Practical considerations of the pharmacology of angiotensin receptor blockers

Drug in Adhesive Transdermal Formulation of Valsartan and Nifedipine: Pharmacokinetics and Pharmacodynamics in Rats

Background:

The increasing complications associated with hypertension often require a combination of two or more drugs acting through different routes to counter the elevated blood pressure.

Objective:

The present investigation envisaged at preparing and evaluating a transdermal formulation containing gelled microemulsion drug in adhesive (DIA) patch for simultaneous systemic delivery of valsartan and nifedipine aimed at effective management of hypertension.

Methods:

An optimized microemulsion was prepared by using Captex® 500 (7.34% w/w), Capmul® MCM (4.24% w/w), Acrysol EL 135 (24.43% w/w), Transcutol P® (5% w/w) and water (58.9% w/w). Gelling was contributed by polyvinylpyrrolidone K 90F and polyethyleneimine where the latter also conferred skin adhesion properties to the patch. DIA patches were evaluated for in vitro drug release as well as in vivo pharmacokinetics and pharmacodynamics in rats.

Results:

In vitro permeation of nifedipine or valsartan from the selected DIA patch was 10.67-fold and 1.25-fold higher as compared to their aqueous dispersions. The relative bioavailability of nifedipine was 1.34 and that of valsartan was 2.18 from this DIA patch with respect to the oral administration of their aqueous suspension.

Conclusion:

Transdermal delivery of either drug alone was not effective in reducing methyl prednisolone acetate-induced hypertension, whereas, simultaneous transdermal delivery of both drugs from DIA patch effectively maintained systolic blood pressure at a normal level in these rats for 20 h.

Treatment of Life-Threatening ACE-Inhibitor-Induced Angioedema

Incidence of angioedema associated with angiotensin-converting enzyme inhibitors (ACE-I) has been estimated at 0.1%-2.2% of patients receiving treatment. Despite the potential severity of this disease state, standardized treatment is lacking. Traditional pharmacotherapy options include medications that target inflammatory mediators and the angiotensin pathway. However, because ACE-I-induced angioedema is caused by accumulation of bradykinin, these medications fail to target the underlying pathophysiology. Recently, novel therapies that target the kallikrein-bradykinin pathway have been studied. These include icatibant, ecallantide, C1 esterase inhibitors, and fresh-frozen plasma. Recent randomized controlled trials exhibit contradictory results with the use of icatibant. This is a focused review on traditional and novel treatment strategies for ACE-I-induced angioedema.

The effect of angiotensin II on blood pressure in patients with circulatory shock: a structured review of the literature

BACKGROUND

Circulatory shock is a common syndrome with a high mortality and limited therapeutic options. Despite its discovery and use in clinical and experimental settings more than a half-century ago, angiotensin II (Ang II) has only been recently evaluated as a vasopressor in distributive shock. We examined existing literature for associations between Ang II and the resolution of circulatory shock.

METHODS

We searched PubMed, MEDLINE, Ovid, and Embase to identify all English literature accounts of intravenous Ang II in humans for the treatment of shock (systolic blood pressure [SBP] ≤ 90 mmHg or a mean arterial pressure [MAP] ≤ 65 mmHg), and hand-searched the references of extracted papers for further studies meeting inclusion criteria. Of 3743 articles identified, 24 studies including 353 patients met inclusion criteria. Complete data existed for 276 patients. Extracted data included study type, publication year, demographics, type of shock, dosing of Ang II or other vasoactive medications, and changes in BP, lactate, and urine output. BP effects were grouped according to type of shock, with additional analyses completed for patients with absent blood pressure. Shock was distributive (n = 225), cardiogenic (n = 38), or from other causes (n = 90). Blood pressure as absent in 18 patients.

RESULTS

For the 276 patients with complete data, MAP rose by 23.4% from 63.3 mmHg to 78.1 mmHg in response to Ang II (dose range: 15 ng/kg/min to 60 mcg/min). SBP rose by 125.2% from 56.9 mmHg to 128.2 mmHg (dose range: 0.2 mcg/min to a 1500 mcg bolus). A total of 271 patients with complete data were determined to exhibit a BP effect which was directly associated with Ang II. Subgroups (patients with cardiogenic, septic, and other types of shock) exhibited similar increases in BP. In patients with absent BP, deemed to be cardiac arrest, return of spontaneous circulation (ROSC) was achieved, and BP increased by an average of 107.3 mmHg in 11 of 18 patients. The remaining seven patients with cardiac arrest did not respond.

CONCLUSIONS

Intravenous Ang II is associated with increased BP in patients with cardiogenic, distributive, and unclassified shock. A role may exist for Ang II in restoring circulation in cardiac arrest.

Left Ventricular Hypertrophy – the Problem and Possible Solutions

Left ventricular hypertrophy (LVH), which describes pathological changes in cardiac structure, is a powerful and reversible predictor of cardiovascular risk. There is a continuous relationship between left ventricular mass (LVM) and the likelihood of cardiovascular events, with no cut-off between the absence of such events and heightened risk. A correlation between LVH and blood pressure is well established. There is a paradox, however, that the structural changes to the heart as a result of increased workload due to high blood pressure appear to promote cardiovascular disease. This may be partially explained by the fact that ambulatory blood pressure measurements correlate more closely with LVH than resting blood pressure. Blood pressure variation throughout the day is also emerging as an important correlate of LVH, and a strong association has been identified between an early morning rise in blood pressure and increased LVM. Use of anti-hypertensive agents not only lowers blood pressure, but can also bring about LVH regression. The pathological role of angiotensin II in LVH and target-organ damage within the cardiovascular continuum suggest that agents targeting the renin – angiotensin - aldosterone system (RAAS), such as the angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, may prove particularly effective and may confer beneficial effects in addition to the lowering of blood pressure. The angiotensin II receptor blockers may be very appropriate treatment options because of their placebo-like tolerability and the possibility of more complete blockade of the RAAS. Within this class of anti-hypertensive agents, pharmacological differences may mean that some agents afford greater cardioprotection than others.

Role of chymase in the local renin-angiotensin system in keloids: inhibition of chymase may be an effective therapeutic approach to treat keloids

Background

Histologically, keloids contain excess fibroblasts and an overabundance of dermal collagen. Recently, it was reported that chymase induced a profibrotic response via transforming growth factor-β1 (TGF-β1)/Smad activation in keloid fibroblasts (KFs). However, the role of chymase in the local renin-angiotensin system (RAS) in keloids has not been elucidated. This study aims to determine whether chymase plays an important role in the local RAS in keloids.

Methods

We compared the expression and activity of chymase in keloids and normal skin tissues using Western blotting and radioimmunoassay, and studied the expression of TGF-β1, interleukin-1β, collagen I, hydroxyproline, and angiotensin II in KFs after chymase and inhibitors’ treatment.

Results

The results revealed an increased activity of chymase in keloid tissues, and that chymase enhanced the expression of angiotensin II, collagen I, TGF-β1, and interleukin-1β in KFs. Blockade of the chymase pathway involved in the local RAS lowered the expression of these signaling factors.

Conclusion

This research suggests that inhibition of chymase might be an effective therapeutic approach to improve the clinical treatment of keloids.

Pycnogenol® in Metabolic Syndrome and Related Disorders

The present review provides an update of the biological actions of Pycnogenol® in the treatment of metabolic syndrome and related disorders such as obesity, dyslipidaemia, diabetes and hypertension. Pycnogenol® is a French maritime pine bark extract produced from the outer bark of Pinus pinaster Ait. Subsp. atlantica. Its strong antioxidant, antiinflammatory, endothelium-dependent vasodilator activity, and also its anti-thrombotic effects make it appropriate for targeting the multifaceted pathophysiology of metabolic syndrome. Clinical studies have shown that it can reduce blood glucose levels in people with diabetes, blood pressure in mild to moderate hypertensive patients, and waist circumference, and improve lipid profile, renal and endothelial functions in metabolic syndrome. This review highlights the pathophysiology of metabolic syndrome and related clinical research findings on the safety and efficacy of Pycnogenol®. The results of clinical research studies performed with Pycnogenol® are discussed using an evidence-based, target-oriented approach following the pathophysiology of individual components as well as in metabolic syndrome overall.

Design, synthesis, pharmacological evaluation and in silico ADMET prediction of novel substituted benzimidazole derivatives as angiotensin II-AT1 receptor antagonists based on predictive 3D QSAR models

In this study we designed novel substituted benzimidazole derivatives and predicted their absorption, distribution, metabolism, excretion and toxicity (ADMET) properties, based on a predictive 3D QSAR study on 132 substituted benzimidazoles as AngII-AT1 receptor antagonists. The two best predicted compounds were synthesized and evaluated for AngII-AT1 receptor antagonism. Three different alignment tools for comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were used. The best 3D QSAR models were obtained using the rigid body (Distill) alignment method. CoMFA and CoMSIA models were found to be statistically significant with leave-one-out correlation coefficients (q(2)) of 0.630 and 0.623, respectively, cross-validated coefficients (r(2)cv) of 0.651 and 0.630, respectively, and conventional coefficients of determination (r(2)) of 0.848 and 0.843, respectively. 3D QSAR models were validated using a test set of 24 compounds, giving satisfactory predicted results (r(2)pred) of 0.727 and 0.689 for the CoMFA and CoMSIA models, respectively. We have identified some key features in substituted benzimidazole derivatives, such as lipophilicity and H-bonding at the 2- and 5-positions of the benzimidazole nucleus, respectively, for AT1 receptor antagonistic activity. We designed 20 novel substituted benzimidazole derivatives and predicted their activity. In silico ADMET properties were also predicted for these designed molecules. Finally, the compounds with best predicted activity were synthesized and evaluated for in vitro angiotensin II-AT1 receptor antagonism.

Pharmacokinetics of CS-866, a New Angiotensin II Receptor Blocker, in Healthy Subjects

CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.

Association of E/E' and NT-proBNP with renal function in patients with essential hypertension

Objectives

To evaluate the association of left ventricular (LV) diastolic function and N-terminal pro-brain natriuretic peptide (NT-proBNP) with renal function in essential hypertension.

Methods

LV diastolic function was estimated by the ratio of early diastolic velocities (E) from transmitral inflow to early diastolic velocities (E′) of tissue Doppler at mitral annulus (septal corner); NT-proBNP was measured in 207 hypertensive patients (mean age 56±14 years). The subjects were classified into 3 groups: E/E′≤10 group (n = 48), 10<E/E′≤15 group (n = 109) and E/E′>15 group (n = 50). The renal function was estimated by glomerular filtration rate (GFR) with ^99mTc-DTPA. GFR from 30 to 59 ml/min/1.73 m² was defined as Stage 3 chronic kidney disease (CKD). GFR was also estimated using the modified MDRD equation. Albuminuria was defined by urinary albumin/creatinine ratio (UACR).

Results

GFR was lower and UACR was higher in E/E′ >15 group than in 10< E/E′ ≤15 group or E/E′ ≤10 group (p<0.0001), GFR was significantly negative and UACR was positive correlated with E/E′ and NT-proBNP (p<0.0001). In multivariate stepwise linear analysis, GFR had significant correlation with age (p = 0.001), gender (p = 0.003), E/E′ (p = 0.03), lgNT-proBNP (p = 0.001) and lgUACR (p = 0.01), while eGFR had no significant correlation with E/E′ or lgNT-proBNP. Multivariate logistic regression analysis, adjusted for potential confounding factors, showed that participants in E/E′>15 group were more likely to have Stage 3 CKD compared with those in E/E′≤10 group with an adjusted odds ratio of 8.31 (p = 0.0036).

Conclusions

LV diastolic function, assessed with E/E′ and NT-proBNP is associated with renal function in essential hypertension.

The role of irbesartan in the treatment of patients with hypertension: a comprehensive and practical review

Irbesartan is an orally active angiotensin II type 1 receptor antagonist (angiotensin receptor blocker [ARB]) whose pharmacological profile differs significantly from those of many other compounds of the same class. In particular, according to its pharmacokinetic and pharmacodynamic profile, irbesartan has a high bioavailability, a long duration of action and a small potential for pharmacological interactions due to the nature of the enzymatic pathway involved in its metabolic process. Morbidity data with irbesartan have been mainly accumulated in patients with renal impairment where the drug has demonstrated the most remarkable evidence of efficacy among the ARBs class, regardless of the stage of the renal disease (from early to late) and the length of the observational period. The efficacy of irbesartan has also been demonstrated in patients with left ventricular hypertrophy and congestive heart failure. The drug is indicated for the treatment of hypertension and renal impairment in patients with type 2 diabetes mellitus (T2D) and hypertension, and its tolerability and safety profile have been extensively investigated and reported to be similar to placebo. From the pharmacoeconomic point of view, treating patients with T2D, hypertension and overt nephropathy using irbesartan was both a cost- and life-saving procedure compared with the use of amlodipine and standard antihypertensive treatment in an Italian setting. The role of irbesartan in the management of hypertension with or without T2D and renal impairment is clearly recognized by national and international guidelines and largely acknowledged by the medical community according to the efficacy of the drug in the prevention of cardiovascular risk in addition to and beyond kidney prevention.

Vascular and metabolic effects of angiotensin II receptor blockers

Angiotensin II receptor blockers (ARBs) are widely used in patients with hypertension, heart failure and type 2 diabetes mellitus (T2DM). Several large clinical trials have demonstrated that these agents are effective in reducing cardiovascular mortality and morbidity. These benefits are partly independent of the degree of blood pressure reduction and most likely related to ARBs' anti-inflammatory, metabolic and vascular effects. Clinical studies showed that the anti-inflammatory effect of ARBs could be related to the dosage and/or the length of the treatment. In large clinical trials, ARBs have inconsistently reduced the risk of new-onset T2DM. Among ARBs, only losartan significantly reduced serum uric acid levels. Moreover, it has been demonstrated that ARBs improve endothelial dysfunction in patients with hypertension and/or coronary artery disease (CAD), while all but one of the studies proved that these agents could usually, after 6-12 months of therapy, induce regression of vascular hypertrophy in hypertensive patients. These positive effects could be relevant to vascular protection and, together with the blood pressure reduction, constitute the background of the improved outcome observed in clinical studies on mortality and/or morbidity in hypertensive, high-risk and CAD patients. The clinical significance of the different potency of ARBs needs to be investigated further in specific and adequately powered trials.

Early use of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers: evidence from clinical trials

Following acute myocardial infarction, patients are at increased risk of developing heart failure, which is more prevalent in those with reduced ventricular systolic function. Activation of the renin-angiotensin-aldosterone system, which occurs early after myocardial injury, plays a central role in the pathogenesis of subsequent cardiac structural and functional abnormalities. The early use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers has been tested in several large randomized clinical trials. The results of these trials show that this treatment strategy reduces the incidence of heart failure and mortality in the postmyocardial infarction patient. The magnitude of benefit is larger in patients with high-risk features, particularly those with large infarct size and the presence of heart failure or left ventricular systolic dysfunction at the time of myocardial injury. Careful use of these agents is essential in avoiding clinically significant hypotension in the critical period.

Anti-angiotensin therapy: new perspectives

Activation of the renin-angiotensin system (RAS) plays an important role in the pathogenesis of heart failure. Thus, strategies for the treatment of heart failure have focused on agents that block the RAS. More recently, the role of angiotensin receptor blockers (ARBs) in heart failure therapy has been better defined. This article examines the rationale and role of ARBs in the treatment of patients with heart failure on the basis of evidence from clinical trials.

Chymase: a new pharmacologic target in cardiovascular disease

Chymase is a chymotrypsin-like serine protease stored as an inactive enzyme within the secretory granules of mast cells. An important action of chymase is the angiotensin-converting enzyme (ACE)-independent synthesis of angiotensin II, which occurs immediately after its release into the interstitial tissues after vascular injury. Under physiological conditions, the role of chymase is uncertain, but under pathologic situations, chymase may have an important role. Pharmacologic strategies that serve to inhibit chymase function may prove to be useful in the setting of vascular injury.

Treatments with losartan or enalapril are equally sensitive to deterioration in renal function from cyclooxygenase inhibition

BACKGROUND

The beneficial effects of angiotensin converting enzyme (ACE)-inhibitors are in part mediated through the inhibition of the degradation of the vasodilator bradykinin. The bradykinin effect is counteracted by cyclooxygenase-inhibitors. Angiotensin receptor blockers (ARBs) do not affect bradykinin.

AIMS

To test the hypothesis that renal counteraction from a cyclooxygenase-inhibitor, diclofenac, is different in subjects treated with an ACE-inhibitor, enalapril compared with an ARB, losartan.

METHODS

Twelve elderly, healthy, slightly over-hydrated subjects received diclofenac orally after pre-treatment with a diuretic, bendroflumethiazide, and enalapril or bendroflumethiazide and losartan, in a double-blind cross-over fashion, with a wash-out period of at least 1 week.

RESULTS

Diclofenac reduced GFR significantly from 81(64-98) ml/min at first observations after dose for enalapril to 29(16-42) and from 76(64-88) after losartan to 35(24-46). There was no significant difference between enalapril and losartan in GFR. Diclofenac induced decreases in urine flow, excretion rates and clearances of sodium, osmolality clearance and free water clearance, irrespective of treatment with enalapril or losartan. However, serum potassium and handling of potassium were significantly lower after losartan-treatment.

CONCLUSION

The negative renal effects of diclofenac administration in subjects with activation of the renin-angiotensin system and enalapril treatment are the same in subjects with activation of the renin-angiotensin system and losartan treatment.

Angiotensin Receptor Blockers: New Considerations in Their Mechanism of Action

Angiotensin receptor blockers are one of several drug classes that act by hindering activity of the renin-angiotensin axis. Angiotensin receptor blockers act by selectively blocking the binding of angiotensin II to the angiotensin type 1 receptor but not the angiotensin type 2 receptor. Compounds in this class are as effective as most other antihypertensive drug classes in reducing blood pressure in the patient with hypertension. The mechanism of action of an angiotensin receptor blocker, which seemed a straightforward proposition early on, has of late become more convoluted with a host of class and compound-specific concerns having emerged. As the mechanistic basis for the action(s) of angiotensin receptor blockers more completely unfolds, added credence may ultimately be lent to widely touted and often overstated intraclass differences.

New NO-Releasing Pharmacodynamic Hybrids of Losartan and Its Active Metabolite: Design, Synthesis, and Biopharmacological Properties

In a preliminary work, we reported two NO-sartans, possessing the characteristics of an AT(1) antagonist and a "slow NO donor", obtained by adding NO-donor side chains to losartan 1. The NO release from an NO-sartan should be modulated in order to strengthen the antihypertensive activity of the native drug and to ensure additional effects, such as the antiplatelet and anti-ischemic ones. To obtain a collection of prototypical NO-sartans, showing different rates of NO release, new NO-donor moieties have been linked to 1 or its active metabolite 2 (EXP 3174). Almost all the synthesized compounds exhibited both AT(1)-antagonist and NO-mediated vasorelaxing properties, with a wide range of NO-releasing rates. Further pharmacological investigation on compound 4a showed that it possessed antihypertensive and cardiac antihypertrophic effects similar to those of the reference AT(1)-blocking or ACE-inhibiting drugs. Furthermore, the additional anti-ischemic cardio-protective properties and antiplatelet effects of 4a have been preliminarily investigated.

Angiotensin II receptor blockers in congestive heart failure

The benefits of angiotensin-converting enzyme (ACE) inhibitors for the treatment of congestive heart failure (CHF) are well-established. A newer class of medications, angiotensin II receptor blockers (ARBs), may be a suitable replacement for ACE inhibitors as a result of a more complete inhibition of angiotensin II and better tolerability among patients. To examine the current literature on the efficacy and safety of ARBs in the setting of CHF, a Medline search was conducted of the English language literature for the years 1987 to 2005. Clinical trials that reported data on cardiac outcomes were reviewed. The earlier trials were direct ARB to ACE inhibitor comparisons (ELITE I and ELITE II). These studies indicated that ARBs do not confer an improvement in cardiac outcomes over ACE inhibitors. RESOLVD, Val-HeFT, and the 3 separate trials of the CHARM program investigated the addition of an ARB to standard therapy. The RESOLVD trial showed no significant differences in clinical events among ACE inhibitor, ARB, and their combination. Although no mortality benefit was evident in the Val-HeFT trial, a substantial reduction in CHF rehospitalizations was reported among patients who were not receiving ACE inhibitor therapy. The CHARM-Overall program demonstrated a significant benefit in cardiovascular death and hospital admissions for CHF with the addition of ARB to standard therapy, a benefit that was more pronounced in patients with depressed left ventricular ejection fraction. In the setting of CHF, rates of cardiac outcomes do not differ substantially between ARBs and ACE inhibitors. However, their combination may improve outcomes for patients with CHF.

Effects of Long-Term Treatment with Candesartan on Hemodynamics and Organ Damage in Spontaneously Hypertensive Rats

This study was designed to investigate the effects of candesartan on blood pressure (BP) and blood pressure variability (BPV) reductions, baroreflex sensitivity (BRS) amelioration, and organ protection in spontaneously hypertensive rats (SHR).

METHODS

Studies were performed in two groups of SHR (n = 13 for control rats; and n = 20 for candesartan-treated rats) and one group of WKY rats (n = 13). Candesartan (3 mg /kg/d) was given in rat chow for 4 months. BP was then continuously recorded for 24 hours in conscious state. After the determination of BRS, rats were killed for organ-damage evaluation.

RESULTS

Long-term treatment with candesartan significantly reduced BP and BPV expressed by both standard deviation and variation coefficient of BP, enhanced BRS and produced obvious organ protection. Compared with BP level, BPV and BRS values showed a closer or similar relationship with organ-damage parameters in SHR. Multiple regression analysis showed that the decrease in left ventricular hypertrophy was most closely associated with the increase in BRS, whereas the decrease in aortic hypertrophy was most closely associated with the decrease in 24-hour systolic BPV, and the amelioration in renal lesions, with the increase in BRS and the decrease in 24-hour systolic BPV.

CONCLUSION

long-term treatment with candesartan results in organ protection in SHR. Besides BP reduction, the decrease in BPV and the restoration of BRS are significantly related to this organ protection.

Effect of losartan and spironolactone on left ventricular mass and heart sympathetic activity in prehypertensive obese subjects: a 16-week randomized trial

Obesity has been shown to be associated with increased left ventricular mass (LVM) and heart sympathetic activity even in nonhypertensive subjects. These factors are predictors of cardiovascular morbidity and mortality independent of other traditional risk factors. We evaluated the effect of losartan and spironolactone on LVM and heart sympathetic activity in prehypertensive obese subjects. A 16-week blinded randomized trial was performed in middle-aged men selected from a Health Public program. Anthropometric and clinical variables were measured at baseline and after losartan (50 mg/day; n=25) or spironolactone (25 mg/day; n=25) treatment. Heart sympathetic activity was evaluated with 60-min electrocardiograph monitoring, and spectral analysis was carried out. LVM was measured by echocardiography according to Devereux and Reicheck's formula indexed for body height (m2.7) to account for obesity. Anthropometric variables, systolic, and diastolic blood pressure levels decreased in both groups of treatment without statisticall difference between them. Losartan increased heart rate variability (from 70.0 to 82.3 ms; P=0.01), and decreased low frequency-high frequency index (from 6.6 to 4.9; P=0.001), and LVM (from 49.2 to 45.2 g; P=0.004). In the multiple regression analysis for factors associated with reduction in LVM; treatment with losartan, and decrease in SBP were the only factors included in the model (R2=0.60; P=0.003). To conclude losartan, but not spironolactone, decreased LVM and heart sympathetic overactivity in prehypertensive obese subjects after 16 weeks of treatment. Regression on LVM was associated with reduction on SBP levels.

Long-term antiproteinuric and renoprotective efficacy and safety of losartan in children with proteinuria

BACKGROUND

Angiotensin receptor antagonists are effective in reducing proteinuria by an action independent of blood pressure. As a consequence, such agents retard progressive renal dysfunction in adults with chronic proteinuria. Long-term efficacy and tolerability data in children are unavailable.

METHODS

Efficacy of losartan in reducing proteinuria and in preserving renal function was prospectively assessed in 52 consecutive children under 18 years of age with chronic proteinuric renal disorders, an initial creatinine clearance > or =25 mL/min/1.73 m(2), and a minimum of two or more follow-up visits. Thirty had proteinuria (P), and 22 had proteinuria combined with hypertension (P+H). Adverse effects were also evaluated.

RESULTS

Proteinuria had persisted or increased during a mean interval of 8.5 months before initiation of losartan at a mean dosage of 0.8 mg/kg/d. Mean protein excretion before starting losartan was 2453 mg/m(2)/d and fell by 34% at a mean follow-up time of six weeks (visit I, P<.05), and between 64% and 67% at mean follow-up periods of 0.38, 0.71, and 2.48 years corresponding to visits II, III, and IV (all P<.001 compared with baseline). The proportion of children with protein excretion exceeding 40 mg/m(2)/h (nephrotic range proteinuria) or nephrotic syndrome (>3500 mg/1.73 m(2)/d) fell from 42% and 40% at the start, to 24% and 8%, respectively, at visit IV (P<.01). Mean creatinine clearance as well as serum potassium and total CO(2) levels remained unchanged during the time of follow-up. Reduction in proteinuria in the P subgroup alone correlated with lowering in diastolic blood pressure at visit II and with both diastolic and systolic blood pressure at visits III and IV (all P<.05); it was largely independent of reduction in blood pressure in the P+H subgroup. The concomitant use of immunosuppressive agents in 28 of the 52 children had an influence on proteinuria only at baseline and at visit I (P<.05). There was no significant change in height or body mass index Z scores. Thirteen children had adverse effects potentially ascribed to losartan; most of these either improved or resolved with dosage adjustment or resulted in its discontinuation in 9 of the 52 children (17%).

CONCLUSION

Losartan therapy was associated with a marked and sustained reduction in proteinuria and in preservation of GFR in children with chronic proteinuric disorders. The association between proteinuria and systemic blood pressure reduction was complex: it was largely limited to the first year of losartan therapy and was more pronounced in the normotensive subgroup. Losartan was generally well tolerated.

Aldosterone receptor antagonists: focus on eplerenone

Despite the development of hypertension treatment guidelines, blood pressure control in the general population remains inadequate, indicating the need for ongoing re-evaluation of treatment strategies to further improve blood pressure control. Hypertension results from alterations in cardiac output and/or peripheral resistance. The renin-angiotensin-aldosterone system may be responsible, at least in part, for these alterations. Despite pharmacologic intervention with angiotensin-converting enzyme inhibitors and angiotensin type-1 receptor antagonists, aldosterone continues to be produced. Therapeutic modalities for treating hypertension directed toward antagonizing aldosterone might more effectively control blood pressure. Eplerenone, a new selective aldosterone receptor antagonist, recently received approval from the US Food and Drug Administration for the treatment of hypertension, either alone or in combination with other antihypertensive agents. The objective of this review is to summarize the renin-angiotensin-aldosterone system, emphasizing the role for aldosterone antagonism in the management of hypertension, with a focus on eplerenone.

Effects of long-term treatment with candesartan on organ damages in sinoaortic denervated rats

The study was designed to observe the effects of long-term treatment with candesartan cilexetil (candesartan) on blood pressure (BP), blood pressure variability (BPV), baroreflex sensitivity (BRS) and end-organ damage (EOD) in sinoaortic denervated (SAD) rats. Candesartan was mixed in rat chow at an estimated dose of 3 mg/kg/day. After 12 weeks of drug administration, rats were instrumented to determine BP, BPV and BRS in conscious state. Organ damage was estimated by observation of morphologic changes. When compared with sham-operated rats, SAD rats exhibited increased BPV, decreased BRS, and normal BP and plasma angiotensin II level. Left ventricular and aortic hypertrophies and renal lesion were found in SAD rats. Candesartan significantly decreased BP and BPV, ameliorated impaired BRS, increased plasma angiotensin II level and obviously diminished the EOD in SAD rats. Multiple-regression analysis shows that decrease in left ventricular hypertrophy was mainly related to decrease in systolic BPV. Decrease in aortic hypertrophy was mainly determined by increase in BRS and decrease in systolic BP. Amelioration in renal lesion was predicted by increase in BRS and decrease in systolic BPV. BRS was the most important determinant for renal lesion and aortic hypertrophy in SAD rats. In addition, plasma angiotensin II level was higher in candesartan-treated rats. In conclusion, long-term treatment with candesartan prevented SAD-induced organ damage. Restoration of arterial baroreflex function, decrease in BPV, and blockade of activated renin-angiotensin system may contribute to the organ protective action of candesartan in SAD rats.

The Evolving Role of Angiotensin Receptor Blockers in Heart Failure

This continuing feature will update readers on recent developments in cardiovascular pharmacotherapy. Cardiovascular disease remains the number one killer in the US, and more clinical outcome trials have been conducted in cardiology than in any other field of medicine. Given this rapidly expanding knowledge base, pharmacists can have a significant impact on the prevention and treatment of cardiovascular disease—if they keep current with developments in drug therapy.

L-163,491 is a partial angiotensin AT(1) receptor agonist in the hindquarters vascular bed of the cat

Responses to the nonpeptide angiotensin II agonist 5, 7-Dimethyl-2-ethyl-3-[[2'-([butyloxycarbonyl) aminosulfonyl]-5'-(3-methyoxybenzyl)-[1, 1'-biphenyl]-4-yl]methyl]-3H-imidazo[4,5-b]pyridine (L-163,491) were investigated and compared with responses to angiotensin II, angiotensin IV and norepinephrine in the hindquarters vascular bed of the cat under constant-flow conditions. Injections of L-163,491 into the hindquarter perfusion circuit caused dose-related increases in hindquarters perfusion pressure. In relative terms, angiotensin II was more potent than norepinephrine, which was more potent than angiotensin IV and L-163,491 in increasing hindlimb vascular resistance. The slope of the dose-response curve for L-163,491 was flat, while the apparent affinity of the compound for angiotensin AT(1) receptors was slightly greater than angiotensin IV. Responses to L-163,491 were inhibited by the angiotensin AT(1) receptor antagonist DuP 532 (2-propyl-4-pentafluoroethyl-1-[2'-(1H-tetrazol-5-yl)bipheny l-4-yl)me thyl]imidazole-5-carboxylic acid) and were not altered by the angiotensin AT(2) receptor antagonist PD123,319 (S(+)-1-[[4-(Dimethylamino)-3-methylphenyl]methyl]-5-(diphenylacetyl+ ++) -4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditribluoroacetate). However, the increase in hindlimb perfusion pressure in response to angiotensin II and angiotensin IV was significantly decreased following injection of L-163,491. These data suggest that the nonpeptide angiotensin analog L-163,491 has partial agonist activity, which is dependent on the stimulation of angiotensin AT(1) receptors in the hindquarters vascular bed of the cat.

Eprosartan: a review of its use in the management of hypertension

Eprosartan is a potent and selective angiotensin II subtype 1 receptor antagonist. Results of large (n > 100) randomised double-blind studies in patients with mild, moderate or severe hypertension demonstrated that the antihypertensive efficacy of eprosartan (usually 400 to 800 mg/day as a single daily dose or in 2 divided doses) is significantly greater than that of placebo and at least as good as that of enalapril. In placebo-controlled trials, eprosartan achieved mean reductions from baseline in trough sitting systolic blood pressure of 6.3 to 15 mm Hg and in diastolic blood pressure of 4.1 to 9.7 mm Hg. Response rates associated with once daily administration of eprosartan 400 to 800 mg were approximately double those with placebo. Overall, eprosartan was well tolerated with a similar tolerability profile to that of placebo. In comparative trials, in which the incidence of persistent dry cough was evaluated as the primary end-point, enalapril was several-fold more likely to induce this adverse event than eprosartan (the difference being statistically significant regardless of study population and definition of cough). In conclusion, the angiotensin II receptor antagonist eprosartan is a well tolerated and effective antihypertensive agent that is administered once or twice daily without regard to meals. Eprosartan has a low potential for serious adverse events, and the drug has not been associated with clinically significant drug interactions. Unlike ACE inhibitors such as enalapril, eprosartan does not have a high propensity to cause persistent nonproductive cough. Thus, eprosartan represents a useful therapeutic option in the management of patients with hypertension.