Contributing factors to the apparent clearance of bepridil in patients with paroxysmal or persistent atrial fibrillation: analysis using population pharmacokinetics.

BACKGROUND: Bepridil is used as an antiarrhythmic drug due to its class I, class III, and class IV electrophysiological properties, but it has serious adverse effects such as QT prolongation and torsade de pointes. Bepridil has complex pharmacokinetic (PK) properties with large interindividual differences in plasma concentrations. The aim of this study was to evaluate the contributing factors to changes in the dose-concentration relationship of bepridil and the risk factors for excessive QT prolongation in patients with paroxysmal or persistent atrial fibrillation (AF). METHODS: A population PK analysis was performed by using NONMEM based on 425 concentration points from 76 patients receiving bepridil. A 1-compartment model approximating an intravenous model was used to examine the interindividual variability of the apparent systematic clearance (CL/F) of bepridil. A population PK-pharmacodynamic analysis was performed using the linear regression. RESULTS: Age was a contributing factor to the CL/F of bepridil in AF patients. The QTc interval increased as the area under the plasma bepridil concentration time curve (AUC) increased. The AUC in patients without a bundle branch block, the baseline QT interval, and the existence of structural heart disease in patients with a bundle branch block were explanatory variables of excessive QTc prolongation (QTc > 500 ms) during bepridil therapy. CONCLUSIONS: Using population PK methodology, this study showed that age was a contributing factor to the apparent clearance of bepridil in Japanese patients with AF and that excessive QT prolongation might be related to a larger AUC.

Population pharmacokinetic analysis and dosage recommendations for digoxin in Japanese patients with atrial fibrillation and heart failure using real-world data.

BACKGROUND: Digoxin is an important treatment option for reducing the ventricular rate in patients with atrial fibrillation (AF) and heart failure (HF). Digoxin has a narrow therapeutic window and large interindividual variability. A low target blood concentration, especially ≤0.9 ng/mL, is recommended for patients with HF who are taking digoxin. This study aimed to develop a population pharmacokinetic model and to identify clinical factors that affect digoxin exposure and an optimal digoxin dosing regimen in Japanese patients with AF and HF. METHODS: A population pharmacokinetic analysis was performed by using a nonlinear mixed effects model based on 3465 concentration points from 391 patients (>18 years) who were receiving oral digoxin. Using trough serum digoxin concentrations and clinical data, a population pharmacokinetic model was developed for determining covariates of clearance. A 1-compartment model was used to examine the interindividual variability of the oral clearance (CL/F) of digoxin. An appropriate dosage of digoxin was identified using Monte Carlo simulation. RESULTS: The final model demonstrated that creatinine clearance (CLCR) and the use of amiodarone were factors that contributed to the CL/F of digoxin. Monte Carlo simulation results showed that with a daily maintenance dose of 0.25 mg, the intoxication risk window of a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients regardless of renal function category or concurrent use of amiodarone. The appropriate maintenance dosage was 0.125 mg daily for most Japanese patients with AF and HF. However, with a daily dose of 0.125 mg, a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients with renal impairments (CLCR 30 mL/min) or concurrent use of amiodarone. A daily maintenance dose of 0.0625 mg was acceptable for these patients. CONCLUSIONS: CLCR and the use of amiodaron were found to contribute to digoxin clearance using a population pharmacokinetic methodology. For Japanese patients with AF and HF, 0.125 mg is an appropriate daily digoxin maintenance dose, but a dose reduction is required for patients with CLCR <30 mL/min or concurrent amiodarone use.

Clinical outcome in patients with paroxysmal or persistent atrial fibrillation receiving bepridil.

BACKGROUND: It is unknown whether bepridil improves cardiovascular events in atrial fibrillation (AF) patients, so this study evaluated the clinical outcome in paroxysmal or persistent AF patients receiving bepridil. METHODS AND RESULTS: We conducted a cohort study of 284 consecutive patients who received bepridil for AF (25% female, 5913 years) with a median follow-up period of 17 months (4-157 months). A total of 135 (48%) patients had structural heart disease, and 231 patients (81%) had previously received class I or class III antiarrhythmic drugs. The cumulative rates for cardiovascular events were 2.4%, 8.1%, and 10.1% at 1, 3, and 5 years, respectively. The cumulative rates for a composite of mortality, cerebral infarction, systemic embolism, major bleeding and heart failure were 9.7%, 18.2%, and 29.6% at 1, 3, and 5 years, respectively. The probability of progression to permanent AF was 23.5% at 5 years. Sudden death occurred in a patient with a prior myocardial infarction who was taking 200mg daily, and torsade de pointes (Tdp) occurred in two patients without structural heart disease taking 200mg daily. Excessive corrected QT interval prolongation (>0.50s) was observed when plasma concentrations were higher than 800 ng/ml. CONCLUSIONS: Bepridil might not improve the clinical outcome in refractory AF patients. Bepridil-related adverse events, including QT prolongation and Tdp, occurred in a dose- and concentration-dependent manner.

Clinical Outcomes of Direct Oral Anticoagulants and Warfarin in Japanese Patients with Atrial Fibrillation Aged ≥ 85 Years: A Single-Center Observational Study.

BACKGROUND: Increasing age is associated with an increase in stroke in patients with nonvalvular atrial fibrillation (NVAF). Elderly patients have several comorbidities and increased bleeding risk. OBJECTIVE: The aim of this study was to evaluate the clinical outcomes of Japanese patients with NVAF aged ≥ 85 years who were treated with direct oral anticoagulants (DOACs) or warfarin. METHODS: We retrospectively studied the records of 358 patients with NVAF aged ≥ 85 years who had taken DOACs or warfarin between 2014 and 2018. The primary endpoints were the first occurrences of thromboembolic and bleeding events and death. The secondary endpoint was the discontinuation of oral anticoagulation (OAC) therapy. RESULTS: During a median follow-up period of 17 months, 24 patients died. The incidence (per 100 patient-years [PY]) of thromboembolic events was 1.8 in patients treated with DOACs and 2.2 in those treated with warfarin (adjusted subdistribution hazard ratio [SHR] 0.69; 95% confidence interval [CI] 0.23-2.12 in a competing model), and the incidence of major bleeding events was 3.1 and 4.2 in patients treated with DOACs and warfarin, respectively (adjusted SHR 0.95; 95% CI 0.32-2.86). The most common cause of bleeding events was gastrointestinal bleeding. A total of 33 patients permanently discontinued OAC therapy, at a median age of 89 years and with no differences between DOACs and warfarin. The most common reason for discontinuing OAC therapy was bleeding events. CONCLUSION: Our results revealed that the incidences of thromboembolism and major bleeding among patients with NVAF aged ≥ 85 years were similar for those treated with DOACs and those treated with warfarin. Approximately 10% of patients permanently discontinued OAC therapy.

Effectiveness and safety of dabigatran versus warfarin in "real-world" Japanese patients with atrial fibrillation: A single-center observational study.

BACKGROUND: In "real-world" practice, anticoagulant therapy is indicated for patients whose clinical profiles are not addressed in randomized clinical trials. We assessed the effectiveness and safety of dabigatran versus warfarin in "real-world" Japanese patients with non-valvular atrial fibrillation (NVAF). METHODS: Among 613 NVAF patients who initiated dabigatran or warfarin therapy during the period between 2011 and 2013, 362 patients were included in the study after propensity score adjustment. The median follow-up period was 1.3 years. The effectiveness and safety outcomes were thromboembolism and major bleeding, respectively. RESULTS: The propensity-matched hazard ratios of thromboembolism and major bleeding with dabigatran were 1.03 (95% CI: 0.12-8.04, p=0.971) and 0.15 (95% CI: 0.01-0.90, p=0.037), respectively. CONCLUSIONS: The ability of dabigatran to prevent thromboembolism is comparable to that of warfarin; however, the major bleeding rate is lower with dabigatran in "real-world" NVAF patients.

Persistence of non-vitamin K antagonist oral anticoagulant use in Japanese patients with atrial fibrillation: A single-center observational study.

BACKGROUND: Non-vitamin K antagonist oral anticoagulants (NOACs) show a favorable balance between efficacy and safety compared with warfarin for patients with non-valvular atrial fibrillation (NVAF). In "real-world" practice, however, NOAC adherence and persistence among patients are not clear. The aim of this study is to evaluate NOAC and warfarin persistence in Japanese patients with NVAF who newly started these drugs. METHODS: We retrospectively studied 401 patients with NVAF who had newly started NOACs during the first 18 months after our hospital adopted their use (197 dabigatran, 107 rivaroxaban, 102 apixaban) and 200 patients with NVAF who had newly started warfarin during the same period. The endpoint was drug discontinuation for each drug. RESULTS: During the follow-up period (up to a maximum of 24 months), 113 (28%) patients who had newly started NOACs and 33 (17%) patients who had newly started warfarin discontinued the drug. The persistence rates of patients prescribed NOACs was lower than that of patients prescribed warfarin at 3, 6, and 12 months (85% versus 93%, 79% versus 88%, and 70% versus 82%, respectively). One-tenth of patients who had newly started NOACs discontinued the drug by their own decision. Drug adverse events, worsening renal dysfunction, and patient desire were the major causes of NOAC discontinuation. CONCLUSIONS: The rate of persistence of prescribed NOACs was significantly lower than that of warfarin in Japanese patients with NVAF.

Clinical outcome in Japanese elderly patients with non-valvular atrial fibrillation taking warfarin: a single-center observational study.

BACKGROUND: Although a lower target prothrombin time-international normalized ratio (PT-INR) with warfarin therapy is recommended in Japan for atrial fibrillation (AF) patients ≥70 years of age, few studies have provided supporting data. The current study aimed to evaluate the clinical outcome in elderly Japanese patients with non-valvular AF who were taking warfarin. METHODS: We conducted a cohort study of 845 consecutive non-valvular AF patients ≥70 years of age who were taking warfarin (median age, 74 years; 30.5% women) with a median follow-up period of 27 months (4-69 months). Of these patients, 29.7% had a history of stoke/transient ischemic attack (TIA), and 73.1% of the patients had a CHADS(2) score ≥2. The occurrence of thromboembolic events, including ischemic stroke, TIA and other systemic embolisms, and major bleeding events were validated through a review of medical records. RESULTS: The incidence of thromboembolic and major bleeding events were 3.8 and 2.1% per year, respectively. A higher incidence of both events was observed in patients with a CHADS(2) score ≥3. The multivariate analysis showed that prior stroke/TIA (odds ratio 1.7, 95% CI 1.0-2.7) and diabetes (odds ratio 1.7, 95% CI 1.0-2.8) were independent risks of thromoembolic events. A HAS-BLED score ≥3 represented a risk for major bleeding (hazard ratio 2.8, 95% CI 1.7-4.6). A PT-INR of 1.5-2.5 indicated a low incidence of thromboembolic and major bleeding events in patients with a CHADS(2) score ≥2. CONCLUSIONS: Our results demonstrate that a target PT-INR of 2.0 and a range of 1.5-2.5 may be safe for elderly Japanese patients with non-valvular AF.

Low-dose systemic phosphodiesterase III inhibitor pimobendan combined with prostacyclin therapy in a patient with severe primary pulmonary hypertension.

Pimobendan, an oral inotropic drug with phosphodiesterase III-inhibitory activity, induces cAMP-dependent relaxation of vascular smooth muscle in the pulmonary artery, as well as in the systemic cardiovascular system. We report here a patient with severe primary pulmonary hypertension (PPH), who had developed right heart failure (New York Heart Association functional class IV) despite uptitrated intravenous epoprostenol, and who was treated with extremely low-dose (0.625-1.25 mg daily) pimobendan as an adjunct to prostacyclin therapy. The combination therapy of low-dose pimobendan, prostacyclin, intravenous epoprostenol and oral beraprost has been continued for over 2 years without occurrence of fatal arrhythmia, and her six-minute walk test has exceeded 400 m. We suggest that low-dose pimobendan may enhance the hemodynamic effect of prostacyclin in severe PPH.