Aliskiren and valsartan in stage 2 hypertension: subgroup analysis of a randomized, double-blind study

Renin inhibitors versus angiotensin receptor blockers for primary hypertension

BACKGROUND

Renin inhibitors, which inhibit the first and rate-limiting step in the renin angiotensin system (RAS), are thought to be more effective than other RAS inhibitors in blocking the RAS. Previous meta-analyses have shown that renin inhibitors have a favourable tolerability profile in people with mild-to-moderate hypertension and a blood-pressure-lowering magnitude that is similar to that of angiotensin receptor blockers (ARBs). ARBs inhibit the RAS by interfering with the binding of angiotensin II with its receptors. ARBs are widely prescribed and recommended as first-line therapy by some hypertension guidelines. However, a drug's efficacy in lowering blood pressure cannot be considered as a definitive indicator of its effectiveness in reducing mortality and morbidity. The benefits and harms of renin inhibitors compared to ARBs in treating hypertension are unknown.

OBJECTIVES

To evaluate the benefits and harms of renin inhibitors compared to angiotensin receptor blockers in people with primary hypertension.

SEARCH METHODS

On 26 January 2024, the Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials: Cochrane Hypertension's Specialised Register, Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Ovid Embase. The World Health Organization International Clinical Trials Registry Platform and the US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov) were also searched for ongoing trials. We contacted authors of relevant papers regarding further published and unpublished work and checked the bibliographies of included studies and relevant systematic reviews. The searches had no language restrictions.

SELECTION CRITERIA

We included randomised, double-blind, parallel-design clinical trials comparing renin inhibitors and ARBs for people with primary hypertension. Studies recruiting people with proven secondary hypertension were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected the included trials, evaluated the risks of bias using the RoB 1 tool, and entered the data for analysis. We reported dichotomous outcomes as a risk ratio (RR) with a 95% confidence interval (CI) and continuous variables as mean difference (MD) with a 95% CI. The primary outcomes were all-cause mortality, total cardiovascular events, end-stage renal disease (ESRD), withdrawal due to adverse effects (WDAE), serious adverse events (SAE), and adverse events. The secondary outcomes were fatal and non-fatal myocardial infarction, fatal and non-fatal stroke, fatal heart failure or hospitalisation for heart failure, systolic and diastolic blood pressure (SBP and DBP), and heart rate. We used the GRADE approach to rate our confidence in the evidence.

MAIN RESULTS

We included 11 double-blind RCTs involving 6780 participants with mild primary hypertension and without cardiovascular complications (mean age range 52 to 59 years), with a mean follow-up ranging from four weeks to nine months. Risk of bias was low or unclear for most domains except for other bias, which was high risk for 10 of the 11 trials due to industry funding. All the studies compared aliskiren, the only marketed molecule in the class of renin inhibitors, with an ARB. The ARB comparator was losartan in four trials, valsartan in three trials, irbesartan in three trials, and telmisartan in one trial. There were very limited or no data on cardiovascular outcomes and ESRD. There may be little to no difference between renin inhibitors and ARBs in all-cause mortality (RR 0.35, 95% CI 0.07 to 1.64; 3 studies, 1932 participants; low-certainty evidence). There is probably little to no difference between renin inhibitors and ARBs in WDAE (RR 0.71, 95% CI 0.49 to 1.02; 9 studies, 4634 participants; moderate-certainty evidence), SAE (RR 0.75, 95% CI 0.45 to 1.27; 6 studies, 3283 participants; moderate-certainty evidence), and adverse events (RR 0.98, 95% CI 0.90 to 1.06; 10 studies, 4722 participants; moderate-certainty evidence). There is probably little to no difference between renin inhibitors and ARBs in lowering SBP (MD -0.25 mmHg, 95% CI -1.05 to 0.56; 10 studies, 4222 participants; moderate-certainty evidence) and there may be little to no difference in lowering DBP (MD 0.25 mmHg, 95% CI -0.14 to 0.64; 10 studies, 4222 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

The available RCT evidence suggests little to no difference between renin inhibitors and ARBs in terms of mortality, SAE, WDAE, adverse events, and blood pressure in people with mild primary hypertension. The evidence was derived from short-term trials with a limited occurrence of morbidity outcomes, leaving any potential differences unknown. Larger RCTs of longer duration with a wider range of participants and a focus on cardiovascular outcomes are needed.

The Angiotensin-Converting-Enzyme-Induced Angioedema

The bradykinin B2 receptor antagonist icatibant is effective in angiotensin-converting enzyme inhibitor-induced angioedema. The drug is not approved officially for this indication and has to be administered in an emergency situation off-label. Corticosteroids or antihistamines do not seem to work in this condition. The effectiveness of C1-esterase-inhibitor in angiotensin-converting enzyme-induced angioedema must be verified in a double-blind study.

Aliskiren therapy in hypertension and cardiovascular disease: a systematic review and a meta-analysis

The efficacy and safety of aliskiren combination therapy with angiotensin converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) in patients with hypertension and cardiovascular disease remains attractive attention. We searched the Cochrane Central Register, the Clinical Trials Registry, EMBASE, MEDLINE and PubMed for relevant literatures up to January 2017. A total of 13 randomized controlled trials (RCTs) with 12222 patients were included in this study, and the combined results indicated that aliskiren in combination therapy with ACEIs or ARBs had remarkable effects in reducing systolic blood pressure (SBP) [weighted mean differences (WMD), -4.20; 95% confidential intervals (CI) -5.44 to -2.97; I² , 29.7%] and diastolic blood pressure (DBP: WMD, -2.09; 95% CI -2.90 to -1.27; I² , 0%) when compared with ACEIs or ARBs monotherapy, but with significantly increased the risk of hyperkalaemia [relative risk (RR), 1.45; 95% CI 1.28 to 1.64; I² ,10.6 %] and kidney injury ( RR, 1.92; 95% CI 1.14 to 3.21; I² , 0%). Besides, there was no significant difference in the incidence of major cardiovascular events (RR, 0.95; 95% CI 0.89 to 1.02; I² , 0%) between the combined therapy and ACEIs or ARBs monotherapy. In conclusion, this meta-analysis demonstrated that aliskiren in combination therapy with ACEs/ARBs could control BP effectively, but is associated with increasing risks of hyperkalaemia and kidney injury, and have no benefit in preventing of major cardiovascular events.

Renin inhibition improves metabolic syndrome, and reduces angiotensin II levels and oxidative stress in visceral fat tissues in fructose-fed rats

Renin–angiotensin system in visceral fat plays a crucial role in the pathogenesis of metabolic syndrome in fructose-fed rats. However, the effects of renin inhibition on visceral adiposity in metabolic syndrome are not fully investigated. We investigated the effects of renin inhibition on visceral adiposity in fructose-fed rats. Male Wistar–Kyoto rats were divided into 4 groups for 8-week experiments: Group Con (standard chow diet), Group Fru (high-fructose diet; 60% fructose), Group FruA (high-fructose diet and concurrent aliskiren treatment; 100 mg/kg body weight [BW] per day), and Group FruB (high-fructose diet and subsequent, i.e. 4 weeks after initiating high-fructose feeding, aliskiren treatment; 100 mg/kg BW per day). The high-fructose diet induced metabolic syndrome, increased visceral fat weights and adipocyte sizes, and augmented angiotensin II (Ang II), NADPH oxidase (NOX) isoforms expressions, oxidative stress, and dysregulated production of adipocytokines from visceral adipose tissues. Concurrent and subsequent aliskiren administration ameliorated metabolic syndrome, dysregulated adipocytokines, and visceral adiposity in high fructose-fed hypertensive rats, and was associated with reducing Ang II levels, NOX isoforms expressions and oxidative stress in visceral fat tissues. Therefore, this study demonstrates renin inhibition could improve metabolic syndrome, and reduce Ang II levels and oxidative stress in visceral fat tissue in fructose-fed rats, and suggests that visceral adipose Ang II plays a crucial role in the pathogenesis of metabolic syndrome in fructose-fed rats.

Evidence and evidence gaps of medical treatment of non-tumorous diseases of the head and neck

Unfortunately, the treatment of numerous otolaryngological diseases often lacks of evidence base because appropriate studies are missing.

Whereas sufficient high-quality trials exist for the specific immunotherapy of allergic rhinitis and in a limited measure also for the angiotensin-converting enzyme inhibitor induced angioedema, the evidence for Menière’s disease or for pharmacotherapy of postoperative laryngeal edema is rather poor. This contribution will discuss the trial situation and evidence of the respective diseases.

Is there benefit in dual renin-angiotensin-aldosterone system blockade? No, yes and maybe: a guide for the perplexed

Since the initial discovery of Angiotensin converting enzyme inhibitors (ACEI) in the 1960s and the launch of Captopril as the first available for clinical use in the 1970s, there now exist three other classes of drugs that block the renin angiotensin aldosterone system (RAAS): the angiotensin II receptor blockers (ARB), aldosterone antagonists (AA) and direct renin inhibitors (DRI). With the proven efficacy of RAAS blockers as monotherapy in many arenas there has been considerable interest in the use of dual therapy combinations of these medications that target different points in the pathway. By potentially offering a more complete RAAS blockade with a commensurate enhanced clinical effect, the strong biological rationale for dual therapy has led to it being embraced by clinicians as a treatment option, for hypertension and nephroprotection in particular. However, the initial enthusiasm for this treatment has been tempered by the recent results from several large trials such as ONTARGET and ALTITUDE, which do not support a specific dual therapy approach. In contrast, there is supportive evidence for dual blockade of specific combinations in selected patient groups and data are lacking for others. In the wake of this complex contemporary evidence, the conundrum now faced by clinicians committed to individualised care is, for which patients dual therapy could still be of benefit. This review examines for the practising clinician the current 'state of play' for dual blockade of various combinations and a perspective on its use in cardio-renal disease and diabetic complications.

Nebivolol monotherapy for patients with systolic stage II hypertension: results of a randomized, placebo-controlled trial

BACKGROUND

Elevated systolic blood pressure (SBP) is an independent risk factor for cardiovascular events and mortality.

OBJECTIVE

The goal of this study was to assess whether nebivolol (NEB), a vasodilatory β(1)-selective blocker, is a safe and efficacious monotherapy for individuals with systolic stage II hypertension.

METHODS

In this multicenter trial, 18- to 64-year-olds who had not used antihypertensive treatment for at least 4 weeks and had SBP/diastolic blood pressure (DBP) of 160 to 180/90 to 110 mm Hg were randomized to receive double-blind medication for 6 weeks (NEB, n = 290; placebo [PBO], n = 142). Depending on response, the starting dose (5 mg/d) could be increased directly to 20 mg/d. Primary parameters were baseline-end point changes in trough seated SBP and DBP (intent-to-treat [ITT] population); the Hochberg method was used to control the type I error (α = 0.05). Responder analysis was also performed. Safety and tolerability assessment included monitoring of adverse events (AEs).

RESULTS

Mean age at baseline (ITT) was 50.7 years, and the mean SBP/DBP values were 167/101 mm Hg; 202 (47.3%) participants were women, 276 (63.9%) had body mass index ≥30 kg/m(2), 152 (35.2%) were black, and 161 (37.3%) were Hispanic. Completion rates were 79.7% (PBO) and 90.3% (NEB). After 2 weeks of treatment, 92% and 95% participants in the NEB and PBO groups, respectively, had SBP in the range of 130 to 180 mm Hg and were titrated to the 20-mg/d NEB dose or its matching PBO tablet. After 6 weeks of treatment, the NEB group experienced significant mean reductions compared with the PBO group for both SBP (-18.2 vs -12.3 mm Hg; P < 0.001) and DBP (-12.3 vs -5.7 mm Hg; P < 0.001), down to mean SBP/DBP values of 149/89 mm Hg and 155/95 mm Hg, respectively, and had a significantly higher percentage of individuals who achieved BP control (SBP/DBP <140/90 mm Hg, 30.6% vs 17.3%; P = 0.004). Post hoc analyses suggest that NEB was not efficacious in reducing SBP in black participants. Mean changes in pulse rate were -12.8 beats/min for the NEB group and -1.6 beats/min for the PBO group (P < 0.001). Rates of discontinuations due to an AE (NEB vs PBO) were 1.4% in both groups, rates of any treatment-emergent AEs were 19.7% versus 19.0%, and rates of serious AEs were 0.3% versus 2.1%. The most common AEs (NEB vs PBO) were headache (2.1% vs 2.8%) and hypertension (0.7% vs 2.1%).

CONCLUSIONS

NEB monotherapy was an efficacious and well-tolerated treatment option for these study individuals with systolic stage II hypertension, but most of them would need combination therapy to achieve BP control.

Direct renin inhibitor prevents and ameliorates insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats

Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers can improve insulin resistance and vascular dysfunction in insulin-resistant rats; however, there are few reports on the effects of direct renin inhibitors on these conditions. We investigated the effects of a direct renin inhibitor, aliskiren, on insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats. Male Wistar-Kyoto rats were divided into four groups (n=6 per group) and studied for 8 weeks: Group Con: standard chow diet; group Fru: high-fructose diet (60% fructose); Group FruA: high-fructose diet with concurrent aliskiren treatment (100 mg kg(-1) per day); and Group FruB: high-fructose diet with subsequent aliskiren treatment 4 weeks later. Blood was collected for biochemical assays, and isolated rings of the thoracic aorta were obtained for analysis of vascular reactivity, vascular structure and lipid peroxide. Rats fed with high-fructose diets developed significant systolic hypertension, decreased plasma nitrite (NO(2); nitric oxide metabolite) levels and increased plasma glucose, insulin, triglyceride, total cholesterol and aortic lipid peroxide levels, and aortic wall thickness compared with control rats. Aliskiren treatment, either concurrent or subsequent, elevated plasma NO(2) levels and reduced systolic hypertension, insulin resistance, dyslipidemia, aortic lipid peroxide levels and aortic wall hypertrophy in FHR. The peak endothelium-dependent aortic relaxations were significantly higher in rats that received aliskiren treatment than in those that did not. In conclusion, our findings suggest that aliskiren prevents and ameliorates insulin resistance, aortic endothelial dysfunction and oxidative vascular remodeling in fructose-fed hypertensive rats.

Telmisartan: just an antihypertensive agent? A literature review

INTRODUCTION

The modulation of the renin angiotensin aldosterone system (RAAS) is an important pathway in managing high blood pressure, and its overexpression plays a key role in target end-organ damage. Telmisartan is an angiotensin II receptor blocker (ARB) with unique pharmacologic properties, including the longest half-life among all ARBs; this leads to a significant and 24-h sustained reduction of blood pressure. Telmisartan has well-known antihypertensive properties, but there is also strong clinical evidence that it reduces left ventricular hypertrophy, arterial stiffness and the recurrence of atrial fibrillation, and confers renoprotection.

AREAS COVERED

This paper reviews telmisartan's pharmacological properties in terms of efficacy for hypertension control and, importantly, focuses on its new therapeutic indications and their clinical implications.

EXPERT OPINION

ONTARGET (ongoing telmisartan alone and in combination with ramipril global endpoint trial) demonstrated, that telmisartan confers cardiovascular protective effects similar to those of ramipril, but with a better tolerability. Moreover, recent investigations focused on the capability of telmisartan to modulate the peroxisome proliferator-activated receptor-gamma (PPAR-γ), an established target in the treatment of insulin resistance, diabetes and metabolic syndrome, whose activation is also correlated to anti-inflammatory and, finally, anti-atherosclerotic properties. Telmisartan shows peculiar features that go beyond blood pressure control. It presents promising and unique protective properties against target end-organ damage, potentially able to open a scenario of new therapeutic approaches to cardiovascular disease.

Comparison of the effects of aliskiren/valsartan in combination versus valsartan alone in patients with stage 2 hypertension

The extent to which the combination of a renin inhibitor with an angiotensin receptor blocker (ARB) lowers clinic and ambulatory blood pressure (BP) versus an ARB alone in stage 2 hypertension is not well known. Hence, we performed an 8-week, randomized, double-blind study in 451 patients with stage 2 hypertension to compare the efficacy of the combination of aliskiren/valsartan 300/320 mg versus valsartan 320 mg. The primary endpoint was change in seated systolic BP from baseline to week 8 analyzed on the intent-to-treat (ITT) population using the last-observation-carried-forward (LOCF) approach; patients completing the entire treatment period (per-protocol completers) were similarly analyzed. For the predefined primary analysis, systolic BP reductions for aliskiren/valsartan (n = 230) and valsartan (n = 217) were -22.1 and -20.5 mm Hg, respectively (P = .295). In per-protocol completers, aliskiren/valsartan (n = 201) lowered BP significantly greater than valsartan (n = 196); -23.7 mm Hg versus -20.3 mm Hg, respectively (P = .028). Although limited by a small sample size (n = 76) using ambulatory BP monitoring, aliskiren/valsartan lowered the 24-hour BP significantly more than valsartan alone (-14.6/-9.0 mm Hg versus -5.9/-4.2 mm Hg; P < .01). Safety and tolerability were similar for the two treatment groups. These data demonstrate the importance of multiple modalities to assess BP changes in clinical trials of antihypertensive therapies, particularly in stage 2 hypertension.

Aliskiren as a novel therapeutic agent for hypertension and cardio-renal diseases

Objectives

High blood pressure (BP) is a major risk factor for cardiovascular and renal complications. A majority of treated hypertensive patients still complain of high BP. The renin-angiotensin aldosterone system (RAAS) has been a centre-stage target for all the cardiovascular and cardio-renal complications. Aliskiren, is the first direct renin inhibitor (DRI) to be approved by the US FDA. Renin controls the rate-limiting step in the RAAS cascade and hence is the most favorable target for RAAS suppression.

Key findings

This review article strives to summarize the pharmacokinetic, preclinical and clinical studies done so far pertaining to the efficacy of aliskiren. Further, the pharmacology of aliskiren has been comprehensively dealt with to enhance understanding so as to further research in this unfathomed area in the multitude of cardiovascular disorders and renal diseases.

Summary

Aliskiren has been shown to have comparable BP-lowering effects to other RAAS inhibitors. Recent clinical trials have indicated that it might contribute significantly in combination with other agents for the protection of end-organ diseases.

Aliskiren prevents and ameliorates metabolic syndrome in fructose-fed rats

INTRODUCTION

The renin-angiotensin system plays a major role in the pathogenesis of metabolic syndrome. The objective of this study was to examine the effects of aliskiren, a direct renin inhibitor, on the metabolic syndrome of fructose-fed rats.

MATERIAL AND METHODS

Male Sprague-Dawley rats were divided into 4 groups (n = 6 for each group). Group Con: rats were fed a standard chow diet for 8 weeks, group Fru: rats were fed a high fructose diet (60% fructose) for 8 weeks, group FruA: rats were fed a high fructose diet and were co-infused with aliskiren (100 mg/kg/day), and group FruB: rats were treated as group Fru, but aliskiren was administered 4 weeks later. Systolic blood pressure (SBP), homeostasis model assessment-insulin resistance (HOMA-IR), and blood profiles were measured.

RESULTS

By the end of week 4 and 8 of a high fructose diet, SBP had increased significantly from 111 ±5 to 142 ±4 and 139 ±5 mmHg (p < 0.05), respectively. A high fructose diet significantly increased HOMA-IR from baseline (6.15 ±1.59) to 21.25 ±2.08 and 21.28 ±3.1 (p < 0.05) at week 4 and 8, respectively, and significantly induced metabolic syndrome. Concurrent aliskiren treatment prevented the development of hypertension and metabolic syndrome in fructose-fed rats. When fructose-induced hypertension was established, subsequent aliskiren treatment for 4 weeks reversed the elevated SBP and ameliorated metabolic syndrome. There were no significant differences in food, water intake, urine flow or body weight gain among groups.

CONCLUSIONS

Aliskiren not only prevents but also ameliorates metabolic syndrome in fructose-fed rats.

Direct renin inhibition: update on clinical investigations with aliskiren

The renin–angiotensin–aldosterone system (RAAS) plays a pivotal role in regulating blood pressure, volume, and electrolytes. The final product of RAAS cascade is angiotensin II, which exerts diverse biological activities via binding to one of three known receptor types, with different binding consequences. Despite the success with conventional strategies to limit angiotensin II production and action, these agents promote a reflex rise in plasma renin activity, which is thought to be associated with an increased incidence of cardiovascular events. Several renin inhibitors have been synthesized in order to counteract deleterious consequences of renin activity and RAAS activation; aliskiren is the first of these new non-peptide direct renin inhibitors to be approved for the treatment of hypertension. The paper reviews pharmacokinetics of aliskiren and its role in hypertension, with particular regard to those studies that compared clinical efficacy of aliskiren in comparison and in addition to other antihypertensive drug strategies.

A systematic review and meta-analysis of aliskiren and angiotension receptor blockers in the management of essential hypertension

Aliskiren is a novel antihypertensive agent and the first direct renin inhibitor (DRI) in clinical use. Several clinical trials have compared DRI with angiotensin receptor blockers (ARBs) in the management of essential hypertension. However, systematic comparison of efficacy and safety between DRIs and ARBs is still lacking. We reviewed randomized controlled trials (RCTs) comparing aliskiren with ARBs for net reduction of blood pressure from baseline, achieved rate of control, and incidences of common and serious adverse events. Weighted mean differences (WMD) and relative risk (RR) with 95% confidence intervals (CI) were calculated for continuous and dichotomous data, respectively. Seven RCTs with 5488 patients were included in this meta-analysis. We compared the efficacy of aliskiren and ARBs in reducing systolic blood pressure (SBP) and diastolic blood pressure (DBP). No differences were found between the two groups. Aliskiren combined with ARBs was superior to aliskiren monotherapy at the maximum recommended dose on SBP and DBP reduction. (WMD -4.80, 95% CI -6.22— -3.39, p < 0.0001; WMD -2.96, 95% CI -4.63—-1.28, p = 0.0001; respectively). Similar results were found with aliskiren combined with ARBs versus ARB monotherapy (WMD -4.43, 95% CI -5.91—-2.96, p < 0.0001; WMD -2.40; 95% CI -3.41—-1.39, p < 0.0001; respectively). No differences were found in adverse events between the aliskiren and ARB groups. Similar results were found with aliskiren and ARB combination therapy and its respective monotherapy. We conclude that aliskiren’s BP-lowering capabilities were comparable to those of ARBs. Aliskiren and ARB combination therapy provided more effective BP reduction than each respective monotherapy without increasing adverse events.

Renin-angiotensin-aldosterone system blockade in high-risk hypertensive patients: current approaches and future trends

Agents that block the renin-angiotensin-aldosterone system (RAAS) are the cornerstones of antihypertensive therapy in patients at high risk for cardiovascular or renal disease. Recently, it was shown that activation of RAAS may occur through alternate pathways not inhibited by angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), or mineralocorticoid receptor antagonists (MRAs), and that ACEIs, ARBs, or MRAs may actually cause a reactive increase in plasma renin concentration and activity. While these agents, alone or in combination, decrease blood pressure and cardiovascular events to varying degrees, the direct renin inhibitor is a new class of RAAS blocking agent. Aliskiren is the first US Food and Drug Administration-approved direct renin inhibitor with good oral bioavailability. ASPIRE HIGHER is an ongoing series of clinical trials designed to investigate the effect of aliskiren on cardiovascular/renal surrogate endpoints and morbidity/mortality in patients with hypertension and high risk for cardiovascular or renal disease.

Aliskiren and valsartan combination therapy for the management of hypertension

Combination therapy is necessary for most patients with hypertension, and agents that inhibit the renin-angiotensin-aldosterone system (RAAS) are mainstays in hypertension management, especially for patients at high cardiovascular and renal risk. Single blockade of the RAAS with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) confers some cardiorenal protection; however, these agents do not extinguish the RAAS as evidenced by a reactive increase in plasma renin activity (PRA), a cardiovascular risk marker, and incomplete cardiorenal protection. Dual blockade with an ACE inhibitor and an ARB offers no additional benefit in patients with hypertension and normal renal and left ventricular function. Indeed, PRA increases synergistically with dual blockade. Aliskiren, the first direct renin inhibitor (DRI) to become available has provided an opportunity to study the merit of DRI/ARB combination treatment. By blocking the first and rate-limiting step in the RAAS, aliskiren reduces PRA by at least 70% and buffers the compensatory increase in PRA observed with ACE inhibitors and ARBs. The combination of a DRI and an ARB or an ACE inhibitor is an effective approach for lowering blood pressure; available data indicate that such combinations favorably affect proteinuria, left ventricular mass index, and brain natriuretic peptide in patients with albuminuria, left ventricular hypertrophy, and heart failure, respectively. Ongoing outcome studies will clarify the role of aliskiren and aliskiren-based combination RAAS blockade in patients with hypertension and those at high cardiorenal risk.

Blocking the RAAS at different levels: an update on the use of the direct renin inhibitors alone and in combination

The renin–angiotensin–aldosterone system (RAAS), an important regulator of blood pressure and mediator of hypertension-related complications, is a prime target for cardiovascular drug therapy. Angiotensin-converting enzyme inhibitors (ACEIs) were the first drugs to be used to block the RAAS. Angiotensin II receptor blockers (ARBs) have also been shown to be equally effective for treatment. Although these drugs are highly effective and are widely used in the management of hypertension, current treatment regimens with ACEIs and ARBs are unable to completely suppress the RAAS. Combinations of ACEIs and ARBs have been shown to be superior than to either agent alone for some, but certainly not all, composite cardiovascular and kidney outcomes, but dual RAAS blockade with the combination of an ACEI and an ARB is sometimes associated with an increase in the risk for adverse events, primarily hyperkalemia and worsening renal function. The recent introduction of the direct renin inhibitor, aliskiren, has made available new combination strategies to obtain a more complete blockade of the RAAS with fewer adverse events. Renin system blockade with aliskiren and another RAAS agent has been, and still is, the subject of many large-scale clinical trials and furthermore, is already available in some countries as a fixed combination.

Aliskiren/valsartan combination for the treatment of cardiovascular and renal diseases

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) plays a key role in the development of hypertension, and cardiac and renal diseases. RAAS inhibitors, such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), improve cardiovascular and renal outcomes. However, studies have shown that residual morbidity and mortality remains high, despite current optimal treatment. More comprehensive control of the RAAS might provide additional reductions in morbidity and mortality. Direct renin inhibitors offer the potential for enhanced RAAS control as they target the system at the point of activation, thereby reducing plasma renin activity (PRA); by contrast, ARBs and ACE inhibitors increase PRA. Elevated PRA is independently associated with cardiovascular morbidity and mortality. A single-pill combination of the direct renin inhibitor, aliskiren, and the ARB, valsartan, at once-daily doses of 150/160 mg and 300/320 mg, has recently been approved by the US FDA for the treatment of hypertension in patients not adequately controlled on aliskiren or ARB monotherapy, and as initial therapy in patients likely to need multiple drugs to achieve their blood pressure goals. This article examines the efficacy, safety and tolerability of aliskiren/valsartan combination therapy, and considers the evidence for the potential organ-protection benefits of this treatment.

Addressing the theoretical and clinical advantages of combination therapy with inhibitors of the renin-angiotensin-aldosterone system: antihypertensive effects and benefits beyond BP control

AIMS

This article reviews the importance of the renin-angiotensin-aldosterone system (RAAS) in the cardiometabolic continuum; presents the pros and cons of dual RAAS blockade with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs); and examines the theoretical and practical benefits supporting the use of direct renin inhibitors (DRIs) in combination with ACEIs or ARBs.

MAIN METHODS

The author reviewed the literature for key publications related to the biochemical physiology of the RAAS and the pharmacodynamic effects of ACEIs, ARBs, and DRIs, with a particular focus on dual RAAS blockade with these drug classes.

KEY FINDINGS

Although ACEI/ARB combination therapy produces modest improvement in BP, it has not resulted in the major improvements predicted given the importance of the RAAS across the cardiorenal disease continuum. This may reflect the fact that RAAS blockade with ACEIs and/or ARBs leads to exacerbated renin release through loss of negative-feedback inhibition, as well as ACE/aldosterone escape through RAAS and non-RAAS-mediated mechanisms. Plasma renin activity (PRA) is an independent predictor of morbidity and mortality, even for patients receiving ACEIs and ARBs. When used alone or in combination with ACEIs and ARBs, the DRI aliskiren effectively reduces PRA. Reductions in BP are greater with these combinations, relative to the individual components alone.

SIGNIFICANCE

It is possible that aliskiren plus either an ACEI or ARB may provide greater RAAS blockade than monotherapy with ACEIs or ARBs, and lead to additive improvement in BP and clinically important outcomes.

ACE inhibitors, angiotensin receptor blockers and direct renin inhibitors in combination: a review of their role after the ONTARGET trial

BACKGROUND

Clinical trials have shown organ-protective effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs); however, cardiovascular mortality and morbidity rates, and decline in renal function remain high. In the ONTARGET trial in patients with hypertension at high cardiovascular risk, ACE inhibitor/ARB combination therapy provided no significant clinical outcome benefits over monotherapy, and was associated with a worse safety and tolerability profile. These results raise the question of whether ACE inhibitor/ARB, direct renin inhibitor (DRI)/ACE inhibitor and DRI/ARB combinations are of clinical value.

SCOPE

Using PubMed and EMBASE databases, we conducted a systematic review of clinical trials published before June 2008 evaluating dual intervention with ACE inhibitors and ARBs, and compared these with trials of DRI/ACE inhibitor or DRI/ARB combinations.

FINDINGS

A total of 70 studies met the inclusion criteria for this analysis. In patients with hypertension, ACE inhibitor/ARB combinations provided limited additional reductions in blood pressure (BP) over monotherapy. Outcomes benefits were unclear: VALIANT and ONTARGET demonstrated no enhanced outcome benefit of combination therapy over monotherapy; Val-HeFT and CHARM-Added showed reduced morbidity/mortality in patients with heart failure, but at the expense of poorer tolerability. Combination therapy with the DRI aliskiren and an ACE inhibitor or ARB provided significant additional BP reductions over monotherapy in patients with mild-to-moderate hypertension, and reduced surrogate markers of organ damage in patients with heart failure or diabetic nephropathy, with generally similar safety and tolerability to the component monotherapies. No morbidity and mortality data for DRI/ACE inhibitor or DRI/ARB combinations are currently available.

CONCLUSIONS

ACE inhibitor/ARB combinations showed equivocal effects on clinical outcomes. DRI/ACE inhibitor and DRI/ARB combinations reduced markers of organ damage, but longer-term trials are required to establish whether more complete renin--angiotensin--aldosterone system control with aliskiren-based therapy translates into improved outcome benefits.

Direct inhibition of renin: a physiological approach to treat hypertension and cardiovascular disease

Despite the last three decades of progress in improving cardiovascular outcomes via renin–angiotensin–aldosterone system (RAAS) blockade in hypertensive patients, substantial residual morbidity/mortality remains. Attempts to improve clinical outcomes by combining angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have yielded mixed results. Adverse effects of RAAS blockade with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may relate to compensatory increases in plasma renin activity (PRA). The first-in-class direct renin inhibitor, aliskiren, blocks the RAAS at its point-of-activation, suppressing PRA and attenuating increases associated with other antihypertensives. Aliskiren (with or without other agents) provides significant and prolonged blood pressure reductions in a broad range of hypertensive patients and is well tolerated. Initial results from organ-protection studies are promising. Long-term outcomes studies should yield valuable information regarding the significance of direct renin inhibition in clinical practice.

Renin-angiotensin-aldosterone system in the elderly: rational use of aliskiren in managing hypertension

The overall purpose of hypertension treatment is 2-fold. First, patients often have symptoms that are related to their high blood pressure and although subtle in many instances may be improved dramatically by blood pressure control. The main reason for blood pressure treatment, however, is to reduce the burden of cardiovascular complications and end organ damage related to the condition. This may be considered the ultimate goal of blood pressure treatment. In this respect, actual blood pressure measurements may be seen as surrogate end points as the organ protective effects of two antihypertensive agents may differ significantly even though their blood pressure lowering effects are similar. Thus beta-blockers, once seen as first-line treatment of hypertension for most patients, now are considered as third- or fourthline agents according to the latest NICE guidelines (National Institute for Health and Clinical Excellence, www.nice.org.uk/CG034). On the other hand, agents that inhibit the activity of the renin-angiotensin-aldosterone system (RAAS) system are being established as safe, effective and end organ protective in numerous clinical trials, resulting in their general acceptance as first-line treatment in most patients with stage 2 hypertension. This shift in emphasis from beta-blockers and thiazide diuretics is supported by numerous clinical trials and has proven safe and well tolerated by patients. The impact of this paradigm shift will have to be established in future long-term randomized clinical trials. The optimal combination treatment with respect to end organ protection has yet to be determined. Most combinations will include either a RAAS active agent and calcium channel blocker or two separate RAAS active agents working at different levels of the cascade. In this respect direct renin inhibitors and angiotensin receptor blockers seem particularly promising but the concept awaits evaluation in upcoming randomized clinical trials. Although safety data from the randomized clinical trials to date have been promising, we still lack data on the long-term effect of aliskiren on mortality and there still are patient groups where the safety of aliskiren is unexplored.