Candesartan cilexetil in hypertension: effects of six weeks' treatment on haemodynamics, baroreceptor sensitivity and the renin-angiotensin-aldosterone system

Safety and efficacy of candesartan versus valsartan combined with amlodipine on peripheral and central blood pressure

INTRODUCTION

"Amlodipine/valsartan" or "amlodipine/candesartan" combinations represent two effective antihypertensive agents with complementary mechanisms of action. Nevertheless, a study has yet to be done to evaluate the effect of amlodipine/candesartan on central blood pressure and compare it with amlodipine/valsartan combination. To see how "amlodipine plus candesartan combination" reduces peripheral and central blood pressure compared to the most studied combination, "amlodipine plus valsartan".

MATERIAL AND METHODS

Eighty-six patients were randomized in an open-label, prospective study by 1:1 ratio to two groups. Group I (n=42) received the amlodipine and valsartan combination, and group II (n=44) received the amlodipine and candesartan combination. Peripheral and central blood pressure (CBP) was measured at baseline, at 6 and 12 weeks of follow-up.

DISCUSSION

Both treatment groups reduced peripheral systolic, diastolic, and mean blood pressure. There was no significant difference between and within both groups. The amlodipine/candesartan combination showed more reduction in peripheral systolic blood pressure (PSBP) after 12 weeks of treatment (p=<0.001). Both groups decreased CBP without significant differences between groups. The amlodipine/candesartan combination showed additional efficacy in decreasing CSBP after 12 weeks (p=<0.001). The two treatment groups did not exert significant efficacy in lowering heart rate (HR) and augmentation index% (AIx%).

CONCLUSION

To conclude, the amlodipine 10mg/candesartan 16mg combination was non-inferior to the amlodipine 10mg/valsartan 160mg combination in terms of reducing peripheral and CBP over time.

The Role of Angiotensin Receptor Blockers in the Personalized Management of Diabetic Neuropathy

Neuropathy is a frequent complication of diabetes mellitus (DM) and is associated with the increased risk ofamputation and vascular events. Tight glycemic control is an important component inthe prevention of diabetic neuropathy. However, accumulating data suggest that angiotensin receptor blockers (ARBs) might also be useful in this setting. We discuss the findings of both experimental and clinical studies that evaluated the effects of ARBs on indices of diabetic neuropathy. We also review the implicated mechanisms of the neuroprotective actions of these agents. Overall, it appears that ARBs might be a helpful tool for preventing and delaying the progression of diabetic neuropathy, but more data are needed to clarify their role in the management of this overlooked complication of DM.

A bedtime dose of ARB was better than a morning dose in improving baroreflex sensitivity and urinary albumin excretion--the J-TOP study

The hypothesis that the bedtime dosing of angiotensin receptor blocker (ARB) is superior to morning dose in improving baroreflex sensitivity (BRS) and urinary albumin/creatinine ratio (UACR) was tested in this study. Baroreflex sensitivity was measured at baseline and at 6th month (N = 109) and was found to increase in the bedtime-dose group (P = .004), but not in the morning-dose group. The correlations between the change in BRS and the change in UACR were insignificant in the morning-dose group (r = 0.17, P = .26), but were significant in the bedtime-dose group (r = -0.29, P = .04). In conclusion, the improvement of BRS could be one of the mechanisms by which bedtime dosing of ARB confers renal protection.

Angiotensin II Type 1 Receptors and Systemic Hemodynamic and Renal Responses to Stress and Altered Blood Volume in Conscious Rabbits

We examined how systemic blockade of type 1 angiotensin (AT(1)-) receptors affects reflex control of the circulation and the kidney. In conscious rabbits, the effects of candesartan on responses of systemic and renal hemodynamics and renal excretory function to acute hypoxia, mild hemorrhage, and plasma volume expansion were tested. Candesartan reduced resting mean arterial pressure (MAP, -8 ± 2%) without significantly altering cardiac output (CO), increased renal blood flow (RBF, +38 ± 9%) and reduced renal vascular resistance (RVR, -32 ± 6%). Glomerular filtration rate (GFR) was not significantly altered but sodium excretion (U(Na+)V) increased fourfold. After vehicle treatment, hypoxia (10% inspired O(2) for 30 min) did not significantly alter MAP or CO, but reduced heart rate (HR, -17 ± 6%), increased RVR (+33 ± 16%) and reduced GFR (-46 ± 16%) and U(Na+)V (-41 ± 17%). Candesartan did not significantly alter these responses. After vehicle treatment, plasma volume expansion increased CO (+35 ± 7%), reduced total peripheral resistance (TPR, -26 ± 5%), increased RBF (+62 ± 23%) and reduced RVR (-32 ± 9%), but did not significantly alter MAP or HR. It also increased U(Na+)V (803 ± 184%) yet reduced GFR (-47 ± 9%). Candesartan did not significantly alter these responses. After vehicle treatment, mild hemorrhage did not significantly alter MAP but increased HR (+16 ± 3%), reduced CO (-16 ± 4%) and RBF (-18 ± 6%), increased TPR (+18 ± 4%) and tended to increase RVR (+18 ± 9%, P = 0.1), but had little effect on GFR or U(Na+)V. But after candesartan treatment MAP fell during hemorrhage (-19 ± 1%), while neither TPR nor RVR increased, and GFR (-64 ± 18%) and U(Na+)V (-83 ± 10%) fell. AT(1)-receptor activation supports MAP and GFR during hypovolemia. But AT(1)-receptors appear to play little role in the renal vasoconstriction, hypofiltration, and antinatriuresis accompanying hypoxia, or the systemic and renal vasodilatation and natriuresis accompanying plasma volume expansion.

Blood pressure lowering efficacy of angiotensin receptor blockers for primary hypertension

BACKGROUND

Angiotensin receptor blockers (ARBs) are widely prescribed for hypertension so it is essential to determine and compare their effects on blood pressure (BP), heart rate and withdrawals due to adverse effects (WDAE).

OBJECTIVES

To quantify the dose-related systolic and/or diastolic BP lowering efficacy of ARBs versus placebo in the treatment of primary hypertension.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library 2007, Issue 1), MEDLINE (1966 to February 2007), EMBASE (1988 to February 2007) and reference lists of articles.

SELECTION CRITERIA

Double-blind, randomized, controlled trials evaluating the BP lowering efficacy of fixed-dose monotherapy with an ARB compared with placebo for a duration of 3 to 12 weeks in patients with primary hypertension.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information. WDAE information was collected from the trials.

MAIN RESULTS

Forty six RCTs evaluated the dose-related trough BP lowering efficacy of 9 ARBs in 13 451 participants with a baseline BP of 156/101 mm Hg. The data do not suggest that any one ARB is better or worse at lowering BP. A dose of 1/8 or 1/4 of the manufacturers' maximum recommended daily dose (Max) achieved a BP lowering effect that was 60 to 70% of the BP lowering effect of Max. A dose of 1/2 Max achieved a BP lowering effect that was 80% of Max. ARB doses above Max did not significantly lower BP more than Max. Due to evidence of publication bias, the largest trials provide the best estimate of the trough BP lowering efficacy for ARBs as a class of drugs: -8 mm Hg for SBP and -5 mm Hg for DBP. ARBs reduced BP measured 1 to 12 hours after the dose by about 12/7 mm Hg.

AUTHORS' CONCLUSIONS

The evidence from this review suggests that there are no clinically meaningful BP lowering differences between available ARBs. The BP lowering effect of ARBs is modest and similar to ACE inhibitors as a class; the magnitude of average trough BP lowering for ARBs at maximum recommended doses and above is -8/-5 mmHg. Furthermore, 60 to 70% of this trough BP lowering effect occurs with recommended starting doses. The review did not provide a good estimate of the incidence of harms associated with ARBs because of the short duration of the trials and the lack of reporting of adverse effects in many of the trials.

Small artery remodelling in hypertension: causes, consequences and therapeutic implications

Essential hypertension is treated primarily with a view to reducing blood pressure, and not with regard to normalizing the main pathological changes: the peripheral resistance and the cardiovascular structure. The aim of this review is to discuss whether normalization of the latter parameters, in particular resistance vessel structure, may also be a target for therapy. The review presents first the evidence for altered structure of the resistance vasculature, an increase in the media:lumen ratio of the vessels due to inward eutrophic remodelling. Secondly the degree to which it may be possible to rectify the abnormal structure is discussed, where it is shown that there is strong evidence that this requires a therapy which causes vasodilatation in the patient concerned. Thirdly evidence is presented that altered small artery structure appears to have prognostic consequences. Fourthly, the cellular mechanisms which may be involved are discussed, where there is evidence that vasoconstriction in itself can cause inward remodelling, and that this can be prevented by vasodilators. Finally, the consequences of these findings are considered as regards clues for strategies that may be able to improve the outcome of antihypertensive therapy. The review concludes that there is reasonably strong evidence that a treatment which reduces peripheral resistance in the individual patient will, apart from reducing blood pressure, also improve the abnormal structure.

Why is blood pressure so hard to control in patients with type 2 diabetes?

Resistance to antihypertensive drugs is common in hypertensive patients with type 2 diabetes. This is unfortunate because hypertension is one of the most important risk factors for development of cardiovascular events, and the goal blood pressure level is set lower in diabetic subjects than in nondiabetic subjects. Previous outcome trials in diabetic subjects have mainly focused on end points such as microalbuminuria or the incidence of cardiovascular events rather than on reduction of blood pressure; some reports, however, have suggested mechanisms for the drug resistance. These include several clinical conditions known to be associated with difficulty in reducing blood pressure specifically in diabetes mellitus: change in the renin-angiotensin system and chymase, volume overload, central sympathetic hyperactivity, sleep apnea, secondary hypertension, pseudoresistance (white coat hypertension), and poor compliance related to subclinical depression. In this review, the authors focus on the mechanisms of resistance to antihypertensive therapy (particularly for monotherapy with either angiotensin-converting enzyme inhibitors or angiotensin II antagonists) in the treatment of diabetic hypertension.

Candesartan

Candesartan cilexetil is the prodrug of candesartan, an angiotensin II receptor antagonist. Candesartan binds selectively and non-competitively to the angiotensin II receptor type 1, thus preventing the actions of angiotensin II. Clinical trials have demonstrated its efficacy at a dose range of 2 to 32 mg once daily in hypertension of all grades, heart failure, in reducing urinary albumin excretion in diabetes mellitus and in coexisting hypertension and renal failure. Pharmacokinetic properties of candesartan cilexetil in elderly patients are not significantly different from those in younger individuals. Hepatic impairment does not change pharmacokinetics of candesartan cilexetil at doses up to 12 mg/day. No dose adjustment is necessary in patients with mild or moderate renal impairment. Tolerability of candesartan cilexetil is not much different from that of placebo. All adverse events are usually of mild to moderate severity and not dose-related. The most common adverse events were headache, upper respiratory tract infection, back pain, and dizziness. The incidence of these adverse effects, as well as of cough, was similar in patients treated with candesartan cilexetil or placebo. The incidence of adverse events in long-term trials was not different from that in short-term trials. Tolerability of candesartan cilexetil does not differ with either age or gender.

Effects of Atenolol and Losartan on Baroreflex Sensitivity and Heart Rate Variability in Uncomplicated Essential Hypertension

Baroreflex sensitivity (BRS) and heart rate variability (HRV) are potential therapeutic targets. The present study was conducted to assess changes in BRS and HRV after monotherapy with losartan versus that of atenolol in uncomplicated essential hypertension. Thirty subjects with uncomplicated essential hypertension were randomized to receive atenolol 50 mg to 100 mg (n = 15) or losartan 50 mg to 100 mg (N = 15) daily for 6 months. Instantaneous systolic blood pressure (SBP) and heart rate were assessed using servo-controlled infrared finger plethysmography before treatment and at the end of 3 months and 6 months after treatment. The fluctuation in SBP and interpulse interval (IPI) was divided into three specific frequency ranges by fast Fourier transform as high frequency (HF; 0.15 Hz-0.4 Hz), low frequency (LF; 0.04 Hz-0.15 Hz), and very low frequency (VLF; 0.004 Hz-0.04 Hz). The BRS was expressed as (1) SBP-IPI transfer function with its magnitude in the HF and LF ranges and (2) BRS index alpha. The HRV was expressed as total power and power in the LF and HF ranges of interpulse interval. Blood pressure was reduced to a similar extent in both groups. Compared with the baseline, BRS did not improve in both groups at month 3. However, BRS was significantly improved in the losartan group (P < 0.05) but not in the atenolol group at month 6. In addition, BRS was significantly higher in the losartan group than the atenolol group at month 3 and month 6 (P < 0.05). Moreover, heart rate variability was significantly reduced in the atenolol group at month 6 (P < 0.05), but not in the losartan group. The HRV in the losartan group was significantly higher than that in the atenolol group at month 6 (P < 0.05). These findings suggest superior effects of losartan on BRS and HRV than atenolol in uncomplicated essential hypertension, which may be beyond blood pressure reduction/resetting.

Nocturnal hemodialysis increases arterial baroreflex sensitivity and compliance and normalizes blood pressure of hypertensive patients with end-stage renal disease

BACKGROUND

Impaired neural control of heart rate, elevated arterial stiffness, and hypertension place patients with end-stage renal disease (ESRD) at increased risk of cardiovascular mortality. Nocturnal hemodialysis (6 x 8 hours/week), a more intense program than conventional hemodialysis (3 x 4 hours/week), lowers blood pressure and restores brachial dilator responses to hyperemia and nitrates.

METHODS

We hypothesized that nocturnal hemodialysis would increase arterial baroreflex sensitivity for heart rate of hypertensive ESRD patients by an afferent vascular mechanism. Ten consecutive hypertensive ESRD patients (age 42 +/- 4) (mean +/- SEM) receiving conventional hemodialysis were studied before and 2 months after conversion to nocturnal hemodialysis. Regression slopes relating RR interval responses to rises or falls in systolic blood pressure were averaged to derive spontaneous baroreflex sensitivity for heart rate for each patient, and the stroke volume/pulse pressure ratio was used to estimate total arterial compliance.

RESULTS

Dialysis dose (Kt/V per session) increased from 1.2 +/- 0.05 to 2.1 +/- 0.1 (P < 0.05). Despite withdrawal of antihypertensive medications (from 2.9 to 0.1 drugs/patient), nocturnal hemodialysis lowered systolic blood pressure (from 143 +/- 4 to 120 +/- 6 mm Hg) (P= 0.001). Both baroreflex sensitivity (from 4.76 +/- 1.1 msec/mm Hg to 6.91 +/- 1.1 msec/mm Hg) (P= 0.04) and total arterial compliance (from 0.98 +/- 0.13 mL/mm Hg to 1.43 +/- 0.2 mL/mm Hg) (P= 0.02) were higher following conversion to nocturnal hemodialysis. Increases in baroreflex sensitivity correlated with increases in stroke volume/pulse pressure (r= 0.845, P= 0.002).

CONCLUSION

These findings are consistent with the concept that nocturnal hemodialysis increases baroreflex sensitivity via greater afferent baroreceptor responsiveness to pulsatile pressure. A more favorable risk profile, due to enhanced baroreflex regulation of the circulation and vascular compliance, may translate into lower cardiovascular event rates in ESRD patients receiving nocturnal hemodialysis.

Persistent sympathetic activation during chronic antihypertensive therapy: a potential mechanism for long term morbidity?

Previous studies have demonstrated that antihypertensive treatment resets baroreflex control of heart rate (HR) and increases cardiac vagal baroreflex sensitivity. However, it is uncertain whether baroreflex control of muscle sympathetic nerve activity (MSNA) also resets after treatment. We tested the hypothesis that chronic antihypertensive therapy alters baroreflex regulation of MSNA in patients with untreated moderate hypertension. Seven newly diagnosed patients with systolic blood pressure (BP) of 159+/-5 mm Hg (mean+/-SE) and diastolic BP of 103+/-4 mm Hg were studied before and after 1 to 2 weeks ' and 3 months (chronic) of antihypertensive treatment with losartan-hydrochlorothiazide (Hyzaar). MSNA and hemodynamics were measured supine, during a Valsalva maneuver (VM), and at 70 degrees head-up tilt (HUT) for 10 minutes. Data were compared with those obtained in 7 age-matched healthy controls. We found that Hyzaar lowered mean BP acutely and chronically by 20+/-4 and 23+/-3 mm Hg (both P<0.01) but did not change HR. Supine MSNA increased by 43+/-11% and 34+/-11% after acute and chronic treatment (both P<0.01). However, MSNA responses to VM and HUT did not differ after treatment compared with before treatment, indicating unchanged reflex control. These data indicate that sympathetic neural activity was augmented substantially by antihypertensive treatment with Hyzaar, consistent with an ongoing baroreflex unloading, and did not return to baseline or "reset" after 3 months of therapy. We speculate that persistent and marked sympathetic activation by the baroreflex may be a potential mechanism for hypertension that is refractory to antihypertensive therapy and may provide a target mechanism for persistent morbidity despite adequate BP control.

Candesartan cilexetil: an update of its use in essential hypertension

Candesartan cilexetil is converted to the angiotensin II receptor antagonist candesartan during absorption from the gastrointestinal tract. The selective and competitive binding of candesartan to the angiotensin II type 1 (AT(1)) receptor prevents binding of angiotensin II, a key mediator in the renin-angiotensin system. Significant reductions in systolic BP and diastolic BP are achieved with a once-daily dosage of candesartan cilexetil 2 to 32 mg/day in patients with mild to moderate hypertension. In randomised studies, candesartan cilexetil 8 to 16 mg/day was at least as effective as therapeutic dosages of losartan or other angiotensin II receptor antagonists. At a dosage of up to 32 mg/day candesartan cilexetil demonstrated greater antihypertensive efficacy than losartan 50 or 100 mg/day. In comparative trials, candesartan cilexetil demonstrated similar or greater antihypertensive efficacy compared with enalapril or hydrochlorothiazide and equivalent efficacy compared with amlodipine. The efficacy of candesartan cilexetil is not affected by age, and the drug provided significant BP reductions in Black patients and in those with severe hypertension. Long-term clinical studies to assess the effects of treatment with candesartan cilexetil on cardiovascular morbidity and mortality are ongoing. Regression of left ventricular hypertrophy has been seen with candesartan cilexetil treatment in patients with hypertension. Furthermore, the drug has favourable effects on renal function in patients with hypertension with or without coexisting diabetes mellitus. Renal vascular resistance and albumin excretion were reduced following treatment with candesartan cilexetil. Glucose homeostasis and lipid metabolism were not affected by treatment in patients with type 2 diabetes mellitus. Candesartan cilexetil is well tolerated and is not associated with cough, a common adverse effect of angiotensin converting enzyme inhibitor treatment. A pooled analysis of clinical trials found that the tolerability profile of candesartan cilexetil is not significantly different from that of placebo. Adverse events are not dose-related and are generally of mild to moderate severity.

CONCLUSIONS

Candesartan cilexetil is an effective antihypertensive agent with a tolerability profile similar to that of placebo. Comparative data indicate that candesartan cilexetil has antihypertensive efficacy equivalent to that of other major classes of antihypertensive agents and has a long duration of action. Therefore, candesartan cilexetil is a useful therapeutic option in the management of patients with hypertension.

Long-term effects of olmesartan, an Ang II receptor antagonist, on blood pressure and the renin-angiotensin-aldosterone system in hypertensive patients

The object of this study is to evaluate the long-term effects of olmesartan on hypertension and the renin-angiotensin-aldosterone system in hypertensive patients. This study evaluated 26 hypertensive male and female outpatients, 38-69 years of age, with a systolic blood pressure > or = 160 mmHg and/or a diastolic blood pressure > or = 95 mmHg. Oral doses of 5 to 40 mg olmesartan were administered once daily. Blood pressure and renin-angiotensin-aldosterone parameters (plasma renin activity and plasma angiotensin I, II, and aldosterone concentrations) were evaluated at 12-16 weeks, 6 months, and 1 year after the start of olmesartan administration. Systolic and diastolic blood pressures were significantly decreased following the administration of olmesartan. The observed decreases in systolic and diastolic blood pressures after 1 year of treatment were 28.8+/-2.1 mmHg and 15.8+/-1.3 mmHg, respectively. No change was observed in the pulse rate. The plasma renin activity increased significantly from a baseline premedication mean of 1.26+/-0.31 ng/ml/h to a mean of 2.58+/-0.74 ng/ml/h and 2.87+/-0.72 ng/ml/h after 6 months and 1 year of treatment, respectively. Angiotensin II levels decreased significantly from a baseline of 20.4+/-3.2 pg/ml to a mean of 8.6+/-2.1 pg/ml and 6.8+/-1.8 pg/ml after 6 months and 1 year of treatment, respectively. The plasma aldosterone level also decreased significantly after 6 months of treatment. In hypertensive patients, the long-term administration of olmesartan, a novel AT1 receptor antagonist, decreased both blood pressure and plasma angiotensin II levels.