Propafenone

Influence of CYP2D6 Genetic Variation on Adverse Events with Propafenone in the Pediatric and Young Adult Population

Propafenone is an antiarrhythmic drug metabolized primarily by cytochrome P450 2D6 (CYP2D6). In adults, propafenone adverse events (AEs) are associated with CYP2D6 poor metabolizer status; however, pediatric data are lacking. Subjects were tested for 10 CYP2D6 allelic variants and copy number status, and activity scores assigned to each genotype. Seventy‐six individuals (median 0.3 [range 0–26] years old) were included. Propafenone AEs occurred in 29 (38%); 14 (18%) required drug discontinuation due to AE. The most common AEs were QRS (n = 10) and QTc (n = 6) prolongation. Those with AEs were older at the time of propafenone initiation (1.58 [0.13–9.92] vs. 0.20 [0.08–2.01] years old; p = 0.042). CYP2D6 activity scores were not associated with presence of an AE (odds ratio [OR] 0.48 [0.22–1.03]; p = 0.055) but with the total number of AE (β₁ = −0.31 [−0.60, −0.03]; p = 0.029), systemic AEs (OR 0.33 [0.13–0.88]; p = 0.022), and drug discontinuation for systemic AEs (OR 0.28 [0.09–0.83]; p = 0.017). Awareness of CYP2D6 activity score and patient age may aid in determining an individual's risk for an AE with propafenone administration.

Electrophysiological effects and clinical utility of propafenone in children

AIM

This retrospective case series study sought to describe the safety and clinical effectiveness of propafenone for the control of arrhythmias in children with and without CHD or cardiomyopathy.

METHODS

We reviewed baseline characteristics and subsequent outcomes in a group of 63 children treated with propafenone at 2 sites over a 15-year period Therapy was considered effective if no clinically apparent breakthrough episodes of arrhythmias were noted on the medication.

RESULTS

Sixty-three patients (29 males) were initiated on propafenone at a median age of 2.3 years. CHD or cardiomyopathy was noted in 21/63 (33%). There were no significant differences between demographics, clinical backgrounds, antiarrhythmic details, side effect profiles, and outcomes between children with normal hearts and children with CHD or cardiomyopathy. Cardiac depression at the initiation of propafenone was more common amongst children with CHD or cardiomyopathy compared to children with normal hearts. Systemic ventricular function was diminished in 15/63 patients (24%) prior to starting propafenone and improved in 8/15 (53%) of patients once better rhythm control was achieved. Other than one child in whom medication was stopped due to gastroesophageal reflux, no other child experienced significant systemic or cardiac side effects during treatment with propafenone. Propafenone achieved nearly equal success in controlling arrhythmias in both children with normal hearts and children with congenital heart disease or cardiomyopathy (90% versus 86%, p = 0.88).

CONCLUSION

Propafenone is a safe and effective antiarrhythmic medication in children.

Antiarrhythmic effects of newly developed propafenone derivatives

It is well known that the presence of different chemical groups in drug molecules influences their pharmacological properties. The aim of our study is to investigate whether newly synthesized derivatives of propafenone, with changes in benzyl moiety, have a different effect upon arrhythmia, compared to propafenone. 5OCl-PF and 5OF-PF are derivatives of propafenone with -Cl or -F substituent on the ortho position of the benzyl moiety. For verification of their antiarrhythmic effect, we used an in vivo rat model of aconitine-induced arrhythmia. 5OCl-PF speeded the appearance of supraventricular premature beats (SVPB) and death more than aconitine. All animals treated with 5OCl-PF developed ventricular premature beats in salvos (VPBS), bigeminies (VPBB) and paroxysmal ventricular tachycardia (PVT). 5OF-PF had a negative chronotropic effect and potentiated atrial excitability (more SVPB). It had a positive effect on the occurrence and onset time of supraventricular tachycardia, VPBS, and PVT. Based on the obtained results, it can be concluded that newly synthesized propafenone derivatives have no better antiarrhythmic effect than the parent compound. In the future, our research will be focused on the synthesis of different derivatives and examining their antiarrhythmic effects.

The Efficacy Comparison Between Guan-Fu Base A Hydrochloric Injection vs. Propafenone Hydrochloric Injection in the Treatment of Arrhythmia: Systemic Review and Meta-Analysis

Objective: To determine using a systematic assessment and meta-analysis if GFA injection is an appropriate substitute of propafenone for arrhythmic. Design: Conduct a systematic review and meta-analysis of randomized controlled trials. Data Source: PubMed, Web of Science, Cochrane Library, Embase, Wan-Fang Database, VIP, CNKI, and Sino Med from their inception to 7 March 2021. Eligibility Criteria for Selecting Studies: Inclusion of randomized controlled trials, which draws a comparison between GFA and propafenone. Evaluation of study integrity and conducted an extraction of independent data. Main Outcome Measure: Efficacy for supraventricular tachycardia, it is considered effective if it is reversed within 40 min (without considering recurrence); for premature ventricular beats, if they are reduced by more than 50% within 6 h. Results: Included in this current study are 1,294 research subjects pooled from 14 clinical studies. From the pooled assessment, GFA is demonstrated to be the equivalent of propafenone regarding the potency of effectiveness for tachycardia (RR = 1.11, 95% CI: 0.96, 1.28, P = 0.15). The subset analysis indicated that GFA has a better effect on premature ventricular beats (RR = 1.35, 95% CI: 1.07, 1.70, P = 0.01) and a similar effect on supraventricular tachycardia (RR = 1.07, 95% CI: 0.98, 1.12, P = 0.21). GFA effectiveness is lesser than propafenone in the case of mean converting time (WMD = -1.18, 95% CI: -2.30, -0.07, P = 0.04), systolic blood pressure (WMD = -3.53, 95% CI: -6.97, -0.09, P = 0.04), and QRS complex (WMD = -3.82, 95% CI: -6.96, -0.69, P = 0.02). Both GFA and propafenone have identical effects for diastolic blood pressure, heart rate, P-R interval, and QTc interval. Conclusion: A meta-analysis of RCTs was performed across 14 clinical trials, whereby 1,294 patients are used as research subjects. From the results, it is revealed that the effect exhibited by GFA injection is similar to the propafenone injection when treating premature ventricular beats or supraventricular tachycardia. Nevertheless, in certain academic disciplines, it was found that GFA is safer and beneficial compared to propafenone. Based on facts from relevant studies, GFA is deemed applicable during clinical practice. Systematic Review Registration: https://www.inplasy.com/inplasy-2021-3-0077/, identifier: INPLASY202130077.

Propafenone Poisoning of a Female Adolescent After a Suicide Attempt

Propafenone is an antiarrhythmic agent for the management of ventricular and supraventricular tachycardia and atrial fibrillation. Propafenone poisoning is rare but may be life-threatening due to drug-induced arrhythmias. Electrocardiographic changes in PR, QRS, and QT intervals have been recorded. We present a case of a 15-year-old female adolescent who developed arrhythmias and convulsions due to propafenone intoxication, in an attempt to commit suicide. The outcome of the case was a full recovery from the arrhythmias and the seizures. The aim of this article is to highlight the possibility of a lethal intoxication by a common antiarrhythmic drug. Our case aims to present our therapeutic strategy that relies mainly on close monitoring of patients and cardiac output support.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

Neurological complications of cardiovascular drugs

Cardiovascular drugs are used to treat arterial hypertension, hyperlipidemia, arrhythmias, heart failure, and coronary artery disease. They also include antiplatelet and anticoagulant drugs that are essential for prevention of cardiogenic embolism. Most neurologic complications of the cardiovascular drugs are minor or transient and are far outweighed by the anticipated benefits of treatment. Other neurologic complications are more serious and require early recognition and management. Overtreatment of arterial hypertension may cause lightheadedness or fatigue but often responds readily to dose adjustment or an alternative drug. Other drug complications may be more troublesome as in myalgia associated with statins or headache associated with vasodilators. The recognized bleeding risk of the antithrombotics requires careful calculation of risk/benefit ratios for individual patients. Many neurologic complications of cardiovascular drugs are well documented in clinical trials with known frequency and severity, but others are rare and recognized only in isolated case reports or small case series. This chapter draws on both sources to report the adverse effects on muscle, nerve, and brain associated with commonly used cardiovascular drugs.

Propafenone and propranolol dual toxicity

Propranolol is a highly lipid-soluble beta-receptor antagonist and propafenone is a potent class 1c anti-arrhythmic agent with strong Na-channel blockade effect. We describe a novel case of dual overdose of propafenone and propranolol resulting in hypotension, generalized seizures, and reduced level of consciousness that was successfully treated. A 52-year-old female ingested 500 mg of propranolol and 1.5 g of propafenone. The patient was brought to the emergency department (ED) and exhibited signs of systemic toxicity and reduced level of consciousness. The patient was treated as a case of combined β-blocker and propafenone toxicity using high dose insulin, NaHCO3, glucagon, atropine, and dopamine. She started improving and becoming more alert, with subsequent ECGs revealing normal sinus rhythm. The patient was discharged 4 days later. We believe that early administration of NaHCO3 should be administered in patients exhibiting signs of Na-channel blockade.

Propafenone-associated Gross Hematuria: A Case Report and Review of the Literature

PURPOSE

Propafenone hydrochloride has been widely used for the treatment of supraventricular and ventricular arrhythmias. We present a case report of an 81-year-old patient with propafenone-associated gross hematuria.

METHODS

The Naranjo Adverse Drug Reaction Probability Scale was used to assess causality. We also performed a literature search to find publications that report propafenone-associated gross hematuria.

FINDINGS

The Naranjo scale generated a score of 6, suggesting a probable association between gross hematuria and propafenone therapy. Thirteen publications that reported an association between gross hematuria and propafenone administration were found.

IMPLICATIONS

A probable association exists between gross hematuria and propafenone.

Propafenone HCl fast dissolving tablets containing subliming agent prepared by direct compression method

Propafenone HCl (PPH), an antiarrhythmic drug, has a bitter taste, short half-life, delayed drug dissolution and side effects. Thus, the purpose of this work is to develop orally fast dissolving tablets (OFDTs) containing PPH to provide a rapid drug dissolution and subsequently give rapid onset of action of PPH as an antiarrhythmic drug. Moreover, OFDTs of PPH reduce its side effects and improve its bioavailability. Propafenone HCl (PPH), an antiarrhythmic drug, has a bitter taste, short half-life, delayed drug dissolution and side effects. Direct compression method was used for the preparation of 15 formulations OFDTs containing PPH using directly compressible excipients, subliming agent and superdisintegrants. The prepared tablets were undergone physical characterization, in vitro dissolution and stability studies. All pre- and post-compression tests met the pharmacopoeia specifications. In vitro dissolution of the prepared PPH OFDTs exhibited high dissolution rate than compared to the marketed tablets. It was found that the tablets prepared by using the higher concentration of crospovidone were found to dissolute the drug at a faster rate when compared to other concentrations. A formula containing croscarmellose sodium showed the higher present of PPH dissolved as compared to the other formulations. It was concluded that PPH OFDTs were formulated successfully with acceptable physical and chemical properties with rapid disintegration in the oral cavity, rapid onset of action, and enhanced patient compliance. It was found that F10 showed good stability upon storage at 25 and 40 °C for 3 months. Formulation of PPH OFDTs can result in a significant improvement in the PPH bioavailability since the first pass metabolism will be avoided.

Drug trapping in hERG K+ channels: (not) a matter of drug size?

Inhibition of hERG K+ channels by structurally diverse drugs prolongs the ventricular action potential and increases the risk of torsade de pointes arrhythmias and sudden cardiac death. The capture of drugs behind closed channel gates, so-called drug trapping, is suggested to harbor an increased pro-arrhythmic risk. In this study, the trapping mechanisms of a trapped hERG blocker propafenone and a bulky derivative (MW: 647.24 g mol-1) were studied by making use of electrophysiological measurements in combination with molecular dynamics simulations. Our study suggests that the hERG cavity is able to accommodate very bulky compounds without disturbing gate closure.

Novel sustained-release of propafenone through pellets: preparation and in vitro/in vivo evaluation

In this study, an extrusion-spheronization method was applied successfully to fabricate propafenone hydrochloride (PPF) sustained-release pellets. Using scanning electron microscopy, it was shown that the PPF pellets had a mean size of approximately 950 µm with a spherical shape. The in vitro release profiles indicated that the release of PPF from the pellets exhibited a sustained release behavior. The relatively high correlation coefficient (r) values obtained from the analysis of the amount of the drug released versus the square root of time indicated that the release followed a zero order kinetic model. A similar phenomenon was also observed in a pharmacokinetic study in dogs, in which the area under the curve (AUC) of the pellet formulation was 1.2-fold higher than that of PPF tablets. The present work demonstrated the feasibility of controlled delivery of PPF utilizing microcrystalline cellulose (MCC)-based pellets.

Efficacy of dronedarone versus propafenone in the maintenance of sinus rhythm in patients with atrial fibrillation after electrical cardioversion

PURPOSE

Our objective was to compare the efficacy of dronedarone and propafenone in maintaining sinus rhythm in patients with atrial fibrillation (AF) after electrical cardioversion.

METHODS

In this single-center, open-label, randomized trial, we randomly assigned patients with AF after electrical cardioversion to receive dronedarone 400 mg BID or propafenone 150 mg TID. Follow-up clinical evaluations were conducted at 1, 2, 3, and 6 months of treatment. The primary end point was the time to the first recurrence of AF.

FINDINGS

A total of 98 patients were enrolled (79 men; mean age, 59.2 years; n = 49 per group). The median times to first recurrence of AF were 31 days in the dronedarone group and 32 days in the propafenone group (P = 0.715). The median (interquartile range) ventricular rates at first recurrence of AF were 76.5 (67.3-86.5) beats/min in the dronedarone group and 83.0 (71.0-96.0) beats/min in the propafenone group (P = 0.059).

IMPLICATIONS

Dronedarone and propafenone had similar efficacies in maintaining sinus rhythm in patients with AF after electrical cardioversion. The ventricular rate at the first recurrence of AF was numerically but not statistically significantly lower in the dronedarone group than in the propafenone group. ClinicalTrials.gov identifier: NCT01991119.

Atrial fibrillation

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

Propafenone hepatotoxicity: report of a new case and review of the literature

Propafenone is a class Ic antiarrhythmic drug. It is a beta-adrenergic blocker that causes bradycardia and bronchospasm. It is metabolized primarily in the liver. Its bioavailability and plasma concentration differ among patients under long-term therapy. They are genetically determined by the hepatic cytochrome P-450 2D6. Hepatic toxicity is highly uncommon. To date, only eight patients were reported in the reviewed world literature. In this article, one new case will be reported emphasizing the importance of medication history taking in patients presenting with new-onset liver enzymes abnormalities.

How Does Genetics Influence the Efficacy and Safety of Antiarrhythmic Drugs?

Recent progress in genomic sequencing has begun to elucidate the basic mechanisms for several adverse responses, as well as the clinical efficacy, for antiarrhythmic drugs. DNA variants in drug metabolizing enzymes have been implicated in excessive drug accumulation, and genetic variability in drug targets can identify individuals at increased risk for serious side effects, in particular proarrhythmia. It is hoped that future advances in the area of genomic medicine will lead to more individually tailored or personalized pharmacologic therapy in the management of cardiac arrhythmias.

Acute management of atrial fibrillation and atrial flutter in the critical care unit: should it be ibutilide?

BACKGROUND

Ibutilide is currently indicated for the rapid conversion of atrial fibrillation (Afb) or atrial flutter (Afl) of recent onset but limited to patients who are hemodynamically stable and without symptomatic cardiovascular conditions.

HYPOTHESIS

The study was undertaken to assess the efficacy and safety of ibutilide in patients with Afb or Afl associated with acute cardiovascular-medical disorders and in patients receiving prior selective antiarrhythmic drug therapy.

METHODS

The study included 34 patients, mean age 75 +/- 16.3 years, with Afb (n = 25) or Afl (n = 9) having a variety of disorders, for example, congestive heart failure, unstable angina, borderline hypotension, respiratory failure, and chronic renal failure. Prior antiarrhythmic drugs consisted of propafenone (n = 5) or amiodarone (n = 3). Eligibility for cardioversion was established with appropriate anticoagulation or transesophageal echocardiography findings. Ibutilide was given as up to two 10 min infusions of 1 mg separated by 10 min.

RESULTS

The overall conversion rate after ibutilide was 79.4% (27/34 patients): 80% for Afb and 78% for Afl. More than 90% converted within 1 h of treatment. A high conversion rate of 92% resulted in those with an arrhythmia duration of < or = 1 week. All eight patients with prior antiarrhythmic therapy converted to sinus rhythm. The average baseline QTc interval for all patients increased 17.1% (397 +/- 63.3 to 465 +/- 60.2 ms) at 30 min. For eight patients (including four who received prior antiarrhythmic drugs), QTc interval prolongation > or = 500 ms was associated with nearly half the entire incidence of arrhythmic events. Proarrhythmia, the exclusive adverse effect, consisted of ventricular extrasystoles (n = 10) and nonsustained monomorphic ventricular tachycardia (VT) (n = 2) managed with intravenous MgSO4, and sustained polymorphic VT (n = 1) requiring electrical cardioversion.

CONCLUSION

Ibutilide is an effective and well tolerated drug for the rapid termination of Afb or Afl of recent onset associated with symptomatic and/or hemodynamically unstable disorders, and it is most efficacious (> or = 90%) when the atrial arrhythmia is < or = 1 week in duration. Proarrhythmic events are readily manageable in a monitored unit with access to appropriate treatment.

Pharmacologic targets for atrial fibrillation

Despite advances in treatment, atrial fibrillation (AF) remains the most common arrhythmia in humans. Antiarrhythmic drug therapy continues to be a cornerstone of AF treatment, even in light of emerging non-pharmacologic therapies. Conventional antiarrhythmic drugs target cardiac ion channels and are often associated with modest AF suppression and the risk of ventricular proarrhythmia. Ongoing drug development has focused on targeting atrial-specific ion channels as well as novel non-ionic targets. Targeting non-ionic mechanisms may also provide new drugs directed towards the underlying mechanisms responsible for AF and possibly greater antiarrhythmic potency. Agents that act against these new targets may offer improved safety and efficacy in AF treatment.

Inhibitory Effects of Propafenone on the Pharmacokinetics of Caffeine in Humans

CYP1A2 is involved in the metabolism of both caffeine and propafenone, a class Ic antiarrhythmic agent. Despite the widespread consumption of caffeine, drug-drug interactions with this agent are often overlooked. This study investigated effects of propafenone on the pharmacokinetics of caffeine. Eight healthy volunteers were included in our study. A total of 300 mg of caffeine was given on 2 occasions, once alone and once during the coadministration of 300 mg propafenone. Serial blood samples were collected and pharmacokinetic parameters were estimated using a population pharmacokinetic approach. A one-compartment PK model with first-order absorption and elimination described plasma concentration profiles. Concomitant administration of propafenone decreased caffeine oral clearance from 8.3 +/- 0.9 L/h to 5.4 +/- 0.7 L/h (P < 0.05). Elimination half-life of caffeine was also increased 54% by propafenone. One of our volunteers was a poor metabolizer of CYP2D6. Concomitant administration of propafenone to this volunteer caused the greatest increase in caffeine plasma concentrations. These results support the concept of competitive inhibition between propafenone and caffeine. Our results suggest that propafenone causes significant inhibition of CYP1A2 activity leading to a decrease in the clearance of caffeine. Caffeine has intrinsic proarrhythmic effects; thus, its coadministration with an antiarrhythmic agent such as propafenone should be used with caution, especially in patients with poor CYP2D6 activity.

Characterisation of (R/S)-propafenone and its metabolites as substrates and inhibitors of P-glycoprotein

Digoxin is a drug with a narrow therapeutic index, which is a substrate of the ATP-dependent efflux pump P-glycoprotein. Increased or decreased digoxin plasma concentrations occur in humans due to the inhibition or induction of this drug transporter in organs with excretory function such as small intestine, liver and kidney. It is well known that serum concentrations of digoxin increase considerably in humans if propafenone is given simultaneously. However, it has not been investigated in detail whether propafenone and its metabolites are substrates and/or inhibitors of human P-glycoprotein. The aim of this study, therefore, was to investigate the P-glycoprotein-mediated transport and inhibition properties of propafenone and its major metabolites 5-hydroxypropafenone and N-desalkylpropafenone in Caco-2 cell monolayers. Inhibition of P-glycoprotein-mediated transport by propafenone and its metabolites was determined using digoxin as a P-glycoprotein substrate. No polarised transport was observed for propafenone and N-desalkylpropafenone in Caco-2 cell monolayers. However, 5-hydroxypropafenone translocation was significantly greater from basal-to-apical compared with apical-to-basal (P(app) basal-apical vs. P(app) apical-basal, 10.21+/-2.63 x 10(-6) vs. 4.34+/-1.84 x 10(-6) cm/s; P<0.01). Moreover, propafenone, 5-hydroxypropafenone and N-desalkylpropafenone inhibited P-glycoprotein-mediated digoxin transport with IC(50) values of 6.8, 19.9, and 21.3 microM, respectively. In summary, whereas propafenone and N-desalkylpropafenone are not substrates of P-glycoprotein, 5-hydroxypropafenone is translocated by human P-glycoprotein across cell monolayers. In addition, propafenone and its two major metabolites 5-hydroxypropafenone and N-desalkylpropafenone are inhibitors of human P-glycoprotein and therefore contribute to the digoxin-propafenone interaction observed in humans.

NONLINEAR PHARMACOKINETICS OF PROPAFENONE IN RATS AND HUMANS: APPLICATION OF A SUBSTRATE DEPLETION ASSAY USING HEPATOCYTES FOR ASSESSMENT OF NONLINEARITY

Linear pharmacokinetic profiles of propafenone in female Wistar rats were found after oral administration of up to 20 mg/kg. These profiles differed from nonlinear pharmacokinetics in a dose-dependent manner with increasing plasma concentrations in humans (Hollmann M, Brode E, Hotz D, Kaumeier S, and Kehrhahn OH (1983) Arzneim-Forsch 33:763-770). We investigated the species differences in pharmacokinetics of propafenone between rats and humans. In rats, after intravenous administration, clearance was constant at all doses examined (0.2-10 mg/kg), whereas the distribution volume at a steady state increased and the resultant elimination half-life was prolonged with increasing doses. In a substrate depletion assay without plasma, rat and human hepatocytes showed a concentration-dependent elimination of propafenone with low Km values (<0.4 microM). However, in the depletion assay with plasma incubation, the profiles were altered to a concentration-independent profile in rat but not human hepatocytes. The differing effect of adding plasma in rat and human hepatocytes can be explained by species differences in plasma binding (unbound fraction, 0.0071 versus 0.0754 for rats and humans, respectively, at 0.1 microg/ml). In rat plasma, the unbound fraction increased with concentrations of 0.1 to 1.0 microg/ml, whereas it was constant in human plasma. Accordingly, the in vivo nonlinear disposition in humans can be ascribed to the saturation of hepatic metabolism due to the low Km values. In contrast, the influence of saturable metabolism is canceled out with nonlinear plasma binding in rats leading to the apparent linear pharmacokinetic behavior. The newly developed depletion assay with plasma incubation gave insights into the nonlinear pharmacokinetics of propafenone.

The low-potency, voltage-dependent HERG blocker propafenone--molecular determinants and drug trapping

The molecular determinants of high-affinity human ether-a-go-go-related gene (HERG) potassium channel blockade by methanesulfonanilides include two aromatic residues (Phe656 and Tyr652) on the inner helices (S6) and residues on the pore helices that face into the inner cavity, but determinants for lower-affinity HERG blockers may be different. In this study, alanine-substituted HERG channel mutants of inner cavity residues were expressed in Xenopus laevis oocytes and were used to characterize the HERG channel binding site of the antiarrhythmic propafenone. Propafenone's blockade of HERG was strongly dependent on residue Phe656 but was insensitive or weakly sensitive to mutation of Tyr652, Thr623, Ser624, Val625, Gly648, or Val659 and did not require functional inactivation. Homology models of HERG based on KcsA and MthK crystal structures, representing the closed and open forms of the channel, respectively, suggest propafenone is trapped in the inner cavity and is unable to interact exclusively with Phe656 in the closed state (whereas exclusive interactions between propafenone and Phe656 are found in the open-channel model). These findings are supported by very slow recovery of wild-type HERG channels from block at -120 mV, but extremely rapid recovery of D540K channels that reopen at this potential. The experiments and modeling suggest that the open-state propafenone binding-site may be formed by the Phe656 residues alone. The binding site for propafenone (which may involve pi-stacking interactions with two or more Phe656 side-chains) is either perturbed or becomes less accessible because of closed-channel gating. This provides further evidence for the existence of gating-induced changes in the spatial location of Phe656 side chains.

Efficacy and safety of sustained-release propafenone (propafenone SR) for patients with atrial fibrillation

The objective of this randomized, double-blind, placebo-controlled clinical trial was to test the efficacy and safety of a new sustained-release preparation of the antiarrhythmic drug propafenone (propafenone SR) in reducing the frequency of symptomatic arrhythmia recurrences in patients with atrial fibrillation (AF). Patients with a history of symptomatic AF who were in sinus rhythm were randomly assigned to receive placebo or propafenone SR 425, 325, or 225 mg, all twice daily. Recurrent symptomatic arrhythmias were documented using transtelephone electrocardiographic monitoring. Electrocardiograms were reviewed by an event committee that was blinded to treatment assignment. In the primary efficacy analysis, propafenone SR significantly lengthened the time to first symptomatic atrial arrhythmia recurrence at all 3 doses compared with placebo as assessed by log-rank test: propafenone SR 425 mg twice daily versus placebo twice daily, p <0.001; 325 mg twice daily versus placebo twice daily, p <0.001; and 225 mg twice daily versus placebo twice daily, p = 0.014. The median time to recurrence was 41 days in the placebo twice daily group, >300 days in the propafenone SR 425-mg group, 291 days in the 325-mg group, and 112 days in the 225-mg group. Adverse effects leading to withdrawal were higher in the propafenone SR 425-mg twice daily group than in any other group. Thus, propafenone SR has important and statistically significant antiarrhythmic effects in patients with AF.

Propafenone hepatotoxicity: report of two new cases

Two patients developed acute cholestatic hepatitis during treatment with propafenone. Viral infections, alcohol abuse, hepatotoxicity by other drugs, and biliary obstruction were excluded as causes. In one patient, liver biopsy showed changes consistent with a drug-associated injury. Another patient had autoimmune antibodies (ANA) in the serum. Following propafenone withdrawal, the clinical and biochemical profiles of both patients improved. Hepatic toxicity from the antiarrhythmic drug propafenone is highly uncommon. Moreover, the drug produces hepatocellular injury by an unknown mechanism. Most of the seven cases reported here had acute cholestatic hepatitis after a latency period of two to four weeks.

The effect of propafenone on premature ventricular contractions (PVC): an analysis based on heart rate dependency of PVCs

The effect of 450 mg/day propafenone for two weeks on premature ventricular contractions (PVCs) was studied in combination with an assessment of heart rate (HR) dependency of PVCs using Holter ECG monitoring in patients with more than 720 PVCs per day. The PVC-HR correlation was classified into positive (P), bidirectional (B), and flat and negative (FN) correlation groups. The positive group included only patients in whom PVC frequency increased with a heart rate increase, while the bidirectional group included patients with PVCs whose frequency increased at low heart rates and decreased at high heart rates. The FN group contained both flat (PVC frequency was almost fixed regardless of heart rate changes) and negative (PVC frequency decreased as heart rate increased) correlations. The effectiveness of propafenone was 70% in the positive group and 50% in the nonpositive group which included both bidirectional (67%) and FN (0%) groups, using a > 70% PVC reduction as a criterion of efficacy. From this, we concluded that propafenone is effective in patients showing either positive or bidirectional PVC-HR correlation. The coupling interval (CI) of PVCs was also prolonged by propafenone as a whole. The present study suggests that there are differences in the mechanism of PVC development in patients with flat or negative correlation and those with a positive or bidirectional correlation. Thus, this type of analysis contributes to an understanding of the action of antiarrhythmic agents, and may allow the prediction of their efficacy on PVCs.

Familial and acquired long qt syndrome and the cardiac rapid delayed rectifier potassium current

1. Long QT syndrome (LQTS) is a cardiac disorder characterized by syncope, seizures and sudden death; it can be congenital, idiopathic, or iatrogenic. 2. Long QT syndrome is so-named because of the connection observed between the distinctive polymorphic ventricular tachycardia torsade de pointes and prolongation of the QT interval of the electrocardiogram, reflecting abnormally slowed ventricular action potential (AP) repolarization. Acquired LQTS has many similar clinical features to congenital LQTS, but typically affects older individuals and is often associated with specific pharmacological agents. 3. A growing number of drugs associated with QT prolongation and its concomitant risks of arrhythmia and sudden death have been shown to block the 'rapid' cardiac delayed rectifier potassium current (IKr) or cloned channels encoded by the human ether-a-go-go-related gene (HERG; the gene believed to encode native IKr). Because IKr plays an important role in ventricular AP repolarization, its inhibition would be expected to result in prolongation of both the AP and QT interval of the electrocardiogram. 4. The drugs that produce acquired LQTS are structurally heterogeneous, including anti-arrhythmics, such as quinidine, non-sedating antihistamines, such as terfenadine, and psychiatric drugs, such as haloperidol. In addition to heterogeneity in their structure, the electrophysiological characteristics of HERG/IKr inhibition differ between agents. 5. Here, clinical observations are associated with cellular data to correlate acquired LQTS with the IKr/HERG potassium (K+) channel. One strategy for developing improved compounds in those drug classes that are currently associated with LQTS could be to design drug structures that preserve clinical efficacy but are modified to avoid pharmacological interactions with IKr. Until such time, awareness of the QT-prolongation risk of particular agents is important for the clinician.

Disposition of propafenone in a poor metabolizer of CYP2D6 with Gilbert's syndrome

Gilbert's syndrome, a genetic deficiency in bilirubin UDP-glucuronosyltransferase (UGT1A1), may dispose to increased toxicity of propafenone in poor metabolizers (PMs) of cytochrome P4502D6 because glucuronidation of propafenone is the major metabolic pathway for drug elimination in PMs. A patient with Gilbert's syndrome who is also PM participated in an interaction study with propafenone and rifampicin along with five otherwise healthy PMs. Using stable isotope techniques, the pharmacokinetics of single doses of 140 mg propafenone i.v. (unlabelled) and 300 mg propafenone p.o. (labelled) were compared between the index patient and the five healthy controls. Propafenone did not accumulate in the plasma of the index patient either before or during induction: AUC(0-infinity) of propafenone in the index patient was within the 95% confidence interval of controls; AUC(0-infinity) of propafenone glucuronide and amount of urinary excretion of propafenone glucuronide in the patient were within or even greater than the 95% confidence intervals of controls. Therefore, individuals with Gilbert's syndrome who also have a PM phenotype appear to be at no higher risk for toxicity of propafenone than otherwise healthy PMs. An indirect conclusion from these in vivo data might be that propafenone is not a substrate of the UGT1A1 isoform.

Review of common adverse effects of selected antiarrhythmic drugs

The management of cardiac arrhythmias has changed dramatically over the past several years. New drugs and devices are now available to treat various arrhythmias. Many new agents have been developed that rely on different electrophysiologic mechanisms to elicit their effect on the heart rhythm. Though often effective, these drugs also pose a risk because all of them have a variety of potential adverse effects associated with their use. Many of these adverse reactions are common to all antiarrhythmic drugs, whereas others are unique to particular agents. This review discusses the notable adverse effects of selected antiarrhythmic drugs.

Comparison of the effects of liposomal amphotericin B and conventional amphotericin B on propafenone metabolism and hepatic cytochrome P-450 in rats

The effects of conventional amphotericin B (AmB) dissolved in sodium deoxycholate on microsomal cytochrome P-450 concentrations and propafenone metabolism to 5-hydroxy-propafenone and N-desalkyl-propafenone were compared with those of liposomal AMB (Li-AMB) in rats. AmB (3 mg/kg/day, intravenously [i.v.]) given for 4 days caused a significant decrease in the concentration of hepatic microsomal cytochrome P-450 (0.43 +/- 0.06 nmol/mg versus 0.62 +/- 0. 05 nmol/mg for the control [P < 0.05]). Following the application of Li-AMB (15 mg/kg/day, i.v.), hepatic microsomal cytochrome P-450 concentrations were unchanged at 0.64 +/- 0.08 nmol/mg. AmB decreased ex vivo propafenone metabolism to 5-hydroxy-propafenone and N-desalkyl-propafenone significantly. Sodium deoxycholate (the vehicle of AmB) by itself induced a significant decline of 5-hydroxy-propafenone and N-desalkyl-propafenone production, while microsomal cytochrome P-450 concentrations remained unchanged. In contrast, Li-AMB did not change the levels of production of 5-hydroxy-propafenone or of N-desalkyl-propafenone at either substrate concentration tested (50 micromol and 200 micromol). Microsomal AmB concentrations were significantly higher following Li-AMB application (21.1 +/- 6.2 microg/g versus 3.7 +/- 1.4 microg/g for AmB [P < 0.05]). We conclude that Li-AMB, in contrast to AmB, decreases neither hepatic microsomal cytochrome P-450 nor hepatic propafenone metabolism in rats ex vivo. Sodium deoxycholate alone decreases propafenone metabolism in a similar way to AmB, suggesting that it participates in AmB-induced disturbance of hepatic metabolic function.

Effects of propafenone and 5-hydroxy-propafenone on hKv1.5 channels

1. The goal of this study was to analyse the effects of propafenone and its major metabolite, 5-hydroxy-propafenone, on a human cardiac K+ channel (hKv1.5) stably expressed in Ltk- cells and using the whole-cell configuration of the patch-clamp technique. 2. Propafenone and 5-hydroxy-propafenone inhibited in a concentration-dependent manner the hKv1.5 current with K(D) values of 4.4+/-0.3 microM and 9.2+/-1.6 microM, respectively. 3. Block induced by both drugs was voltage-dependent consistent with a value of electrical distance (referenced to the cytoplasmic side) of 0.17+/-0.55 (n=10) and 0.16+/-0.81 (n=16). 4. The apparent association (k) and dissociation (l) rate constants for propafenone were (8.9+/-0.9) x 10(6) M(-1) s(-1) and 39.5+/-4.2 s(-1), respectively. For 5-hydroxy-propafenone these values averaged (2.3+/-0.3) x 10(6) M(-1) s(-1) and 21.4+/-3.1 s(-1), respectively. 5. Both drugs reduced the tail current amplitude recorded at -40 mV after 250 ms depolarizing pulses to +60 mV, and slowed the deactivation time course resulting in a 'crossover' phenomenon when the tail currents recorded under control conditions and in the presence of each drug were superimposed. 6. Both compounds induced a small but statistically significant use-dependent block when trains of depolarizations at frequencies between 0.5 and 3 Hz were applied. 7. These results indicate that propafenone and its metabolite block hKv1.5 channels in a concentration-, voltage-, time- and use-dependent manner and the concentrations needed to observe these effects are in the therapeutical range.

Stereoselective steady state disposition and action of propafenone in Chinese subjects

AIMS

To investigate the steady state disposition and action of racemic propafenone and its enantiomers and the potential for an enantiomer-enantiomer interaction in Chinese subjects.

METHODS

Eight healthy male Chinese individuals received in a double-blind, randomized, cross-over study racemic propafenone (150 mg every 6 h), (S)-, and (R)-propafenone (150 mg each every 6 h) and placebo orally for 4 days. During the last dosing interval the plasma concentrations of both enantiomers of propafenone were measured and ECG, blood pressure (MAP) and heart rate were monitored.

RESULTS

Whereas the apparent elimination half-life (t1/2,z), mean residence time (MRT) and time to reach peak concentrations (tmax) of (S)- and (R)-propafenone were similar and independent of the administered agent, significant differences were observed in the apparent oral clearance (CLO) of the enantiomers. During dosing with racemic propafenone CLO of (S)- and (R)-propafenone averaged (+/-s.d.) 1226+751 and 1678+625 ml min(-1), respectively (P=0.024). Following the administration of the pure enantiomers CLO of (S)-propafenone increased (P= 0.007) to 2028+/-959 ml min(-1) and that of (R)-propafenone was reduced (P= 0.042) to 1318+/-867 ml min(-1). Both enantiomers and the racemate caused about a 10% increase in the QRS duration (P<0.05) and PR-interval (P<0.01) when compared with placebo. The increase in maximum exercise heart rate was significantly (P<0.05) attenuated only at 3 h following the administration of the racemate and the S-enantiomer. MAP and QTC were not affected significantly.

CONCLUSIONS

These data indicate that the stereoselective disposition of propafenone is similar in Chinese and Caucasian subjects (previously published findings), the (R)-enantiomer being cleared more rapidly. A similar enantiomer-enantiomer interaction also occurred. Thus, when the racemate was given, the elimination of (S)-propafenone was impaired and that of the (R)-form accelerated compared with single enantiomer administration. The results indicate that dosage adjustments are probably not required in Chinese patients receiving propafenone.

Safety of oral propafenone in the treatment of arrhythmias in infants and children (European retrospective multicenter study). Working Group on Pediatric Arrhythmias and Electrophysiology of the Association of European Pediatric Cardiologists

This study was designed to assess adverse effects of oral propafenone in a large number of pediatric patients. Retrospective data from 27 European centers covering 772 patients treated with oral propafenone were analyzed. The following arrhythmias were treated: reentrant supraventricular tachycardia in 388 patients, atrial ectopic tachycardia in 66, junctional ectopic tachycardia in 39, atrial flutter in 21, ventricular premature complexes in 140, ventricular tachycardia in 78, and other arrhythmias in 39 patients. Two hundred forty-nine patients (32.3%) had structural heart disease. Significant electrophysiologic side effects and proarrhythmia were found in 15 of 772 patients (1.9%): sinus node dysfunction in 4, complete atrioventricular block in 2, aggravation of supraventricular tachycardia in 2, acceleration of ventricular rate during atrial flutter in 1, ventricular proarrhythmia in 5, and unexplained syncope in 1 patient. Cardiac arrest or sudden death occurred in 5 of 772 patients (0.6%): 2 patients had supraventricular tachycardia due to the Wolff-Parkinson-White syndrome and a normal heart; the remaining 3 patients had structural heart disease. Overall, adverse cardiac events were more common in the presence (12 of 249 patients, 4.8%) than in the absence (8 of 523 patients, 1.5%) of structural heart disease (p <0.01). There was no difference between patients treated for supraventricular and ventricular arrhythmias. Thus, propafenone is a relatively safe drug for the treatment of several pediatric tachyarrhythmias. Proarrhythmic effects seem to be less frequent than those reported for encainide or flecainide and occur predominantly in patients with structural heart disease.

Intravenous propafenone for converting recent onset atrial fibrillation in emergency departments: a randomized placebo-controlled multicenter trial. FAPS Investigators Study Group

Atrial fibrillation (AF) is one of the most frequent dysrhythmias in patients coming to emergency departments (EDs), and pharmacological treatment is frequently performed. The aim of this randomized placebo-controlled multicenter trial was to compare propafenone (a class 1C antidysrhythmic agent), administered i.v. in the ED, with placebo in the treatment of recent-onset AF (<72 h). We randomly allocated 156 patients (88 males; 68 females) from 18 to 80 years old, with recent-onset AF, to receive i.v. propafenone (2 mg/kg for 10 min) or the matching placebo. The patients were followed for 2 h. Exclusion criteria were the presence of one of the following: lack of informed consent, clinical evidence of heart failure, clinical hyperthyroidism, recent acute myocardial infarction, atrioventricular block, cardiac valve dysfunction, a history of bronchial asthma, and current treatment with antidysrhythmic agents including digitalis. The two groups did not differ significantly in terms of sex, age, body weight, or estimated time elapsed since the beginning of atrial fibrillation. Conversion to sinus rhythm occurred in 13 of the 75 patients who received the placebo (17.3%) and in 57 of the 81 patients who were given propafenone (70.3%). In conclusion, intravenous propafenone administration in the ED can be considered a safe and effective approach for converting AF to sinus rhythm.

Efficacy of intravenous propafenone in termination of atrial flutter by overdrive transesophageal pacing previously ineffective

Fifty patients with symptomatic type I atrial flutter in whom termination of the arrhythmia with transesophageal stimulation was unsuccessful were randomized to undergo a repeat procedure after intravenous propafenone (n = 25) or placebo (n = 25). Immediate sinus rhythm recovery rate was 36% in the propafenone group and 4% in the placebo group (p = 0.005), indicating that intravenous propafenone increases the rate of successful transesophageal stimulation and can be used when a first attempt at conversion is ineffective.

Conversion of recent onset atrial fibrillation with single loading oral dose of propafenone: is in-hospital admission absolutely necessary?

A population of 283 patients with recent onset (< 72 hours) AF, without heart failure, who received a single 450- or 600-mg oral dose of propafenone, or digoxin 1 mg, or placebo for conversion to sinus rhythm (SR), was studied to determine whether a routine admission to the hospital for drug administration is justified. Previous bradyarrhythmias or sick sinus syndrome (SSS), and concomitant use of antiarrhythmic drugs were exclusion criteria. None of the 283 patients studied experienced VT or VF and none of them needed implantation of a temporary pacemaker. Periods of atrial tachyarrhythmias with regularization of atrial waves and 1:1 AV conduction were observed in only two cases, both receiving placebo. No predictor of proarrhythmia was found among the clinical variables considered (age, etiology, arrhythmia duration, atrial dimension, and blood potassium). No serious hemodynamic adverse effects were noted in either group. The rates of conversion to SR after 4 hours were: 80 (57%) of 141 patients who received propafenone and 35 (25%) of 142 patients who received digoxin or placebo (P < 0.001). Acute oral treatment with propafenone is simple and effective for the conversion of recent onset AF to SR in patients without clinical signs of heart failure. The routine admission of these patients to the hospital is not necessary. Home-based administration of oral propafenone to a selected group of patients could significantly increase the cost effectiveness of this treatment.

Propafenone: an effective agent for the management of supraventricular arrhythmias

Propafenone is a sodium channel blocking antiarrhythmic drug. It also has beta-adrenergic, potassium channel, and weak calcium channel blocking activity. The drug is metabolized in the liver with rates dependent on the debrisoquin phenotype. The saturable metabolism results in nonlinear pharmacokinetics. The metabolites retain sodium channel blocking activity but little beta-adrenergic blocking activity. Both controlled and noncontrolled studies have documented its efficacy in a variety of supraventricular arrhythmias. Intravenous propafenone is effective in converting atrial fibrillation to normal sinus rhythm. Chronic oral administration decreases the frequency of recurrence of atrial fibrillation and paroxysmal supraventricular tachycardia. The drug is particularly effective in the Wolff-Parkinson-White syndrome. The drug may produce SA block in patients with underlying sinus node dysfunction. Propafenone has comparatively few noncardiac side effects. It is a useful primary drug or an alternative to more commonly used drugs used for the treatment of supraventricular arrhythmias.

Propafenone in a usual dose produces severe side-effects: the impact of genetically determined metabolic status on drug therapy

We report the case of an elderly lady presenting with dizziness, a head injury resulting from a fall and bradycardia. Propafenone 150 mg t.i.d. had been prescribed for atrial fibrillation with tachyarrhythmia, induced by hyperthyroidism, 18 months earlier. A toxic concentration of parent propafenone, and no 5-hydroxy metabolite, was detected in a plasma sample. Symptoms disappeared after the discontinuation of propafenone. The poor metaboliser (PM) phenotype of sparteine/debrisoquine was assumed and subsequently confirmed by phenotyping (sparteine test) and genotyping (allele-specific polymerase chain reaction). The PM phenotype is common in European populations, with a prevalence of about 7%. If drugs with narrow therapeutic ranges undergo genetically polymorphic metabolism, toxicity may arise even with recommended doses. Individualization of doses is required to avoid adverse effects.

Influence of renal function on the steady-state pharmacokinetics of the antiarrhythmic propafenone and its phase I and phase II metabolites

The aim of this study was to investigate the disposition of propafenone and its Phase I and II metabolites in relation to kidney function under steady-state conditions. The mechanism of the renal handling of propafenone glucuronides (filtration, secretion) was also examined. Racemic (R/S) propafenone was administered to 7 young volunteers, to 5 older patients with a normal glomerular filtration rate and to 4 patients with chronic renal failure. No difference was found in the plasma concentrations of propafenone and 5-hydroxypropafenone between the three groups. The propafenone glucuronide (PPFG) concentration was elevated in the older compared to the younger subjects (S-PPFG: 544 vs. 222 nmol.ml-1.mol-1; R-PPFG: 576 vs. 304 nmol.ml-1.mol-1). Although Glomerular filtration rate did not differ, the renal clearance of propafenone glucuronides was reduced in the former group, which could be attributed to their impaired renal secretion. A dramatic increase in propafenone glucuronide concentration was observed in the patients with renal failure (S-PPFG: 2783 nmol.ml-1.mol-1; R-PPFG: 7340 nmol.ml-1.mol-1). In summary, the disposition of propafenone and of its active metabolite 5-hydroxypropafenone was not affected by kidney dysfunction, indicating that no dose adjustment is necessary in patients with renal failure. The accumulation of drug glucuronides in older patients with apparently normal kidney function should be taken into account as a possible factor modifying drug therapy.