Utilizing physiologically based pharmacokinetic modeling to predict theoretically conceivable extreme elevation of serum flecainide concentration in an anuric hemodialysis patient with cirrhosis.

PURPOSE: Higher drug concentrations in complex clinical scenarios in which multiple factors such as drug-drug interactions (DDIs) and comorbidities are simultaneously present are not necessarily rationalized in prospective clinical studies. Physiologically based pharmacokinetic (PBPK) modeling and simulation of the anti-arrhythmic drug flecainide, as an example, were utilized to quantitatively rationalize the higher flecainide concentration in a complex clinical case involving end-stage renal disease (ESRD), cirrhosis, and the co-administration of mexiletine, a CYP1A2 inhibitor. METHODS: The developed flecainide PBPK model was used to evaluate the DDI effect (as measured by AUC ratio before and after inhibition) of mexiletine and the combined disease effects of ESRD and cirrhosis on flecainide exposure. RESULTS: The predicted DDI effect of mexiletine was negligible or weak in anuric hemodialysis with cirrhosis population (mean [5th/95th percentiles], 1.23 [0.97-1.67]), although it was negligible in healthy volunteers (1.03 [1.02-1.05]). The predicted flecainide concentrations after multiple flecainide doses (50 mg BID) in the anuric hemodialysis with cirrhosis population were comparable with the observed value (3602 ng/mL), which fell between the predicted concentrations in the absence and presence of mexiletine (3043 [718-8499] and 5914 [880-20,624] ng/mL, respectively). CONCLUSIONS: The PBPK simulation proposed a likely explanation that the observed higher flecainide concentration could be attributed to the combined effects of ESRD, cirrhosis, and a potential DDI with mexiletine. This approach provides quantitative insight into theoretically conceivable extremes in drug exposure occurring in complex clinical situations even if uncommon.

High-throughput quantification of ten antiarrhythmic drugs in human plasma using UPLC-MS/MS.

In this paper we present an FDA validated method to analyze ten antiarrhythmic drugs (atenolol, bisoprolol, carvedilol, diltiazem, flecainide, lidocaine, metoprolol, propranolol, sotalol and verapamil). A simple and fast sample preparation protocol with protein precipitation followed by ultra performance liquid chromatography (UPLC) for chromatographic separation and mass spectrometric detection applying electrospray ionization (ESI+) and selected reaction monitoring mode (MS/MS) was used. Only 50 µl plasma sample is needed for the simultaneous quantification of all compounds within a 5 min run-to-run analysis time. Sotalol-D6, carvedilol-D5 and verapamil-D6 were used as internal standards. The method was validated according to the FDA guidelines. Correlation coefficients were higher than 0.998 for all compounds. Intra- and interday accuracies were within 15 CV(%) for all analytes. The method is currently successfully applied for routine analysis in our hospital.

Antenatal Therapy for Fetal Supraventricular Tachyarrhythmias: Multicenter Trial.

BACKGROUND: Standardized treatment of fetal tachyarrhythmia has not been established. OBJECTIVES: This study sought to evaluate the safety and efficacy of protocol-defined transplacental treatment for fetal supraventricular tachycardia (SVT) and atrial flutter (AFL). METHODS: In this multicenter, single-arm trial, protocol-defined transplacental treatment using digoxin, sotalol, and flecainide was performed for singleton pregnancies from 22 to <37 weeks of gestation with sustained fetal SVT or AFL ≥180 beats/min. The primary endpoint was resolution of fetal tachyarrhythmia. Secondary endpoints were fetal death, pre-term birth, and neonatal arrhythmia. Adverse events (AEs) were also assessed. RESULTS: A total of 50 patients were enrolled at 15 institutions in Japan from 2010 to 2017; short ventriculoatrial (VA) SVT (n = 17), long VA SVT (n = 4), and AFL (n = 29). One patient with AFL was excluded because of withdrawal of consent. Fetal tachyarrhythmia resolved in 89.8% (44 of 49) of cases overall and in 75.0% (3 of 4) of cases of fetal hydrops. Pre-term births occurred in 20.4% (10 of 49) of patients. Maternal AEs were observed in 78.0% (39 of 50) of patients. Serious AEs occurred in 1 mother and 4 fetuses, thus resulting in discontinuation of protocol treatment in 4 patients. Two fetal deaths occurred, mainly caused by heart failure. Neonatal tachyarrhythmia was observed in 31.9% (15 of 47) of neonates within 2 weeks after birth. CONCLUSIONS: Protocol-defined transplacental treatment for fetal SVT and AFL was effective and tolerable in 90% of patients. However, it should be kept in mind that serious AEs may take place in fetuses and that tachyarrhythmias may recur within the first 2 weeks after birth.

Telemetered common marmosets is useful for the assessment of electrocardiogram parameters changes induced by multiple cardiac ion channel inhibitors.

The objective of this study is to assess the response of telemetered common marmosets to multiple cardiac ion channel inhibitors and to clarify the usefulness of this animal model in evaluating the effects of drug candidates on electrocardiogram (ECG). Six multiple cardiac ion channel inhibitors (sotalol, astemizole, flecainide, quinidine, verapamil and terfenadine) were orally administered to telemetered common marmosets and changes in QTc, PR interval and QRS duration were evaluated. Drugs plasma levels were determined to compare the sensitivity in common marmosets to that in humans. QTc prolongation was observed in the marmosets dosed with sotalol, astemizole, flecainide, quinidine, verapamil and terfenadine. PR prolongation was noted after flecainide and verapamil administration, and QRS widening occurred following treatment with flecainide and quinidine. Drugs plasma levels associated with ECG changes in marmosets were similar to those in humans, except for verapamil-induced QTc prolongation. Verapamil-induced change is suggested due to body temperature decrease. These results indicate that telemetered common marmoset is a useful animal for evaluation of the ECG effects of multiple cardiac ion channel inhibitors and the influence of body temperature change should be considered in the assessment.

Rapid Quantitation of Flecainide in Human Plasma for Therapeutic Drug Monitoring Using Liquid Chromatography and Time-of-Flight Mass Spectrometry.

BACKGROUND: Measurement of flecainide is useful to optimize dosage and minimize risks of toxicity. Furthermore, there is a need for urgent sample analysis when flecainide is used in transplacental therapy for fetal tachycardia. To this end, we have developed and validated a rapid assay for the measurement of flecainide in human plasma or serum, using a small sample volume (50 µL). METHODS: After a simple deproteination with zinc sulfate and methanol, prepared samples were injected onto a short (30 mm) analytical column and eluted using a rapid gradient elution. Detection was performed using time-of-flight mass spectrometry. Flecainide was quantified using flecainide-D4 as internal standard, with both compounds extracted from the total ion chromatogram using a ±5 ppm extraction window based on the theoretical m/z values for the protonated ions. RESULTS: The assay was linear over a putative therapeutic range (100-1500 mcg/L). Between- and within-assay imprecision and accuracy were <4.6% and 94.8%-110.0%, respectively. Matrix effects were minimal and were compensated for by flecainide-D4. There were no effects due to hemolysis or lipemia, and no carryover was apparent. Total analysis time was just 1.2 minutes (72 seconds). CONCLUSIONS: We have developed and validated a rapid method for the analysis of flecainide. The method is particularly suited for flecainide therapeutic drug monitoring, when analyzing samples from mothers receiving flecainide for the treatment of fetal tachycardia.

When potion becomes poison! A case report of flecainide toxicity.

We report a 48-day-old female infant, who developed cardiac conduction abnormalities and seizures secondary to supratherapeutic doses of oral flecainide. Flecainide was started in this infant for treatment of supraventricular tachycardia. The drug was withdrawn with successful normalization of the QRS complex and no further recurrence of seizures. The Naranjo probability score for adverse drug reaction was 8, making the causality "probable." The case restates an important message that physicians should be aware of the side effects of the drugs that they prescribe, especially of those drugs which have a narrow therapeutic window.

Flecainide versus digoxin for fetal supraventricular tachycardia: Comparison of two drug treatment protocols.

BACKGROUND: The optimal treatment for fetal supraventricular tachycardia (SVT) with 1:1 atrioventricular relationship is unclear. OBJECTIVE: We compared the effectiveness of transplacental treatment protocols used in 2 centers. METHODS: Pharmacologic treatment was used in 84 fetuses. Maternal oral flecainide was the primary therapy in center 1 (n = 34) and intravenous maternal digoxin in center 2 (n = 50). SVT mechanism was classified by mechanical ventriculoatrial (VA) time intervals as short VA or long VA. Treatment success was defined as conversion to sinus rhythm (SR), or rate control, defined as >15% rate reduction. RESULTS: Short VA interval occurred in 67 fetuses (80%) and long VA in 17 (20%). Hydrops was present 28 of 84 (33%). For short VA SVT, conversion to SR was 29 of 42 (69%) for digoxin and 24 of 25 (96%) for flecainide (P = .01). For long VA SVT, conversion to SR and rate control was 4 of 8 (50%) and 0 of 8, respectively, for digoxin, and 6 of 9 (67%) and 2 of 9 (cumulative 89%) for flecainide (P = .13). In nonhydropic fetuses, digoxin was successful in 23 of 29 (79%) and flecainide in 26 of 27 (96%) (P = .10). In hydrops, digoxin was successful in 8 of 21 (38%), flecainide alone in 6 of 7 (86%, P = .07 vs digoxin), and flecainide ± amiodarone in 7 of 7 (100%) (P = .01). Intrauterine or neonatal death occurred in 9 of 21 hydropic fetuses treated with digoxin (43%), compared to 0 of 7 (P = .06) treated with flecainide. CONCLUSIONS: Flecainide was more effective than digoxin, especially when hydrops was present. No adverse fetal outcomes were attributed to flecainide.

Quantitation of Flecainide, Mexiletine, Propafenone, and Amiodarone in Serum or Plasma Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Flecainide, mexiletine, propafenone, and amiodarone are antiarrhythmic drugs that are used primarily in the treatment of cardiac arrhythmias. The monitoring of the use of these drugs has applications in therapeutic drug monitoring and overdose situations. LC-MS/MS is used to analyze plasma/serum extracts with loxapine as the internal standard to ensure accurate quantitation and control for any potential matrix effects. Positive ion electrospray is used to introduce the analytes into the mass spectrometer. Selected reaction monitoring of two product ions for each analyte allows for the calculation of ion ratios which ensures correct identification of each analyte, while a matrix matched calibration curve is used for quantitation.

Serum flecainide S/R ratio reflects the CYP2D6 genotype and changes in CYP2D6 activity.

The aims of this study were to clarify whether the ratio of S- to R-flecainide (S/R ratio) in the serum flecainide concentration was associated with the stereoselectivity of flecainide metabolism, and to investigate the effects of the cytochrome P450 (CYP) 2D6 (CYP2D6) genotype and CYP2D6 inhibitor on the serum flecainide S/R ratio. In vitro studies using human liver microsomes and cDNA-expressed CYP isoforms suggested that variability in the serum flecainide S/R ratio was associated with the stereoselectivity of CYP2D6-mediated flecainide metabolism. We examined the serum flecainide S/R ratio in 143 patients with supraventricular tachyarrhythmia. The S/R ratio was significantly lower in intermediate metabolizers and poor metabolizers (IMs/PMs) than in extensive metabolizers (EMs) identified by the CYP2D6 genotype. The cut-off value for the S/R ratio to allow the discrimination between CYP2D6 EMs and IMs/PMs was 0.99. The S/R ratio in patients with co-administration of bepridil, a potent CYP2D6 inhibitor, was lower than 0.99, regardless of the CYP2D6 genotype status. Other factors, including age, sex, body weight, and renal function, did not affect the serum flecainide S/R ratio. This study suggests that the serum flecainide S/R ratio reflects the CYP2D6 genotype and changes in CYP2D6 activity on co-administration of a CYP2D6 inhibitor.

Lesson of the month 1: Acute flecainide overdose and the potential utility of lipid emulsion therapy.

Lipid-emulsion therapy (Intralipid®) has been advocated as a potential treatment for the management of cardio-toxicity arising from lipid-soluble drugs, particularly those acting upon sodium channels. This, on the basis of a number of ex vivo studies and animal models, suggests that partitioning a drug into lipid could alter its pharmacokinetics and result in significant clinical improvements. Its subsequent use in clinical case series has been seen as confirmation of this mechanism of action. While there are undoubtedly instances where lipid emulsion therapy has been associated with a desirable outcome in humans, as described in this case report, clinicians are reminded that they should not attribute causality, on this basis alone.

Validation of an ultra-performance liquid chromatography-tandem mass spectrometry method for the determination of flecainide in human plasma and its clinical application.

A simple and reproducible bioanalytical method for the determination of flecainide in human plasma was developed and validated using an ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) to obtain higher sensitivity than the current available methods. After simple protein precipitation, flecainide and a stable isotope-labeled internal standard (IS) were chromatographed on an Acquity UPLC BEH C18 column (2.1 × 100 mm, 1.7 µm) with isocratic elution of mobile phase consisting of 45% methanol containing 0.1% formic acid at a flow rate 0.25 mL/min. Detection was performed in positive electrospray ionization by monitoring the selected ion transitions at m/z 415.4/301.1 for flecainide and m/z 419.4/305.1 for the IS. The method was validated according to current bioanalytical method validation guidelines. The calibration standard curve was linear from 2.5 to 1000 ng/mL using 0.1 mL of plasma. No significant interferences were detected in blank human plasma. Accuracy and precision in the intra- and inter-batch reproducibility study were within acceptance criteria. Neither hemolysis effects nor matrix effects were observed. The UPLC-MS/MS method developed was successfully applied to determine plasma flecainide concentrations to support clinical studies and incurred sample reanalysis also ensured the reproducibility of the method.

Stereoselective analysis of flecainide enantiomers using reversed-phase liquid chromatography for assessing CYP2D6 activity.

Stereoselective analyses of flecainide enantiomers were performed using reversed-phase high-performance liquid chromatography (HPLC) equipped with a polysaccharide-based chiral column (Chiralpak AS-RH) and fluorescence detector. Excitation and emission wavelengths were set at 300 and 370 nm, respectively. Flecainide enantiomers in serum and urine were extracted using diethyl ether. The mobile phase solution, comprising 0.1 m potassium hexafluorophosphate and acetonitrile (65:35, v/v), was pumped at a flow rate of 0.5 mL/min. The recoveries of flecainide enantiomers were greater than 94%, with the coefficients of variation (CVs) <6%. The calibration curves of flecainide enantiomers in serum and urine were linear in the concentration range 5-500 ng/mL and 0.75-15 µg/mL (r > 0.999), respectively. CVs in intra-day and inter-day assays were 1.8-5.8 and 3.4-7.5%, respectively. In a pharmacokinetic study, the ratios of (S)- to (R)-flecainide (S/R ratio) in the area under the curve and the amount of flecainide enantiomers excreted in urine were lower in a subject carrying CYP2D6*10/*10 than in subjects carrying CYP2D6*1/*2. The S/R ratio of trough serum flecainide concentration ranged from 0.79 to 1.16 in patients receiving oral flecainide. The present HPLC method can be used to assess hepatic flecainide metabolism in a pharmacokinetic study and therapeutic drug monitoring.

Electrophysiological and haemodynamic effects of vernakalant and flecainide in dyssynchronous canine hearts.

AIMS: About one-third of patients with mild dyssynchronous heart failure suffer from atrial fibrillation (AF). Drugs that convert AF to sinus rhythm may further slowdown ventricular conduction. We aimed to investigate the electrophysiological and haemodynamic effects of vernakalant and flecainide in a canine model of chronic left bundle branch block (LBBB). METHODS AND RESULTS: Left bundle branch block was induced in 12 canines. Four months later, vernakalant or flecainide was administered using a regime, designed to achieve clinically used plasma concentrations of the drugs, n = 6 for each drug. Epicardial electrical contact mapping showed that both drugs uniformly prolonged myocardial conduction time. Vernakalant increased QRS width significantly less than flecainide (17 ± 13 vs. 34 ± 15%, respectively). Nevertheless, both drugs equally decreased LVdP/dtmax by ∼15%, LVdP/dtmin by ∼10%, and left ventricular systolic blood pressure by ∼5% (P = n.s. between drugs). CONCLUSIONS: Vernakalant prolongs ventricular conduction less than flecainide, but both drugs had a similar, moderate negative effect on ventricular contractility and relaxation. Part of these reductions seems to be related to the increase in dyssynchrony.

Pharmacokinetic-pharmacodynamic modeling of QRS-prolongation by flecainide: heart rate-dependent effects during sinus rhythm in conscious telemetered dogs.

INTRODUCTION: The duration of the QRS interval is determined by the ion currents involved in cardiac depolarization. Class I antiarrhythmic drugs reduce cardiac excitability and conduction by inhibiting Nav1.5 channels responsible for I(Na), thus increasing the QRS interval. Previous studies in humans as well as in animal models have demonstrated a more pronounced effect on QRS-prolongation during higher heart rates. In the present study, the effects of the Nav1.5 inhibitor flecainide on cardiovascular parameters, were studied in the telemetered beagle dog under normal autonomic control. The heart rate dependency of QRS prolongation was characterized using pharmacokinetic-pharmacodynamic (PKPD) modeling. METHODS: Four male telemetered beagle dogs were administered placebo or flecainide (100, 150 and 200 mg) in a Latin square design. The QRS interval and heart rate were recorded, and blood samples were taken. Plasma concentrations of flecainide were fitted to a one compartment oral model and the intrapolated plasma concentrations were fitted to QRS and heart rate data sampled during 5 h after dosing. RESULTS: Flecainide increased the QRS interval in all dogs, whereas there were no effects on heart rate. Using the PKPD model, a statistically significant heart rate-dependent QRS prolongation was linked to individual concentration-time profiles of flecainide. DISCUSSION: PKPD analysis of QRS interval data from unrestrained dogs with sinus rhythm can elucidate mechanisms previously only described during controlled heart rhythm. Specific questions can therefore be addressed in generically designed cardiovascular telemetry safety studies and different types of relationships between parameters can be uncovered. In addition, the present approach can be used to better characterize drug-induced QRS effects in cardiovascular dog models.

SCN5A promoter haplotype affects the therapeutic range for serum flecainide concentration in Asian patients.

OBJECTIVE: An increased slowing of cardiac conduction induced by sodium channel blockers is remarkably observed in carriers of an Asian-specific promoter haplotype [haplotype B (HapB)] of the cardiac sodium channel gene (SCN5A). We investigated the effect of HapB on the therapeutic range for serum flecainide concentration in Asian patients. PATIENTS AND METHODS: We examined the serum concentration and antiarrhythmic efficacy of flecainide, together with the SCN5A promoter haplotype, in 146 patients with supraventricular tachyarrhythmias. Trough serum flecainide concentrations were determined by HPLC. The antiarrhythmic efficacy of flecainide was assessed for at least 2 months through examination of symptomatology, ECG, and Holter monitoring. RESULTS: The serum flecainide concentration did not differ between the wild-type HapA homozygotes and HapB carriers under treatment with the usual dose. A genetic difference in the antiarrhythmic efficacy of flecainide was observed between the HapA homozygotes and HapB carriers at serum flecainide concentrations less than 300 ng/ml (42.9 vs. 68.8%; P=0.022). PR prolongation and QRS widening were observed more commonly among the HapB carriers with serum flecainide concentrations of at least 300 ng/ml than in the HapA homozygotes (PR, 210 ± 25 vs. 195 ± 25 ms; P=0.036; and QRS, 112 ± 10 vs. 105 ± 9 ms; P=0.030). CONCLUSION: These findings suggest that the therapeutic range for serum flecainide concentration is lower in HapB carriers than in HapA homozygotes.

Arrhythmogenic effect of flecainide toxicity.

Flecainide is a class 1C antiarrhythmic drug especially used for the management of supraventricular arrhythmia. In overdose cases, flecainide can induce life treating ventricular arrhythmias and cardiogenic shock. We report the case of a 72-year-old woman admitted to our intensive care unit for a regular monomorphic wide complex tachycardia (QRS duration 240 ms, right bundle branch block and superior axis morphology) without apparent P waves. Clinical examination showed slight left congestive heart failure signs without cardiogenic shock. An intravenous bolus of 10 mg adenosine 5'-triphosphate (ATP) was ineffective to stop the tachycardia. The diagnosis of ventricular tachycardia induced by flecainide overdose was considered. 500 mL of intravenous 84‰ sodium bicarbonate was administrated. The patient's QRS narrowed immediately and 12-lead ECG showed sinus rhythm. Blood samples confirmed the flecainide overdose and the clinical status progressively improved.

Usefulness of postmortem biochemistry in forensic pathology: illustrative case reports.

The aim of this work is to present some practical, postmortem biochemistry applications to illustrate the usefulness of this discipline and reassert the importance of carrying out biochemical investigations as an integral part of the autopsy process. Five case reports are presented pertaining to diabetic ketoacidosis in an adult who was not known to suffer from diabetes and in presence of multiple psychotropic substances; fatal flecainide intoxication in a poor metabolizer also presenting an impaired renal function; diabetic ketoacidosis showing severe postmortem changes; primary aldosteronism presented with intracranial hemorrhage and hypothermia showing severe postmortem changes. The cases herein presented can be considered representative examples of the importance of postmortem biochemistry investigations, which may provide significant information useful in determining the cause of death in routine forensic casework or contribute to understanding the pathophysiological mechanisms involved in the death process.

Translation of flecainide- and mexiletine-induced cardiac sodium channel inhibition and ventricular conduction slowing from nonclinical models to clinical.

INTRODUCTION: Nonclinical in vivo models used for cardiovascular safety testing have not previously been studied for their sensitivity for detection of conduction slowing resulting from cardiac sodium channel block. The goal of this study was to examine the sensitivity of in vivo models to cardiac sodium channel block, and translation of the effect from in vitro to in vivo models using sodium channel inhibitors flecainide and mexiletine; flecainide, but not mexiletine is commonly associated with QRS complex prolongation in humans. METHODS: Inhibition of cloned cardiac sodium channels (hNav1.5) was studied using the IonWorks platform. Conduction slowing was measured in vitro in the rabbit isolated ventricular wedge (RVW) and in vivo in the conscious telemetered rat and dog, and anaesthetised dog. RESULTS: Flecainide and mexiletine inhibited hNav1.5 channels with IC50 values of 10.7 and 67.2 µM respectively. In the RVW, QRS was increased by flecainide at 60 bpm, and at 120bpm, there was an increased effect of both drugs. In conscious rats, flecainide significantly increased QRS complex duration; mexiletine had no significant effect, but there was an increase at the highest dose in 4/6 animals. QRS complex was increased by flecainide and mexiletine in anaesthetised dogs but this was not statistically significant; in conscious dog, only flecainide produced a significant increase in QRS complex. DISCUSSION: When compared to clinical data, effects of flecainide and mexiletine in RVW and conscious dog compared well with effects in patients and healthy volunteers in terms of sensitivity. The anaesthetised dog was least sensitive for detection of changes in QRS. All assays showed some differentiation between the expected conduction slowing activity of flecainide and mexiletine. Based on these data, RVW and conscious dog were most predictive for effects of compounds on QRS complex and cardiac conduction.