QT prolongation associated with azithromycin/amiodarone combination

Retrospective Analysis of Potential Adverse Drug Interactions in the Drugs Prescribed to the Elderly at a Tertiary Health Care Center in Raipur, Chhattisgarh, Central India

Background The elderly population differs from adults in having various physiological changes and multiple diseases, which demand the use of multiple medications. The practice of polypharmacy in the elderly leads to numerous harmful effects like adverse drug reactions, adverse drug-drug interactions (DDIs), poor compliance, etc. Methodology This study collected 295 case files of elderly patients retrospectively in the Departments of General Medicine, Cardiology and Nephrology after obtaining Institute Ethics Committee approval to look for the potential adverse DDIs with their severity according to the clinical significance. Results and interpretation The total number of adverse DDIs identified was 156, the maximum in Category 'C.' Salbutamol plus carvedilol/propranolol, ramipril plus telmisartan and ivabradine plus diltiazem were the adverse DDIs categorized under severity 'X'. The identified DDIs were categorised according to the mechanism such as increased bleeding risk, hypokalemia, hyperkalaemia, reduced effect of drugs and increased effect of drugs.  Conclusion Polypharmacy can lead to several adverse consequences in the elderly, of which adverse DDIs play a crucial role in harmful health outcomes. This study brings out the significance of predicting drug interactions beforehand which can reduce the risk of bleeding and other risks of hyper/hypokalaemia, hyponatremia and hypoglycaemia.

Detecting drug-drug interactions between therapies for COVID-19 and concomitant medications through the FDA adverse event reporting system

Background: COVID-19 patients with underlying medical conditions are vulnerable to drug-drug interactions (DDI) due to the use of multiple medications. We conducted a discovery-driven data analysis to identify potential DDIs and associated adverse events (AEs) in COVID-19 patients from the FDA Adverse Event Reporting System (FAERS), a source of post-market drug safety.

Materials and Methods: We investigated 18,589 COVID-19 AEs reported in the FAERS database between 2020 and 2021. We applied multivariate logistic regression to account for potential confounding factors, including age, gender, and the number of unique drug exposures. The significance of the DDIs was determined using both additive and multiplicative measures of interaction. We compared our findings with the Liverpool database and conducted a Monte Carlo simulation to validate the identified DDIs.

Results: Out of 11,337 COVID-19 drug-Co-medication-AE combinations investigated, our methods identified 424 signals statistically significant, covering 176 drug-drug pairs, composed of 13 COVID-19 drugs and 60 co-medications. Out of the 176 drug-drug pairs, 20 were found to exist in the Liverpool database. The empirical p-value obtained based on 1,000 Monte Carlo simulations was less than 0.001. Remdesivir was discovered to interact with the largest number of concomitant drugs (41). Hydroxychloroquine was detected to be associated with most AEs (39). Furthermore, we identified 323 gender- and 254 age-specific DDI signals.

Conclusion: The results, particularly those not found in the Liverpool database, suggest a subsequent need for further pharmacoepidemiology and/or pharmacology studies.

Delivering macrolide antibiotics to heal a broken heart - And other inflammatory conditions

Drug carriers to deliver macrolide antibiotics, such as azithromycin, show promise as antibacterial agents. Macrolide drug carriers have largely focused on improving the drug stability and pharmacokinetics, while reducing adverse reactions and improving antibacterial activity. Recently, macrolides have shown promise in treating inflammatory conditions by promoting a reparative effect and limiting detrimental pro-inflammatory responses, which shifts the immunologic setpoint from suppression to balance. While macrolide drug carriers have only recently been investigated for their ability to modulate immune responses, the previous strategies that deliver macrolides for antibacterial therapy provide a roadmap for repurposing the macrolide drug carriers for therapeutic interventions targeting inflammatory conditions. This review describes the antibacterial and immunomodulatory activity of macrolides, while assessing the past in vivo evaluation of drug carriers used to deliver macrolides with the intention of presenting a case for increased effort to translate macrolide drug carriers into the clinic.

Cardioprotective effects of amiodarone in a rat model of epilepsy-induced cardiac dysfunction

Cardiac dysfunction is one of the leading causes of death in epilepsy. The anti-arrhythmic drug, amiodarone, is under investigation for its therapeutic effects in epilepsy. We aimed to evaluate the possible effects of amiodarone on cardiac injury during status epilepticus, as it can cause prolongation of the QT interval. Five rat groups were enrolled in the study; three control groups (1) Control, (2) Control-lithium and (3) Control-Amio, treated with 150 mg/kg/intraperitoneal amiodarone, (4) Epilepsy model, induced by sequential lithium/pilocarpine administration, and (5) the epilepsy-Amio group. The model group expressed a typical clinical picture of epileptiform activity confirmed by the augmented electroencephalogram alpha and beta spikes. The anticonvulsive effect of amiodarone was prominent, it diminished (p < 0.001) the severity of seizures and hence, deaths and reduced serum noradrenaline levels. In the model group, the electrocardiogram findings revealed tachycardia, prolongation of the corrected QT (QTc) interval, depressed ST segments and increased myocardial oxidative stress. The in-vitro myocardial performance (contraction force and - (df/dt)_max ) was also reduced. Amiodarone decreased (p < 0.001) the heart rate, improved ST segment depression, and myocardial contractility with no significant change in the duration of the QTc interval. Amiodarone preserved the cardiac histological structure and reduced the myocardial injury markers represented by serum Troponin-I, oxidative stress and IL-1. Amiodarone pretreatment prevented the anticipated cardiac injury induced during epilepsy. Amiodarone possessed an anticonvulsive potential, protected the cardiac muscle and preserved its histological architecture. Therefore, amiodarone could be recommended as a protective therapy against cardiac dysfunction during epileptic seizures with favourable effect on seizure activity.

Hydroxychloroquine and Azithromycin Combination in The Management of COVID-19 Infection: Safety and Effectiveness Challenges

BACKGROUND

The treatment of COVID-19 disease remains a dilemma so far because there is no approved therapy for it. This study aimed to evaluate the use of hydroxychloroquine and azithromycin combination in treatment.

OBJECTIVE

This study was carried out to determine the safety and effectiveness of hydroxychloroquine and azithromycin combination in COVID 19 patients.

METHODS

This study included 90 adult COVID 19 patients. Treatment of all patients followed Egyptian Ministry of Health COVID-19 protocols, receiving a combination of hydroxychloroquine 400mg twice on day 1, then 200 mg twice daily in addition to azithromycin 500mg/day for 5 days. ECG findings especially the QTc interval was assessed before and after 5 days from the administration.

RESULTS

All patients showed a statistically significant higher post-treatment QTc readings (433.6 ± 37.2) compared to baseline QTc (402.4 ± 31.3) at p<0.005 with a median QTc prolongation by 26 mSec and IQR (17.8-41.3), but without serious clinical complications. Only 5.6% of patients showed QTc more than 500 mSec and no torsade de points or cardiac arrest. Geriatric patients were at higher risk for QTc prolongation compared to patients aged less than 65 years but without a significant difference as regards the median max QTc difference p˂0.65. The expected therapeutic effectiveness was 82.5% for moderate patients compared to 26% in severe patients (P<0.005).

CONCLUSION

In a modest safety profile, we support the evidence that HQ/AZ therapy can be used to treat Covid-19 infection with more effectiveness in moderate rather than severe cases, which might be a reflection to the time of administration in the disease course.

Effect of Hydroxychloroquine and Azithromycin on QT Interval Prolongation and Other Cardiac Arrhythmias in COVID-19 Confirmed Patients

BACKGROUND

Hydroxychloroquine with or without azithromycin was one of the common therapies at the beginning of the COVID-19 pandemic. They can prolong QT interval, cause torsade de pointes, and lead to sudden cardiac death. We aimed to assess QT interval prolongation and its risk factors in patients who received hydroxychloroquine with or without azithromycin.

METHODS

This study was a retrospective cohort study. One hundred seventy-two confirmed COVID-19 patients were included in this study, hospitalized at Babol University of Medical Sciences hospitals between March 5, 2020, and April 3, 2020. Patients were divided into two groups: hydroxychloroquine alone and hydroxychloroquine with azithromycin. Electrocardiograms were used for outcome assessment.

RESULTS

83.1% of patients received hydroxychloroquine plus azithromycin vs. 16.9% of patients who received only hydroxychloroquine. The mean age of patients was 59.2 ± 15.4.The mean of posttreatment QTc interval in the monotherapy group was shorter than the mean of posttreatment QTc interval in the combination therapy group, but it had no significant statistical difference (462.5 ± 43.1 milliseconds vs. 464.3 ± 59.1 milliseconds; p = 0.488). Generally, 22.1% of patients had a prolonged QTc interval after treatment. Male gender, or baseline QTc ≥ 450 milliseconds, or high-risk Tisdale score increased the likelihood of prolonged QTc interval. Due to QTc prolongation, fourteen patients did not continue therapy after four days.

CONCLUSIONS

Hospitalized patients treated by hydroxychloroquine with or without azithromycin had no significant difference in prolongation of QT interval and outcome. The numbers of patients with prolonged QT intervals in this study emphasize careful cardiac monitoring during therapy, especially in high-risk patients.

Immunomodulatory Effects of Azithromycin Revisited: Potential Applications to COVID-19

The rapid advancement of the COVID-19 pandemic has prompted an accelerated pursuit to identify effective therapeutics. Stages of the disease course have been defined by viral burden, lung pathology, and progression through phases of the immune response. Immunological factors including inflammatory cell infiltration and cytokine storm have been associated with severe disease and death. Many immunomodulatory therapies for COVID-19 are currently being investigated, and preliminary results support the premise of targeting the immune response. However, because suppressing immune mechanisms could also impact the clearance of the virus in the early stages of infection, therapeutic success is likely to depend on timing with respect to the disease course. Azithromycin is an immunomodulatory drug that has been shown to have antiviral effects and potential benefit in patients with COVID-19. Multiple immunomodulatory effects have been defined for azithromycin which could provide efficacy during the late stages of the disease, including inhibition of pro-inflammatory cytokine production, inhibition of neutrophil influx, induction of regulatory functions of macrophages, and alterations in autophagy. Here we review the published evidence of these mechanisms along with the current clinical use of azithromycin as an immunomodulatory therapeutic. We then discuss the potential impact of azithromycin on the immune response to COVID-19, as well as caution against immunosuppressive and off-target effects including cardiotoxicity in these patients. While azithromycin has the potential to contribute efficacy, its impact on the COVID-19 immune response requires additional characterization so as to better define its role in individualized therapy.

Possible Azithromycin-Induced Life-Threatening Arrhythmia Requiring Extracorporeal Membrane Oxygenation Support: A Case Report

Patient: Female, 37-year-old

Final Diagnosis: Ventricular arrhythmia

Symptoms: Arrhythmia

Medication: Azithromycin

Clinical Procedure: ECMO insertion

Specialty: Cardiac surgery • Cardiology • Critical Care Medicine

Frequency of Long QT in Patients with SARS-CoV-2 Infection Treated with Hydroxychloroquine: A Meta-analysis

Introduction Hydroxychloroquine (HCQ) has been proposed as a SARS-CoV-2 treatment but the frequency of long QT (LQT) during use is unknown.

Objective To conduct a meta-analysis of the frequency of LQT in patients with SARS-CoV-2 infection treated with HCQ.

Data Sources PubMed, EMBASE, Google Scholar, the Cochrane Database of Systematic Reviews and preprint servers (medRxiv, Research Square) were searched for studies published between December 2019 and June 30, 2020.

Methods Effect statistics were pooled using random effects. The quality of observational studies and randomized controlled trials was appraised with STROBE and the Cochrane Risk of Bias Assessment tools, respectively.

Outcomes Critical LQT was defined as: (1) maximum QT corrected (QTc)≥500 ms (if QRS<120 ms) or QTc≥550 ms (if QRS≥120 ms), and (2) QTc increase ≥60 ms.

Results In the 28 studies included (n=9124), the frequency of LQT during HCQ treatment was 6.7% (95% confidence interval [CI]: 3.7-10.2). In 20 studies (n=7825), patients were also taking other QT-prolonging drugs. The frequency of LQT in the other 8 studies (n=1299) was 1.7% (95% CI: 0.3-3.9). Twenty studies (n=6869) reported HCQ discontinuation due to LQT, with a frequency of 3.7% (95% CI: 1.5-6.6). The frequency of ventricular arrhythmias during HCQ treatment was 1.68% (127/7539) and that of arrhythmogenic death was 0.69% (39/5648). Torsades de Pointes occurred in 0.06% (3/5066). Patients aged >60 years were at highest risk of HCQ-associated LQT (P<0.001).

Conclusions HCQ-associated cardiotoxicity in SARS-CoV-2 patients is uncommon but requires ECG monitoring, particularly in those aged >60 years and/or taking other QT-prolonging drugs.

Azithromycin in COVID-19 Patients: Pharmacological Mechanism, Clinical Evidence and Prescribing Guidelines

The global COVID-19 pandemic has led to a race to find medications that can improve the prognosis of the disease. Azithromycin, in association with hydroxychloroquine or chloroquine, has been proposed as one such medication. The aim of this review is to describe the pharmacological mechanism, clinical evidence and prescribing guidelines concerning azithromycin in COVID-19 patients. There is weak evidence on the antiviral and immunomodulating effects of azithromycin, which in addition is not based on results from COVID-19 patients specifically. Therefore, this antibacterial should be considered only as empirical treatment of community-acquired pneumonia (CAP), although not all current treatment guidelines are in agreement. After the initial expectations raised by a small trial, more recent evidence has raised serious safety concerns on the use of hydroxychloroquine or chloroquine with azithromycin to treat COVID-19 patients, as all these drugs have arrhythmogenic potential. The World Health Organization has not made recommendations suggesting the use of azithromycin with hydroxychloroquine or chloroquine as treatment for COVID-19, but some national organisations have taken a different position, recommending this as first-line treatment. Several scientific societies, including the American College of Cardiology, have cautioned about the risks of this treatment in view of the lack of evidence concerning its benefits.

Effect of Chloroquine, Hydroxychloroquine, and Azithromycin on the Corrected QT Interval in Patients With SARS-CoV-2 Infection

BACKGROUND

The novel SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is responsible for the global coronavirus disease 2019 pandemic. Small studies have shown a potential benefit of chloroquine/hydroxychloroquine±azithromycin for the treatment of coronavirus disease 2019. Use of these medications alone, or in combination, can lead to a prolongation of the QT interval, possibly increasing the risk of Torsade de pointes and sudden cardiac death.

METHODS

Hospitalized patients treated with chloroquine/hydroxychloroquine±azithromycin from March 1 to the 23 at 3 hospitals within the Northwell Health system were included in this prospective, observational study. Serial assessments of the QT interval were performed. The primary outcome was QT prolongation resulting in Torsade de pointes. Secondary outcomes included QT prolongation, the need to prematurely discontinue any of the medications due to QT prolongation, and arrhythmogenic death.

RESULTS

Two hundred one patients were treated for coronavirus disease 2019 with chloroquine/hydroxychloroquine. Ten patients (5.0%) received chloroquine, 191 (95.0%) received hydroxychloroquine, and 119 (59.2%) also received azithromycin. The primary outcome of torsade de pointes was not observed in the entire population. Baseline corrected QT interval intervals did not differ between patients treated with chloroquine/hydroxychloroquine (monotherapy group) versus those treated with combination group (chloroquine/hydroxychloroquine and azithromycin; 440.6±24.9 versus 439.9±24.7 ms, P=0.834). The maximum corrected QT interval during treatment was significantly longer in the combination group versus the monotherapy group (470.4±45.0 ms versus 453.3±37.0 ms, P=0.004). Seven patients (3.5%) required discontinuation of these medications due to corrected QT interval prolongation. No arrhythmogenic deaths were reported.

CONCLUSIONS

In the largest reported cohort of coronavirus disease 2019 patients to date treated with chloroquine/hydroxychloroquine±azithromycin, no instances of Torsade de pointes, or arrhythmogenic death were reported. Although use of these medications resulted in QT prolongation, clinicians seldomly needed to discontinue therapy. Further study of the need for QT interval monitoring is needed before final recommendations can be made.

Guidelines for the treatment of dysentery (shigellosis): a systematic review of the evidence

BACKGROUND

Shigella remains the primary cause of diarrhoea in paediatric patients worldwide and accounts for up to 40,000 deaths per year. Current guidelines for the treatment of shigellosis are based on data which are over a decade old. In an era of increasing antimicrobial resistance, an updated review of the appropriate empirical therapy for shigellosis in children is necessary, taking into account susceptibility patterns, cost and the risk of adverse events.

METHODS

A systematic review of the current published literature on the treatment of shigella dysentery was undertaken in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

The initial search produced 131 results, of which nine studies met the inclusion criteria. The quality of the studies was assessed as per the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines. International guidelines were also reviewed. There is a lack of current research regarding the clinical treatment of shigellosis in paediatric and adult patients, despite rising antimicrobial resistance worldwide. In particular, there is a lack of studies assessing the non-susceptibility of community-acquired strains, with almost all published research pertaining to microbiological data from hospital-based settings.

DISCUSSION

Current WHO guidelines support the use of fluoroquinolones (first-line), β-lactams (second-line) and cephalosporins (second-line) which accords with currently available evidence and other international guidelines, and there is no strong evidence for changing this guidance. Azithromycin is appropriate as a second-line therapy in regions where the rate of non-susceptibility of ciprofloxacin is known to be high, and research suggests that, from a cardiac point of view, azithromycin is safer than other macrolide antibiotics. Cefixime is also a reasonable alternative, although its use must be weighed against the risk of dissemination of extended-spectrum β-lactamase-producing organisms.

Guidelines for the management of paediatric cholera infection: a systematic review of the evidence

Background Vibrio cholerae is a highly motile Gram-negative bacterium which is responsible for 3 million cases of diarrhoeal illness and up to 100,000 deaths per year, with an increasing burden documented over the past decade. Current WHO guidelines for the treatment of paediatric cholera infection (tetracycline 12.5 mg/kg four times daily for 3 days) are based on data which are over a decade old. In an era of increasing antimicrobial resistance, updated review of the appropriate empirical therapy for cholera infection in children (taking account of susceptibility patterns, cost and the risk of adverse events) is necessary. Methods A systematic review of the current published literature on the treatment of cholera infection in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was undertaken. International clinical guidelines and studies pertaining to adverse effects associated with treatments available for cholera infection were also reviewed. Results The initial search produced 256 results, of which eight studies met the inclusion criteria. Quality assessment of the studies was performed as per the Grading of Recommendations Assessment, Development and Evaluation guidelines. Conclusions In view of the changing non-susceptibility rates worldwide, empirical therapy for cholera infection in paediatric patients should be changed to single-dose azithromycin (20 mg/kg), a safe and effective medication with ease of administration. Erythromycin (12.5 mg/kg four times daily for 3 days) exhibits similar bacteriological and clinical success and should be listed as a second-line therapy. Fluid resuscitation remains the cornerstone of management of paediatric cholera infection, and prevention of infection by promoting access to clean water and sanitation is paramount.

Is cardiovascular risk a concern when prescribing azithromycin?

The FDA has updated azithromycin package labeling to include the risk of prolonged cardiac repolarization and QT prolongation, which increase the possibility of cardiac dysrhythmias and torsades de pointes, especially in older adults. The update was initiated by a study that found an increased risk of death in patients taking azithromycin compared with those taking amoxicillin. However, cardiovascular results of other azithromycin studies have demonstrated discordant results, and more research is needed. In the meantime, providers should recognize that azithromycin has a role in the management of bacterial infections and should prescribe the antibiotic when warranted.

Electrophysiologic Studies on the Risks and Potential Mechanism Underlying the Proarrhythmic Nature of Azithromycin

The mechanisms underlying arrhythmia induced by the clinical use of azithromycin are poorly understood. We aimed to investigate the proarrhythmic effects of azithromycin using electrocardiogram (ECG) and ion channel models. In vivo and in vitro guinea pig ECG and current and voltage clamp recordings were carried out. Azithromycin at 114.6 mg/kg (three times the clinically relevant dose) reduced heart rate (HR) and prolonged the PR, QRS and rate-corrected QT (QTc) intervals of guinea pig ECG in vivo. In vitro technique revealed that azithromycin at 207.5 and 415 mg/L [five and ten times clinically relevant concentration (CRC)] reduced HR and prolonged the PR, QRS and QTc intervals in the isolated guinea pig heart ECG. Both arrhythmias presented bradyarrhythmic features, mainly with reduced HR and prolonged PR interval. Action potential analysis from the guinea pig cardiomyocytes indicated that azithromycin at 830 mg/L (20 times CRC) significantly prolonged the action potential durations at 50% (APD₅₀) and 90% (APD₉₀) of full repolarization levels with a rectangular pattern. Azithromycin significantly suppressed the L-type Ca²⁺ and Na⁺ currents from the left ventricular myocytes of guinea pig at 50% inhibiting concentrations (IC₅₀) of 942.5 ± 68.4 mg/L (22.7 times CRC) and 1123.0 ± 87.7 mg/L (27.1 times CRC), respectively. However, azithromycin at 50 times CRC (2075 mg/L) inhibited I_Kr current at an inhibition rate of 30.99 ± 5.23% with an undetectable IC₅₀. Azithromycin caused bradyarrhythmia primarily by inhibiting L-type Ca²⁺ and Na⁺ currents.

Antimicrobials and QT prolongation

Solithromycin, a ketolide/macrolide antibiotic, has recently been reported to be free of the expected QT-prolonging effect of macrolides. It appears that its keto substitution provides a structural basis for this observation, as the other two tested ketolides also have minimal QT effect.Among non-cardiovascular therapies, antimicrobials probably carry the greatest potential to cause cardiac arrhythmias. This is a result of their propensity to bind to the delayed rectifier potassium channel, IKr, inducing QT prolongation and risk of torsades de pointes ventricular tachycardia, their frequent interference with the metabolism of other QT prolongers and their susceptibility to metabolic inhibition by numerous commonly used drugs.Unfortunately, there is evidence that medical practitioners do not take account of the QT/arrhythmia risk of antimicrobials in their prescribing practices. Education on this topic is sorely needed. When a macrolide is indicated, a ketolide should be considered in patients with a QT risk.

Appraisal of the cardiovascular risks of azithromycin: an observational analysis

AIM

To assess the association of cardiovascular mortality in patients prescribed azithromycin compared with patients prescribed alternative antibiotics in an outpatient setting.

METHODS

This study was a retrospective observational analysis using the South Carolina Medicaid claims and pharmacy databases over the years from 2000 to 2011 housed at the Revenue and Fiscal Affairs Office. Study antibiotics included azithromycin, amoxicillin, clindamycin, clarithromycin and quinolones (levofloxacin, ciprofloxacin and moxifloxacin), and excluded patients at a high risk of death from causes other than the study antibiotics. This study used both matching and regression adjustment with propensity scores to reduce possible bias in the estimated treatment (group) effect from confounders.

RESULTS

The total number of prescriptions evaluated in the study include: 283,743 azithromycin; 143,191 amoxicillin; 52,714 clindamycin; 38,133 clarithromycin and 49,734 for the quinolones. After propensity score weighting, cardiac deaths per million within the first 5 days were: 84.6 for azithromycin, 78.3 for clarithromycin, 69.4 for amoxicillin, 61.6 for quinolones and 15.0 for clindamycin. Our multivariate models reveal that the study antibiotics' (amoxicillin, clindamycin, clarithromycin, levofloxacin, ciprofloxacin and moxifloxacin) mortality rates are not statistically different from azithromycin in any time interval (days: 0-5, 6-10, 0-10 and 0-30). In comparison with previous studies, the results are consistent in Amoxicillin. In the first 5 and 10 days, it is associated with lower odds of cardiovascular death than azithromycin (5 days: odds ratio [OR]: 0.70 [95% CI: 0.25-1.99]; 10 days: OR: 0.92 [95% CI: 0.39-2.14]). However, we find no statistically significant difference between the two antibiotics.

CONCLUSION

Our study shows that the odds of cardiovascular mortality between azithromycin and other antibiotics are not statistically significantly different and previous published findings may not be applicable to the general population. Additionally our results suggest that while we cannot rule out the increased risk of cardiovascular death from azithromycin in patients at low risk of death, the risk may not be as large initial studies suggest. Further research is needed to define the population at greatest risk.

Azithromycin Causes a Novel Proarrhythmic Syndrome

BACKGROUND

The widely used macrolide antibiotic azithromycin increases risk of cardiovascular and sudden cardiac death, although the underlying mechanisms are unclear. Case reports, including the one we document here, demonstrate that azithromycin can cause rapid, polymorphic ventricular tachycardia in the absence of QT prolongation, indicating a novel proarrhythmic syndrome. We investigated the electrophysiological effects of azithromycin in vivo and in vitro using mice, cardiomyocytes, and human ion channels heterologously expressed in human embryonic kidney (HEK 293) and Chinese hamster ovary (CHO) cells.

METHODS AND RESULTS

In conscious telemetered mice, acute intraperitoneal and oral administration of azithromycin caused effects consistent with multi-ion channel block, with significant sinus slowing and increased PR, QRS, QT, and QTc intervals, as seen with azithromycin overdose. Similarly, in HL-1 cardiomyocytes, the drug slowed sinus automaticity, reduced phase 0 upstroke slope, and prolonged action potential duration. Acute exposure to azithromycin reduced peak SCN5A currents in HEK cells (IC₅₀=110±3 μmol/L) and Na⁺ current in mouse ventricular myocytes. However, with chronic (24 hour) exposure, azithromycin caused a ≈2-fold increase in both peak and late SCN5A currents, with findings confirmed for I_Na in cardiomyocytes. Mild block occurred for K⁺ currents representing I_Kr (CHO cells expressing hERG; IC₅₀=219±21 μmol/L) and I_Ks (CHO cells expressing KCNQ1+KCNE1; IC₅₀=184±12 μmol/L), whereas azithromycin suppressed L-type Ca⁺⁺ currents (rabbit ventricular myocytes, IC₅₀=66.5±4 μmol/L) and I_K1 (HEK cells expressing Kir2.1, IC₅₀=44±3 μmol/L).

CONCLUSIONS

Chronic exposure to azithromycin increases cardiac Na⁺ current to promote intracellular Na⁺ loading, providing a potential mechanistic basis for the novel form of proarrhythmia seen with this macrolide antibiotic.

Use of azithromycin and risk of ventricular arrhythmia

BACKGROUND

There are conflicting findings from observational studies of the arrhythrogenic potential of azithromycin. Our aim was to quantify the association between azithromycin use and the risk of ventricular arrhythmia.

METHODS

We conducted a nested case-control study within a cohort of new antibiotic users identified from a network of 7 population-based health care databases in Denmark, Germany, Italy, the Netherlands and the United Kingdom for the period 1997-2010. Up to 100 controls per case were selected and matched by age, sex and database. Recency of antibiotic use and type of drug (azithromycin was the exposure of interest) at the index date (occurrence of ventricular arrhythmia) were identified. We estimated the odds of ventricular arrhythmia associated with current azithromycin use relative to current amoxicillin use or nonuse of antibiotics (≥ 365 d without antibiotic exposure) using conditional logistic regression, adjusting for confounders.

RESULTS

We identified 14 040 688 new antibiotic users who met the inclusion criteria. Ventricular arrhythmia developed in 12 874, of whom 30 were current azithromycin users. The mean age of the cases and controls was 63 years, and two-thirds were male. In the pooled data analyses across databases, azithromycin use was associated with an increased risk of ventricular arrhythmia relative to nonuse of antibiotics (adjusted odds ratio [OR] 1.97, 95% confidence interval [CI] 1.35-2.86). This increased risk disappeared when current amoxicillin use was the comparator (adjusted OR 0.90, 95% CI 0.48-1.71). Database-specific estimates and meta-analysis confirmed results from the pooled data analysis.

INTERPRETATION

Current azithromycin use was associated with an increased risk of ventricular arrhythmia when compared with nonuse of antibiotics, but not when compared with current amoxicillin use. The decreased risk with an active comparator suggests significant confounding by indication.

Cardiac Arrest in Pediatric Patients Receiving Azithromycin

OBJECTIVE

To compare outcomes of pediatric patients treated with azithromycin compared with penicillin or cephalosporin. We hypothesized that azithromycin use would not be associated with increased cardiac mortality in the pediatric population.

STUDY DESIGN

Retrospective cohort study from the Pediatric Health Information System database between 2008 and 2012. Patients <19 years of age with a principal diagnosis of community-acquired pneumonia who received an antibiotic were included. Primary outcomes were cardiopulmonary resuscitation (CPR) and mortality. Secondary outcomes were ventricular arrhythmias incidences and readmission for ventricular arrhythmia. Statistical analysis was performed with the χ² test. Multivariable analysis was performed to control for potential confounders among patient, event, and treatment characteristics.

RESULTS

A total of 82 982 patients (54.3% males) met study criteria. Median age was 2.6 years (IQR 1.2-5.9 years) and median length of stay was 2 days (IQR 2-4 days). Azithromycin was used in 5039 (6.1%); penicillin or cephalosporin was used in 77 943 (93.9%). Overall prevalence of antibiotic-associated CPR was 0.14%. Patients receiving a macrolide antibiotic had a lower prevalence of CPR compared with patients receiving a penicillin or cephalosporin (0.04% vs 0.14%, P = .04), and there was no difference in mortality. Multivariable analysis did not find an association between macrolide use and CPR.

CONCLUSIONS

In contrast to recent adult studies, among children hospitalized for community-acquired pneumonia, azithromycin use was not associated with a greater prevalence of cardiac arrest compared with penicillin or cephalosporin use.

Continuous intravenous antiarrhythmic agents in the intensive care unit: strategies for safe and effective use of amiodarone, lidocaine, and procainamide

The development of cardiac arrhythmias in the intensive care unit is common and associated with poor prognoses and outcomes. Because of the complexity of patients admitted to the intensive care unit, the management of arrhythmias is often difficult and may require multiple therapeutic interventions. In order for clinicians to appropriately manage arrhythmias, a thorough understanding of all available therapies, including intravenous antiarrhythmic agents, is essential. Suitable antiarrhythmic agents for use in the critical care setting include amiodarone, lidocaine, and procainamide. While these agents can be effective in managing cardiac arrhythmias, they also possess significant disadvantages and require additional monitoring during use. Therapy with these agents is often complicated because of the presence of significant associated adverse effects, clinician unfamiliarity, variable dosing strategies, and the potential for drug-drug interactions. The purpose of this review is to discuss indications and strategies for safe and effective use of amiodarone, lidocaine, and procainamide.

Protective Effects of Carvedilol and Vitamin C against Azithromycin-Induced Cardiotoxicity in Rats via Decreasing ROS, IL1-β, and TNF-α Production and Inhibiting NF-κB and Caspase-3 Expression

The Food and Drug Administration recently warned of the fatal cardiovascular risks of azithromycin in humans. In addition, a recently published study documented azithromycin-induced cardiotoxicity in rats. This study aimed to justify the exact cardiovascular events accompanying azithromycin administration in rats, focusing on electrocardiographic, biochemical, and histopathological changes. In addition, the underlying mechanisms were studied regarding reactive oxygen species production, cytokine release, and apoptotic cell-death. Finally, the supposed protective effects of both carvedilol and vitamin C were assessed. Four groups of rats were used: (1) control, (2) azithromycin, (3) azithromycin + carvedilol, and (4) azithromycin + vitamin C. Azithromycin resulted in marked atrophy of cardiac muscle fibers and electrocardiographic segment alteration. It increased the heart rate, lactate dehydrogenase, creatine phosphokinase, malondialdehyde, nitric oxide, interleukin-1 beta (IL1-β), tumor necrosis factor alpha (TNF-α), nuclear factor kappa beta (NF-κB), and caspase-3. It decreased reduced glutathione, glutathione peroxidase, and superoxide dismutase. Carvedilol and vitamin C prevented most of the azithromycin-induced electrocardiographic and histopathological changes. Carvedilol and vitamin C decreased lactate dehydrogenase, malondialdehyde, IL1-β, TNF-α, NF-κB, and caspase-3. Both agents increased glutathione peroxidase. This study shows that both carvedilol and vitamin C protect against azithromycin-induced cardiotoxicity through antioxidant, immunomodulatory, and antiapoptotic mechanisms.

Azithromycin Can Prolong QT Interval and Suppress Ventricular Contraction, but Will Not Induce Torsade de Pointes

Azithromycin has been reported to increase the risk of death from cardiovascular causes among patients with high baseline risk. Since the information is still limited to bridge the gap between electrophysiological properties of azithromycin in vitro and cardiac death in patients, we initially assessed its electropharmacological effects in doses of 3 and 30 mg/kg, i.v., with the halothane-anesthetized dogs (n = 4). The low dose provided 5.2 times higher than the therapeutic concentration, whereas the high dose attained 17.0 times higher. The high dose delayed the ventricular repolarization in a reverse use-dependent manner, reflecting blockade of the rapid component of delayed rectifier K(+) current, and the potency was relatively weak; namely, maximum change in QTc was +20 ms (+5.6%). The high dose also induced the negative inotropic effect possibly through Ca(2+) channel-independent pathway. In order to clarify proarrhythmic risk, 30 mg/kg, i.v., of azithromycin was examined with the chronic atrioventricular block dogs (n = 4). Azithromycin neither induced torsade de pointes nor affected beat-to-beat variability of repolarization. Thus, azithromycin can be considered to lack proarrhythmic potential, but caution has to be paid on its use for patients with left ventricular dysfunction.

Macrolide antibiotics and the risk of ventricular arrhythmia in older adults

BACKGROUND

Many respiratory tract infections are treated with macrolide antibiotics. Regulatory agencies warn that these antibiotics increase the risk of ventricular arrhythmia. We examined the 30-day risk of ventricular arrhythmia and all-cause mortality associated with macrolide antibiotics relative to nonmacrolide antibiotics.

METHODS

We conducted a population-based retrospective cohort study involving older adults (age > 65 yr) with a new prescription for an oral macrolide antibiotic (azithromycin, clarithromycin or erythromycin) in Ontario from 2002 to 2013. Our primary outcome was a hospital encounter with ventricular arrhythmia within 30 days after a new prescription. Our secondary outcome was 30-day all-cause mortality. We matched patients 1:1 using propensity scores to patients prescribed nonmacrolide antibiotics (amoxicillin, cefuroxime or levofloxacin). We used conditional logistic regression to measure the association between macrolide exposure and outcomes, and repeated the analysis in 4 subgroups defined by the presence or absence of chronic kidney disease, congestive heart failure, coronary artery disease and concurrent use of a drug known to prolong the QT interval.

RESULTS

Compared with nonmacrolide antibiotics, macrolide antibiotics were not associated with a higher risk of ventricular arrhythmia (0.03% v. 0.03%; relative risk [RR] 1.06, 95% confidence interval [CI] 0.83-1.36) and were associated with a lower risk of all-cause mortality (0.62% v. 0.76%; RR 0.82, 95% CI 0.78-0.86). These associations were similar in all subgroups.

INTERPRETATION

Among older adults, macrolide antibiotics were not associated with a higher 30-day risk of ventricular arrhythmia than nonmacrolide antibiotics. These findings suggest that current warnings from the US Food and Drug Administration may be overstated.

Azithromycin and the risk of cardiovascular complications

The purpose of this review was to evaluate the literature to assess the incidence and true clinical relevance of recent Food and Drug Administration warnings regarding QT prolongation with azithromycin, given its widespread use, with over 40 million US outpatient prescriptions written in 2011. A literature search of MEDLINE (1946 to May 2013) and International Pharmaceutical Abstracts (1970 to May 2013) was conducted using the terms azithromycin, QT prolongation, torsades de pointes, arrhythmia, and cardiovascular death. A bibliographic search was also performed. Several relevant studies and case reports were identified and reviewed. One cohort study revealed an increased risk of cardiovascular death with azithromycin compared to no antibiotic, especially in those with higher cardiovascular risk. Another cohort study comparing azithromycin, penicillin V, and no antibiotic in a younger Danish population with less cardiac risk found no increased cardiovascular death associated with azithromycin use. The majority of case reports involved ill and/or elderly patients with multiple comorbidities and concomitant medications who were already at a higher risk of cardiovascular events. Although there is evidence that azithromycin may induce QT prolongation and adverse cardiac events, the incidence is fairly limited to patients with high baseline risk, including those with preexisting cardiovascular conditions and concomitant use of other QT-prolonging drugs.

Drug-induced proarrhythmia: risk factors and electrophysiological mechanisms

Drug-induced ventricular tachyarrhythmias can be caused by cardiovascular drugs, noncardiovascular drugs, and even nonprescription agents. They can result in arrhythmic emergencies and sudden cardiac death. If a new arrhythmia or aggravation of an existing arrhythmia develops during therapy with a drug at a concentration usually considered not to be toxic, the situation can be defined as proarrhythmia. Various cardiovascular and noncardiovascular drugs can increase the occurrence of polymorphic ventricular tachycardia of the 'torsade de pointes' type. Antiarrhythmic drugs, antimicrobial agents, and antipsychotic and antidepressant drugs are the most important groups. Age, female sex, and structural heart disease are important risk factors for the occurrence of torsade de pointes. Genetic predisposition and individual pharmacodynamic and pharmacokinetic sensitivity also have important roles in the generation of arrhythmias. An increase in spatial or temporal dispersion of repolarization and a triangular action-potential configuration have been identified as crucial predictors of proarrhythmia in experimental models. These studies emphasized that sole consideration of the QT interval is not sufficient to assess the proarrhythmic risk. In this Review, we focus on important triggers of proarrhythmia and the underlying electrophysiological mechanisms that can enhance or prevent the development of torsade de pointes.

Cardiac risks associated with antibiotics: azithromycin and levofloxacin

INTRODUCTION

Azithromycin and levofloxacin have been shown to be efficacious in treating infections. The adverse drug events associated with azithromycin and levofloxacin were considered rare. However, the US FDA released warnings regarding the possible risk of QT prolongation with azithromycin and levofloxacin.

AREAS COVERED

Case reports/case series, observational studies and clinical trials assessing cardiovascular risks associated with azithromycin and levofloxacin were critically reviewed, including 15 case reports/series, 5 observational studies and 5 clinical trials that investigated the cardiac risks associated azithromycin and levofloxacin.

EXPERT OPINION

Results are discordant. Two retrospective studies utilizing large databases demonstrated an increased risk of cardiovascular death with azithromycin, when azithromycin was compared with amoxicillin. Two other retrospective studies found no difference in cardiovascular death associated with azithromycin and other antibiotics. For levofloxacin, the increased risk of cardiovascular death was only found in one retrospective study. Therefore, the risks and benefits of antibacterial therapies should be considered when making prescription decisions. This study should not preclude clinicians from avoiding azithromycin and levofloxacin. If a patient has an indication to receive an antibiotic and if azithromycin or levofloxacin is needed, it may be used, but the potential risks must be understood.

Macrolide antibiotics and the risk of cardiac arrhythmias

Randomized, controlled trials have demonstrated that chronic therapy with macrolide antibiotics reduces the morbidity of patients with cystic fibrosis, non-cystic fibrosis bronchiectasis, chronic obstructive pulmonary disease, and nontuberculous mycobacterial infections. Lower levels of evidence indicate that chronic macrolides are also effective in treating patients with panbronchiolitis, bronchiolitis obliterans, and rejection after lung transplant. Macrolides are known to cause torsade des pointes and other ventricular arrhythmias, and a recent observational study prompted the FDA to strengthen the Warnings and Precautions section of azithromycin drug labels. This summary describes the electrophysiological effects of macrolides, reviews literature indicating that the large majority of subjects experiencing cardiac arrhythmias from macrolides have coexisting risk factors and that the incidence of arrhythmias in absence of coexisting risk factors is very low, examines recently published studies describing the relative risk of arrhythmias from macrolides, and concludes that this risk has been overestimated and suggests an approach to patient evaluation that should reduce the relative risk and the incidence of arrhythmias to the point that chronic macrolides can be used safely in the majority of subjects for whom they are recommended.

Azithromycin and levofloxacin use and increased risk of cardiac arrhythmia and death

PURPOSE

Azithromycin use has been associated with increased risk of death among patients at high baseline risk, but not for younger and middle-aged adults. The Food and Drug Administration issued a public warning on azithromycin, including a statement that the risks were similar for levofloxacin. We conducted a retrospective cohort study among US veterans to test the hypothesis that taking azithromycin or levofloxacin would increase the risk of cardiovascular death and cardiac arrhythmia compared with persons taking amoxicillin.

METHODS

We studied a cohort of US veterans (mean age, 56.8 years) who received an exclusive outpatient dispensation of either amoxicillin (n = 979,380), azithromycin (n = 594,792), or levofloxacin (n = 201,798) at the Department of Veterans Affairs between September 1999 and April 2012. Azithromycin was dispensed mostly for 5 days, whereas amoxicillin and levofloxacin were dispensed mostly for at least 10 days.

RESULTS

During treatment days 1 to 5, patients receiving azithromycin had significantly increased risk of death (hazard ratio [HR] = 1.48; 95% CI, 1.05-2.09) and serious arrhythmia (HR = 1.77; 95% CI, 1.20-2.62) compared with patients receiving amoxicillin. On treatment days 6 to 10, risks were not statistically different. Compared with patients receiving amoxicillin, patients receiving levofloxacin for days 1 to 5 had a greater risk of death (HR = 2.49, 95% CI, 1.7-3.64) and serious cardiac arrhythmia (HR = 2.43, 95% CI, 1.56-3.79); this risk remained significantly different for days 6 to 10 for both death (HR = 1.95, 95% CI, 1.32-2.88) and arrhythmia (HR = 1.75; 95% CI, 1.09-2.82).

CONCLUSIONS

Compared with amoxicillin, azithromycin resulted in a statistically significant increase in mortality and arrhythmia risks on days 1 to 5, but not 6 to 10. Levofloxacin, which was predominantly dispensed for a minimum of 10 days, resulted in an increased risk throughout the 10-day period.

QT interval prolongation and the risk of torsades de pointes: essentials for clinicians

OBJECTIVE

QT interval prolongation signifies an increased risk of the life-threatening arrhythmia torsades de pointes (TdP). The purpose of this paper is to review the diverse methods for assessing and monitoring the risk of TdP, discuss risk factors for TdP, and recommend interventions that may mitigate the risk of TdP.

METHODS

A non-systematic search of PubMed (through March 2013) was conducted to determine the optimal approach to assessing and monitoring QT interval, prevention of TdP, and to identify risks factors for TdP. Papers known to the authors were included, as were scientific statements. Articles were chosen based on the judgment of the authors.

RESULTS

Risk factors for drug-induced TdP include hypokalemia, female sex, drug-drug interactions, advancing age, genetic predisposition, hypomagnesemia, heart failure, bradycardia, and corrected QT (QTc) interval prolongation. Many risk factors, including hypokalemia, use of QT-interval-prolonging drugs, and drug interactions are potentially modifiable and should be corrected in persons at risk for QT interval prolongation. Given the variable onset of TdP following initiation of QT-interval-prolonging drugs, careful and regular monitoring of electrocardiography (EKG) and electrolytes are necessary. Patients at risk for QT interval prolongation should be educated to go directly to the emergency room if they experience palpitations, lightheadedness, dizziness or syncope. When the QTc interval is 470-500 ms for males, or 480-500 ms for females, or the QTc interval increases 60 ms or more from pretreatment values, dose reduction or discontinuation of the offending drug should be considered where possible, and electrolytes corrected as needed. Furthermore, if the QTc interval is ≥500 ms, the offending drug should be discontinued, and continuous EKG telemetry monitoring should be performed, or the 12-lead EKG should be repeated every 2-4 hours, until the QT interval has normalized.

CONCLUSIONS

Close monitoring for QTc prolongation is necessary to prevent TdP. The recommendations in this paper are limited by the available evidence and additional studies are needed to better define the approach to monitoring.

Azithromycin, cardiovascular risks, QTc interval prolongation, torsade de pointes, and regulatory issues: A narrative review based on the study of case reports

Over the past year, three articles have appeared in the New England Journal of Medicine describing conflicting findings about azithromycin and cardiac safety, particular azithromycin-induced QTc interval prolongation and torsade de pointes. The FDA wants healthcare providers to consider azithromycin-induced fatal cardiac arrhythmias for patients already at risk for cardiac death and other potentially arrhythmogenic cardiovascular conditions. In a systematic review of case reports we sought to determine factors that link to azithromycin-induced/associated QTc interval prolongation and torsade de pointes. We found 12 cases: seven female and five male. Of the nine adults with reported azithromycin doses, concurrent QTc interval measurement, and without congenital long QT syndrome, we found no significant relationship between dose and QTc interval duration. Additional risk factors were female sex, older age, heart disease, QTc interval prolonging drugs and metabolic inhibitors, hypokalemia, and bradycardia. All 12 subjects had at least two additional risk factors. Elderly women with heart disease appear to be at particularly risk for drug-related QTc interval prolongation and torsade de pointes.

Use of QT-prolonging medications in US emergency departments, 1995-2009

PURPOSE

Emergency department (ED) patients receive medications that place them at risk for adverse events, including drug-induced prolongation of the QT interval, which can lead to Torsade de Pointes and sudden cardiac death. We report the frequency of prescription and co-prescription of QT-prolonging medications in US EDs and factors associated with high-risk prescribing practices.

METHODS

We analyzed the ED component of the National Hospital Ambulatory Medical Care Survey for 1995 through 2009. Yearly rates of visits involving the prescription of QT-prolonging medications were determined. Multivariate regression analyses identified factors associated with the prescription of two or more QT-prolonging medications.

RESULTS

Approximately 16.5 million visits annually (15.0%) involved prescription of a QT-prolonging drug, with 1.7 million (1.6%) involving multiple prescriptions. Visits associated with QT-prolonging drugs more than doubled over the study period (10.4% to 22.2%). Diphenhydramine, azithromycin, and ondansetron were most frequently implicated (46.1% of cases). The most commonly prescribed combination was diphenhydramine and famotidine, both QT-prolonging medications available over-the-counter. Female gender and older age were associated with co-prescription of QT-prolonging medications. The rate of EKG screening among visits associated with QT-prolonging drug combinations was low (20.9%), but more common than among visits without a QT-prolonging drug (OR 1.3; 95% CI 1.2-1.5).

CONCLUSION

Use of QT-prolonging medications is increasing in EDs nationally. A small number of agents account for a large proportion of these visits and may represent an area for targeted screening or monitoring interventions in the ED.

Acquired long QT syndrome: frequency, onset, and risk factors in intensive care patients

BACKGROUND

Acquired long QT syndrome is a reversible condition that can lead to torsades de pointes and sudden cardiac death.

OBJECTIVE

To determine the frequency, onset, frequency of medications, and risk factors for the syndrome in intensive care patients.

METHODS

In a retrospective chart review of 88 subjects, hourly corrected QT intervals calculated by using the Bazett formula were collected. Acquired long QT syndrome was defined as a corrected QT of 500 milliseconds or longer or an increase in corrected QT of 60 milliseconds or greater from baseline level. Risk factors and medications administered were collected from patients' medical records.

RESULTS

The syndrome occurred in 46 patients (52%); mean time of onset was 7.4 hours (SD, 9.4) from time of admission. Among the 88 patients, 52 (59%) received a known QTc-prolonging medication. Among the 46 with the syndrome, 23 (50%) received a known QT-prolonging medication. No other risk factor studied was significantly predictive of the syndrome.

CONCLUSIONS

Acquired long QT syndrome occurs in patients not treated with a known QT-prolonging medication, indicating the importance of frequent QT monitoring of all intensive care patients.

Azithromycin: more lethal than chloramphenicol?

Azithromycin is commonly used in sexual health and respiratory medicine, often when the diagnosis is presumptive. A recent article by Ray et al. reported that 1 out of 20 000 courses of low-dose azithromycin was associated with (sudden) cardiovascular death (including 1 out of 4000 courses in high-risk cardiovascular patients), ascribing these deaths to azithromycin itself. Here, we critique the actual study and examine conflicting data from randomised control trials, animal studies and observational data.

Azithromycin and the risk of cardiovascular death

BACKGROUND

Although several macrolide antibiotics are proarrhythmic and associated with an increased risk of sudden cardiac death, azithromycin is thought to have minimal cardiotoxicity. However, published reports of arrhythmias suggest that azithromycin may increase the risk of cardiovascular death.

METHODS

We studied a Tennessee Medicaid cohort designed to detect an increased risk of death related to short-term cardiac effects of medication, excluding patients with serious noncardiovascular illness and person-time during and shortly after hospitalization. The cohort included patients who took azithromycin (347,795 prescriptions), propensity-score-matched persons who took no antibiotics (1,391,180 control periods), and patients who took amoxicillin (1,348,672 prescriptions), ciprofloxacin (264,626 prescriptions), or levofloxacin (193,906 prescriptions).

RESULTS

During 5 days of therapy, patients taking azithromycin, as compared with those who took no antibiotics, had an increased risk of cardiovascular death (hazard ratio, 2.88; 95% confidence interval [CI], 1.79 to 4.63; P<0.001) and death from any cause (hazard ratio, 1.85; 95% CI, 1.25 to 2.75; P=0.002). Patients who took amoxicillin had no increase in the risk of death during this period. Relative to amoxicillin, azithromycin was associated with an increased risk of cardiovascular death (hazard ratio, 2.49; 95% CI, 1.38 to 4.50; P=0.002) and death from any cause (hazard ratio, 2.02; 95% CI, 1.24 to 3.30; P=0.005), with an estimated 47 additional cardiovascular deaths per 1 million courses; patients in the highest decile of risk for cardiovascular disease had an estimated 245 additional cardiovascular deaths per 1 million courses. The risk of cardiovascular death was significantly greater with azithromycin than with ciprofloxacin but did not differ significantly from that with levofloxacin.

CONCLUSIONS

During 5 days of azithromycin therapy, there was a small absolute increase in cardiovascular deaths, which was most pronounced among patients with a high baseline risk of cardiovascular disease. (Funded by the National Heart, Lung, and Blood Institute and the Agency for Healthcare Quality and Research Centers for Education and Research on Therapeutics.).

Azithromycin-induced torsade de pointes

Although erythromycin frequently induces long QT interval and torsade de pointes, the newer drug, azithromycin, has rarely been reported to be associated with torsade de pointes. We report here the occurrence of a significant typical QT prolongation within a few hours after taking azithromycin which lead to torsade de pointes.

Azithromycin as a cause of QT-interval prolongation and torsade de pointes in the absence of other known precipitating factors

During treatment with azithromycin, a 55 year-old woman developed a newly prolonged QT interval and torsade de pointes in the absence of known risk factors. Female gender and acute renal failure may be considerations in patients treated with azithromycin.

Antimicrobial-associated QT interval prolongation: pointes of interest

Until recently, cardiac toxicity manifesting in the form of arrhythmias related to QT interval prolongation was uncommonly appreciated within the antimicrobial class of drugs, but it was well described among antiarrhythmic agents. Antimicrobials that are associated with QT prolongation include the macrolides/ketolides, certain fluoroquinolones and antimalarials, pentamidine, and the azole antifungals. Although, in most cases, mild delays in ventricular repolarization caused by these drugs are clinically unnoticeable, they may serve to amplify the risk for torsades de pointes (TdP) when prescribed in the setting of other risk factors. Conditions or variables that influence proarrhythmic risk include sex, age, electrolyte derangements, structural heart disease, pharmacokinetic/pharmacodynamic interactions, and genetic predisposition. It is important that clinicians be knowledgeable about drugs with QT liability, as well as the risk factors that increase the probability of TdP. Additionally, because TdP remains a difficult-to-measure adverse event, we must rely upon multiple data sources to determine the risk versus the benefit for newly approved drugs.

No proarrhythmic properties of the antibiotics Moxifloxacin or Azithromycin in anaesthetized dogs with chronic-AV block

BACKGROUND & PURPOSE

The therapeutically available quinolone antibiotic moxifloxacin has been used as a positive control for prolonging the QT interval in both clinical and non-clinical studies designed to assess the potential of new drugs to delay cardiac repolarization. Despite moxifloxacin prolonging QT, it has not been shown to cause torsades de pointes arrhythmias (TdP). Azithromycin is a macrolide antibiotic that has rarely been associated, clinically, with cases of proarrhythmia. As there is a lack of clinical data available, the cardiac safety of these drugs was assessed in a TdP-susceptible animal model by evaluating their repolarization and proarrhythmia effects.

EXPERIMENTAL APPROACH & KEY RESULTS

In transfected HEK cells, the IC(50)s for I (hERG) were 45+/-6 and 856+/-259 microg ml(-1) for moxifloxacin and azithromycin, respectively. Intravenous administration of 2 and 8 mg kg(-1) moxifloxacin (total peak-plasma concentrations 4.6+/-1.5 and 22.9+/-6.8 microg ml(-1)) prolonged the QT(c) in 6 anaesthetized dogs with chronic AV block by 7+/-3 and 21+/-19%, respectively. Similar intravenous doses of azithromycin (total peak-plasma concentrations 5.4+/-1.3 and 20.8+/-4.9 microg ml(-1)) had no electrophysiological effects in the same dogs. The reference compound, dofetilide (25 microg kg(-1) i.v.) caused QT(c) prolongation (29+/-15%) and TdP in all dogs. Beat-to-beat variability of repolarization (BVR), quantified as short-term variability of the left ventricular monophasic action potential duration, was only increased after dofetilide (1.8+/-0.7 to 3.8+/-1.5 ms; P<0.05).

CONCLUSION & IMPLICATIONS

As neither moxifloxacin nor azithromycin caused TdP or an increase in the BVR, we conclude that both drugs can be used safely in clinical situations.