopram overdose. Current trends toward nonuse of activated charcoal should be evaluated to determine whether patients poisoned by specific agents may benefit from activated charcoal administration.

Serotonin toxicity: a practical approach to diagnosis and treatment

Excess serotonin in the central nervous system leads to a condition commonly referred to as the serotonin syndrome, but better described as a spectrum of toxicity - serotonin toxicity. Serotonin toxicity is characterised by neuromuscular excitation (clonus, hyperreflexia, myoclonus, rigidity), autonomic stimulation (hyperthermia, tachycardia, diaphoresis, tremor, flushing) and changed mental state (anxiety, agitation, confusion). Serotonin toxicity can be: mild (serotonergic features that may or may not concern the patient); moderate (toxicity which causes significant distress and deserves treatment, but is not life-threatening); or severe (a medical emergency characterised by rapid onset of severe hyperthermia, muscle rigidity and multiple organ failure). Diagnosis of serotonin toxicity is often made on the basis of the presence of at least three of Sternbach's 10 clinical features. However, these features have very low specificity. The Hunter Serotonin Toxicity Criteria use a smaller, more specific set of clinical features for diagnosis, including clonus, which has been found to be more specific to serotonin toxicity. There are several drug mechanisms that cause excess serotonin, but severe serotonin toxicity only occurs with combinations of drugs acting at different sites, most commonly including a monoamine oxidase inhibitor and a serotonin reuptake inhibitor. Less severe toxicity occurs with other combinations, overdoses and even single-drug therapy in susceptible individuals. Treatment should focus on cessation of the serotonergic medication and supportive care. Some antiserotonergic agents have been used in clinical practice, but the preferred agent, dose and indications are not well defined.