Angiotensin II Receptor Blockers Inhibit the Generation of Epoxyeicosatrienoic Acid from Arachidonic Acid in Recombinant CYP2C9, CYP2J2 and Human Liver Microsomes

Cytochrome P450 (CYP) 2C9, CYP2C8 and CYP2J2 enzymes, which metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids, have cardioprotective effects including anti‐inflammation and vasodilation. We have recently shown that some angiotensin II receptor blockers (ARBs) may inhibit AA metabolism via CYP2C8. Using recombinant CYP2C9, CYP2J2 and human liver microsomes (HLMs), the aim was now to compare the ability of six different clinically used ARBs to inhibit AA metabolism in vitro. The rank order of the ARBs for the 50% inhibitory concentration (IC₅₀) of AA metabolism was losartan <telmisartan <irbesartan <candesartan <olmesartan <valsartan via CYP2C9, and telmisartan <irbesartan <olmesartan <losartan <candesartan and valsartan via CYP2J2. The order for the HLMs was losartan <telmisartan <irbesartan <olmesartan <candesartan <valsartan. Some ARBs having lower concentration of IC₅₀ indicate that these ARBs might inhibit the AA metabolism in the liver.     

Cardiovascular Outcomes in High-Risk Patients without Heart Failure Treated with ARBs

Background and objective

Angiotensin II type 1 receptor antagonists (ARBs) are widely used as a substitute for angiotensin-converting enzyme inhibitors (ACEIs) to treat patients without heart failure, but their effect on cardiovascular morbidity and mortality has not been clearly determined. A systematic review and metaanalysis was undertaken to determine the impact of ARBs on cardiovascular outcomes in high-risk patients without heart failure.

Methods

A computerized literature search was carried out using PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, and EMBASE, from January 1990 to April 2008. The following search terms were used: ‘hypertension’, ‘clinical trial’, ‘sartan’, ‘ARB’, ‘angiotensin receptor antagonist’, ‘losartan’, ‘candesartan’, ‘valsartan’, ‘irbesartan’, ‘eprosartan’, ‘telmisartan’, ‘olmesartan’, ‘coronary disease’, ‘coronary heart disease’, ‘myocardial infarction’, ‘cardiovascular disease’, ‘cerebrovascular disease’, and ‘stroke’. Criteria for inclusion of clinical trials in our meta-analysis were the use of a randomized control group not receiving an ARB and the availability of outcome data for any one of four endpoints: myocardial infarction (MI), stroke, cardiovascular death, and all-cause death (these were not always pre-specified endpoints in all trials). Out of 45 potentially relevant studies, 37 trials met the inclusion criteria. We tabulated all occurrences of these four adverse outcomes.

Results

Homogenous subgroups were combined by means of a fixed-effects model, while heterogenous subgroups were not combined. In the subgroup without heart failure, ARBs, when compared with the control group, had an odds ratio of 1.09 (95% CI 1.00, 1.18; p = 0.05) for MI. Other endpoints, namely, cardiovascular death and all-cause death, did not reach statistical significance. There was a clear trend for fewer strokes in the ARB group, but these studies were clearly heterogenous, and therefore a pooled risk estimate was not computed.

Conclusion

After pooling more than 89 000 patients, there is no evidence to suggest that ARBs confer cardiovascular protection akin to ACEIs, and the results that emerged are not in favor of ARB therapy in terms of its use as a substitute for ACEIs in non-heart failure patients. ARBs may have a small benefit in terms of stroke risk, but the studies are heterogenous, making it very difficult to quantify this effect. Given that ACEIs protect against both stroke and MI, caution is advised in the use of ARBs as a substitute for ACEIs in patients without a heart failure indication, who are tolerant of an ACEI.     

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.     

Inhibitory effects of angiotensin receptor blockers on CYP2C9 activity in human liver microsomes

We investigated the inhibitory effects of the angiotensin receptor blockers (ARBs), candesartan, irbesartan, losartan, losartan active metabolite (EXP-3174), olmesartan, telmisartan and valsartan (0.3-300 microM), on the CYP2C9 activity in human liver microsomes using (S)-(-)-warfarin as a typical CYP2C9 substrate. Except for olmesartan and valsartan, these ARBs inhibited the activity of 7-hydroxylation of (S)-(-)-warfarin with IC50 values of 39.5-116 microM. Of six synthetic derivatives of olmesartan, five compounds which possess either alkyl groups or a chloro group at the same position as that of the hydroxyisopropyl group in olmesartan inhibited CYP2C9 activity with IC50 values of 21.7-161 microM. Olmesartan and the olmesartan analogue, RNH-6272, both having a hydroxyisopropyl group, showed no inhibition, indicating that the hydrophilicity of this group greatly contributes to the lack of CYP2C9 inhibition by these two compounds. A three-dimensional model for docking between EXP-3174 and CYP2C9 indicated that the chloro group of EXP-3174 is oriented to a hydrophobic pocket in the CYP2C9 active site, indicating that the lipophilicity of the group present in ARBs at the position corresponding to that of the hydroxyisopropyl group in olmesartan is important in inhibiting CYP2C9 activity.     

Antihypertensive Effects of Olmesartan Compared with Other Angiotensin Receptor Blockers

Objectives: Angiotensin II type 1 receptor antagonists (angiotensin receptor blockers [ARBs]) have been shown to be effective and well tolerated in hypertensive patients. Olmesartan is the seventh angiotensin receptor blocker licensed by the US Food and Drug Administration. The aim of this meta-analysis was to determine the efficacy and tolerability of olmesartan medoxomil in comparison with other ARBs. Data Sources: Reports of randomized controlled trials (RCTs) of olmesartan versus other ARBs were identified through a systematic search of PubMed (up to July 2010), EMBASE (1980 to July 2010), SinoMed (up to July 2010), and the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 7, 2010). Review Methods: Pertinent studies were selected through extensive searches of PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and SinoMed. Two of the authors abstracted data from the identified studies independently. Criteria for inclusion in our meta-analyses were randomized clinical trials in which patients were receiving an ARB and outcome data for blood pressure reduction or the incidence of adverse events were available. Quantitative and qualitative analyses of data from all RCTs meeting the criteria were performed. Our meta-analysis was undertaken according to the Quality of Reporting Meta-analyses (QUOROM) statement. Results: Twenty-two studies with data from 4892 patients were considered for analyses. Olmesartan provided greater diastolic blood pressure (DBP) and systolic blood pressure (SBP) reductions compared with losartan (DBP: 95% confidence interval [CI] 0.59, 2.62; SBP: 95% CI 0.46, 5.92). Olmesartan provided greater SBP reductions compared with valsartan (95% CI 0.29, 3.16). Similar blood pressure response rates and incidence of adverse events were found with losartan, valsartan, candesartan, and irbesartan. Conclusion: Olmesartan provides better antihypertensive efficacy than losartan and valsartan and has no association with an increased risk of adverse events in comparison with losartan, valsartan, candesartan, and irbesartan.     

The value of irbesartan in the management of hypertension

Elevated blood pressure levels are highly prevalent and are a major reason for cardiovascular events and thus place a significant financial burden on healthcare systems worldwide. Guidelines recommend five first-line anti-hypertensive drug classes, but compelling indications may indicate favoring one drug class over another. Angiotensin receptor blockers (ARBs) have demonstrated a blood pressure lowering efficacy which is at least comparable with other drug classes, including ACE inhibitors (ACE-I), β-blockers, calcium channel blockers and diuretics. They have, in addition, a lower side effect profile than other drug classes and patients on ARBs are more persistent with therapy. Compelling indications for the use of ARBs are heart failure, post-myocardial infarction, diabetic nephropathy, proteinuria/microalbuminuria, left ventricular hypertrophy, atrial fibrillation, metabolic syndrome and ACE-I induced cough. The ARB irbesartan has demonstrated a high efficacy in lowering blood pressure, which has been shown to be at least comparable with ACE-Is and superior to other ARBs such as losartan and valsartan. This translated into a better cost-effectiveness for irbesartan than for valsartan and losartan in the treatment of hypertension. In addition, irbesartan has been shown to be effective in both early and late stage diabetic nephropathy. It has further demonstrated considerable cost savings over standard therapy including β-blockers, diuretics and non-dihydropyridine calcium channel blockers at all stages of kidney disease. Based on efficacy data from the Irbesartan Diabetic Nephropathy Trial and Reduction of Endpoints in NIDDM (non insulin dependant diabetes melitis) with the Angiotensin II Antagonist Losartan Study, it has also demonstrated cost savings over losartan in late stage renal disease. While both losartan and irbesartan are registered for the treatment of late stage diabetic nephropathy, irbesartan is also registered for early stage diabetic nephropathy in the EU. In summary, the data from randomized clinical trials on the efficacy of antihypertensive drugs provides an indication of their real value to patients. In addition observational data from clinical practice and proven end-organ protection in diabetic nephropathy provides further evidence of the true value of irbesartan compared to other ARBs in 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.     

Telmisartan has the strongest binding affinity to angiotensin II type 1 receptor: comparison with other angiotensin II type 1 receptor blockers

There is a growing body of evidence that the renin-angiotensin system (RAS) plays a pivotal role in the pathogenesis of cardiovascular diseases. Indeed, large clinical trials have demonstrated a substantial benefit of the blockade of this system for cardiovascular-organ protection. Although several types of angiotensin II type 1 (AT1) receptor blockers (ARBs) are commercially available for the treatment of patients with hypertension, comparisons of the binding affinity to AT1 receptor among them remain to be elucidated. In this study, we examined the dissociation rate of several ARBs from AT1 receptor in vitro. Angiotensin II time-dependently dissociated telmisartan, olmesartan, candesartan, valsartan, losartan and an active metabolite of losartan, EXP3174, from membrane components containing human AT1 receptor The dissociation rate constant of each ARB was 0.003248, 0.004171, 0.005203, 0.009946, 0.01027 and 0.008561 min(-1), with corresponding half-lives of 213, 166, 133, 70, 67 and 81 min, respectively. These results demonstrate that telmisartan has the strongest binding affinity to AT1 receptor among various ARBs examined herein. The rank order of affinity was telmisartan > olmesartan > candesartan > EXP3174 > or = valsartan > or = losartan. The present findings suggest that telmisartan (Micardis) may have long-lasting blood pressure-lowering effects and superior cardioprotective properties in patients with hypertension due to its strongest AT1 receptor antagonistic ability.     

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.     

4种血管紧张素Ⅱ受体拮抗药治疗轻中度高血压的成本-效果分析

目的:评价4种血管紧张素Ⅱ受体拮抗药治疗轻中度高血压的成本-效果。方法:104例轻、中度高血压患者分为4组,分别应用替米沙坦、氯沙坦钾、厄贝沙坦、缬沙坦治疗,8wk后比较临床效果并进行成本-效果分析。结果:4种用药方案在疗效比较上差异无统计学意义(P>0·05),成本分别为684·00、760·80、659·20、720·80元,成本-效果比分别为7·74、9·51、7·91、8·07。结论:替米沙坦从药物经济学的角度分析为治疗轻中度高血压的较优药物。     

Involvement of Uric Acid Transporters in Alteration of Serum Uric Acid Level by Angiotensin II Receptor Blockers

Purpose To examine the mechanisms of the alteration of serum uric acid level by angiotensin II receptor blockers (ARBs), the effects of ARBs on renal uric acid transporters, including OAT1, OAT3, OAT4, and MRP4, were evaluated. Materials and Methods Uptakes of uric acid by OAT1-expressing Flp293 cells, by Xenopus oocytes expressing OAT3 or OAT4, and by membrane vesicles from Sf9 cells expressing MRP4 were evaluated in the presence or absence of ARBs. Results All ARBs inhibited uptake of uric acid or estrone-3-sulfate by OAT1, OAT3 and OAT4 in concentration dependent manners. Among them, the IC₅₀ values of valsartan, olmesartan and pratosartan for OAT3 were comparable to clinically observed unbound maximum plasma concentration of ARBs. Candesartan, losartan, and telmisartan inhibited ATP-dependent uptake of uric acid by MRP4 at 10 μM. The IC₅₀ value of losartan for MRP4 was comparable to the estimated kidney tissue concentration of losartan. No ARBs showed trans-stimulatory effects on the uptake of estrone-3-sulfate by OAT4. Conclusion Valsartan, olmesartan, and pratosartan could inhibit the OAT3-mediated uric acid secretion in clinical situations. Furthermore losartan could inhibit ATP-dependent uric acid secretion by MRP4. These effects may explain partially the alteration of serum uric acid level by ARBs.     

Investigation of Carcinogenic Impurities of N-Nitrosamines in Sartan Pharmaceutical Products Marketed in Brazil: Development and Validation of Method Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry

N-nitrosamines (NA) impurities have unexpectedly been found in sartan products, angiotensin II receptor antagonists that are used to control hypertension, representing an urgent concern for industry, global regulators and for the patients. In this study, an HPLC-MS/MS method was developed and validated for the quantification of six NA (N-nitrosodimethylamine, N-Nitroso-N-methyl-4-aminobutyric acid, N-Nitrosodiethylamine, N-ethyl-N-nitroso-2-propanamine, N-nitroso-diisopropylamine and N-nitroso-di-n-butylamine) in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan products. The method was validated in terms of sensitivity, linearity, accuracy, precision, robustness and stability. The limits of quantification were 100, 31.25, 250, 33, 312.5 and 125 µg kg⁻¹ in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan samples, respectively, which met the sensitivity requirements for the limits set by Food and Drug Administration of the United States. The standard curves showed good linearity. The recoveries ranged from 93.06 to 102.23% in losartan matrix, 83 to 85.9% in valsartan, 96.1 to 101.2% in olmesartan, 89.2 to 97.5% in irbesartan, 93.4 to 132.0% in candesartan and 62.3 to 106.2% in telmisartan matrix. The other parameters met the validation criteria, the good sensitivity and precision, high accuracy and simple and fast analysis provides a reliable method for quality control of NA in sartan pharmaceutical products. The developed method was successfully applied for the determination of N-nitrosamines in 71 sartan products marketed in Brazil.     

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.     

Comparison of angiotensin II type 1 receptor antagonists in the treatment of essential hypertension

Hypertension is a major health problem worldwide, yet remains under-diagnosed and under-treated. Angiotensin II type 1 receptor antagonists (angiotensin receptor blockers [ARBs]) are highly effective at reducing blood pressure (BP), exhibit renoprotective properties and have placebo-like tolerability. However, it is unclear whether there are clinical differences in efficacy and tolerability between the available ARBs. A review of published, randomized, comparative clinical trials suggests that differences in BP-lowering efficacy and 24-hour BP control may exist between ARBs, although it appears that there is no evidence for important differences in tolerability between ARBs. Few studies have assessed attainment rates for important combined systolic BP (SBP)/diastolic BP (DBP) goals recommended in treatment guidelines. Likewise, few studies have directly compared more than two agents or ARB/hydrochlorothiazide fixed-dose combinations, and most ARBs have not been compared across their full recommended dosage ranges. Overall, there is insufficient weight of evidence to allow definitive conclusions to be drawn regarding the comparative efficacy of the available ARBs. However, newer ARBs (e.g. olmesartan medoxomil and telmisartan) appear to be more effective than older ARBs (e.g. losartan and valsartan) in reducing DBP and/or SBP in some trials. In addition, olmesartan medoxomil treatment regimens resulted in high BP control rates in several trials, but head-to-head trials with other ARBs are required to put these control rates into perspective, especially for SBP control with various agents. The purpose of this review is to present published data from ARB efficacy trials for a comparison of various efficacy parameters among the agents within this drug class.     

Substrate recognition of renally eliminated angiotensin II receptor blockers by organic anion transporter 4

Organic anion transporter (OAT) 4, which is localized at the apical membrane of human renal proximal tubules, transports olmesartan, an angiotensin II receptor blocker (ARB). Many ARBs, including olmesartan, undergo partial tubular secretion as active forms, and inhibit OAT4-mediated uptake activity. Here, we examined the substrate recognition of various ARBs by OAT4 in order to assess whether OAT4 might be involved in the renal handling of ARBs. Concentration-dependent OAT4-mediated uptake of azilsartan, candesartan, carboxylosartan, losartan, and valsartan was observed with K_m values of 6.6, 31, 7.2, 13, and 1.7 μM, respectively, in the absence of extracellular Cl⁻. In the presence of extracellular Cl⁻, OAT4-mediated uptake of dianionic ARBs (azilsartan, candesartan, carboxylosartan, and valsartan) was lower and reached a steady state faster than in the absence of extracellular Cl⁻. Thus, OAT4 is proposed to use extracellular Cl⁻ as a counterpart for anion efflux. Our results suggest that OAT4 may play a role in the excretion of azilsartan, candesartan, carboxylosartan, and valsartan, as well as olmesartan. In contrast, OAT4-mediated uptake of losartan, a monoanionic ARB, was little affected by extracellular Cl⁻, suggesting that only OAT4-mediated dianion transport is Cl⁻-sensitive.     

Irbesartan: a review of its use in hypertension and in the management of diabetic nephropathy

Irbesartan (Avapro, Aprovel) is a potent and selective angiotensin II subtype 1 receptor antagonist indicated for use in patients with hypertension, including those with type 2 diabetes mellitus and nephropathy. Once-daily administration of irbesartan provided 24-hour control of blood pressure (BP). In patients with mild-to-moderate hypertension irbesartan was as effective as enalapril, atenolol and amlodipine, and more effective than valsartan in terms of absolute reduction in BP and response rates. Irbesartan produced a greater reduction in diastolic BP at trough than once-daily losartan, but had a smaller effect than olmesartan; the reduction in systolic BP achieved with irbesartan was similar or greater than that with losartan and similar to that seen with olmesartan. The combination of irbesartan with hydrochlorothiazide produced additive effects on BP reduction. Irbesartan also induced regression of left ventricular mass in patients with hypertension and left ventricular hypertrophy. In two large studies (IRbesartan MicroAlbuminuria type 2 diabetes mellitus in hypertensive patients [IRMA 2] and the Irbesartan Diabetic Nephropathy Trial [IDNT]) irbesartan exerted a renoprotective effect in hypertensive patients with type 2 diabetes at both the early and later stages of diabetic nephropathy. The renoprotective effect was at least partly independent of the BP-lowering effect. In the IRMA 2 trial, the proportion of patients progressing to overt nephropathy was significantly lower for recipients of irbesartan 300mg once daily than placebo. In patients with overt nephropathy in the IDNT, irbesartan 300mg once daily provided significantly greater renoprotection than amlodipine 10mg once daily or placebo. The relative risk of doubling of serum creatinine was significantly lower with irbesartan than amlodipine or placebo. Irbesartan is well tolerated in hypertensive patients, including those with type 2 diabetes and incipient or overt nephropathy. The overall incidence of adverse events with irbesartan was similar to that with placebo. Irbesartan was associated with a lower incidence of cough than enalapril and was not associated with ankle oedema or with any clinically significant drug interactions. In conclusion, irbesartan is a well tolerated and effective antihypertensive agent. It also slows the progression of renal disease in hypertensive patients with type 2 diabetes at both the early and later stages of diabetic nephropathy. Thus, irbesartan is a valuable agent in the management of patients with these indications.     

Comparative cost effectiveness of angiotensin II receptor blockers in a US managed care setting: olmesartan medoxomil compared with losartan,valsartan, and irbesartan

OBJECTIVE: To compare the cost effectiveness of the angiotensin II receptor blockers (ARBs) olmesartan medoxomil, losartan, valsartan and irbesartan for the treatment of hypertension, from the perspective of a US managed care setting. METHODS: The evaluation was based on a recently completed, prospective, randomised, double-blind clinical trial comparing the antihypertensive efficacy of these agents. Differences in diastolic blood pressure reductions among the comparative agents were used to estimate reductions in the annualised risk of cardiovascular (CV) and cerebrovascular events using the Framingham model. These annualised risks were translated into reductions in healthcare expenditures associated with treating CV events covered by managed care in the US. Data sources included: the recently published clinical trial of ARB antihypertensive efficacy, the Framingham Heart Study and a managed care database. Actual reimbursed amounts were used. RESULTS: Based on antihypertensive efficacy data versus irbesartan, the use of olmesartan medoxomil is expected to reduce the number of new cases of CV disease, resulting in a first-year reduction in cost in a cohort of 100,000 patients of 906,000 US dollars. Similarly, a reduction in new cases of coronary heart disease (CHD) resulted in a cost reduction of 701,000 US dollars; a cost reduction of 196,000 US dollars for fewer myocardial infarctions (MI); and a cost reduction of 28,000 US dollars for fewer strokes. Over 5 years, these estimates increase to 5,410,000 US dollars for fewer cases of CV disease; 3,975,000 US dollars for fewer cases of CHD; 1,430,000 US dollars for fewer MI; and 497,000 US dollars for fewer strokes. Compared with valsartan, the use of olmesartan medoxomil is estimated to reduce by 3,397,000 US dollars the expected cost of treating a cohort of 100 000 patients in the first year for fewer cases of CV disease; by 2,426,000 US dollars for fewer cases of CHD; by 565,000 US dollars for fewer MI; and by 124,000 US dollars for fewer strokes. Over 5 years, these estimates increase to 16,231,000 US dollars for CV disease; 11,955,000 US dollars for CHD; 4,505,000 US dollars for MI; and 1,741,000 dollars for stroke. Compared with losartan, the estimated reduction in first-year cost is 2,969,000 US dollars for CV disease for the cohort of 100,000 patients; 2,163,000 US dollars for CHD; 732,000 US dollars for MI; and 124,000 US dollars for stroke. Over 5 years, these estimates increase to 15,149,000 US dollars for CV disease; 11,107,000 US dollars for CHD; 4,057,000 US dollars for MI; and 1,437,000 dollars for stroke. CONCLUSION: Based on comparative antihypertensive efficacy data, treatment of hypertensive patients with olmesartan medoxomil instead of the other leading ARBs has the potential to reduce overall cost of medical care in a US managed care setting.     

Rapid Quantitation of Four Nitrosamine Impurities in Angiotensin Receptor Blocker Drug Substances

Starting in July 2018, the FDA alerted patients and health care professionals to the recall of ARBs such as valsartan by several pharmaceutical companies because of their potential contamination with carcinogenic nitrosamine impurities, including: (1) N-nitrosodimethylamine (NDMA), (2) N-nitrosodiethylamine (NDEA), (3) N-nitrosoethylisopropylamine (NEIPA), (4) N-nitrosodiisopropylamine (NDIPA), (5) N-nitrosodibutylamine (NDBA) and (6) N-nitroso-N-methyl-4-aminobutyric acid (NMBA). The FDA initiated a laboratory investigation to develop analytical procedures to test multiple lots of marketed ARB drugs to determine the possible presence of carcinogenic impurities and, if present, quantitate the levels of these impurities.Here the FDA laboratory developed and validated an automated micro-solid phase extraction MS/MS method, where all the analytes are not separated prior to elution to the MS, to simultaneously quantify NEIPA, NDIPA, NDBA and NMBA in ARB drug substances with an instrument sample analysis time of 12 seconds. The method was validated according to the ICH Q2(R1) guideline, and was determined to be specific, accurate, precise and linear over the corresponding nitrosamine analytical ranges. The method has been successfully implemented to quantitate the four nitrosamine impurities in 129 generic losartan, valsartan, olmesartan, irbesartan and telmisartan drug substance samples from 32 lots; and 32 losartan and valsartan drug product samples from 6 lots.     

Effects of angiotensin receptor blockers on endothelial nitric oxide release: the role of eNOS variants

AIM

Angiotensin II receptor blockers (ARBs) improve endothelial cell (EC)-dependent vasodilation in patients with hypertension through suppression of angiotensin II type 1 receptors but may have additional and differential effects on endothelial nitric oxide (NO) synthase (eNOS) function. To investigate this question, we tested the effects of various ARBs on NO release in ECs from multiple donors, including those with eNOS genetic variants linked to higher cardiovascular risk.

METHODS

The effects of ARBs (losartan, olmesartan, telmisartan, valsartan), at 1 µm, on NO release were measured with nanosensors in human umbilical vein ECs obtained from 18 donors. NO release was stimulated with calcium ionophore (1 µm) and its maximal concentration was correlated with eNOS variants. The eNOS variants were determined by a single nucleotide polymorphism in the promoter region (T-786C) and in the exon 7 (G894T), linked to changes in NO metabolism.

RESULTS

All of the ARBs caused an increase in NO release as compared with untreated samples (P < 0.01, n = 4–5 in all eNOS variants). However, maximal NO production was differentially influenced by eNOS genotype. Olmesartan increased maximal NO release by 30%, which was significantly greater (P < 0.01, n = 4–5 in all eNOS variants) than increases observed with other ARBs.

CONCLUSIONS

The ARBs differentially enhanced NO release in ECs in a manner influenced by eNOS single nucleotide polymorphisms. These findings provide new insights into the effects of ARBs on EC-dependent vasodilation and eNOS function.     

Effect of an Olmesartan Medoxomil-Based Treatment Algorithm on Systolic Blood Pressure in Patients with Stage 1 or 2 Hypertension

Background and Objective

Elevated systolic BP (SBP) is a major contributor to cardiovascular disease. SBP control reduces the occurrence of stroke, heart failure, and cardiovascular and total mortality. The aim of this study was to analyze the magnitude of SBP reductions and the achievement of individual SBP targets in the original BENIFORCE study.

Methods

An olmesartan medoxomil-based treatment algorithm was evaluated in a double-blind, placebo-controlled titration study in 276 patients with stage 1 (47.1%) or 2 (52.9%) hypertension. After placebo run-in, patients were randomized to placebo (12 weeks) or olmesartan medoxomil 20 mg/day (weeks 1–3). Olmesartan medoxomil was uptitrated to 40 mg/day (weeks 4–6), then olmesartan medoxomil/hydrochlorothiazide (HCTZ) 40/12.5 mg per day (weeks 7–9), and olmesartan medoxomil/HCTZ 40/25 mg per day (weeks 10–12) if BP remained ≥120/80 mmHg at any time interval.

Setting

The BENIFORCE study was a multicenter (29 sites) study conducted between January and October 2007 in the US.

Results

In patients receiving olmesartan medoxomil-based therapy, 81.0%, 67.2%, and 46.6% of patients with stage 1 hypertension and 70.4%, 49.4%, and 23.5% of patients with stage 2 hypertension achieved SBP targets of <140, <130, and <120 mmHg, respectively (all p<0.01 vs placebo). The proportions of patients achieving SBP targets increased with escalating doses of olmesartan medoxomil and HCTZ, administered alone or in combination, and was highest for combination therapy. Similarly, escalating doses of olmesartan medoxomil or olmesartan medoxomil/HCTZ increased the proportion of patients achieving SBP reductions of >15 but ≤30, >30 but ≤45, and >45 mmHg compared with placebo.

Conclusion

An olmesartan medoxomil-based treatment algorithm effectively reduced SBP and achieved SBP targets in patients with stage 1 or 2 hypertension. This regimen resulted in >80% of patients achieving SBP reductions of ≥15 mmHg while 44% achieved SBP reductions of >30 mmHg.