Selective serotonin reuptake inhibitors and torsade de pointes: new concepts and new directions derived from a systematic review of case reports

Exploring the Role of Serotonin as an Immune Modulatory Component in Cardiovascular Diseases

Serotonin, also known as 5-hydroxytryptamine (5-HT) is a well-known neurotransmitter in the central nervous system (CNS), but also plays a significant role in peripheral tissues. There is a growing body of evidence suggesting that serotonin influences immune cell responses and contributes to the development of pathological injury in cardiovascular diseases, such as atherosclerosis, as well as other diseases which occur as a result of immune hyperactivity. In particular, high levels of serotonin are able to activate a multitude of 5-HT receptors found on the surface of immune cells, thereby influencing the process of atherosclerotic plaque formation in arteries. In this review, we will discuss the differences between serotonin production in the CNS and the periphery, and will give a brief outline of the function of serotonin in the periphery. In this context, we will particularly focus on the effects of serotonin on immune cells related to atherosclerosis and identify caveats that are important for future research.

The modifying effect of the serum-to-dialysate potassium gradient on the cardiovascular safety of SSRIs in the hemodialysis population: a pharmacoepidemiologic study

BACKGROUND

Hypokalemia is a risk factor for drug-induced QT-prolongation. Larger serum-to-dialysate potassium gradients during hemodialysis may augment the proarrhythmic risks of selective serotonin reuptake inhibitors (SSRIs).

METHODS

We conducted a cohort study using 2007-2017 data from the United States Renal Data System and a large dialysis provider to examine if the serum-to-dialysate potassium gradient modifies SSRI cardiac safety. Using a new-user design, we compared 1-year sudden cardiac death (SCD) risk among hemodialysis patients newly treated with higher (citalopram, escitalopram) vs. lower (fluoxetine, fluvoxamine, paroxetine, sertraline) QT-prolonging potential SSRIs, overall and stratified by baseline potassium gradient (≥4 vs. <4 mEq/L). We used inverse probability of treatment weighted survival models to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs), and conducted a confirmatory nested case-control study.

RESULTS

The study included 25,099 patients: 11,107 (44.3%) higher QT-prolonging potential SSRI new-users and 13,992 (55.7%) lower QT-prolonging potential SSRI new-users. Overall, higher vs. lower QT-prolonging potential SSRI use was not associated with SCD, weighted HR of 1.03 (95% CI, 0.86-1.24). However, a greater risk of SCD was associated with higher vs. lower QT-prolonging potential SSRI use among patients with baseline potassium gradients ≥4 mEq/L, but not among those with gradients <4 mEq/L, weighted HR of 2.17 (95% CI, 1.16-4.03) vs. 0.95 (0.78-1.16). Nested case-control analyses yielded analogous results.

CONCLUSIONS

The serum-to-dialysate potassium gradient may modify the association between higher vs. lower QT-prolonging SSRI use and SCD among people receiving hemodialysis. Minimizing the potassium gradient in the setting of QT-prolonging medication use may be warranted.

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.

Response to sertraline and antiepileptic drugs in pentylenetetrazole kindling in rats

Anti-epileptic drugs (AEDs) are the mainstay of epilepsy treatment but these may be a potential risk factor for behavioral disturbances particularly depression which requires treatment. In this study, the effect of antidepressant sertraline (SRT) in combination with AEDs sodium valproate (SV) and levetiracetam (LEV) on seizures, cognitive impairment and oxidative stress in rats was evaluated. After administration of 24th injection of pentylenetetrazole (PTZ), 77.8% rats were kindled. Administration of SRT showed no protective effect on kindling development while SV was 100% protective. With LEV 42.9% were kindled. On combining SRT with SV or LEV 25% and 20% rats were kindled. A significant increase in latency to reach platform zone in Morris water maze(MWM), and increased transfer latencies in Elevated plus maze(EPM) was observed in PTZ kindled rats as compared to normal control on day 49 and when LEV was combined with SRT. In EPM test, however none of the drug treatments had any effect on transfer latencies except LEV pretreated kindled group. In Passive avoidance (PA) test, kindling was associated with a significant decrease in retention time(p = 0.018) while LEV and SV had no effect. The PTZ kindled rats showed significantly higher malondialdehyde(MDA) levels in brain hippocampus(p = 0.0286) while both SRT and SV were associated with significantly lower MDA levels as compared to kindled control group. In case of glutathione (GSH), kindling had no significant effect. The use of sertraline for depression in persons with epilepsy on AEDs needs to be carefully evaluated and monitored due to likelihood of individual variation.

Escitalopram Induced Torsade de Pointes and Cardiac Arrest in a Patient With Surgically Treated Mitral Valve Prolapse

A 54-year-old female, with a history of prosthetic mitral valve replacement due to mitral valve prolapse one year prior, was admitted after suffering a cardiopulmonary arrest. Her initial rhythm demonstrated Torsade de Pointes with the initial electrocardiogram (ECG) showing a prolonged QT interval. Laboratory test results were normal including potassium and magnesium serum levels, and imaging did not show significant abnormalities. A review of patients' medicines showed that the patient started taking escitalopram one month prior to the presentation for major depressive disorder. Selective serotonin reuptake inhibitors (SSRI) are widely prescribed and continue to be a mainstay of treatment for multiple psychiatric conditions. It is important to keep the potential cardiovascular side effects of SSRIs in mind when prescribing. Consideration of underlying cardiac conditions is vital to decrease the likelihood of poor outcomes.

Increased Odds of Ventricular Arrhythmias Associated with Selective Serotonin Reuptake Inhibitor Use among the Pediatric and Young Adult Population: A Case-Control Study

OBJECTIVE

To measure the association between selective serotonin reuptake inhibitor (SSRI) use and out-of-hospital ventricular arrhythmia among the pediatric and young adult population.

STUDY DESIGN

Case-control study using US claims data from 2007 to 2018. Cases were subjects with at least 1 event between ages 2 and 24 years. Controls (matched 10:1 on index date, age, sex, and continuous enrollment) had no events during study period. Independent association between current SSRI use (prescription fill with continuous exposure ending on, or after, the index date) and incident out-of-hospital ventricular arrhythmia (hospitalization or emergency room encounter with primary diagnostic code for ventricular arrhythmia) was estimated using multivariable conditional logistic regression. Separate analyses were performed for pediatric (2-17 years of age) vs young adult (18-24 years of age) subjects and between citalopram/escitalopram vs other SSRIs.

RESULTS

During the study period, 237 eligible cases were identified with 2370 matched controls. Cases were more likely to have government insurance and have a mental health, cardiac, or other complex chronic condition. Thirteen cases (5%) and 15 controls (<1%) had current SSRI exposure. After adjustment for mental health and chronic conditions, there was an increased odds of current SSRI use among cases compared with controls (OR 5.11, 95% CI 1.22-21.37). No difference was observed between pediatric and young adult ages, nor between citalopram/escitalopram and other SSRIs.

CONCLUSIONS

These findings demonstrate increased odds of out-of-hospital ventricular arrhythmia associated with SSRI use in the pediatric and young adult population, suggesting a need for heightened awareness and ongoing monitoring of this potential adverse effect.

QT interval prolongation and Torsades de Pointes with donepezil, rivastigmine and galantamine

Background

Acetylcholinesterase inhibitors (AChEis) including donepezil, galantamine and rivastigmine are used to treat Alzheimer's disease (AD). This study aimed to evaluate evidence from the case report literature for an association between these agents and risk of QT interval prolongation and Torsades de Pointes (TdP) arrhythmia.

Methods

Published literature was mined with predetermined MeSH terms for each of donepezil, galantamine and rivastigmine, to identify cases of QT interval prolongation and TdP. Case reports were analysed using causality scales and a QT interval nomogram.

Results

A total of 13 case reports were found (10 for donepezil, 2 for galantamine and 1 for rivastigmine) with rate corrected QT interval (QT_c) prolongation. Five cases with donepezil exhibited TdP. TdP was not reported in the cases with galantamine and rivastigmine. The use of a QT heart rate nomogram highlighted risk with donepezil compared with the other two drugs and the application of the Naranjo causality scale suggested probable or possible causation for all donepezil cases. All patients had at least two other risk factors for TdP, including modifiable risk factors such as electrolyte disturbances, bradycardia, co-administration of QT prolonging drugs. A number of recent cases involved recent changes in medication.

Conclusion

Our evaluation of the case report literature suggests that there is evidence for a causal association between donepezil and QT_c/TdP risk. Attention to risk factors for QT_c prolongation/TdP should be exercised when prescribing donepezil and modifiable risk factors corrected. Owing to the low number of cases with galantamine and rivastigmine, further work is needed to establish whether these drugs may be more suitable than donepezil for patients with other risk factors for TdP.

Effects of antidepressants on QT interval in people with mental disorders

INTRODUCTION

Drug-induced QT prolongation is associated with higher cardiovascular mortality.

MATERIAL AND METHODS

We conducted a protocol-based comprehensive review of antidepressant-induced QT prolongation in people with mental disorders.

RESULTS

Based on findings from 47 published randomized controlled trials (RCTs), 3 unpublished RCTs, 14 observational studies, 662 case reports of torsades de pointes, and 168 cases of QT prolongation, we conclude that all antidepressants should be used only with licensed doses, and that all patients receiving antidepressants require monitoring of QT prolongation and clinical symptoms of cardiac arrhythmias. Large observational studies suggest increased mortality associated with all antidepressants (RR = 1.62, 95% CI: 1.60-1.63, number of adults: 1,716,552), high doses of tricyclic antidepressants (OR = 2.11, 85% CI 1.10-4.22), selective serotonin reuptake inhibitors (OR = 2.78, 95% CI: 1.24-6.24), venlafaxine (OR = 3.73, 95% CI: 1.33-10.45, number of adults: 4,040), and nortriptyline (OR = 4.60, 95% CI: 1.20-18.40, number of adults: 5,298).

CONCLUSIONS

Evidence regarding the risk of QT prolongation in children is sparse.

Lack of relationship between plasma levels of escitalopram and QTc-interval length

Despite safety concerns raised by the European Medicines Agency (EMA), evidence supporting QT-lengthening effects of escitalopram is far to be conclusive. We aimed to evaluate the relationship between escitalopram plasma levels (Escit-PL) and corrected QT-interval length (QTc-length) in 91 outpatients recruited from a hospital setting. Fifteen patients had an abnormally prolonged QTc-interval, and 3 had QTc-intervals ≥500 ms. No correlation between Escit-PL and QTc-length was found (r = 0.08; p = 0.45). Linear/logistic regression analyses were also conducted taking into account potential confounders such as age, gender, personal history of heart disease, medication load and concomitant use of antipsychotic/tricyclic antidepressants. Escit-PL did not predict either QTc-length or abnormally prolonged QTc-interval. Only antipsychotics/tricyclics use (adjusted β = 0.26, SE = 9.1; p = 0.01) was an independent predictor of QTc-length (R ² = 0.096, F = 4.68, df = 2,88; p = 0.01). Only antipsychotics/tricyclics use (OR 3.56 [95% CI 1.01-12.52]; p < 0.05) and medication load (OR 1.32 [95% CI 1.06-1.64]; p < 0.01) were significantly associated with an increased risk of abnormally prolonged QTc-interval (Omnibus test χ ² = 9.5, df = 2; p < 0.01). Our study did not find a significant relationship between Escit-PL and QTc-length even when recognized modulating factors of the QT-interval were controlled for. Concomitant use of other potentially arrhythmogenic agents may help to explain the apparent link between escitalopram and QT prolongation previously suggested. The advisability of maintaining the EMA warning is once again called into question.

AVP-786 for the treatment of agitation in dementia of the Alzheimer's type

INTRODUCTION

Agitation is common and distressing in patients with Alzheimer-type dementia, but safe, effective treatments remain elusive. Psychological treatments are first-line options, but they have limited efficacy. Off-label psychotropic medications are frequently used, but they also have limited effectiveness, and their use may have harmful side effects, including death. Areas covered: This review discusses the history leading to the conception of AVP-786 (deuterated (d6)-dextromethorphan/quinidine), its pharmacokinetic and pharmacodynamic profiles and safety issues, together with an overview of recent clinical trials. Data were found in the medical literature, in US and EU clinical trial registries and in information provided by the manufacturer. Expert opinion: AVP-786 is one of six investigational compounds in recent phase III clinical development for agitation in Alzheimer disease (AD). Quinidine and deuteration appear to prolong dextromethorphan's plasma half-life and facilitate brain penetration. The FDA granted fast-track designation to AVP-786 and allowed use of data generated on dextromethorphan-quinidine (AVP-923, Nuedexta®) for regulatory filings. AVP-923 reduced agitation in AD and was well tolerated in a phase II RCT that included more than 200 patients. A phase III clinical development program of AVP-786 for AD agitation was recently initiated. This program is expected to start generating results in July 2018.

Prevalence and correlates of QTc prolongation in Italian psychiatric care: cross-sectional multicentre study

AIMS

In recent years several warnings have been issued by regulatory authorities on the risk of electrocardiogram abnormalities in individuals exposed to psychotropic drugs. As a consequence of these warnings, monitoring of the QT interval corrected for heart rate (QTc) has become increasingly common. This study was conducted to measure the frequency of QTc prolongation in unselected psychiatric patients, and to document the associated factors using a cross-sectional approach.

METHOD

The study was carried out in 35 Italian psychiatric services that are part of the STAR (Servizi Territoriali Associati per la Ricerca) Network, a research group established to produce scientific knowledge by collecting data under ordinary circumstances. During a three-month period, a consecutive unselected series of both in- and out-patients were enrolled if they performed an ECG during the recruitment period and were receiving psychotropic drugs on the day ECG was recorded.

RESULTS

During the recruitment period a total of 2411 patients were included in the study. The prevalence of QTc prolongation ranged from 14.7% (men) and 18.6% (women) for the cut-off of 450 ms, to 1.26% (men) and 1.01% (women) for the cut-off of 500 ms. In the multivariate model conducted in the whole sample of patients exposed to psychotropic drugs, female sex, age, heart rate, alcohol and/or substance abuse, cardiovascular diseases and cardiovascular drug treatment, and drug overdose were significantly associated with QTc prolongation. In patients exposed to antipsychotic drugs, polypharmacy was positively associated with QTc prolongation, whereas use of aripiprazole decreased the risk. In patients exposed to antidepressant drugs, use of citalopram, citalopram dose and use of haloperidol in addition to antidepressant drugs, were all positively associated with QTc prolongation.

CONCLUSIONS

The confirmation of a link between antipsychotic polypharmacy and QTc prolongation supports the current guidelines that recommend avoiding the concurrent use of two or more antipsychotic drugs, and the confirmation of a link between citalopram and QTc prolongation supports the need for routine QTc monitoring. The relatively low proportion of patients with QTc prolongation not only suggests compliance with current safety warnings issued by regulatory authorities, but also casts some doubts on the clinical relevance of QTc prolongation related to some psychotropic drugs.

Selective serotonin reuptake inhibitors and cardiovascular events: A systematic review

BACKGROUND

Given the importance of the role of depression in predicting the outcome of cardiovascular disorders, current medications for treating depression, particularly selective serotonin reuptake inhibitors (SSRIs), are taken into consideration. This study aimed to systematically review the published findings in the use of SSRIs and the risk for cardiac events.

MATERIALS AND METHODS

An independent review of the Web of Science, PubMed, Scopus, Cochrane, CINAHL, index Copernicus, and Google Scholar, up to 2014, was performed. We identified studies evaluating the effect of SSRIs, on cardiovascular events. Articles in English with full text availability, review articles, and experimental studies were included in the study. Among 150 studies reviewed based on the included keywords, 17 met the study criteria and were finally reviewed.

RESULTS

The use of some types of SSRIs may prevent platelet adhesion and aggregation; control the cardiovascular risk profile including hypertension, insulin resistance, and body weight; and also inhibit inflammatory processes. The appearance of adverse cardiac events, including cardiac arrhythmias (torsade de pointes and QT prolongation), syncope, increased systolic and diastolic right ventricular volume, and the production of pro-inflammatory cytokines leading atherosclerosis development, has also been expected with the chronic use of some types of SSRIs.

CONCLUSION

According to our systematic review, both beneficial and adverse cardiovascular events can be established following the chronic use of various types of SSRIs. Therefore, when taking SSRIs, the cardiovascular effect of each SSRI has to be carefully considered, based on patients' cardiovascular risk profiles.

Investigational drugs for treating agitation in persons with dementia

INTRODUCTION

Agitation is common and distressing in persons with dementia, but safe, effective treatments remain elusive. In this review, the authors describe investigational compounds in ongoing or recently completed clinical trials for this indication and provide an opinion on how they may meet current therapeutic needs.

AREAS COVERED

Phase II and phase III clinical trials for agitation in persons with dementia were searched in US and EU clinical trial registries and in the medical literature for the period January 2013-February 2016 EXPERT OPINION: The authors searches identified 24 recent clinical trials investigating new treatments for agitation in persons with dementia. Candidate drugs in phase III development included the antipsychotic brexpiprazole, the antidepressant citalopram, the novel compound AVP-786 (deuterated-dextromethorphan/quinidine combination) and the cannabinoid nabilone. Of the compounds in phase II clinical trials, ELND005 (scyllo-inositol) is intended to progress into phase III development, based on evidence from a subgroup analysis and biomarker data. After many years without an FDA/EMA (Food and Drug Administration/European Medicines Agency) approved medication to treat agitation in persons with dementia, we may see the arrival of the first approved drug in the near future.

The Effects of the Adenosine Receptor Antagonists on the Reverse of Cardiovascular Toxic Effects Induced by Citalopram In-Vivo Rat Model of Poisoning

BACKGROUND

Citalopram is a selective serotonin reuptake inhibitor that requires routine cardiac monitoring to prevent a toxic dose. Prolongation of the QT interval has been observed in acute citalopram poisoning. Our previous experimental study showed that citalopram may be lead to QT prolongation by stimulating adenosine A1 receptors without affecting the release of adenosine.

AIMS

We examined the effects of adenosine receptor antagonists in reversing the cardiovascular toxic effects induced by citalopram in rats.

STUDY DESIGN

Animal experimentation.

METHODS

Rats were divided into three groups randomly (n=7 for each group). Sodium cromoglycate (20 mg/kg) was administered to all rats to inhibit adenosine A3 receptor mast cell activation. Citalopram toxicity was achieved by citalopram infusion (4 mg/kg/min) for 20 minutes. After citalopram infusion, in the control group (Group 1), rats were given an infusion of dextrose solution for 60 minutes. In treatment groups, the selective adenosine A1 antagonist DPCPX (Group 2, 8-cyclopentyl-1,3-dipropylxanthine, 20 μg/kg/min) or the selective A2a antagonist CSC (Group 3, 8-(3-chlorostyryl)caffeine, 24 μg/kg/min) was infused for 60 minutes. Mean arterial pressure (MAP), heart rate (HR), QRS duration and QT interval measurements were followed during the experiment period. Statistical analysis was performed by ANOVA followed by Tukey's multiple comparison tests.

RESULTS

Citalopram infusion reduced MAP and HR and prolonged the QT interval. It did not cause any significant difference in QRS duration in any group. When compared to the control group, DPCPX after citalopram infusion shortened the prolongation of the QT interval after 40, 50 and 60 minutes (p<0.01). DPCPX infusion shortened the prolongation of the QT interval at 60 minutes compared with the CSC group (p<0.05). CSC infusion shortened the prolongation of the QT at 60 minutes compared with the control group (p<0.05).

CONCLUSION

DPCPX improved QT interval prolongation in citalopram toxicity. The results of this study show that mechanism of cardiovascular toxicity induced by citalopram may be related adenosine A1 receptor stimulation. Adenosine A1 receptor antagonists may be used for the treatment of citalopram toxicity.

Effects of antipsychotics, antidepressants and mood stabilizers on risk for physical diseases in people with schizophrenia, depression and bipolar disorder

People with severe mental illness have a considerably shorter lifespan than the general population. This excess mortality is mainly due to physical illness. Next to mental illness-related factors, unhealthy lifestyle, and disparities in health care access and utilization, psychotropic medications can contribute to the risk of physical morbidity and mortality. We systematically reviewed the effects of antipsychotics, antidepressants and mood stabilizers on physical health outcomes in people with schizophrenia, depression and bipolar disorder. Updating and expanding our prior systematic review published in this journal, we searched MEDLINE (November 2009 - November 2014), combining the MeSH terms of major physical disease categories (and/or relevant diseases within these categories) with schizophrenia, major depressive disorder and bipolar disorder, and the three major psychotropic classes which received regulatory approval for these disorders, i.e., antipsychotics, antidepressants and mood stabilizers. We gave precedence to results from (systematic) reviews and meta-analyses wherever possible. Antipsychotics, and to a more restricted degree antidepressants and mood stabilizers, are associated with an increased risk for several physical diseases, including obesity, dyslipidemia, diabetes mellitus, thyroid disorders, hyponatremia; cardiovascular, respiratory tract, gastrointestinal, haematological, musculoskeletal and renal diseases, as well as movement and seizure disorders. Higher dosages, polypharmacy, and treatment of vulnerable (e.g., old or young) individuals are associated with greater absolute (elderly) and relative (youth) risk for most of these physical diseases. To what degree medication-specific and patient-specific risk factors interact, and how adverse outcomes can be minimized, allowing patients to derive maximum benefits from these medications, requires adequate clinical attention and further research.

Evaluation of the pharmacokinetics, safety and clinical efficacy of ziprasidone for the treatment of schizophrenia and bipolar disorder

INTRODUCTION

Multiple strategies exist for the pharmacological treatment of schizophrenia and related disorders. In the last 20 years, several 'new' compounds have been introduced, called 'atypical antipsychotics', which have higher efficacy and better tolerability than first-generation neuroleptics. Among them, ziprasidone (ZPR) is currently finding widespread use, and it has also been shown to be active as an augmenter in bipolar disorder therapy.

AREAS COVERED

This review aims to provide the latest information on ZPR, an 'atypical' agent for the pharmacological therapy of schizophrenia and bipolar disorder. A literature search has been carried out with the keywords 'ziprasidone', 'schizophrenia', 'psychosis', 'bipolar', 'pharmacokinetics' and 'clinical trials'. In this process, particular attention has been paid to the drug pharmacokinetic characteristics and its safety in clinical use.

EXPERT OPINION

ZPR shares most advantages and disadvantages with other atypical antipsychotics. However, it can be useful for its low tendency to cause metabolic syndrome and hyperprolactinaemia, especially in patients suffering from excess weight, hyperlipidaemia, diabetes or who have suffered from hyperprolactinaemia when using other antipsychotics. However, there are serious doubts as to whether ZPR should be administered to patients suffering from arrhythmias or QTc prolongation, and even more for administration to bipolar patients undergoing polypharmacy with antidepressants.

Pharmacokinetic and pharmacodynamic interactions between antiepileptics and antidepressants

INTRODUCTION

Antiepileptic-antidepressant combinations are frequently used by clinicians; their pharmacokinetic (PK) and pharmacodynamic (PD) drug interactions (DIs) have not been well studied but are frequently likely to be clinically relevant.

AREAS COVERED

This article provides a comprehensive review of PK DIs between antiepileptics and antidepressants. In the absence of PD DI studies, PD information on pharmacological mechanisms and studies on efficacy and safety of individual drugs are reviewed.

EXPERT OPINION

The clinical relevance of the inductive properties of carbamazepine, phenytoin, phenobarbital and primidone and the inhibitory properties of valproic acid and some antidepressants are well understood; correction factors are provided if appropriate DI studies have been completed. More PK studies are needed for: i) antiepileptics with potent inductive effects for all recently approved antidepressants; ii) high doses of mild CYP3A4 inducers, such as clobazam, eslicarbazepine, oxcarbazepine, rufinamide and topiramate for reboxetine and vilazodone; iii) valproate as a possible inhibitor, mild inducer or both a mild inducer and competitive inhibitor of some antidepressants; and iv) inhibitory effects of long-term fluoxetine use on clobazam, lacosamide, phenobarbital, primidone, carbamazepine, felbamate, tiagabine and zonisamide. Possible synergistic or additive beneficial PD DIs in generalized anxiety disorder, chronic pain, migraine prophylaxis, weight control and menopausal symptoms need study.

Erythromycin, QTc interval prolongation, and torsade de pointes: Case reports, major risk factors and illness severity

OBJECTIVES

Erythromycin is a macrolide antibiotic that is widely used for various infections of the upper respiratory tract, skin, and soft tissue. Similar to other macrolides (clarithromycin, azithromycin), erythromycin has been linked to QTc interval prolongation and torsade de pointes (TdP) arrhythmia. We sought to identify factors that link to erythromycin-induced/associated QTc interval prolongation and TdP.

METHODS AND RESULTS

In a critical evaluation of case reports, we found 29 cases: 22 women and 7 men (age range 18-95 years). With both oral and intravenous erythromycin administration, there was no significant relationship between dose and QTc interval duration in these cases. Notably, all patients had severe illness. Other risk factors included female sex, older age, presence of heart disease, concomitant administration of either other QTc prolonging drugs or agents that were substrates for or inhibitors of CYP3A4. Most patients had at least two risk factors.

CONCLUSIONS

On the basis of case report evaluation, we believe that major risk factors for erythromycin-associated TdP are female sex, heart disease and old age, particularly against a background of severe illness. Coadministration of erythromycin with other drugs that inhibit or are metabolized by CYP3A4 or with QTc prolonging drugs should be avoided in this setting.

Multifactorial QT Interval Prolongation and Takotsubo Cardiomyopathy

A 71-year-old woman collapsed while working as a grocery store cashier. CPR was performed and an AED revealed torsades de pointes (TdP). She was subsequently defibrillated resulting in restoration of sinus rhythm with a QTc interval of 544 msec. Further evaluation revealed a diagnosis of Takotsubo Cardiomyopathy (TCM) contributing to the development of a multifactorial acquired long QT syndrome (LQTS). The case highlights the role of TCM as a cause of LQTS in the setting of multiple risk factors including old age, female gender, hypokalemia, and treatment with QT prolonging medications. It also highlights the multifactorial nature of acquired LQTS and lends support to growing evidence of an association with TCM.

Clinically relevant interactions between newer antidepressants and second-generation antipsychotics

INTRODUCTION

Combinations of newer antidepressants and second-generation antipsychotics (SGAs) are frequently used by clinicians. Pharmacokinetic drug interaction (PK DI) and poorly understood pharmacodynamic (PD) drug interaction (PD DI) can occur between them.

AREAS COVERED

This paper comprehensively reviews PD DI and PK DI studies.

EXPERT OPINION

More PK DI studies are needed to better establish dose correction factors after adding fluoxetine and paroxetine to aripiprazole, iloperidone and risperidone. Further PK DI studies and case reports are also needed to better establish the need for dose correction factors after adding i) fluoxetine to clozapine, lurasidone, quetiapine and olanzapine; ii) paroxetine to olanzapine; iii) fluvoxamine to asenapine, aripiprazole, iloperidone, lurasidone, olanzapine, quetiapine and risperidone; iv) high sertraline doses to aripiprazole, clozapine, iloperidone and risperidone: v) bupropion and duloxetine to aripiprazole, clozapine, iloperidone and risperidone; and vi) asenapine to paroxetine and venlafaxine. Possible beneficial PD DI effects occur after adding SGAs to newer antidepressants for treatment-resistant major depressive and obsessive-compulsive disorders. The lack of studies combining newer antidepressants and SGAs in psychotic depression is worrisome. PD DIs between newer antidepressants and SGAs may be more likely for mirtazapine and bupropion. Adding selective serotonin reuptake inhibitors and SGAs may increase QTc interval and may very rarely contribute to torsades de pointes.

Risperidone, QTc interval prolongation, and torsade de pointes: a systematic review of case reports

RATIONALE

A recent publication asserted that even low-dose risperidone may induce corrected QT (QTc) interval prolongation up to 500 ms without drug-induced IKr blockade. We seek to better understand the complexity of any link between risperidone-induced/associated QTc interval prolongation and torsade de pointes (TdP).

OBJECTIVES

The objective of this study is to systematically analyze all available case reports of risperidone, QTc interval prolongation, and/or TdP.

METHOD

We identify case reports using PubMed, Medline, EMBASE, and Cochrane.

RESULTS

Of the 15 cases found, nine were adult women (ages 31, 33, 34, 37, 47, "elderly", 77, 84, and 87 years) and one was a teenager. There were four men (ages 28, 29, 29, and 46 years) and one preadolescent boy. Besides risperidone administration or overdose, traditional risk factors for QTc interval prolongation and TdP included female sex (n = 10), older age (n = 4), heart disease (n = 3), hypokalemia (n = 2), bradycardia (n = 1), liver disease (n = 1), QTc interval prolonging drugs other than risperidone (n = 8), and metabolic inhibitors (n = 2). TdP occurred in four cases. Six patients died, and three deaths were probably related to TdP.

CONCLUSION

Risperidone (when properly prescribed in patients free of other risk factors for QTc interval prolongation and TdP) is a relatively safe drug. Conventional statistics can neither predict the individual patient who will experience TdP nor determine the relationship of drug dose to QTc interval prolongation and TdP. Narrative medicine using a case report format appears to be an alternative and valuable additional approach to advance our understanding of this relationship and to reduce risks.

Clarithromycin, QTc interval prolongation and torsades de pointes: the need to study case reports

BACKGROUND

The manufacturers of clarithromycin sought a drug similar in efficacy to erythromycin but with a superior side-effect profile. They generally achieved this outcome, but postmarketing findings identified a series of reports linking clarithromycin to QTc interval prolongation and torsades de pointes (TdP) ultimately leading to a Black Box Warning. We sought to clarify risk factors associated with TdP among case reports of patients receiving clarithromycin linked to QTc interval prolongation and TdP.

METHODS AND RESULTS

In a detailed literature search, we found 15 women, five men, and one boy meeting our search criteria. Among the 17 adults with reported clarithromycin dose and concurrent QTc interval measurement, we found no statistically significant relationship between clarithromycin dose and QTc interval duration. This did not change for the adults who developed TdP. Among adults, major risk factors were female sex (15), old age (11) and heart disease (17). A total of eight adult subjects had all three major risk factors and 14 of the 20 adults had at least two major risk factors. All adult subjects had at least two risk factors besides clarithromycin. A total of four of the 20 adults received cisapride and three received disopyramide. Three adults were considered to suffer from some aspect of the congenital long QT syndrome.

CONCLUSIONS

We believe that the risk factor description for this drug should be refined to emphasize the major risk factors of (1) female sex, (2) old age and (3) heart disease.