Azilsartan medoxomil: a review of its use in hypertension

Azilsartan medoxomil (Edarbi?; Ipreziv?) is an orally administered angiotensin II receptor type 1 antagonist (blocker) used in the treatment of adults with essential hypertension. This article reviews data on the clinical efficacy and tolerability of azilsartan medoxomil in adults with essential hypertension and provides a summary of its pharmacological properties. Azilsartan medoxomil is a prodrug that undergoes rapid hydrolysis in the gastrointestinal tract after oral administration to the bioactive moiety azilsartan, before systemic absorption. Azilsartan medoxomil produces antihypertensive effects by selectively blocking the binding of angiotensin II to the angiotensin type 1 (AT(1)) receptor, thereby antagonizing the pressor response activity of angiotensin II. In vitro, azilsartan produced greater and more sustained AT(1) receptor binding/blockade activity than several comparator angiotensin II receptor antagonists. Azilsartan medoxomil reduces blood pressure (BP) in hypertensive adults. In addition, the drug has been shown to have pleiotropic effects (i.e. effects beyond AT(1) receptor blockade). In adults with essential hypertension, azilsartan medoxomil 20, 40 or 80?mg effectively reduced BP over a 24-hour period with once-daily administration in three major, randomized, controlled trials in which the primary endpoints were changes from baseline in 24-hour mean systolic BP (SBP) at week 6 (two trials) or week 24, assessed by ambulatory BP monitoring (ABPM). In the two 6-week trials, azilsartan medoxomil showed dose-dependent efficacy over all evaluated dosages and was more effective than placebo in lowering SBP. At the maximum approved dosage of 80?mg once daily, azilsartan medoxomil was significantly more effective than maximum dosages of olmesartan medoxomil (40?mg once daily) or valsartan (320?mg once daily), based on primary endpoint assessments. Mean reductions in clinic measurements of SBP and diastolic BP (DBP) measurements were also generally greater with azilsartan medoxomil 80?mg once daily than with the comparator drugs in these 6-week studies. Over a longer treatment period of 24 weeks, azilsartan medoxomil showed sustained BP-lowering efficacy, with the reduction in 24-hour mean SBP at week 24 significantly greater with azilsartan medoxomil 40 or 80?mg once daily than with valsartan 320?mg once daily. Mean reductions from baseline in mean clinic SBP and DBP as well as DBP by ABPM were also significantly greater with azilsartan medoxomil 40 or 80?mg once daily than with valsartan. Azilsartan medoxomil was generally well tolerated, with a tolerability profile similar to that of placebo in the 6-week trials. Across the three major trials, headache and dizziness were among the most common adverse events. Overall, rates of treatment discontinuation as a result of adverse events were low in the 6-week and 24-week trials. In conclusion, once-daily azilsartan medoxomil effectively lowers BP in adults with essential hypertension and has shown better antihypertensive efficacy than maximum therapeutic dosages of olmesartan medoxomil or valsartan in major trials of up to 24 weeks' duration. Azilsartan medoxomil is generally well tolerated and the low rates of discontinuation due to adverse events suggest that patients are likely to persist with long-term treatment. Azilsartan medoxomil is therefore a useful and attractive new option for lowering BP in patients with essential hypertension, particularly for those not able to tolerate other antihypertensive drugs. Further studies are required to evaluate the effects of azilsartan medoxomil on cardiovascular morbidity and mortality.     

Pharmacological profiles and clinical effects of olmesartan medoxomil, a novel angiotensin II receptor blocker

Olmesartan medoxomil is a new angiotensin II receptor blocker (ARB) indicated for the treatment of hypertension. Olmesartan medoxomil is a pro-drug that is converted to the active metabolite olmesartan. Olmesartan does not undergo further metabolism and does not interact with cytochrome P450 enzymes. Olmesartan is a potent ARB with high selectivity for the type 1 (AT(1)) receptor subtype and shows insurmountable antagonism against the AT(1) receptor in vascular tissues. This antagonistic mode, which could be attributed to tight binding of this drug to the receptor, would underlie the potent and persistent action of olmesartan medoxomil in vivo. In fact, oral administration of olmesartan medoxomil produces a potent and long-lasting antihypertensive action without inducing tachycardia. The preventive effects of olmesartan medoxomil on end-organ damage in the kidney, heart, and blood vessels have been demonstrated in various animal models. In clinical studies, olmesartan medoxomil is shown to be well tolerated and have an excellent safety profile that is comparable to that of placebo. Head-to-head comparisons with other ARBs (losartan, valsartan, irbesartan, and candesartan cilexetil) conducted in the United States and Europe have revealed that olmesartan medoxomil is superior to these other ARBs in lowering blood pressure. These facts suggest that olmesartan medoxomil would be beneficial for the treatment of hypertension and other end-organ diseases.     

Clinical and experimental aspects of olmesartan medoxomil, a new angiotensin II receptor antagonist

Olmesartan medoxomil is a new orally active angiotensin II (Ang II) type 1 receptor antagonist. It is a prodrug and is rapidly de-esterified during absorption to form olmesartan, the active metabolite. Olmesartan is a potent, competitive and selective Ang II type 1 receptor antagonist. Olmesartan is not metabolized by the cytochrome P-450 and has a dual route of elimination, by kidneys and liver. In patients with essential hypertension olmesartan medoxomil administered once daily at doses of 10-80 mg dose-dependently reduced diastolic blood pressure (DBP). Troughto-peak ratios for both DBP and systolic blood pressure (SBP) were above 50%. At the recommended once-daily starting doses, olmesartan medoxomil (20 mg) was more effective than losartan (50 mg), valsartan (80 mg) or irbesartan (150 mg) in reducing cuff DBP in patients with essential hypertension. The results of cuff SBP and mean 24-h DBP and SBP were similar to those of cuff DBP measurement. In mild-to-moderate hypertensive patients the recommended starting dose of olmesartan medoxomil was as effective as that of amlodipine besylate (5 mg/day) in reducing both cuff and 24-h blood pressure. In lowering DBP olmesartan medoxomil, at 10-20 mg/day, was as effective as atenolol at 50-100 mg/day. In mild-to-moderate hypertensive patients, olmesartan medoxomil, at 5-20 mg once daily, was more effective than captopril at 12.5-50 mg twice daily. At 20-40 mg once daily olmesartan medoxomil was as effective as felodipine, at 5-10 mg once daily. Olmesartan medoxomil has minimal adverse effects with no clinically important drug interactions. Animal studies have shown that olmesartan medoxomil provides a wide range of organ protection. Olmesartan medoxomil ameliorated atherosclerosis in hyperlipidemic animals and ameliorated cardiac remodeling and improved survival in rats with myocardial infarction. Olmesartan medoxomil has renoprotective effects in a remnant kidney model and type 2 diabetes models. Future investigation should reveal whether these beneficial effects of olmesartan medoxomil are applicable to human diseases.     

Effects of olmesartan medoxomil as an angiotensin II-receptor blocker in chronic hypoxic rats

We established a rat chronic alveolar hypoxia in vivo model to evaluate the efficacy against hypoxic pulmonary hypertension of a new angiotensin II-receptor I blocker, olmesartan medoxomil. Three groups of rats were established: rats exposed for 2-6 weeks to 10% oxygen atmosphere in a normobaric chamber; hypoxic rats treated with olmesartan medoxomil oral administration (5 mg/day) every day; and control rats fed in a normoxic condition. After hypoxia treatment, the presence, etiology and severity of pulmonary hypertension, was echocardiographically evaluated, and expressions of brain natriuretic peptide (BNP), transforming growth factor (TGF-beta) and endothelin-1 genes measured by both immunohistochemical assay and real-time polymerase chain reaction. Olmesartan medoxomil significantly reduced the induction of hypoxic cor pulmonale not only on echocardiographical observations but also in BNP, TGF-beta and endothelin gene expressions in molecular studies. However, systolic blood pressure was independent of olmesartan medoxomil. The present study clearly indicates that the angiotensin II-type I-receptor blocker olmesartan medoxomil has significant efficacy for hypoxic cor pulmonale.     

Azilsartan medoxomil in the treatment of hypertension: the definitive angiotensin receptor blocker?

Introduction: Azilsartan medoxomil is the newest angiotensin receptor blocker marketed for the treatment of arterial hypertension. The aim of this article was to review the available evidence about this drug alone or combined with other antihypertensive agents in the treatment of hypertensive population.

Areas covered: For this purpose, a search on MEDLINE and EMBASE databases was performed. The MEDLINE and EMBASE search included both medical subject headings (MeSHs) and keywords including azilsartan or azilsartan medoxomil or angiotensin receptor blockers or renin angiotensin system or chlorthalidone and hypertension. References of the retrieved articles were also screened for additional studies. There were no language restrictions.

Expert opinion: Azilsartan medoxomil has a potent and persistent ability to inhibit binding of angiotensin II to AT1 receptors, which may play a role in its superior blood pressure (BP) -lowering efficacy compared with other drugs, including ramipril, candesartan, valsartan or olmesartan, without an increase of side effects. Chlortalidone is a diuretic which significantly differs from other classic thiazides and has largely demonstrated clinical benefits in outcome trials. The fixed-dose combination of azilsartan and chlorthalidone has been shown to be more effective than other potent combinations of angiotensin receptor blockers plus hydrochlorothiazide, with a good tolerability profile.     

Azilsartan medoxomil for the treatment of hypertension

The use of angiotensin receptor blockers (ARBs) represents a favorable approach for the control of blood pressure in patients with hypertension. Azilsartan medoxomil, a prodrug that undergoes rapid hydrolysis to its active moiety azilsartan, is an angiotensin AT(1) receptor antagonist with promising antihypertensive activity and a good safety profile. The agent has been evaluated as monotherapy and in combination with amlodipine or chlorthalidone in phase III trials in patients with essential hypertension. In 2011, azilsartan medoxomil was approved in the U.S. for the treatment of hypertension.     

Olmesartan medoxomil

Olmesartan medoxomil is a nonpeptide angiotensin II receptor antagonist which selectively and competitively inhibits the type 1 angiotensin II receptor without affecting other receptors regulating the cardiovascular system. In well designed randomised trials, olmesartan medoxomil was significantly more effective than placebo, and at dosages of 10 to 20 mg/day was at least as effective as atenolol 50 to 100 mg/day in reducing diastolic blood pressure (DBP). At dosages of 5 to 20 mg/day, olmesartan medoxomil was more effective than captopril 12.5 to 50mg twice daily at lowering seated DBP in patients with mild to moderate hypertension in a dose titration study. Reductions in seated DBP were greater with olmesartan medoxomil 10 to 20 mg/day than losartan 50 to 100 mg/day. Olmesartan medoxomil at 20 mg/day was more effective in lowering seated DBP than losartan 50 mg/day, valsartan 80 mg/day or irbesartan 150 mg/day, and was more efficacious than losartan 50 mg/day or valsartan 80 mg/day at reducing 24-hour ambulatory systolic blood pressure. Olmesartan medoxomil has shown no clinically important pharmacokinetic interactions with digoxin, warfarin or antacid (aluminium magnesium hydroxide). Adverse events were infrequent in clinical studies of olmesartan medoxomil and were similar to those attributed to placebo. With olmesartan medoxomil, the frequency of dizziness was higher than with placebo but similar to that occurring with losartan, valsartan and irbesartan.     

阿齐沙坦与奥美沙坦酯治疗轻中度原发性高血压的疗效比较

目的 比较阿齐沙坦与奥美沙坦酯治疗轻中度原发性高血压的临床疗效。方法 2015年9月—2017年2月从全国多家研究中心筛选轻、中度原发性高血压304例,随机分为奥美沙坦酯组和阿齐沙坦组。受试者从起始剂量开始,阿齐沙坦片20 mg/次和奥美沙坦酯片模拟剂,1次/d,或奥美沙坦酯片20 mg/次和阿齐沙坦片模拟剂,1次/d,开始治疗。用药后第8周末对受试者进行血压评价,如果服药前（药物浓度谷值时）坐位收缩压≥140 mmHg（1 mmHg=133 Pa）和/或舒张压≥90 mmHg则试验药物剂量加倍（阿齐沙坦片40 mg/次口服或奥美沙坦酯片40 mg/次,1次/d）继续治疗8周,如果服药前（药物浓度谷值时）坐位收缩压<140 mmHg且舒张压<90 mmHg则维持原剂量继续治疗8周。治疗总周期16周。观察两组的有效率和达标率。比较两组治疗前,治疗8、12、16周收缩压、舒张压,血压与治疗前差值的变化情况。结果 用药8、16周,奥美沙坦酯组有效率分别是66.89%、69.59%;阿齐沙坦组有效率分别是59.60%、58.94%,两组有效率比较差异没有统计学意义。用药8、16周,奥美沙坦酯组达标率分别是62.16%、61.49%;阿齐沙坦组达标率分别是56.95%、56.29%,两组达标率比较差异均没有统计学意义。治疗8、12、16周,两组受试者的坐位收缩压、舒张压逐渐降低,与同组治疗前比较差异均有统计学意义（P<0.05）;治疗后,两组血压比较差异无统计学意义。用药后两组受试者的坐位收缩压和舒张压均逐渐降低,至16周末时,两组间坐位舒张压下降值比较差异具有统计学意义（P<0.05）;16周末时两组收缩压下降值差异均没有统计学意义。结论 有效性方面,阿齐沙坦组疗效未达非劣效于奥美沙坦酯组,但阿齐沙坦自身的降压效果显著并具临床意义;安全性方面,阿齐沙坦组与奥美沙坦酯组不良事件、严重不良事件、不良反应发生率相当,安全性良好。     

Olmesartan medoxomil: in children and adolescents with hypertension

Olmesartan medoxomil is an orally administered angiotensin II receptor antagonist, selective for the angiotensin II type 1 receptor, which has established antihypertensive efficacy in adults. In children and adolescents with hypertension (n?=?302), oral olmesartan medoxomil significantly and dose-dependently reduced seated systolic blood pressure (BP) and seated dystolic BP from baseline (the primary endpoint) in a 3-week, dose-response period in a well designed phase II/III clinical trial. Patients received olmesartan medoxomil high dose (20 or 40?mg once daily depending on bodyweight) or low dose (2.5 or 5.0?mg once daily depending on bodyweight). The response was significant for both cohorts, which were stratified by race (cohort A was mixed race [62% White] and cohort B was 100% Black). In addition, BP control was maintained in olmesartan recipients relative to placebo recipients in cohort A and the combined cohort A?+?B, but not for patients in cohort B, during a placebo-controlled withdrawal period of this trial. Oral olmesartan medoxomil was generally well tolerated in children and adolescents with hypertension. The majority of adverse events were of mild to moderate intensity.     

Use of 24-Hour Ambulatory Blood Pressure Monitoring to Assess Antihypertensive Efficacy

INTRODUCTION: Goal rates, the percentage of patients with hypertension achieving recommended SBP/DBP, are a clinically important assessment of an antihypertensive agent's efficacy. Twenty-four-hour ambulatory blood pressure monitoring (ABPM) allows accurate assessment of a patient's hypertension and risk for cardiovascular events, and provides the most accurate measure of an antihypertensive agent's efficacy throughout a 24-hour dosing interval. METHODS: A 12-week (4-week single-blind placebo run-in phase followed by an 8-week double-blind active treatment phase) randomized, parallel-group study reported that the recommended starting dose of the angiotensin II receptor antagonist (angiotensin receptor blocker; ARB) olmesartan medoxomil (Benicar(trade mark)) 20 mg/day was more effective than starting doses of losartan potassium (Cozaar) 50 mg/day, valsartan (Diovan) 80 mg/day, or irbesartan (Avapro) 150 mg/day in reducing cuff DBP in patients with essential hypertension. The present report includes analyses of secondary efficacy variables from this 12-week trial. RESULTS: The mean reduction in blood pressure from baseline to week 8 (end of treatment) was significantly greater with olmesartan medoxomil than with valsartan for all ABPM times analyzed (24 hours, daytime, night-time, and last 2 and 4 hours of monitoring). Statistical significance was reached for comparisons of olmesartan medoxomil with losartan potassium for a majority of times analyzed and with irbesartan for SBP in the last 4 hours of monitoring. Goal rates for accepted critical ambulatory blood pressure (ABP) values of <130/80 mm Hg for mean 24-hour ABP, <135/85 mm Hg for mean daytime ABP, and <120/75 mm Hg for mean night-time ABP were significantly greater for patients receiving olmesartan medoxomil than for those receiving losartan potassium or valsartan. Goal rates were numerically superior, but not statistically significant, to those achieved with irbesartan. Compared with losartan potassium or valsartan recipients, a significantly higher percentage of patients treated with olmesartan medoxomil achieved the 24-hour ABP goal of <130/85 mm Hg. The last 2 and 4 hours of ABPM indicated that olmesartan medoxomil maintained larger mean decreases in blood pressure through the morning surge. DISCUSSION/CONCLUSION: ABP goal rates are a meaningful measure of antihypertensive efficacy. The effects on mean change from baseline in ABP and ABP goal rates after 8 weeks of treatment were numerically better, but not statistically significant, for olmesartan medoxomil than for irbesartan. However, olmesartan medoxomil was significantly more effective than losartan potassium or valsartan.     

Evaluation of olmesartan medoxomil in the rat monocrotaline model of pulmonary hypertension

It is suggested that angiotensin II is involved in the pathogenesis of pulmonary hypertension and subsequent right ventricular hypertrophy; therefore, an angiotensin AT1 receptor antagonist could be beneficial for the treatment of this disease. We tested the effect of the new AT1 receptor antagonist olmesartan medoxomil on monocrotaline-induced pulmonary hypertension in rats. At 3 weeks after a single subcutaneous injection of monocrotaline (50 mg/kg), the lung/body weight ratio, the right ventricle/(left ventricle plus septum) weight ratio [RV/(LV+S)], and right ventricular systolic pressure were increased, indicating establishment of pulmonary hypertension and right ventricular hypertrophy. Oral administration of olmesartan medoxomil (2 or 5 mg/kg/day for 3 weeks) restored RV/(LV+S) and right ventricular systolic pressure, and a higher dose (5 mg/kg/day) improved the lung/body weight ratio. Pulmonary arteries isolated from monocrotaline-treated rats exhibited an increase in basal tone in the resting state, indicating that they had intrinsic tone. Three weeks of treatment with olmesartan decreased this intrinsic tone. These data suggest that long-term treatment with olmesartan has beneficial effects on monocrotaline-induced pulmonary hypertension and subsequent right ventricular hypertrophy.     

心血管疾病新药阿齐沙坦酯的药理与临床评价

阿齐沙坦酯(azilsartan medoxomil)是一种血管紧张素II受体拮抗剂,用于治疗高血压,可与其他抗高血压药物联用。本文参照美国FDA有关该药的申报资料,对其药理作用、药代动力学、临床评价、安全性评价及药物相互作用等进行综述。     

Antihypertensive activity of SCH 31846, a non-sulfhydryl angiotensin-converting enzyme inhibitor

The antihypertensive, hemodynamic, and autonomic actions of SCH 31846, a new, potent and long-acting non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor, were evaluated in several experimental preparations. Oral administration of 0.3-3 mg/kg caused dose-related decreases in blood pressure in spontaneously hypertensive rats (SHRs). Pretreatment with a diuretic augmented the maximum hypotensive response attainable. Single doses (3 mg/kg) of SCH 31846 reduced pressure for over 24 h. Five-day treatment lowered pressure progressively. Single oral doses of 3.2 and 10 mg/kg reduced blood pressure of conscious normotensive dogs. Diuretic pretreatment also enhanced the response. The antihypertensive action of SCH 31846 in SHRs was eliminated by nephrectomy, but not attenuated by indomethacin, indicating its dependency on renal renin but not on prostaglandin synthesis. Other studies using SHRs pointed to an absence of a central effect. SCH 31846 (1 mg/kg i.v.) decreased blood pressure and peripheral resistance of anesthetized dogs but did not alter cardiac output. Autonomic interactions were examined in normal and diuretic-pretreated SHRs and anesthetized dogs. SCH 31846 affected the response to sympathetic nerve stimulation and cardiovascular reflexes only minimally. It is concluded that SCH 31846 is a potent and long-lasting antihypertensive agent, the action of which is mediated, in all probability, by ACE inhibition.     

Olmesartan medoxomil: a review of its use in the management of hypertension

Olmesartan medoxomil (Olmetec, Benicar) is an angiotensin II type 1 (AT(1)) receptor antagonist (angiotensin receptor blocker [ARB]) that inhibits the actions of angiotensin II on the renin-angiotensin-aldosterone system, which plays a key role in the pathogenesis of hypertension. Oral olmesartan medoxomil 10-40 mg once daily is recommended for the treatment of adult patients with hypertension. In those with inadequate BP control using monotherapy, fixed-dose olmesartan medoxomil/hydrochlorothiazide (HCTZ) [Olmetec plus, Benicar-HCT] combination therapy may be initiated. Extensive clinical evidence from several large well designed trials and the clinical practice setting has confirmed the antihypertensive efficacy and good tolerability profile of oral olmesartan medoxomil, as monotherapy or in combination with HCTZ, in patients with hypertension, including elderly patients with isolated systolic hypertension (ISH). Notably, BP control is sustained throughout the 24-hour dosage interval, including during the last 4 hours of this period. In clinical trials, olmesartan medoxomil monotherapy provided better antihypertensive efficacy than losartan, candesartan cilexetil or irbesartan monotherapy, and was at least as effective as valsartan treatment, with a faster onset of action than other ARBs in terms of reductions from baseline in diastolic BP (DBP) and, in most instances, systolic BP (SBP). Combination therapy with olmesartan medoxomil plus HCTZ was superior to that with benazepril plus amlodipine, as effective as that with losartan plus HCTZ, noninferior to that with atenolol plus HCTZ, but less effective than that with telmisartan plus HCTZ, in individual trials. Data from ongoing clinical outcome trials are required to more fully determine the relative position of olmesartan medoxomil therapy in the management of hypertension. In the meantime, the consistent antihypertensive efficacy during the entire 24-hour dosage interval and good tolerability profile of olmesartan medoxomil, with or without HCTZ, make it a valuable option for the treatment of adult patients with hypertension, including the elderly.     

抗高血压新药选择性AT1亚型血管紧张素II受体拮抗剂——阿齐沙坦酯

阿齐沙坦酯为新一代选择性AT1血管紧张素II亚型1受体拮抗剂,临床前和临床研究证实其具有平稳持久的抗高血压作用。2011年2月25日,FDA批准阿齐沙坦酯(商品名为Edarbi)用于治疗成人高血压。本综述主要介绍其药物作用机制,药物代谢动力学、疗效、安全性及临床研究进展。     

Olmesartan medoxomil, a newly developed angiotensin II type 1 receptor antagonist, protects against renal damage in advanced glycation end product (age)-injected rats

Diabetic nephropathy is a leading cause of end-stage renal disease in industrialized countries. Although the molecular mechanisms for the development and progression of diabetic nephropathy are not fully understood, the formation of advanced glycation end products (AGEs) and activation of the renin-angiotensin system (RAS) have been considered to be the main factors participating in the pathogenesis of diabetic nephropathy. However, functional cross-talk between AGEs and the RAS remains to be elucidated. In this study, we examined the effects of oral administration of olmesartan medoxomil, a newly developed angiotensin II type 1 receptor antagonist, on renal damage in AGE-treated rats. Administration of olmesartan medoxomil significantly inhibited the increase of systolic and diastolic blood pressure levels and urinary N-acetyl-beta-D-glucosaminidase activity in exogenously AGE-injected rats. Furthermore, olmesartan medoxomil treatment also prevented glomerulosclerosis in AGE-treated rats. These results indicate that exogenous AGE treatment could induce renal damage via the activation of the RAS. Our study suggests that olmesartan medoxomil could be a valuable drug for the treatment of diabetic nephropathy by blocking the deleterious effects of AGEs.     

In vivo pharmacologic profile of SK-1080, an orally active nonpeptide AT1-receptor antagonist

The pharmacologic profile of SK-1080, a newly synthesized AT1-receptor antagonist, was evaluated in conscious normotensive rats, conscious renally (RHRs) and spontaneously (SHRs) hypertensive rats, and conscious furosemide-treated beagle dogs. In angiotensin II-challenged normotensive rats, orally administered SK-1080 had no agonistic effect and dose-dependently inhibited the pressor response to angiotensin II with a slightly weaker potency (ID50: 1.12 and 0.47 mg/kg, respectively), but with a more rapid onset of action than losartan (time to Emax, 30 min and 6 h, respectively). In RHRs, orally given SK-1080 produced a dose-dependent and long-lasting (>24 h) antihypertensive effect with a potency similar to that of losartan (ED20, 5.06 and 3.36 mg/kg, respectively). Intravenously administered SK-1080 exerted a very highly potent antihypertensive effect (ED20, 0.06 mg/kg), thus indicating a poor oral bioavailability in rats. On repeated dosing for 21 days in SHRs, SK-1080 significantly reduced blood pressure without inducing tachycardia and tolerance throughout the dosing period. On repeated dosing, the antihypertensive effect gradually increased from days 1 to 7 (Emax on day 7, 15.0 and 19.7% at 10 and 30 mg/kg, respectively) and remained at a significant level on days 14 and 21. In furosemide-treated dogs, orally given SK-1080 produced a dose-dependent and long-lasting (>8 h) antihypertensive effect with a rapid onset of action (time to Emax, 1-1.5 h) and 10-fold greater potency than losartan (ED20, 0.72 and 8.13 mg/kg, respectively). In furosemide-treated dogs, SK-1080 showed a good oral bioavailability, unlike that in RHRs. These results suggest that SK-1080 is a potent, orally active AT1-receptor antagonist useful for the treatment of hypertension.     

A review of the structural and functional features of olmesartan medoxomil, an angiotensin receptor blocker

The angiotensin II (A-II) type 1 (AT1) receptor-mediated effects of A-II play a key role in the pathophysiology of hypertension. Effective inhibition of A-II is provided by the latest class of antihypertensive medications, the AT1 receptor blockers (ARBs). These orally available agents were developed around a common imidazole-based structural core. The most recent member of this drug class to be approved by the Food and Drug Administration, olmesartan medoxomil, contains unique features that may explain its clinical efficacy. Key structural elements of olmesartan medoxomil include a hydroxyalkyl substituent at the imidazole 4-position and a hydrolyzable ester group at the imidazole 5-position. Inter- and intramolecular hydrogen bonding involving these groups may contribute to the potentiation of antagonist activity. After oral administration, olmesartan medoxomil is deesterified in the intestinal tract to produce the active metabolite olmesartan, which undergoes no additional metabolic change. The marked antihypertensive efficacy of olmesartan medoxomil may result from a unique pharmacological interaction of the drug with the AT1 receptor, resulting in a potent, long-lasting, dose-dependent blockade of A-II. This review article characterizes the structural features of olmesartan that may be responsible for its clinical efficacy. Inferential pharmacological studies compare and contrast the effects of olmesartan to those of other ARBs in comparable preclinical animal models.     

An angiotensin II type 1 receptor antagonist,olmesartan medoxomil,improves experimental liver fibrosis by suppression of proliferation and collagen synthesis in activated hepatic stellate cells

1. We studied the effect of a new angiotensin II type 1 (AT(1)) receptor antagonist, olmesartan medoxomil (olmesartan), on the fibrogenic responses in rat hepatic stellate cells (HSCs) and liver fibrogenesis. 2. Olmesartan (1 mg kg(-1) per day) was orally administered to fibrotic rats, induced by bile duct ligation. Liver hydroxyproline content, the mRNA expression of collagen alpha1(I) and alpha-smooth muscle actin (alpha-SMA), and plasma levels of transforming growth factor-beta1 (TGF-beta1) were significantly reduced by olmesartan treatment, suggesting that olmesartan improved liver fibrosis. Interestingly, AT(1) receptors were found to be expressed in alpha-SMA-positive cells in the fibrotic area of livers in bile duct-ligated rats by immunohistochemical analysis. Olmesartan treatment reduced the number of these cells. 3. In vitro experiments showed that angiotensin II (Ang II) treatment induced proliferation and collagen synthesis, and upregulated the profibrogenic cytokines, TGF-beta1 and connective tissue growth factor (CTGF), in rat primary HSCs. Olmesartan blocked all these effects of Ang II. 4. Based on these results, since activated HSCs were found to express AT(1) receptors and Ang II is thought to play an important role in the pathogenesis of liver fibrosis by binding to these receptors, olmesartan may act as a potent antifibrotic drug to suppress the proliferation, collagen synthesis and the expression of profibrogenic cytokines in activated HSCs by blocking these receptors.