Combination of hydrochlorothiazide or benazepril with valsartan in hypertensive patients unresponsive to valsartan alone

Combined Treatment With Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers: A Review of the Current Evidence

Several studies have shown that angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are useful in the treatment of hypertension, cardiovascular disease, chronic heart failure, and some types of nephropathy. In this context, dual renin-angiotensin system blockade with both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers may be more effective than treatment with each agent alone. Many clinical trials have demonstrated the beneficial effect of this combined treatment on proteinuria, hypertension, heart failure, and cardiovascular events. Moreover, these studies demonstrated that dual renin-angiotensin system blockade is generally safe and well tolerated. Long-term studies are under way to confirm these effects and also investigate the effectiveness of dual reninangiotensin system blockade on cerebrovascular disease and prevention of type 2 diabetes mellitus. These studies are expected to define the optimal use of combination treatment in everyday clinical practice. This review considers the most important clinical trials that evaluated the effect of dual renin-angiotensin system blockade on blood pressure, heart failure, and renal function.

Inhibition of the renin-angiotensin-aldosterone system: is there room for dual blockade in the cardiorenal continuum?

Antagonism of renin-angiotensin-aldosterone system is exerted through angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, renin inhibitors and mineralocorticoid receptor antagonists. These drugs have been successfully tested in numerous trials and in different clinical settings. The original indications of renin-angiotensin-aldosterone system blockers have progressively expanded from the advanced stages to the earlier stages of cardiorenal continuum. To optimize the degree of blockade of renin-angiotensin-aldosterone system, dose uptitrations of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists or the use of a dual blockade, initially identified with the combination of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists, have been proposed. The data from the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) study do not support this specific dual blockade approach. However, the dual blockade of angiotensin-converting enzyme inhibitors/angiotensin receptor antagonists with direct renin inhibitors is currently under investigation while that based on an aldosterone blocker with any of the previous three drugs requires more evidence beyond heart failure. In this review, we revisited potential advantages of dual blockade of renin-angiotensin-aldosterone system in arterial hypertension and diabetes.

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.

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.

Clinical efficacy and safety of olmesartan/hydrochlorothiazide combination therapy in patients with essential hypertension

Hypertension is a major risk factor for cardiovascular disease that contributes to the premature death of millions of people each year, and identification and treatment of hypertension continues to be a challenge. Guidelines recommend that many patients will require two or more antihypertensive agents from different classes. Combining an angiotensin II receptor blocker (ARB) with hydrochlorothiazide (HCTZ) has been shown in clinical studies to increase the antihypertensive efficacy of both agents compared with either agent alone. This review covers several clinical trials and aims to examine several aspects of the efficacy of the combination of olmesartan and HCTZ, including dose-responsiveness, long-term efficacy, goal rate achievement, and efficacy in patients with moderate to severe hypertension. The results presented here demonstrate that olmesartan is effective when added to HCTZ monotherapy or when HCTZ is added to olmesartan monotherapy, both over the short and long term. Moderate to severe hypertension responds well to olmesartan/HCTZ combination therapy, and the great majority of patients are able to achieve recommended blood pressure targets. Thus olmesartan/HCTZ is a well-tolerated option for patients who fail to respond to monotherapy and as initial therapy in those who require large reductions in diastolic blood pressure or systolic blood pressure to achieve goal blood pressure.

Compliance and fixed-dose combination therapy

Despite data on the importance of blood pressure control in preventing cardiovascular and cerebrovascular events, only 34% of hypertensive patients have their blood pressure under control. The National Council on Patient Information and Education has estimated that the compliance rate is just over 30% for chronic conditions like hypertension. Polypharmacy and complex treatment regimens have been identified as important, modifiable risk factors for medication noncompliance. Fixed-dose combination regimens are attractive options because of the improved antihypertensive efficacy resulting from the dual mechanistic action of components targeting different effector mechanisms. One drug in the fixed-dose combination may negate an adverse effect of the other medication. Above all, fixed-dose combination therapy reduces pill burden and improves medication compliance, which can translate into better cardiovascular outcomes. Fixed-dose combinations should be used routinely for the management of hypertension and should also be considered when initiating therapy for patients with newly diagnosed hypertension.

Renin inhibition with aliskiren provides additive antihypertensive efficacy when used in combination with hydrochlorothiazide

OBJECTIVES

Aliskiren is a novel, orally active renin inhibitor. Its antihypertensive efficacy and safety, alone and in combination with hydrochlorothiazide (HCTZ), were investigated in an 8-week, double-blind, placebo-controlled trial in hypertensive patients. The effects of these treatments on plasma renin activity (PRA) were also assessed.

METHODS

A total of 2776 patients aged >or=18 years with mean sitting diastolic blood pressure (MSDBP) 95-109 mmHg were randomized to receive once-daily treatment with aliskiren (75, 150 or 300 mg), HCTZ (6.25, 12.5 or 25 mg), the combination of aliskiren and HCTZ, or placebo, in a factorial design. The primary endpoint was the change in MSDBP from baseline to week 8. PRA was assessed at these timepoints at selected study centers.

RESULTS

Aliskiren monotherapy was superior to placebo (P < 0.001; overall Dunnett's test) in reducing MSDBP and mean sitting systolic blood pressure (MSSBP). Combination treatment was superior to both component monotherapies in reducing BP (maximum MSSBP/MSDBP reduction of 21.2/14.3 mmHg from baseline with aliskiren/HCTZ 300/25 mg), and resulted in more responders (patients with MSDBP < 90 mmHg and/or >or=10 mmHg reduction) and better control rates (patients achieving MSSBP/MSDBP < 140/90 mmHg) than either monotherapy. Aliskiren monotherapy reduced PRA by up to 65% from baseline. Although HCTZ monotherapy increased PRA by up to 72%, PRA decreased in all of the combination therapy groups. All active treatments were well tolerated.

CONCLUSIONS

Aliskiren monotherapy demonstrated significant BP lowering, and its effect was considerably greater when combined with HCTZ. Renin inhibition with aliskiren neutralized the compensatory rise in PRA induced by HCTZ.

Adding hydrochlorothiazide to olmesartan dose dependently improves 24-h blood pressure and response rates in mild-to-moderate hypertension

OBJECTIVE

To test whether adding hydrochlorothiazide (HCTZ) (12.5 or 25 mg) to olmesartan 20 mg improves 24-h blood pressure in patients whose conventional diastolic blood pressure is inadequately controlled by olmesartan monotherapy.

PATIENTS

Male and female patients > or = 18 years with mean sitting diastolic blood pressure (DBP) of 100-115 mmHg, mean sitting systolic blood pressure (SBP) greater than 150 mmHg, mean 24-h DBP of at least 84 mmHg, and at least 30% of DBP daytime readings > 90 mmHg.

INTERVENTIONS

Four weeks of single-blind treatment with olmesartan 20 mg once daily, followed in non-responders by 8 weeks of randomized double-blind treatment with placebo or HCTZ (12.5 or 25 mg) once-daily, added to olmesartan.

RESULTS

HCTZ 25 mg added to olmesartan 20 mg decreased mean daytime DBP significantly more (P = 0.0012) than placebo added to olmesartan 20 mg. Compared to olmesartan monotherapy, mean 24-h DBP and SBP were significantly reduced by combination therapy with olmesartan/HCTZ 20/12.5 mg (-1.9 mmHg, P = 0.0167 and -3.9 mmHg, P = 0.0018, respectively) and 20/25 mg (-3.7 and -7.4 mmHg respectively, P < 0.0001 for both). Mean 24-h DBP and SBP and mean night-time SBP reductions were significantly greater for HCTZ 25 mg than for HCTZ 12.5 mg. Response rates (mean daytime DBP assessed by ambulatory blood pressure measurement < or = 85 mmHg) approximately doubled following the addition of HCTZ (12.5 mg = 57.6% and 25 mg = 69.5%).

CONCLUSION

Combination of olmesartan 20 mg with HCTZ provides significantly better 24-h blood pressure reduction than olmesartan monotherapy in patients with mild-to-moderate hypertension. Moreover, increasing the dose of HCTZ from 12.5 to 25 mg is a reasonable step to reach better daytime and night-time blood pressure control.

Ambulatory blood pressure comparison of the anti-hypertensive efficacy of fixed combinations of irbesartan/hydrochlorothiazide and losartan/hydrochlorothiazide in patients with mild-to-moderate hypertension

This study examined whether the greater anti-hypertensive efficacy of irbesartan monotherapy over losartan monotherapy extends to the respective fixed-dose combinations with hydrochlorothiazide (HCTZ) in patients with mild-to-moderate hypertension. Patients were treated with either irbesartan 150 mg/HCTZ 12.5 mg or losartan 50 mg/HCTZ 12.5 mg over a 4-week period. Twenty-four hour daytime and night-time mean blood pressure (BP), BP load and duration of action were assessed using ambulatory BP monitoring. Both treatment regimens significantly reduced BP from baseline for all efficacy variables assessed. A significant difference was noted in adjusted mean changes from baseline in 24-h ambulatory diastolic BP with irbesartan/HCTZ versus losartan/HCTZ. Reduction in diastolic load was significantly greater with irbesartan/HCTZ than with losartan/HCTZ as was mean ambulatory systolic BP during the last 4 h of the dosing interval. Both regimens were well tolerated, with no significant differences in terms of adverse event profile observed. Irbesartan 150 mg/HCTZ 12.5 mg resulted in greater reductions in ambulatory BP than losartan 50 mg/HCTZ 12.5 mg.

Superiority of combination of thiazide with angiotensin-converting enzyme inhibitor or AT1-receptor blocker over thiazide alone on renoprotection inl-NAME/SHR

The renal and glomerular dynamic effects of combining thiazide and angiotensin antagonists have not been reported. The present study was designed to examine the effects of hydrochlorothiazide (HCTZ) alone or in combination with an angiotensin-converting enzyme inhibitor or ANG II type 1-receptor blocker on renal hemodynamics, glomerular dynamics, renal function, and renal histopathology in the Nω-nitro-l-arginine methyl ester-treated spontaneously hypertensive rat (l-NAME/SHR) model. HCTZ (80 mg·kg−1·day−1) alone or in combination with enalapril (30 mg·kg−1·day−1) or losartan (30 mg·kg−1·day−1) or enalapril (15 mg·kg−1·day−1) plus losartan (15 mg·kg−1·day−1) was administered to l-NAME/SHR (5.0 ± 0.10 mg·kg−1·day−1) for 3 wk. Mean arterial pressure, total peripheral resistance, renal plasma flow, glomerular filtration rate, glomerular hydrostatic pressure, afferent and efferent glomerular arteriolar resistances, single nephron plasma flow, single nephron glomerular filtration rate, serum creatinine concentration, 24-h urinary protein excretion, and glomerular and arteriolar injury scores were determined. HCTZ reduced mean arterial pressure, total peripheral resistance, glomerular hydrostatic pressure, and afferent and efferent glomerular arteriolar resistances ( P < 0.05, at least) but slightly increased renal plasma flow and single nephron plasma flow associated with reduced serum creatinine concentration, urinary protein excretion, and arteriolar injury score compared with l-NAME/SHR control. However, the combination of enalapril and/or losartan with HCTZ markedly improved each of these functions. These results demonstrated minor benefits of HCTZ monotherapy and a marked superiority of its combination with enalapril and/or losartan over HCTZ monotherapy on renoprotection in l-NAME/SHR, thereby providing strong evidence of their clinical benefits for hypertensive patients with renal functional impairment.

Efficacy and safety of combination therapy using high- or low-dose hydrochlorothiazide with valsartan or other Angiotensin-receptor blockers

Only a minority of patients treated for hypertension achieve controlled blood pressure (BP) levels. Therapy with fixed-dose combinations of an angiotensinreceptor blocker (ARB) and low-dose hydrochlorothiazide (HCTZ) is commonly prescribed but not always sufficient to achieve the target BP. The efficacy and safety of the fixed-dose combination of valsartan 160 mg and HCTZ 25 mg was evaluated in patients in whom BP had not been controlled with a fixed-dose combination of another ARB and low-dose HCTZ (12.5 mg) in a multicenter trial. After a wash-out period for antihypertensive drugs, patients with a mean sitting diastolic BP (DBP) at trough (3)100 mm Hg but <110 mm Hg were treated with candesartan cilexetil 16 mg plus HCTZ 12.5 mg or telmisartan 80 mg plus HCTZ 12.5 mg for 4 weeks (phase 1). Patients whose BP was still uncontrolled (DBP (3)90 mm Hg) after 4 weeks of therapy were then given valsartan 160 mg plus HCTZ 25 mg for an additional 4 weeks (phase 2). The primary efficacy parameter was the reduction in DBP between week 4 and week 8 in the intention-to-treat (ITT) population. BP reduction during phase 1 was -14.3+/-11.3/-7.5+/-3.9 mm Hg. DBP was controlled in 26% of the patients after phase 1. In patients treated with valsartan 160 mg plus HCTZ 25 mg during phase 2, DBP decreased by an additional 10.3+/-6.5 mm Hg and the mean sitting systolic BP (SBP) by an additional 11.0+/-11.7 mm Hg. The additional decrease was significant (P<.0001) for both parameters and independent of the fixed-dose combination used during phase 1. Among patients whose BP remained uncontrolled during phase 1, 74% achieved a controlled DBP after phase 2. The incidence of adverse events during both phases was comparably low and the results of laboratory tests were unremarkable. Treatment with valsartan 160 mg/HCTZ 25 mg offered a substantial benefit for patients with hypertension not controlled with the combination of candesartan cilexetil 16 mg or telmisartan 80 mg and low dose HCTZ, while maintaining a comparable safety and tolerability profile.

Comparison of antihypertensive effects of an angiotensin-converting enzyme inhibitor, a calcium antagonist and a diuretic in patients with hypertension not controlled by angiotensin receptor blocker monotherapy

OBJECTIVE

To compare the additional antihypertensive effects of an angiotensin-converting enzyme inhibitor (ACEI), a dihydropyridine calcium antagonist and a diuretic in patients whose hypertension is not controlled by full-dose angiotensin receptor blocker (ARB) monotherapy.

DESIGN AND METHODS

Individuals with an ambulatory blood pressure (ABP) that was not controlled by valsartan 160 mg once daily were allocated randomly to two groups: those in group A (n = 35) were assigned randomly to treatment with benazepril 20 mg once daily or chlorthalidone 12.5 mg once daily, whereas patients in group B (n = 29) were assigned randomly to benazepril 20 mg once daily or amlodipine 5 mg once daily. All individuals continued to receive background valsartan 160 mg once daily. After 5 weeks, patients crossed over to the alternative valsartan-based combination treatment of each group for a second 5-week period. Twenty-four-hour ABP monitoring was performed before the random allocation to groups and at the end of each randomized combination pharmacotherapy period.

RESULTS

Sixty-four individuals completed the study: 32 men and 32 women (mean +/- SD age 48.2 +/- 7.9 years, average 24-h ABP on valsartan monotherapy 143.4 +/- 12.6/87.7 +/- 7.8 mmHg). Significant additional antihypertensive effects on the average 24-h ABP were obtained with benazepril (8.6 +/- 8.8/6.3 +/- 6.7 mmHg), amlodipine (15.2 +/- 12.9/9.9 +/- 6.8 mmHg) and chlorthalidone (13.5 +/- 11.6/9.5 +/- 7.7 mmHg) (P < 0.001 for all additional antihypertensive effects). The additional effects of amlodipine and chlorthalidone added to valsartan were approximately 6/3.5 mmHg (P < 0.05) greater than that of benazepril.

CONCLUSIONS

In patients in whom hypertension was not controlled by full-dose ARB monotherapy, a diuretic, a calcium antagonist or an ACE inhibitor provided significant additional antihypertensive effect. The antihypertensive effects of the ARB-diuretic and the ARB-calcium antagonist combinations were superior to that of the ARB-ACE inhibitor combination.

Comparison of valsartan 160 mg with lisinopril 20 mg, given as monotherapy or in combination with a diuretic, for the treatment of hypertension: the Blood Pressure Reduction and Tolerability of Valsartan in Comparison with Lisinopril (PREVAIL) study

BACKGROUND

The goal of antihypertensive therapy is to provide good blood pressure (BP) control without eliciting adverse effects.

OBJECTIVE

This study compared the risk-benefit profile of the angiotensin II receptor blocker valsartan with that of the angiotensin-converting enzyme inhibitor lisinopril in patients with mild to severe hypertension. The primary objective was to show that the equipotent BP-lowering effect of the valsartan-based treatment is accompanied by a better tolerability profile.

METHODS

This 16-week, randomized, double-blind, parallel-group study was conducted at 88 outpatient centers across Italy. After a 2-week placebo run-in period, patients aged > or = 18 years with mild to severe hypertension (systolic BP [SBP], 160-220 mm Hg; diastolic BP [DBP], 95-110 mm Hg) were eligible. Patients were randomized to receive once-daily, oral, self-administered treatment with valsartan 160-mg capsules or lisinopril 20-mg capsules under double-blind conditions for 4 weeks. Responders continued monotherapy, whereas nonresponders had hydrochlorothiazide 12.5 mg added for the final 12 weeks of the study. The 2 primary variables used to assess the equivalence of therapeutic efficacy of the 2 regimens were sitting SBP and sitting DBP, which were measured at weeks 0 (baseline), 4, 8, and 16. The rate of drug-related adverse events (AEs) was used to assess whether 1 treatment had a better tolerability profile than the other. Tolerability was assessed by collecting information about AEs by means of questioning the patient or physical examination at each visit.

RESULTS

A total of 1213 patients were enrolled (635 men, 578 women; mean [SD] age, 54.5 [10.1] years [range, 28-78 years]). The study was completed by 1100 patients (553 receiving valsartan and 547 receiving lisinopril). Fifty-one patients (8.4%) treated with valsartan and 62 (10.2%) [corrected] treated with lisinopril withdrew, mainly because of AEs (9 [1.5%] and 23 patients [3.8%], respectively). The valsartan- and lisinopril-based treatments were similarly effective in reducing sitting BP, with mean SBP/DBP reductions of 31.2/15.9 mm Hg and 31.4/15.9 mm Hg, respectively. At the end of the study, BP was controlled in 82.6% [corrected] of the patients receiving valsartan and 81.6% of those receiving lisinopril. AEs were experienced by 5.1% of the patients treated with valsartan and 10.7% of those treated with lisinopril (P=.0001), with dry cough observed in 1.0% and 7.2% of patients, respectively (P<0.001).

CONCLUSIONS

Valsartan and lisinopril were both highly effective in controlling BP in these patients with mild to severe hypertension, but valsartan was associated with a significantly reduced risk for AEs, especially cough.

Haemodynamic effects of dual blockade of the renin-angiotensin system in spontaneously hypertensive rats: influence of salt

OBJECTIVE

To elucidate the mechanisms responsible for the adverse renal effects induced by dual blockade of the renin-angiotensin system (RAS) and the role of salt therein.

METHODS

The effects of enalapril, losartan and their combination on blood pressure, renal haemodynamics, renal function and RAS were investigated over a wide range of doses in spontaneously hypertensive rats fed either a low-sodium or a high-sodium diet.

RESULTS

In rats fed the low-sodium diet, the losartan-enalapril combination induced the same dose-dependent haemodynamic and hormonal changes as did three- to 10-fold greater doses of enalapril or losartan alone. When a strong decrease (> 50%) in blood pressure was achieved (with 10 mg/kg enalapril plus 10 mg/kg losartan, 100 mg/kg enalapril or 100 mg/kg losartan), a massive renal vasoplegia occurred and renal insufficiency developed. In addition, because of the huge release of renin, angiotensinogen concentrations were reduced, leading to a decrease in intrarenal angiotensins. In rats fed the high-sodium diet, those treated with the enalapril 30 mg/kg plus losartan 30 mg/kg combination, despite complete functional RAS blockade, exhibited smaller decreases in blood pressure and renal resistance, lesser release of renin and angiotensinogen consumption, and a normal renal function. These effects were similar to those produced by 100 mg/kg of enalapril or losartan in rats fed the high-salt diet, or by 10 mg/kg of enalapril or of losartan in rats fed the low-salt diet.

CONCLUSIONS

Dual RAS blockade could be either beneficial, when sodium intake is unrestricted, or dangerous, when sodium intake is restricted.

Clinical Experience With Angiotensin Receptor Blockers With Particular Reference to Valsartan

The angiotensin II receptor blockers (ARBs), are highly selective for the AT1 subtype and will block the effects of angiotensin II on peripheral vessels. Several short- and long-term studies have shown these agents to be safe and effective antihypertensive drugs. Since monotherapy of hypertension may be ineffective in lowering the blood pressure to goal, the use of an ARB, especially in combination with a diuretic or another medication, is frequently necessary to bring the blood pressure <140/90 mm Hg (<130/80 mm Hg among people with diabetes mellitus or chronic renal failure), according to JNC 7 guidelines. Besides hypertension, the ARBs have been shown to reduce left ventricular hypertrophy in hypertensive patients. Other benefits of these medications, as well as the angiotensin I converting enzyme inhibitors (ACEIs), include a decrease in cardiovascular morbidity and mortality in patients with heart failure, or hypertensive diabetic nephropathy with proteinuria. Some of the beneficial effects noted with the ACEIs and ARBs (congestive heart failure, left ventricular hypertrophy), have also been demonstrated with the use of b blockers alone and in combination with a diuretic. These drugs, i.e., b blockers, ARBs, and ACEIs, seem to exert their beneficial action through the blockade of the renin-angiotensin-aldosterone system. The role of this system in cardiovascular remodeling and its blockade will be discussed in this review, which will specifically summarize data with the ARB, valsartan.

A randomized, double-blind, active-controlled, parallel-group comparison of valsartan and amlodipine in the treatment of isolated systolic hypertension in elderly patients: the Val-Syst study

BACKGROUND

Some antihypertensive therapies are limited by dose-dependent adverse effects (AEs). The angiotensin II receptor blocker valsartan has been shown to reduce blood pressure (BP) in a dose-related manner with minimal dose-limiting AEs. Amlodipine besylate is a potent dihydropyridine calcium channel blocker also with dose-related antihypertensive efficacy, but with possible dose-limiting AEs, particularly peripheral edema.

OBJECTIVES

This study compared the risk/benefit profiles of valsartan and amlodipine in elderly patients who have isolated systolic hypertension (ISH).

METHODS

This 24-week, randomized, double-blind, active-controlled, titration-to-effect, parallel-group study was conducted at 35 outpatient centers in Italy. Elderly (aged 60-80 years) patients with ISH received oral treatment with valsartan 80-mg capsules or amlodipine 5-mg capsules once daily. After 8 weeks of treatment, the dose of the patients with poorly controlled systolic BP (SBP) was titrated to 160 mg (valsartan) or 10 mg (amlodipine) once daily. At week 16, if trough SBP was still not adequately controlled, a low-dose diuretic (hydrochlorothiazide [HCTZ] 12.5 mg) was added to the treatment regimen for an additional 8 weeks. Tolerability was assessed at all study visits using physical examination and patient interview.

RESULTS

Of 421 randomized patients (231 women, 190 men; mean [SD] age, 69 [6] years), 208 were included in the valsartan group, and 213 in the amlodipine group. The efficacy of valsartan-based treatment. in reducing SBP was similar to that of amlodipine-based treatment. With doubled doses, efficacy (change in SBP) increased significantly from baseline (both P < 0.01). The frequency of AEs doubled with amlodipine 10 mg but was not clinically relevant with valsartan 160 mg. Overall, AEs were observed in 31.9% of those receiving amlodipine versus 20.2% of the patients receiving valsartan (P < 0.003), with peripheral edema rates of 26.8% and 4.8%, respectively (P < 0.001).

CONCLUSIONS

In this study population of elderly patients with ISH, valsartan-given alone or in combination with HCTZ 12.5 mg-showed similar efficacy but better tolerability than amlodipine-based treatment.

Implications of oxidative stress and homocysteine in the pathophysiology of essential hypertension

The present review examines the clinical and experimental data to support the view that homocysteine and oxidative stress, two alternative risk factors of vascular disease, may play a role in the pathogenesis of primary or essential hypertension. Although the precise mechanism of this disease has not been elucidated, it may be related to impairment of vascular endothelial and smooth muscle cell function. Thus, the occurrence of endothelial dysfunction could contribute to alterations of the endothelium-dependent vasomotor regulation. Hyperhomocysteinemia limits the bioavailability of nitric oxide, increases oxidative stress, stimulates the proliferation of vascular smooth muscle cells, and alters the elastic properties of the vascular wall. The link between oxidative stress and hyperhomocysteinemia is also biologically plausible, because homocysteine promotes oxidant injury to the endothelium. Cumulated evidence suggests that the diminution of oxidative stress with antioxidants or the correction of hyperhomocysteinemia with vitamins-B plus folic acid, could be useful as an adjuvant therapy for essential hypertension. Further studies involving long-term trials could help to assess the tolerability and efficacy of the use of these therapeutic agents.

Efficacy and Safety of Valsartan 160mg/Hydrochlorothiazide 25mg Combination in Patients with Hypertension not Adequately Controlled by Valsartan 160mg/Hydrochlorothiazide 12.5mg

BACKGROUND AND OBJECTIVE

Hypertension guidelines emphasise the need to treat high blood pressure (BP) early and aggressively, giving fixed-dose combinations special consideration. Hitherto, it has not been assessed in a sequential way whether hypertensive patients with inadequately controlled hypertension with an angiotensin II receptor antagonist/hydrochlorothiazide combination benefit from a dose increase of the diuretic. We investigated the efficacy and safety of valsartan 160mg/hydrochlorothiazide 25mg combination in patients with hypertension that was not adequately controlled by valsartan 160mg/hydrochlorothiazide 12.5mg.

PATIENTS AND METHODS

This was a multicentre, single-group, prospective study of 646 patients with moderate hypertension (diastolic BP [DBP] 100-109mm Hg). Patients were treated for 4 weeks with valsartan 160mg/hydrochlorothiazide 12.5mg (phase 1: weeks 1-4). In case of non-response (DBP >/=90mm Hg; n = 224) patients were treated for a further 4 weeks with valsartan 160mg/hydrochlorothiazide 25mg (phase 2: weeks 5-8). The primary efficacy measure was a change in mean sitting trough DBP at study end compared with the beginning of phase 2 in the intention-to-treat (ITT) population (n = 221).

RESULTS

Mean age of patients at entry was 58.6 years; 53.7% of patients were female. In phase 1, systolic BP (SBP)/DBP decreased from a baseline value of 161.9/103.3mm Hg by -16.1/-12.4mm Hg (normalisation rate 38.3%, response rate 64.5%). In phase 2, in the ITT non-responder population the additional SBP/DBP decrease was -8.4/-8.3mm Hg. Overall, the normalisation rate in all patients was 55.4% and the responder rate was 76.3%.Tolerability of both the valsartan 160mg/hydrochlorothiazide 12.5mg and the valsartan 160mg/hydrochlorothiazide 25mg combinations was very good, and the switch to the higher dose did not result in an increase in adverse events (AEs) or laboratory abnormalities. Only 16.6% of patients in phase 1 and 10.3% of patients in phase 2 experienced one or more AEs.

CONCLUSION

In patients with moderate hypertension, first-line therapy with the fixed-dose valsartan/hydrochlorothiazide combination leads to high normalisation and response rates. Patients with hypertension not controlled by valsartan 160mg/ hydrochlorothiazide 12.5mg clearly benefit from dose titration to valsartan 160mg/hydrochlorothiazide 25mg with a clinically relevant additional BP response and have excellent tolerability.

Cardiovascular pharmacogenetics in the SNP era

In the past pharmacological agents have contributed to a significant reduction in age-adjusted incidence of cardiovascular events. However, not all patients treated with these agents respond favorably, and some individuals may develop side-effects. With aging of the population and the growing prevalence of cardiovascular risk factors worldwide, it is expected that the demand for cardiovascular drugs will increase in the future. Accordingly, there is a growing need to identify the 'good' responders as well as the persons at risk for developing adverse events. Evidence is accumulating to indicate that responses to drugs are at least partly under genetic control. As such, pharmacogenetics - the study of variability in drug responses attributed to hereditary factors in different populations - may significantly assist in providing answers toward meeting this challenge. Pharmacogenetics mostly relies on associations between a specific genetic marker like single nucleotide polymorphisms (SNPs), either alone or arranged in a specific linear order on a certain chromosomal region (haplotypes), and a particular response to drugs. Numerous associations have been reported between selected genotypes and specific responses to cardiovascular drugs. Recently, for instance, associations have been reported between specific alleles of the apoE gene and the lipid-lowering response to statins, or the lipid-elevating effect of isotretinoin. Thus far, these types of studies have been mostly limited to a priori selected candidate genes due to restricted genotyping and analytical capacities. Thanks to the large number of SNPs now available in the public domain through the SNP Consortium and the newly developed technologies (high throughput genotyping, bioinformatics software), it is now possible to interrogate more than 200,000 SNPs distributed over the entire human genome. One pharmacogenetic study using this approach has been launched by GlaxoSmithKline to identify the approximately 4% of patients who are predisposed to developing a hypersensitivity reaction to abacavir, an anti-HIV agent. Data collected thus far on the HLA locus on chromosome 6 indicate that this approach is feasible. Extended linkage disequilibrium can be detected readily, even across several haplotype blocks, thus potentially reducing the number of SNPs for future whole-genome scans. Finally, a modest number of cases and controls appears to be sufficient to detect genetic associations. There is little doubt that this type of approach will have an impact on the way cardiovascular drugs will be developed and prescribed in the future.

Very-low-dose combination: a first-line choice for the treatment of hypertension?

Essential hypertension is a very heterogeneous disease and different pressor mechanisms might interact to increase blood pressure. It is therefore not surprising that antihypertensive drugs given as monotherapies normalize blood pressure in only a proportion of hypertensive patients. This is, for instance, the case for diuretics, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 (AT1) receptor antagonists administered as single agents. The rationale for combining antihypertensive agents relates in part to the concept that the blood pressure-decreasing effect may be enhanced when two classes are coadministered. Also, combination treatment serves to counteract the counter-regulatory mechanisms that are triggered whenever pharmacologic intervention is initiated and act to limit the efficacy of the antihypertensive medication. For example, the compensatory increase in renin secretion induced by sodium depletion may become the predominant factor sustaining high blood pressure. Simultaneous blockade of the renin-angiotensin system, with either an ACE inhibitor or an AT1 receptor blocker, makes this compensatory hyper-reninaemia ineffective and allows maximum benefit from sodium depletion. The increased effectiveness obtained by combining a blocker of the renin-angiotensin system with a low dose of a diuretic is not obtained at the expense of reduced tolerability compared with the individual components administered alone. Fixed very-low-dose combinations containing an ACE inhibitor or an AT1 receptor blocker and a diuretic are therefore likely to become increasingly used, not only as second-line therapy, but also as first-line treatment. This is the case, for instance, for the fixed very-low-dose combination of the ACE inhibitor perindopril (2 mg) and the diuretic indapamide (0.625 mg), as this preparation is very effective in decreasing blood pressure while maintaining a tolerability that is similar to that of placebo.

Losartan for LIFE in hypertension with left ventricular hypertrophy?

When ACE inhibitors are used to lower blood pressure to the same degree as beta-adrenoceptor antagonists or calcium channel blockers, ACE inhibitors do not seem to have additional benefits to these agents. In the Losartan Intervention for End Point Reduction in Hypertension study (LIFE), losartan was compared to atenolol in hypertensives with the additional risk factor of left ventricular hypertrophy (LVH). For similar effects on blood pressure, losartan had a greater benefit on the primary composite end point (cardiovascular mortality, stroke and myocardial infarction) than atenolol in the hypertensives with LVH, including a prespecified subgroup of patients with additional diabetes mellitus. Losartan also had a greater ability to reverse LVH than atenolol. Thus, losartan should become the standard treatment for hypertension when LVH is present.

Angiotensin AT-1 receptor antagonism: complementary or alternative to ACE inhibition in cardiovascular and renal disease?

Both angiotensin-converting enzyme (ACE) inhibitors and AT-1 receptor antagonists reduce the effects of angiotensin II, however they may have different clinical effects. This is because the ACE inhibitors, but not the AT-1 receptor antagonists, increase the levels of substance P, bradykinin and tissue plasminogen activator. The AT-1 receptor antagonists, but not the ACE inhibitors, are capable of inhibiting the effects of angiotensin II produced by enzymes other than ACE. On the basis of the present clinical trial evidence, AT-1 receptor antagonists, rather than the ACE inhibitors, should be used to treat hypertension associated with left ventricular (LV) hypertrophy. Both groups of drugs are useful when hypertension is not complicated by LV hypertrophy, and in diabetes. In the treatment of diabetes with or without hypertension, there is good clinical support for the use of either an ACE inhibitor or an AT-1 receptor antagonist. ACE inhibitors are recommended in the treatment of renal disease that is not associated with diabetes, after myocardial infarction when left ventricular dysfunction is present, and in heart failure. As the incidence of cough is much lower with the AT-1 receptor antagonists, these can be substituted for ACE inhibitors in patients with hypertension or heart failure who have persistent cough. Preliminary studies suggest that combining an AT-1 receptor antagonist with an ACE inhibitor may be more effective than an ACE inhibitor alone in the treatment of hypertension, diabetes with hypertension, renal disease without diabetes and heart failure. However, further trials are required before combination therapy can be recommended in these conditions.