No abstract

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Prior to the commencement of this study, it was already known that rivaroxaban is partially cleared via the kidneys and an influence of renal insufficiency on rivaroxaban pharmacokinetics and exposure was anticipated. WHAT THIS STUDY ADDS• As many patients in the target indications of rivaroxaban will be elderly, a precise quantitative knowledge of the influence of renal function on rivaroxaban pharmacokinetics and exposure is mandatory for adequate labelling recommendations (in the context of benefit/risk provided by phase III studies) to guide therapy. This study provided detailed insight on both rivaroxaban pharmacokinetics and pharmacodynamic behaviour in renal impairment including severely renally impaired subjects. AIMThis study evaluated the effects of impaired renal function on the pharmacokinetics, pharmacodynamics and safety of rivaroxaban (10 mg single dose), an oral, direct Factor Xa inhibitor. METHODSSubjects (n = 32) were stratified based on measured creatinine clearance: healthy controls (Ն80 ml min -1 ), mild (50-79 ml min -1 ), moderate (30-49 ml min -1 ) and severe impairment (<30 ml min -1 ). RESULTSRenal clearance of rivaroxaban decreased with increasing renal impairment. Thus, plasma concentrations increased and area under the plasma concentration-time curve (AUC) LS-mean values were 1.44-fold (90% confidence interval [CI] 1.1, 1.9; mild), 1.52-fold (90% CI 1.2, 2.0; moderate) and 1.64-fold (90% CI 1.2, 2.2; severe impairment) higher than in healthy controls. Corresponding values for the LS-mean of the AUC for prolongation of prothrombin time were 1.33-fold (90% CI 0.92, 1.92; mild), 2.16-fold (90% CI 1.51, 3.10 moderate) and 2.44-fold (90% CI 1.70, 3.49 severe) higher than in healthy subjects, respectively. Likewise, the LS-mean of the AUC for Factor Xa inhibition in subjects with mild renal impairment was 1.50-fold (90% CI 1.07, 2.10) higher than in healthy subjects. In subjects with moderate and severe renal impairment, the increase was 1.86-fold (90% CI 1.34, 2.59) and 2.0-fold (90% CI 1.44, 2.78) higher than in healthy subjects, respectively. CONCLUSIONSRivaroxaban clearance is decreased with increasing renal impairment, leading to increased plasma exposure and pharmacodynamic effects, as expected for a partially renally excreted drug. However, the influence of renal function on rivaroxaban clearance was moderate, even in subjects with severe renal impairment.

Abstract. At present, nine adrenoceptor (AR) subtypes have been identified: α 1A -, α 1B -, α 1D -, α 2A -, α 2B -, α 2C -, β 1 -, β 2 -, and β 3 AR. In the human heart, β 1 -and β 2 AR are the most powerful physiologic mechanism to acutely increase cardiac performance. Changes in βAR play an important role in chronic heart failure (CHF). Thus, due to increased sympathetic activity in CHF, βAR are chronically (over)stimulated, and that results in β 1 AR desensitization and alterations of down-stream mechanisms. However, several questions remain open: What is the role of β 2 AR in CHF? What is the role of increases in cardiac G i -protein in CHF? Do increases in G-protein-coupled receptor kinase (GRK)s play a role in CHF? Does βAR-blocker treatment cause its beneficial effects in CHF, at least partly, by reducing GRK-activity? In this review these aspects of cardiac AR pharmacology in CHF are discussed. In addition, new insights into the functional importance of β 1 -and β 2 AR gene polymorphisms are discussed. At present it seems that for cardiovascular diseases, βAR polymorphisms do not play a role as disease-causing genes; however, they might be risk factors, might modify disease, and / or might influence progression of disease. Furthermore, βAR polymorphisms might influence drug responses. Thus, evidence has accumulated that a β 1 AR polymorphism (the Arg389Gly β 1 AR) may affect the response to βAR-blocker treatment.

Despite the first-line use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), there is still a large need to improve the prevention and progression of diabetic nephropathy and its associated cardiovascular events. Endothelin antagonists have shown anti-inflammatory, antifibrotic, and antiproteinuric effects in experimental studies. This study was a randomized, placebo-controlled, double-blind, parallel-design, dosage-range study of the effect of the endothelin-A antagonist avosentan (SPP301) on urinary albumin excretion rate (UAER) in patients with diabetic nephropathy. We randomly assigned 286 patients with diabetic nephropathy, macroalbuminuria (UAER 0.2 to 5.6 mg/min), and BP Ͻ180/110 mmHg to 12 wk of avosentan (5, 10, 25, and 50 mg) or placebo, in addition to standard ACEI/ARB therapy. Relative to baseline, all avosentan dosages decreased mean relative UAER (Ϫ16.3 to Ϫ29.9%) compared with placebo (35.5%). Median relative UAER decreased with all avosentan dosages (Ϫ28.7 to Ϫ44.8%) compared with placebo (12.1%). Creatinine clearance and BP were unchanged at 12 wk. The main adverse events were peripheral edema (12%), mainly with high (Ն25 mg) dosages of avosentan; significant increases in liver enzymes did not occur. Twenty-one (7.3%) patients experienced adverse events that led to withdrawal from study medication. In summary, the endothelin-A antagonist avosentan given in addition to standard ACEI/ARB treatment decreases UAER in patients with diabetic nephropathy and macroalbuminuria.

The sympathetic and parasympathetic nervous system play a powerful role in controlling cardiac function by activating adrenergic and muscarinic receptors. In the human heart there exist alpha1-, beta1- and beta2-adrenoceptors and M2-muscarinic receptors and possibly also (prejunctional) alpha2-adrenoceptors. Beta1- and beta2-adrenoceptors are quite evenly distributed in the human heart while M2-receptors are heterogeneously distributed (more receptors in atria than in ventricles). Stimulation of beta1- and beta2-adrenoceptors causes increases in heart rate and force of contraction while stimulation of M2-receptors decreases heart rate (directly in atria) and force of contraction (indirectly in ventricles). Pathological situations (such as heart failure) or pharmacological interventions (for example, beta-blocker treatment) can alter the distribution of beta1- and beta2-adrenoceptors in the human heart, while M2-receptors are only marginally affected. On the other hand, relatively little is known on distribution and functional role of alpha1- and alpha2-adrenoceptor subtypes in the human heart.

There can be no doubt that beta(1)-, beta(2)- and beta(3)-adrenoceptor genes have genetic polymorphisms. Two single nucleotide polymorphisms have been described for the beta(1)- (Ser49Gly; Gly389Arg), three for the beta(2)- (Arg16Gly; Gln27Glu; Thr164Ile) and one for the beta(3)-adrenoceptor subtype (Trp64Arg) that might be of functional importance. The possibility that changes in expression or properties of the beta-adrenoceptors due to single nucleotide polymorphisms might have phenotypic consequences influencing their cardiovascular or metabolic function or may contribute to the pathophysiology of several disorders like hypertension, congestive heart failure, asthma or obesity is an idea that has attracted much interest during the last 10 years. At present, it appears that these beta-adrenoceptor polymorphisms are very likely not disease-causing genes, but might be risk factors, might modify disease and/or might influence progression of disease. The aim of this review is to provide an overview of the functional consequences of such beta-adrenoceptor polymorphisms in vitro, ex vivo and in vivo.

Background: Arteriosclerosis and cardiovascular disease are strongly associated with vascular calcification. Hyperphosphatemia is an essential risk factor for increased vascular calcification. End-stage renal disease (ESRD) patients could serve as an in vivo model for accelerated calcification. This study focuses on the most likely protective effects of magnesium ion (Mg²⁺) on phosphate-induced vascular calcification ex vivo/in vitro. Furthermore, plasma Mg²⁺ concentrations of ESRD and healthy controls were investigated for association with surrogate parameters of vascular calcification in vivo. Methods: Aortic segments of male Wistar-Kyoto rats were incubated and the phosphate concentration of the medium was elevated. The aortic segments were incubated in the absence and presence of MgCl₂; tissue calcification was quantified by different methods. Serum Mg²⁺ concentrations of patients with chronic kidney disease (CKD stage 5; ESRD) and patients without CKD (controls) were associated with carotid intima media thickness (IMT) and aortic pulse wave velocity (PWV) as surrogate parameter for arteriosclerosis and arterial stiffening. Results: Incubation of aortic segments in the presence of β-glycerophosphate and NaH₂PO₄ caused an increased tissue Ca²⁺ deposition compared to control conditions. This increased amount of Ca²⁺ in the aortic rings was significantly decreased in the presence of Mg²⁺. In CKD patients, but not in controls, magnesium serum concentration was associated with the IMT of the carotid arteries. In addition, CKD patients with higher magnesium serum concentration had a significantly lower PWV. Discussion and Conclusion: Elevated phosphate concentrations in the culture media induce ex vivo/in vitro medial calcification in intact rat aortic rings in the presence of alkaline phosphatase. Mg²⁺ ions reduced ex vivo/in vitro vascular calcification despite increased phosphate concentration. This hypothesis is additionally based on the fact that CKD patients with high Mg² serum levels had significantly lower IMT and PWV values, which may result in a lower risk for cardiovascular events and mortality in these patients. Therefore, Mg²⁺ supplementation may be an option for treatment and prevention of vascular calcification resulting in a reduction of cardiovascular events in CKD patients.

Codon 389 beta1AR polymorphism is a determinant not only of hemodynamic effects but also of PRA. Thus, beta1AR polymorphisms may be useful for predicting therapeutic responses to betaAR-blocker treatment.