Eplerenone: a review of its use in essential hypertension

Mineralocorticoid Receptor Antagonists Eplerenone and Spironolactone Modify Adrenal Cortex Morphology and Physiology

Mineralocorticoid receptor antagonists (MRAs) are a class of anti-hypertensive drugs that act by blocking aldosterone action. The aim of this study was to evaluate whether the MRAs spironolactone and eplerenone influence adrenal cortical physiology and morphology. Spontaneous hypertensive rats (SHR, n = 18) and normotensive rats (WKY, n = 18) were randomly exposed to a daily dose of spironolactone (n = 6), eplerenone (n = 6), or no drug (n = 6) over 28 days. After that, aldosterone, corticosterone, and 11-deoxycorticosterone plasma concentrations were quantified. Adrenal glands were subjected to morphological analysis to assess lipid droplets content, capsular width, cell proliferation, and steroidogenic proteins expression. The adrenal cortex in untreated SHR showed higher lipid droplet content as than in WKY. In SHR, MRA treatment was associated with higher circulating aldosterone levels and Ki-67 expression in aldosterone-secreting cells. In WKY, the only difference observed after MRA spironolactone treatment was a narrower capsule. There was no difference in abundance of steroidogenic enzyme between groups. In conclusion, MRAs modify adrenal gland function and morphology in SHR. The effects observed within the adrenal glomerulosa with aldosterone-secreting cell proliferation and higher circulating aldosterone levels suggests that MRA treatment provokes activation of the renin angiotensin system. The prognostic value of hyperaldosteronism secondary to MRAs blockade requires further investigation.

Antihypertensive effect of the mineralocorticoid receptor antagonist eplerenone: a pooled analysis of patient-level data from comparative trials using regulatory-approved doses

Purpose

Several options are available for the treatment of hypertension; however, many treated patients are still not below blood pressure (BP) target. Eplerenone, a selective mineralocorticoid receptor antagonist, is an approved treatment option for the management of patients with hypertension in a number of countries. This patient-level pooled analysis was conducted to document the efficacy and safety/tolerability of eplerenone at the dosages approved for use in hypertension in comparison to placebo or other approved antihypertensive agents.

Methods

Seventeen Phase III studies conducted in patients with mild-to-moderate hypertension in the Eplerenone Hypertension Clinical Program were reviewed; eleven met the selection criteria. The primary endpoint was change from baseline in seated diastolic BP and seated systolic BP measured at the end of the study.

Results

A total of 2,698 patients were included in this per-protocol analysis. In patients treated for at least 6 weeks with a stable dose of eplerenone, doses of 50 mg daily and 100 mg daily were associated with greater reductions of seated systolic BP and seated diastolic BP compared with placebo (P<0.001) and active-controlled studies (P< 0.033). In the analysis of covariance model testing of the contribution of four factors (age, body mass index [BMI], history of cardiovascular disease, and diabetes) on the BP lowering effects of eplerenone, only BMI and age were associated with small though statistically significant changes in BP (<0.2 mmHg). Eplerenone was well tolerated; headache was the most common adverse event for patients in any group. Severe hyperkalemia (serum potassium level >6.0 mmol/L) occurred in up to 0.4% in the eplerenone groups, 0.4% in the placebo group, and 0.1% in the active-control group.

Conclusion

This patient-level pooled analysis provides robust evidence that eplerenone, at 50 mg or 100 mg daily, was effective in lowering BP in patients with mild-to-moderate hypertension and was well tolerated.

Preclinical and Early Clinical Profile of a Highly Selective and Potent Oral Inhibitor of Aldosterone Synthase (CYP11B2)

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Primary hyperaldosteronism is a common cause of resistant hypertension. Aldosterone is produced in the adrenal by aldosterone synthase (AS, encoded by the gene CYP11B2). AS shares 93% homology to 11β-hydroxylase (encoded by the gene CYP11B1), responsible for cortisol production. This homology has hitherto impeded the development of a drug, which selectively suppresses aldosterone but not cortisol production, as a new treatment for primary hyperaldosteronism. We now report the development of RO6836191 as a potent (Ki 13 nmol/L) competitive inhibitor of AS, with in vitro selectivity >100-fold over 11β-hydroxylase. In cynomolgus monkeys challenged with synthetic adrenocorticotropic hormone, single doses of RO6836191 inhibited aldosterone synthesis without affecting the adrenocorticotropic hormone–induced rise in cortisol. In repeat-dose toxicity studies in monkeys, RO6836191 reproduced the adrenal changes of the AS^−/− mouse: expansion of the zona glomerulosa; increased expression of AS (or disrupted green fluorescent protein gene in the AS^−/− mouse); hypertrophy, proliferation, and apoptosis of zona glomerulosa cells. These changes in the monkey were partially reversible and partially preventable by electrolyte supplementation and treatment with an angiotensin-converting enzyme inhibitor. In healthy subjects, single doses of RO6836191, across a 360-fold dose range, reduced plasma and urine aldosterone levels with maximum suppression at a dose of 10 mg, but unchanged cortisol, on adrenocorticotropic hormone challenge, up to 360 mg, and increase in the precursors 11-deoxycorticosterone and 11-deoxycortisol only at or >90 mg. In conclusion, RO6836191 demonstrates that it is possible to suppress aldosterone production completely in humans without affecting cortisol production.

Emerging cardiovascular indications of mineralocorticoid receptor antagonists

Mineralocorticoid receptor (MR) antagonism is a well-established treatment modality for patients with hypertension, heart failure, and left ventricular systolic dysfunction (LVSD) post-myocardial infarction (MI). There are emerging data showing potential benefits of MR antagonists in other cardiovascular conditions. Studies have shown association between MR activation and the development of myocardial fibrosis, coronary artery disease, metabolic syndrome, and cerebrovascular diseases. This review examines the preclinical and clinical data of MR antagonists for novel indications including heart failure with preserved ejection fraction (HFPEF), pulmonary arterial hypertension (PAH), arrhythmia, sudden cardiac death, valvular heart disease, metabolic syndrome, renal disease, and stroke. MR antagonists are not licensed for these conditions yet; however, emerging data suggest that indication for MR antagonists are likely to broaden; further studies are warranted.

Mineralocorticoid receptors in vascular disease: connecting molecular pathways to clinical implications

The mineralocorticoid receptor (MR), a steroid-hormone-activated transcription factor, plays a substantial role in cardiovascular diseases. MR antagonists (MRAs) have long been appreciated as effective treatments for heart failure and hypertension; however, recent research suggests that additional patient populations may also benefit from MRA therapy. Experimental evidence demonstrates that in addition to its classic role in the regulating sodium handling in the kidney, functional MR is expressed in the blood vessels and contributes to hypertension, vascular inflammation and remodeling, and atherogenesis. MR activation drives pathological phenotypes in smooth muscle cells, endothelial cells, and inflammatory cells, whereas MRAs inhibit these effects. Collectively, these studies demonstrate a new role for extrarenal MR in cardiovascular disease. This review summarizes these new lines of evidence and how they contribute to the mechanisms of atherosclerosis, pulmonary and systemic hypertension, and vein graft failure, and describes new patient populations that may benefit from MRA therapy.

Smooth muscle cell mineralocorticoid receptors: role in vascular function and contribution to cardiovascular disease

The mineralocorticoid receptor (MR), a member of the steroid receptor family, regulates blood pressure by mediating the effects of the hormone aldosterone on renal sodium handling. In recent years, it has become clear that MR is expressed in vascular smooth muscle cells (SMCs), and interest has grown in understanding the direct role of SMC MR in regulating vascular function. This interest stems from multiple clinical studies where MR inhibitor treatment reduced the incidence of cardiovascular events and mortality. This review summarizes the most recent advances in our understanding of SMC MR in regulating normal vascular function and in promoting vascular disease. Many new studies suggest a role for SMC MR activation in stimulating vascular contraction and contributing to vessel inflammation, fibrosis, and remodeling. These detrimental vascular effects of MR activation appear to be independent of changes in blood pressure and are synergistic with the presence of endothelial dysfunction or damage. Thus, in humans with underlying cardiovascular disease or cardiovascular risk factors, SMC MR activation may promote hypertension, atherosclerosis, and vascular aging. Further exploration of the molecular mechanisms for the effects of SMC MR activation has the potential to identify novel therapeutic targets to prevent or treat common cardiovascular disorders.

Eplerenone, an aldosterone blocker, is more effective in reducing blood pressure in patients with, than without, metabolic syndrome

BACKGROUND

Recently, the role of aldosterone in metabolic syndrome (MS) has aroused interest and several reports have suggested that aldosterone blockade could be beneficial in reducing blood pressure (BP).

METHODS

To examine the add-on effects of eplerenone (EP) on BP in patients with MS, 54 hypertensive patients with MS and 44 without MS were recruited. Systolic and diastolic BPs in mmHg before the initiation of EP was 144/84 ± 13/12 (MS group) and 147/85 ± 12/14 (non-MS group). Before the start of EP, all patients in both groups were treated with at least one antihypertensive drug. BPs were checked on every visit (at least every 2 months) and serum chemistries were measured every 4 months. The levels of microalbuminuria and aminoterminal pro-brain natriuretic peptide (NT pro-BNP) were determined before the start of and at the end of the study. Patients were followed for 1 year. If adverse effects were reported by patients or found in laboratory studies, EP was withdrawn.

RESULTS

One month after the start of EP, BPs were decreased to 140/80 ± 12/12 mmHg (MS group) versus 142/82 ± 11/12 mmHg (non-MS group) and there was no difference between the two groups. Towards the end of the study, BPs of both groups gradually decreased. At the end of the study, BPs of both groups were 129/76 ± 15/13 mmHg (MS group) versus 133/78 ± 13/11 mmHg (non-MS group). There was a significant difference in reduction of systolic BP between the two groups (p < 0.05). Add-on EP significantly decreased the levels of urinary excretion of albumin in MS patients but not in non-MS patients (p < 0.05). There was a significant correlation between reduction of systolic BP and NT pro-BNP but not microalbuminuria in the MS group (p < 0.05). There were no serious adverse effects in both groups.

CONCLUSION

EP may have some beneficial effects in lowering BP in patients with reduction of microalbuminuria.

Management of blood pressure in patients with diabetes

Hypertension is a major modifiable risk factor for cardiovascular morbidity and mortality in patients with diabetes. Lowering blood pressure (BP) to 135/85 mm Hg is the main goal of treatment. A nonpharmcologic approach is recommended in all patients. If BP levels remain above the target despite nonpharmacologic treatment, drug therapy should be initiated. Blockers of the renin-angiotensin-aldosterone system (RAAS) represent the cornerstone of the antihypertensive drug arsenal; however, in most patients, combination therapy is required. For many patients, a combination of RAAS blocker and calcium antagonist is the combination preferred by the treating physician. Often three or even four drugs are needed. Treatment should be individualized according to concomitant risk factors and diseases and depending on the age and hemodynamic and laboratory parameters of the patient. In order to maximally reduce cardio renal risk, control of lipid and glycemic levels should also be ensured.

Diuretics in clinical practice. Part II: electrolyte and acid-base disorders complicating diuretic therapy

IMPORTANCE OF THE FIELD

As with all potent therapeutic agents, the use of diuretic compounds has been linked with several adverse effects that may reduce quality of life and patient compliance and, in some cases, may be associated with considerable morbidity and mortality. Among the various types of adverse effects, disturbances of electrolyte and acid-base balance are perhaps the most common, and some of them are the aetiological factors of other side effects (i.e., hypokalaemia causing ventricular arrhythmias or glucose intolerance). The mechanism and site of action and, therefore, the pharmacological effects of each diuretic class largely determine the specific electrolyte or acid-base abnormalities that will accompany the use of each diuretic agent.

AREAS COVERED IN THE REVIEW

This article reviews the major electrolyte disturbances (hypokalaemia, hyperkalaemia, hyponatraemia, disorders of magnesium and calcium balance), as well as the acid-base abnormalities complicating the use of the various diuretic agents.

WHAT THE READER WILL GAIN

The reader will gain insights into the pathogenesis of the diuretic-induced electrolyte and acid-base disorders together with considerations for their prevention and treatment.

TAKE HOME MESSAGE

Knowledge of the pharmacologic properties of each diuretic class and appropriate monitoring of patients under diuretic treatment represent the most important strategies to prevent the development of diuretic-related adverse events and their consequences.

A new mode of mineralocorticoid receptor antagonism by a potent and selective nonsteroidal molecule

Limitations of current steroidal mineralocorticoid receptor (MR) antagonists have stimulated the search for a new generation of molecules. We screened for novel nonsteroidal compounds and identified MR antagonists derived from the chemical class of dihydropyridines. Chemical optimization resulted in BR-4628, which displays high in vitro and in vivo MR potency as well as selectivity with respect to the other steroid hormone receptors and the L-type calcium channel. Biochemical studies demonstrated that BR-4628 forms complexes with MR that do not promote the recruitment of transcriptional co-regulators. Docking experiments, using the crystal structure of the MR ligand-binding domain in an agonist conformation, revealed that BR-4628 accommodates in the MR ligand-binding cavity differently in comparison with the classical steroidal MR antagonists. An alanine scanning mutagenesis approach, based on BR-4628 docking, allowed identifying its anchoring mode within the ligand-binding cavity. Altogether, we propose that BR-4628 is a bulky antagonist that inactivates MR through a passive mechanism. It represents the prototype of a new class of MR antagonists.

Clinical effects of eplerenone, a selective aldosterone blocker, in Japanese patients with essential hypertension

Eplerenone, a selective aldosterone blocker, has become clinically available in Japan since 2007. It has been reported that eplerenone has a potential antihypertensive effect, with a profile slightly different from that of spironolactone, and has fewer adverse reactions, suggesting that it may become a first-line treatment for hypertension. However, clinical data on hypertensive patients in Japan are lacking for eplerenone. In this study, we explored the clinical efficacy of eplerenone when it is added to an angiotensin-converting enzyme (ACE) inhibitor or a long-acting calcium channel blocker (CCB) in 68 (31 males, 37 females) Japanese patients with essential hypertension. After adding 50 mg of eplerenone to their basal treatment, blood pressure was significantly reduced at 4 weeks, and further reduced after 24 weeks of eplerenone treatment. Urinary albumin excretion decreased significantly after 24 weeks. There were no significant differences in general biochemical test values or electrolytes, but fasting serum triglycerides were significantly decreased after eplerenone treatment. The serum potassium level showed no significant change during treatment. There were no significant correlations between plasma renin activity or plasma aldosterone concentration (PAC) before eplerenone treatment and blood pressure after eplerenone treatment, showing that the antihypertensive effect of eplerenone is not affected by the patient's renin profile or pretreatment PAC values. Eplerenone was also effective in hypertensive patients with metabolic syndrome. In conclusion, eplerenone, when coadministered with an ACE inhibitor or a long-acting CCB, caused an extremely beneficial antihypertensive effect in Japanese patients with essential hypertension, without few clinically important adverse events.

Blood pressure drug therapy and electrolyte disturbances

Antihypertensive pharmacologic treatment may be associated with diverse disturbances of electrolyte homeostasis. These drug-induced disorders are relatively common, typically including hyponatraemia, hypokalaemia, hyperkalaemia, hypomagnesaemia, hypophosphataemia and hypercalcaemia. Diuretics, beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are particularly likely to cause these complications. Recognised risk factors include high-dosage regimens (especially diuretics), old age, diabetes and impairment of renal function. Strategies to prevent these adverse drug reactions involve careful consideration of risk factors and clinical and laboratory evaluation in the course of treatment.

A comparison of the aldosterone-blocking agents eplerenone and spironolactone

Improved understanding of the adverse pharmacological properties of aldosterone has prompted investigation of the clinical benefits of blocking aldosterone at the receptor level. This article reviews the pharmacology, clinical efficacy, and tolerability of the two available blocking agents, spironolactone and eplerenone. A Medline search identified clinical studies assessing spironolactone and eplerenone. Priority was given to large, well-controlled, clinical trials and comparative studies. Pharmacological differences between spironolactone and eplerenone include lower affinity of eplerenone for progesterone, androgen, and glucocorticoid receptors; more consistently demonstrated nongenomic properties for eplerenone; and the presence of long-acting metabolites for spironolactone. Both agents effectively treat hypertension and heart failure but comparisons are complicated by the deficiency of head-to-head trials and differences between patient populations. There are differences in the tolerability profiles; spironolactone is associated with dose-dependent sexual side effects. Both agents produce dose-dependent increases in potassium concentrations, although the effect with spironolactone appears to be greater when both agents are administered at recommended doses. Choice of a specific agent should be based on individual patient issues, such as the nature of heart failure and patient concerns about adverse events.

Evaluation of the aldosterone-blocking agent eplerenone in hypertension and heart failure

Aldosterone blockade is now seen as a crucial therapeutic strategy in the management of cardiovascular disease progression. There is increasing evidence that blocking the rennin-angiotensin-aldosterone system results in a reduction in overall cardiovascular risk. For 40 years, the only agent in this class was spironolactone. Despite its efficacy, the sexual side effects of spironolactone have resulted in poor compliance at best and discontinuation of therapy at worst. A newer agent, eplerenone, has been recently licensed for the treatment of heart failure and in the US also for hypertension. This article reviews the pathophysiology of aldosterone and critically reviews the present evidence for the efficacy and potential role for the new selective aldosterone-receptor antagonist, eplerenone.

The Future of Antihypertensive Treatment

Despite progress in recent years in the prevention, detection, and treatment of high blood pressure (BP), hypertension remains an important public health challenge. Hypertension affects approximately 1 billion individuals worldwide. High BP is associated with an increased risk of mortality and morbidity from stroke, coronary heart disease, congestive heart failure, and end-stage renal disease; it also has a negative impact on the quality of life. Hypertension cannot be eliminated because there are no vaccines to prevent the development of hypertension, but, its incidence can be decreased by reducing the risk factors for its development, which include obesity, high dietary intake of fat and sodium and low intake of potassium, physical inactivity, smoking, and excessive alcohol intake. For established hypertension, efforts are to be directed to control BP by lifestyle modification (LSM). However, if BP cannot be adequately controlled with LSM, then pharmacotherapy can be instituted along with LSM. Normalization of BP reduces cardiovascular risk (for cardiovascular death, myocardial infarction, and cardiac arrest), provides renoprotection (prevention of the onset or slowing of proteinuria and progression of renal dysfunction to end-stage renal disease in patients with hypertension, diabetes mellitus types 1 and 2, and chronic renal disease), and decreases the risk of cerebrovascular events (stroke and cognition impairment), as has been amply demonstrated by a large number of randomized clinical trials. In spite of the availability of more than 75 antihypertensive agents in 9 classes, BP control in the general population is at best inadequate. Therefore, antihypertensive therapy in the future or near future should be directed toward improving BP control in treated hypertensive patients with the available drugs by using the right combinations at optimum doses, individually tailored gene-polymorphism directed therapy, or development of new modalities such as gene therapy and vaccines. Several studies have shown that BP can be reduced by lifestyle/behavior modification. Although, the reductions appear to be trivial, even small reductions in systolic BP (for example, 3-5 mm Hg) produce dramatic reduction in adverse cardiac events and stroke. On the basis of the results of clinical and clinical/observational studies, it has been recommended that more emphasis be placed on lifestyle/behavior modification (obesity, high dietary intake of fat and sodium, physical inactivity, smoking, excessive alcohol intake, low dietary potassium intake) to control BP and also to improve the efficacy of pharmacologic treatment of high BP. New classes of antihypertensive drugs and new compounds in the established drug classes are likely to widen the armamentarium available to combat hypertension. These include the aldosterone receptor blockers, vasodilator beta-blockers, renin inhibitors, endothelin receptor antagonists, and dual endopeptidase inhibitors. The use of fixed-dose combination drug therapy is likely to increase. There is a conceptual possibility that gene therapy may yield long-lasting antihypertensive effects by influencing the genes associated with hypertension. But, the treatment of human essential hypertension requires sustained over-expression of genes. Some of the challenging tasks for successful gene therapy that need to be mastered include identification of target genes, ideal gene transfer vector, precise delivery of genes into the required site (target), efficient transfer of genes into the cells of the target, and prompt assessment of gene expression over time. Targeting the RAS by antisense gene therapy appears to be a viable strategy for the long-term control of hypertension. Several problems that are encountered in the delivery of gene therapy include 1) low efficiency for gene transfer into vascular cells; 2) a lack of selectivity; 3) problem in determining how to prolong and control transgene expression or antisense inhibition; and 4) difficulty in minimizing the adverse effects of viral or nonviral vectors. In spite of the hurdles that face gene therapy administration in humans, studies in animals indicate that gene therapy may be feasible in treating human hypertension, albeit not in the near future. DNA testing for genetic polymorphism and determining the genotype of a patient may predict response to a certain class of antihypertensive agent and thus optimize therapy in individual patients. In this regard, there are some studies that report the effectiveness of antihypertensive therapy based upon the genotype of selected patients. Treatment of human hypertension with vaccines is feasible but is not likely to be available in the near future.

Update of Diuretics in the Treatment of Hypertension

Diuretics, which are primarily used to modify the volume and the composition of body fluids, are widely used to treat hypertension. The diuretics include a) the thiazides and thiazide-like agents, which are the most common drugs used to treat high blood pressure (these drugs inhibit sodium reabsorption in the early distal convoluted tubule); b) loop diuretics, such as furosemide, block chloride and sodium reabsorption by inhibition of the Na/K/2Cl cotransport system in the thick ascending limb of the loop of Henle; and c) potassium-sparing (retaining) diuretics, including aldosterone receptor blockers (such as spironolactone and eplerenone) and epithelial sodium channel blockers (such as amiloride and triamterene, which interfere with the reabsorption of sodium and excretion of potassium and hydrogen that takes place in the late distal tubule, the connecting tubule, and the cortical collecting duct). Hydrochlorothiazide 12.5 mg once daily or equivalent low dosages of other similar agents reduce blood pressure in approximately one-half to two-thirds of patients who are responsive to this class of drugs; higher doses add little to the effect on blood pressure and also increase side effects. Some combinations of very small doses of thiazide diuretics - for example, 6.25 mg hydrochlorothiazide or 0.625 mg indapamide, with a low dose of an antihypertensive drug of a different class - have average antihypertensive efficacy when used once daily. Furosemide is used in patients with renal failure or severe heart failure and is best given by continuous intravenous infusion. The potassium-sparing diuretics are generally used in combination with thiazide diuretics to treat hypertension. Side effects occur at about the same frequency and severity with equipotent doses of all diuretics. The incidence of side effects is dose-dependent and also increases as a function of the duration of the renal excretory and antihypertensive actions. However, longer-acting diuretics provide better 24-hour control of blood pressure and increase compliance and adherence to the treatment regimen.