Comparative vascular and renal tubular effects of angiotensin II receptor blockers combined with a thiazide diuretic in humans

Combining Neprilysin Inhibitor With AT2R Agonist Is Superior to Combination With AT1R Blocker in Providing Reno-Protection in Obese Rats

Clinical use of the combination therapy of the neprilysin inhibitor sacubitril and angiotensin II type 1 receptor blocker valsartan is known to be associated with albuminuria. Albuminuria is both a risk factor for and an indicator of kidney injury. Earlier work from our laboratory reported that the agonist of angiotensin II type 2 receptor Compound 21 (C21) prevents proteinuria, albuminuria, and is reno-protective in obese Zucker rats fed high salt diet (HSD). Thus, we hypothesized that sacubitril/C21 combination provides superior reno-protection compared to sacubitril/valsartan. Male obese Zucker rats 10–11 weeks old were treated daily with vehicle, sacubitril + C21, or sacubitril + valsartan while fed HSD for 16 days. HSD-feeding caused kidney dysfunction, evident by significant increases in urinary protein, osteopontin, and cystatin C. HSD-feeding lowered plasma cystatin C and creatinine concentrations suggestive of hyperfiltration, which was not affected by either treatment. Unlike sacubitril/valsartan, sacubitril/C21 treatment significantly decreases proteinuria, albuminuria, the expression of nephrin, and kidney weight, independent of hyperfiltration, compared with HSD alone. Moreover, sacubitril/valsartan therapy increased plasma renin and did not prevent HSD-induced increases in renal angiotensin II, while sacubitril/C21 completely prevented these changes. Together, this study suggests that sacubitril/C21 afforded superior reno-protection compared to sacubitril/valsartan therapy in high salt-fed obese Zucker rats.

An association of losartan-hydrochlorothiazide, but not losartan-furosemide, completely arrests progressive injury in the remnant kidney

We have previously shown that an association of losartan and hydrochlorothiazide, initiated 1 mo after 5/6 nephrectomy (Nx), reversed hypertension and albuminuria and promoted lasting renoprotection. In this new study, we investigated whether equal or even better protection could be obtained by combining losartan and furosemide. Nx was performed in 58 Munich-Wistar rats. One month later, tail-cuff pressure and albuminuria were markedly elevated. At this time, Nx rats were distributed among the following four groups: untreated Nx rats, Nx rats that received losartan, Nx rats that received losartan + hydrochlorothiazide, and Nx rats that received losartan + furosemide. Seven months later, Nx rats exhibited high mortality, severe hypertension, albuminuria, glomerulosclerosis, and interstitial fibrosis. Losartan treatment limited mortality and attenuated the renal and hemodynamic abnormalities associated with Nx. As previously shown, the losartan + hydrochlorothiazide association normalized tail-cuff pressure and albumin, prevented renal injury, and reduced mortality to zero. The losartan + furosemide treatment failed to reduce tail-cuff pressure or albumin to normal and prevented renal injury less efficiently than the losartan and hydrochlorothiazide regimen. The reasons for the differing efficacies of the losartan + furosemide and losartan + hydrochlorothiazide schemes are unclear and may include beneficial nondiuretic actions of thiazides, such as vasorelaxation and antiproliferative activity. These results refute the established concept that thiazides and thiazide-like diuretics are ineffective at advanced chronic kidney disease stages. Rather, they suggest that, in view of their renoprotective action, these compounds may even be preferable to loop diuretics in the management of hypertension in advanced chronic kidney disease.

Rationale for triple fixed-dose combination therapy with an angiotensin II receptor blocker, a calcium channel blocker, and a thiazide diuretic

Hypertension is a growing global health problem, and is predicted to affect 1.56 billion people by 2025. Treatment remains suboptimal, with control of blood pressure achieved in only 20%-35% of patients, and the majority requiring two or more antihypertensive drugs to achieve recommended blood pressure goals. To improve blood pressure control, the European hypertension guidelines recommend that angiotensin II receptor blockers (ARBs) or angiotensin-converting enzyme inhibitors (ACEIs) are combined with calcium channel blockers (CCBs) and/or thiazide diuretics. The rationale for this strategy is based, in part, on their different effects on the renin-angiotensin system, which improves antihypertensive efficacy. Data from a large number of trials support the efficacy of ACEIs or ARBs in combination with CCBs and/or hydrochlorothiazide (HCTZ). Combining two different classes of antihypertensive drugs has an additive effect on lowering of blood pressure, and does not increase adverse events, with the ARBs showing a tolerability advantage over the ACEIs. Among the different ARBs, olmesartan medoxomil is available as a dual fixed-dose combination with either amlodipine or HCTZ, and the increased blood pressure-lowering efficacy of these two combinations is proven. Triple therapy is required in 15%-20% of treated uncontrolled hypertensive patients, with a renin-angiotensin system blocker, CCB, and thiazide diuretic considered to be a rational combination according to the European guidelines. Olmesartan, amlodipine, and HCTZ are available as a triple fixed-dose combination, and significant blood pressure reductions have been observed with this regimen compared with the possible dual combinations. The availability of these fixed-dose combinations should lead to improvement in blood pressure control and aid compliance with long-term therapy, optimizing the management of this chronic condition.

Olmesartan medoxomil combined with hydrochlorothiazide improves 24-hour blood pressure control in moderate-to-severe hypertension

BACKGROUND

Twenty-four-hour ambulatory blood pressure monitoring (ABPM) has been shown to be more reliable than conventional measurements for hypertension assessment and the associated increased risk of cardiovascular events. Olmesartan/hydrochlorothiazide combination therapy has demonstrated increased blood pressure lowering over 24 hours compared with the component monotherapies. This prespecified pooled analysis of data from two trials investigated the effects of olmesartan/hydrochlorothiazide combination therapy and olmesartan monotherapy on 24-hour blood pressure control in patients with moderate-to-severe hypertension.

METHODS

After 8 weeks' open-label olmesartan 40 mg monotherapy, uncontrolled patients (mean trough seated blood pressure 90-115/140-180 mmHg and 24-hour mean ambulatory diastolic blood pressure ≥80 mmHg with ≥30% of daytime ambulatory diastolic blood pressure readings >85 mmHg) were randomised to 8 weeks' double-blind treatment with olmesartan 40 mg or olmesartan/hydrochlorothiazide 20/12.5, 40/12.5 or 40/25 mg (Study 1) or olmesartan/hydrochlorothiazide 20/25 or 40/25 mg (Study 2). This prespecified analysis of ambulatory blood pressure was performed on patients from the full analysis set of pooled studies 1 and 2, restricted to patients who provided at least one valid ABPM measurement at baseline.

RESULTS

After 8 weeks' double-blind treatment, reductions in 24-hour, daytime and night-time blood pressure from baseline were observed for all treatment groups. These reductions were dose-dependent, with olmesartan/hydrochlorothiazide 40/25 mg demonstrating the greatest reductions in 24-hour blood pressure from baseline to Week 16 versus olmesartan monotherapy: -14.0/-8.8 vs -2.7/-2.0 mmHg, respectively; p < 0.0001.

CONCLUSIONS

Adding hydrochlorothiazide to olmesartan provides more effective 24-hour blood pressure control versus olmesartan monotherapy in patients with moderate-to-severe hypertension.

CLINICAL TRIAL REGISTRATION

Study 1: EudraCT Number: 2006-003876-37; ClinicalTrials.gov identifier: NCT00430508; Study 2: EudraCT Number: 2006-003876-28; ClinicalTrials.gov identifier: NCT00430950.

Angiotensin receptor blockers shift the circadian rhythm of blood pressure by suppressing tubular sodium reabsorption

Recently, we found that an angiotensin II receptor blocker (ARB) restored the circadian rhythm of the blood pressure (BP) from a nondipper to a dipper pattern, similar to that achieved with sodium intake restriction and diuretics (Fukuda M, Yamanaka T, Mizuno M, Motokawa M, Shirasawa Y, Miyagi S, Nishio T, Yoshida A, Kimura G. J Hypertens 26: 583-588, 2008). ARB enhanced natriuresis during the day, while BP was markedly lower during the night, resulting in the dipper pattern. In the present study, we examined whether the suppression of tubular sodium reabsorption, similar to the action of diuretics, was the mechanism by which ARB normalized the circadian BP rhythm. BP and glomerulotubular balance were compared in 41 patients with chronic kidney disease before and during ARB treatment with olmesartan once a day in the morning for 8 wk. ARB increased natriuresis (sodium excretion rate; U(Na)V) during the day (4.5 ± 2.2 to 5.5 ± 2.1 mmol/h, P = 0.002), while it had no effect during the night (4.3 ± 2.0 to 3.8 ± 1.6 mmol/h, P = 0.1). The night/day ratios of both BP and U(Na)V were decreased. The decrease in the night/day ratio of BP correlated with the increase in the daytime U(Na)V (r = 0.42, P = 0.006). Throughout the whole day, the glomerular filtration rate (P = 0.0006) and tubular sodium reabsorption (P = 0.0005) were both reduced significantly by ARB, although U(Na)V remained constant (107 ± 45 vs. 118 ± 36 mmol/day, P = 0.07). These findings indicate that the suppression of tubular sodium reabsorption, showing a resemblance to the action of diuretics, is the primary mechanism by which ARB can shift the circadian BP rhythm into a dipper pattern.

Angiotensin II receptor blocker combinations: from guidelines to clinical practice

European guidelines recommend a combination of at least two antihypertensive drugs to achieve blood pressure (BP) goals in the majority of patients. In addition, they encourage simplification of treatment regimens using single-pill, fixed-dose combinations (FDCs) to aid compliance. Of the preferred combinations, those based on angiotensin II receptor blockers (ARBs) may be more desirable than those based on angiotensin-converting enzyme inhibitors, because of equivalent efficacy and superior tolerability. Significantly better BP reductions and control rates have been observed with the dual combinations of ARBs with amlodipine or hydrochlorothiazide (HCZT) compared with component monotherapies. Furthermore, in the 15-20% of patients who require triple combination therapy to achieve BP goals, fixed-dose triple combinations with an ARB, calcium-channel blocker and diuretic, which have recently become available, provide significantly better BP reductions and control compared with dual combinations. Within the ARB class, olmesartan stands out as being one that has been recently investigated in a considerable number of studies that are relevant to the modern concept of FDC therapy in terms of both dual and triple combination therapy. The availability of such single-pill FDCs has the potential to deliver strong antihypertensive efficacy with good tolerability and improved compliance.

Renal perfusion evaluation with contrast-enhanced ultrasonography

BACKGROUND

Contrast-enhanced ultrasonography (CEUS) is a novel imaging technique that is safe and applicable on the bedside. Recent developments seem to enable CEUS to quantify organ perfusion. We performed an exploratory study to determine the ability of CEUS to detect changes in renal perfusion and to correlate them with effective renal plasma flow.

METHODS

CEUS with destruction-refilling sequences was studied in 10 healthy subjects, at baseline and during infusion of angiotensin II (AngII) at low (1 ng/kg/min) and high dose (3 ng/kg/min) and 1 h after oral captopril (50 mg). Perfusion index (PI) was obtained and compared with the effective renal plasma flow (ERPF) obtained by parallel para-aminohippurate (PAH) clearance.

RESULTS

Median PI decreased from 188.6 (baseline) to 100.4 with low-dose AngII (-47%; P < 0.02) and to 66.1 with high-dose AngII (-65%; P < 0.01) but increased to 254.7 with captopril (+35%; P > 0.2). These changes parallelled those observed with ERPF, which changed from a median of 672.1 mL/min (baseline) to 572.3 (low-dose AngII, -15%, P < 0.05) and to 427.2 (high-dose AngII, -36%, P < 0.001) and finally 697.1 (captopril, +4%, P < 0.02).

CONCLUSIONS

This study demonstrates that CEUS is able to detect changes in human renal cortical microcirculation as induced by AngII infusion and/or captopril administration. The changes in perfusion indices parallel those in ERPF as obtained by PAH clearance.

Long-term use and tolerability of irbesartan for control of hypertension

In this review, we discuss the pharmacological and clinical properties of irbesartan, a noncompetitive angiotensin II receptor type 1 antagonist, successfully used for more than a decade in the treatment of essential hypertension. Irbesartan exerts its antihypertensive effect through an inhibitory effect on the pressure response to angiotensin II. Irbesartan 150-300 mg once daily confers a lasting effect over 24 hours, and its antihypertensive efficacy is further enhanced by the coadministration of hydrochlorothiazide. Additionally and partially beyond its blood pressure-lowering effect, irbesartan reduces left ventricular hypertrophy, favors right atrial remodeling in atrial fibrillation, and increases the likelihood of maintenance of sinus rhythm after cardioversion in atrial fibrillation. In addition, the renoprotective effects of irbesartan are well documented in the early and later stages of renal disease in type 2 diabetics. Furthermore, both the therapeutic effectiveness and the placebo-like side effect profile contribute to a high adherence rate to the drug. Currently, irbesartan in monotherapy or combination therapy with hydrochlorothiazide represent a rationale pharmacologic approach for arterial hypertension and early-stage and late-stage diabetic nephropathy in hypertensive type II diabetics.

Olmesartan/amlodipine: a review of its use in the management of hypertension

Combination therapy is an effective strategy to increase antihypertensive efficacy in those patients with poor blood pressure (BP) control. In order to achieve BP targets, at least 75% of patients may require combination therapy, and European guidelines advocate this approach, particularly in those patients with a high cardiovascular risk. Evidence from large, randomized controlled trials, and the European hypertension treatment guidelines is supportive of the use of an angiotensin receptor blocker (ARB) with a calcium channel blocker (CCB). Fixed-dose combination formulations of olmesartan medoxomil, an ARB, and the CCB amlodipine are approved in several European countries for patients with essential hypertension. The olmesartan/amlodipine combination has demonstrated greater efficacy than its component monotherapies in reducing BP in patients with mild-to-severe hypertension. Significantly greater reductions in seated diastolic BP were observed between baseline and after eight weeks of treatment with olmesartan/amlodipine, compared with equivalent doses of olmesartan or amolodipine monotherapy (P < 0.001), in the factorial Combination of Olmesartan Medoxomil and Amlodipine Besylate in Controlling High Blood Pressure (COACH) trial. About 85% of the maximal BP reductions after the 8-week treatment period were already observed after two weeks. Uptitration as necessary, with or without hydrochlorothiazide, allowed the majority of patients to achieve BP control in a 44-week open-label extension treatment period to the COACH trial. The use of olmesartan/amlodipine allowed up to 54% of patients, with previously inadequate responses to amlodipine or olmesartan monotherapy, to achieve their BP goals. Data from post-registration studies using tight BP control and forced titration regimens have further demonstrated the high efficacy of olmesartan/amlodipine in achieving BP goal rates. Moreover, consistent reductions in BP were observed over the 24-hour dosing interval using ambulatory measurements. Olmesartan/amlodipine was generally well tolerated over the short- and long-term, with a lower frequency of peripheral edema with olmesartan/amlodipine 40/10 mg than with amlodipine 10 mg monotherapy.

Pharmacokinetic evaluation of losartan

INTRODUCTION

Blockade of the renin-angiotensin system is one of the major therapeutic strategies in the management of patients with essential hypertension, congestive heart failure and diabetic as well as non-diabetic renal diseases. As the first angiotensin II receptor blocker (ARB) on the market, losartan belongs to the most frequently prescribed ARB.

AREA COVERED

The present review examines the pharmacokinetics of losartan with a special discussion on the dose of losartan that should be used in clinical practice to obtain the maximal benefits of the drug. Readers are provided with arguments suggesting that the dose of 50 mg losartan is probably too low and that losartan should preferably be prescribed at the dose of 100 mg/day or higher.

EXPERT OPINION

Losartan is an effective antagonist of angiotensin II AT(1) receptors which has been shown to provide important clinical benefits in patients with hypertension, congestive heart failure and renal diseases. Losartan should be prescribed at the dose of 100 mg/day and the use of higher doses should be reconsidered in future studies to improve its clinical efficacy.