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Aims: There is a paucity of studies investigating a dose-dependent association between beta-blocker therapy and risk of outcome. In a nationwide cohort of primary prevention implantable cardioverter-defibrillator (ICD) patients, we aimed to investigate the dose-dependent association between beta-blocker therapy and risk of ventricular tachyarrhythmias (VT/VF), heart failure (HF) hospitalizations, and death.Methods and results: Information on ICD implantation, endpoints, comorbidities, beta-blocker usage, type, and dose were obtained through Danish nationwide registers. The two major beta-blockers carvedilol and metoprolol were examined in three dose levels; low (metoprolol ≤ 25 mg; carvedilol ≤ 12.5 mg), intermediate (metoprolol 26-199 mg; carvedilol 12.6-49.9 mg), and high (metoprolol ≥ 200 mg; carvedilol ≥ 50 mg). Time to events was investigated utilizing multivariate Cox models with beta-blocker as a time-dependent variable. From 2007 to 2012, 2935 first-time ICD devices were implanted. During follow-up, 399 patients experienced VT/VF, 728 HF hospitalizations and 361 died. As compared with patients not on beta-blockers, low, intermediate, and high dose had significantly reduced risk of HF hospitalizations {hazard ratio (HR) = 0.68 [0.54-0.87], P = 0.002; HR = 0.53 [0.42-0.66], P Conclusion: In primary prevention ICD patients, beta-blocker therapy was associated with significantly reduced risk of all endpoints, as compared with patients not on beta-blocker, with the suggestion of a dose-dependent effect. No detectable difference was found between comparable doses of carvedilol and metoprolol.

The present work explores the usefulness of Permeapad® for prediction of buccal absorption. Permeability studies with the model drug metoprolol were carried out using the Permeapad® barrier at pH values 7.4; 8.5; 9.0, and 9.5. It was confirmed that Permeapad® can withstand these conditions, and as expected, a clear increase in permeability was found with increasing pH. The permeation results across Permeapad® were compared to published in vitro, ex vivo and in vivo studies for the same formulations. Results showed that the permeability of metoprolol using the Permeapad® barrier correlated very well to both in vitro and ex vivo studies, (r 2 = 0.98 and 0.97), respectively. Furthermore, excellent in vitro in vivo correlation IVIVC (r 2 = 0.98) was obtained when comparing apparent permeability coefficient to the absolute bioavailability of metoprolol administered buccally to mini-pigs. Results indicate that Permeapad® can be used to mimic the buccal absorption of metoprolol as a faster and less laborious method as compared to any of the other mentioned methods.

Genetic variation in the pharmacokinetics of metoprolol and torsemide due to polymorphisms in CYP2D6, CYP2C9, and OATP1B1 has been extensively studied. However, it is still unknown how much of the variation in pharmacokinetics of these two clinically important drugs in total is due to genetic factors. Metoprolol and torsemide were intravenously administered to 44 monozygotic and 14 dizygotic twin pairs. Metoprolol area under the curve (AUC) varied 4.7-fold and torsemide AUC 3.5-fold. A very high fraction of AUC variations, 91% of metoprolol and 86% of torsemide, were found to be due to additive genetic effects. However, known genetic variants of CYP2D6, -2C9, and OATP1B1 explained only 39%, 2%, and 39% of that variation, respectively. Comparable results for genetically explained variation in pharmacokinetics and pharmacodynamics have been found for other substrates of these enzymes earlier. These findings indicate that a substantial fraction of the heritable variability in the pharmacokinetics of metoprolol and torsemide remains to be elucidated.

AIMS/HYPOTHESIS: The excess mortality in diabetes is mainly due to cardiovascular causes and almost confined to patients with abnormal albuminuria. Compared to healthy subjects, diabetic patients have a prolonged QT interval and increased QT dispersion. In non-diabetic subjects, as well as in Type 1 diabetic patients with overt nephropathy, a prolonged QT interval and increased QT dispersion are associated with cardiac morbidity and mortality. There is an increasing number of studies on effects of beta blocker treatment on QT interval and QT dispersion in non-diabetic subjects. In contrast, there are no studies on the effects of beta blocker treatment on QT interval and QT dispersion in patients with diabetes. The aim of our study was to describe the effects of metoprolol treatment on QT interval and QT dispersion in a group of well-characterised Type 1 diabetic patients with elevated urine albumin excretion.METHODS: We studied the effects of 6 weeks of treatment with metoprolol (100 mg once daily, zero order kinetics formulation) in a randomised, placebo-controlled, double blind, crossover trial including 20 Type 1 diabetic patients. Patients were simultaneously monitored under ambulatory conditions with 24-h Holter-monitoring, 24-h ambulatory blood pressure recording and 24-h fractionated urine collections. On days of investigation 12-lead electrocardiograms were recorded and autonomic tests performed.RESULTS: We found strong associations between both daytime and night-time blood pressure and heart-rate-corrected QT interval dispersion (QTc dispersion). Heart rate variability parameters indicating sympathetic and parasympathetic modulation showed strong correlations with heart-rate-corrected QT interval (QTc interval) and with QTc dispersion. Beta blocker treatment caused a decrease in QTc interval but no change in QTc dispersion.CONCLUSIONS/INTERPRETATION: This study is the first to address the QTc interval and QTc dispersion in Type 1 diabetic patients treated with metoprolol. Beta blocker treatment caused a decrease in QTc interval but no change in QTc dispersion. These results may in part explain the pronounced cardioprotective effect of beta blocker treatment in diabetic patients with cardiovascular disease.

OBJECTIVES: The present study was designed to investigate which characteristics of anginal symptoms or exercise test results could predict the favorable anti-ischemic effect of the beta-adrenergic blocking agent metoprolol and the calcium antagonist nifedipine in patients with stable angina pectoris.BACKGROUND: The characteristics of anginal symptoms and the results of exercise testing are considered of great importance for selecting medical treatment in patients with chronic stable angina pectoris. However, little information is available on how this first evaluation may be used to select the best pharmacologic approach in individual patients.METHODS: In this prospective multicenter study, 280 patients with stable angina pectoris were enrolled in 25 European centers. After baseline evaluation, consisting of an exercise test and a questionnaire investigating patients' anginal symptoms, the patients were randomly allocated to double-blind treatment for 6 weeks with either metoprolol (Controlled Release, 200 mg once daily) or nifedipine (Retard, 20 mg twice daily) according to a parallel group design. At the end of this period, exercise tests were repeated 1 to 4 h after drug intake.RESULTS: Both metoprolol and nifedipine prolonged exercise tolerance over baseline levels; the improvement was greater in the patients receiving metoprolol (p < 0.05). Multivariate analysis revealed that low exercise tolerance was the only variable associated with a more favorable effect within each treatment group. Metoprolol was more effective than nifedipine in patients with a lower exercise tolerance or with a higher rate-pressure product at rest and at ischemic threshold. None of the characteristics of anginal symptoms or exercise test results predicted a greater efficacy of nifedipine over metoprolol.CONCLUSIONS: The results of a baseline exercise test, but not the characteristics of anginal symptoms, may offer useful information for selecting medical treatment in stable angina pectoris.

BACKGROUND: Patients scheduled for myocardial perfusion imaging are often taking several antianginal drugs. There is presently no consensus concerning a regimen of discontinuation before either rest or pharmacologic stress myocardial perfusion imaging. Whether antianginal treatment affects diagnostic sensitivity and specificity is not well documented. Methods and results The effect of the three most commonly used antianginal drugs (nitroglycerin, 400 microg [NTG]; metoprolol, 50 mg [MET]; and amlodipine, 5 mg [AML]) on myocardial perfusion was tested in 49 patients (age, 63 +/- 8 years; 43 men) allocated prospectively to one of the treatments (NTG, n = 25; MET, n = 14; and AML, n = 10). All patients had documented coronary artery disease and were scheduled for elective percutaneous coronary intervention. Patients were studied once on treatment and once off treatment with an interval of 1 to 3 weeks. For NTG, the measurements were performed on the same day with an interval of 1 hour. The MET and AML groups were also studied during dipyridamole-induced hyperemia (0.56 mg. kg(-1). min(-1) for 4 minutes). So that a quantitative value of myocardial perfusion in milliliters per gram per minute could be obtained, myocardial perfusion was quantified with nitrogen 13 ammonia positron emission tomography as an average of the midventricular perfusion in each of the 3 vascular territories. NTG treatment increased the overall resting perfusion (0.75 +/- 0.18 vs 0.86 +/- 0.22, P CONCLUSIONS: Antianginal medication can alter both resting and hyperemic myocardial perfusion and might affect the ability to detect flow-limiting stenosis. NTG increases perfusion, MET reduces perfusion, and AML does not affect perfusion. Larger-scale trials are warranted to establish a consensus for optimal antianginal medication for patients undergoing perfusion imaging.