Efficacy and tolerability of angiotensin II type 1 receptor antagonists in dialysis patients using AN69 dialysis membranes

A systematic review on randomized control trials on rennin angiotensin aldosterone system inhibitors role in managing hypertension among hemodialysis patients

Randomized control trials (RCTs) are considered as most rigors way of determining the cause-effect relationship of a treatment and outcome. Activation of rennin angiotensin aldosterone system (RAAS) is an important contributor to hypertension in hemodialysis patients. The prevalence of hypertension in hemodialysis patients varies from 60% to 80% and hypertension management alone with conventional hemodialysis is insufficient. Hence, the current review was aimed to investigate the effect of RAAS inhibitors in managing hypertension among hemodialysis patients in a randomized control trial. Using PUBMED and EMBASE databases, randomized control trial with primary or secondary outcomes related to the effect of RAAS inhibitors on blood pressure among hemodialysis patients were included for analysis. The current review also assessed the quality of reporting of RCT. A total of eight RCT met inclusion criteria for current review. According to modified jaded scale, one (12.5%) study scored four points for quality reporting, whereas two (25%) studies scored one point that was the least score. The mean score for all included studies was 2.25. Six (75%) of the eight RCT included, involved ARB in hypertension management among hemodialysis patients, whereas two (25%) studies involved angiotensin-converting enzyme (ACE) inhibitors. Of the siz RCT involving ARB, two (33.3%) RCT also included ACE inhibitors comparison group. Altogether six (75%) studies report a reduction in blood pressure with the use of RAAS inhibitors compared to control group; however, of the six studies, two (33.3%) reported that the reduction in blood pressure was not significant. Whereas, two (25%) studies reported no reduction in blood pressure compared to the control group. The findings from current review do not indicate a clear pattern for a role of RAAS inhibitors for hypertension control among hemodialysis patients.

Effects of aliskiren on blood pressure and humoral factors in hypertensive hemodialysis patients previously on angiotensin II receptor antagonists

BACKGROUND

A direct renin inhibitor (DRI), aliskiren, may be effective for blood pressure (BP) control in hemodialysis patients. However, it is unclear whether aliskiren has a greater beneficial effect on BP and humoral factors than angiotensin II receptor antagonists (ARBs) in hypertensive patients on hemodialysis.

METHODS

Eighteen hemodialysis patients (58 ± 14 years) on the recommended dose of an ARB were prospectively randomized into two groups: ARB and DRI groups. Patients in the ARB group continued taking their previous ARB, whereas those in the DRI group switched to aliskiren (150 mg/day) for 12 weeks. Baseline measurements of BP and humoral factors such as plasma renin activity (PRA), plasma aldosterone concentration (PAC) and brain natriuretic peptide (BNP) were performed. Measurements were repeated every 4 weeks.

RESULTS

At baseline, no differences were observed in age, gender or BP between the two groups. Systolic BP was unaffected by treatment in either groups (group effect, p = 0.26; time effect, p = 0.38; group × time effect, p = 0.24). PRA decreased in DRI (p ≤ 0.02, group effect, p = 0.65; time effect, p = 0.13; group × time effect, p = 0.048), but not in ARB (p ≥ 0.94). PAC increased only in DRI (p ≤ 0.03), whereas BNP was unaffected in either group.

CONCLUSION

Aliskiren at a dose of 150 mg/day had a similar effect on BP compared with ARBs, but significantly lowered PRA.

Candesartan cilexetil in haemodialysis patients

OBJECTIVE

Intermittent activation of the renin-angiotensin system during dialysis may be related to the high risk of cardiovascular disease in dialysis patients. The aim of the present study was to investigate the pharmacokinetics and short-term tolerability of the angiotensin II type 1 receptor antagonist candesartan cilexetil in patients receiving chronic haemodialysis.

DESIGN

The study was a double-blind, randomised, placebo-controlled, dose-escalation study. Candesartan cilexetil was administered once daily, starting at 4mg with up-titration biweekly to 8mg and 16mg, respectively. Trough plasma concentrations of candesartan were determined before dialysis. After 2 weeks on the highest dose, plasma concentrations were obtained at frequent intervals after dose administration.

PATIENTS

Twenty patients receiving chronic haemodialysis and with adequately controlled blood pressure were included in the study. Fourteen patients were randomised to candesartan cilexetil and six to placebo.

RESULTS

Nine of the patients randomised to candesartan cilexitil reached the maximum dose of 16mg and completed the study according to protocol. Their blood pressure remained stable. Four patients discontinued active treatment due to hypotension at the lowest dose. Trough plasma concentrations of candesartan determined at the end of each study period increased linearly with dose. Following administration of candesartan cilexetil 16mg the maximum plasma concentration of candesartan was 244 +/- 54 mug/L and the area under the concentration-time curve over 24 hours, i.e. one dosing interval (AUC(tau)), was 2767 +/- 1162 mug/L . h.

CONCLUSION

Steady-state plasma concentrations of candesartan were approximately twice as high in haemodialysis patients as in subjects with normal renal function. Provided blood pressure is carefully monitored, candesartan cilexetil can be titrated from 4mg up to 16mg once daily in haemodialysis patients.

Antihypertensive agents in hemodialysis patients: a current perspective

Hypertension affects most hemodialysis patients and is often poorly controlled. Adequate control of blood pressure is difficult with conventional hemodialysis alone but is important to improve cardiovascular outcomes. Nonpharmacologic interventions to improve blood pressure include educating patients about limiting sodium intake, ensuring adequate sodium solute removal during hemodialysis, and achieving target "dry weight." However, most patients require a number of antihypertensive medications to achieve an appropriate blood pressure. First-line antihypertensive agents include angiotensin converting enzyme inhibitors and angiotensin receptor blockers given their safety profile and demonstrated benefit on cardiovascular outcomes in clinical trials. beta-blockers and combined alpha- and beta-blockers should also be used in patients with cardiovascular disease or congestive heart failure and may improve outcomes in these populations. Calcium channel blockers and direct vasodilators are also effective for controlling blood pressure. Many blood pressure agents can be dosed once daily and should preferentially be administered at night to control nocturnal blood pressure and minimize intradialytic hypotension. In patients who are noncompliant with therapy, renally eliminated agents (such as lisinopril and atenolol) can be given thrice weekly following hemodialysis. Older antihypertensive agents which require thrice daily dosing ought to be avoided given the high pill burden with these regimens and the concern for noncompliance resulting in rebound hypertension. Newer antihypertensive agents, such as direct renin inhibitors, may provide alternative options to improve blood pressure but require testing for efficacy and safety in hemodialysis patients.

Therapeutic efficacy of renin—angiotensin blockade in patients receiving dialysis

Observational data in dialysis patients has indicated an increased cardiovascular mortality. One pathophysiological cause of this cardiovascular mortality in these patients is volume overload. In addition, an inappropriately activated renin—angiotensin system (RAS) has been proposed as another possible mechanism for the increased cardiovascular mortality. With these possible causes in mind, blockade of the RAS with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB) have both emerged as means of preventing cardiovascular events in this population. This review focuses on clinical evidence of the beneficial effects of ACE inhibitors and ARBs in dialysis patients with regard to the improvement of cardiovascular events as well as blood pressure control and maintenance of dialysis therapy.

Candesartan cilexetil on regular hemodialysis: inability to reduce excessive thirst, but good tolerance and efficacy in hypertensive patients

It has been postulated that hypertension and interdialytic weight gain in hemodialysis patients are related to the activation of the renin-angiotensin system. Angiotensin II type 1 (ATI) receptor antagonists are new anti-hypertensive agents and are currently the most specific means of blocking the renin-angiotensin enzymatic cascade. Recent studies show that candesartan cilexetil regulates thirst and hypertension in rodents, via cerebral AT1 receptor blockade. We therefore conducted a prospective open study of candesartan cilexetil in 21 hypertensive patients on long-term hemodialysis during 6 weeks, focusing on thirst regulation. We also performed a prospective follow-up study of tolerance of candesartan and its anti-hypertensive efficacy after this 6-week study, while the patients remained on this therapy. Weight gain between hemodialysis sessions did not differ between the periods before and during candesartan cilexetil therapy. Median absolute interdialytic weight gain was 2.35 kg (range: 0.55-5) before therapy, compared to 2.25 kg (range: 0.35-4.65) during therapy (p > 0.05, Wilcoxon test). The median interdialytic weight gain/dry weight index was 3.7% (range: 1.15-7) before therapy and 3.6% (range: 0.7-6.6) during candesartan therapy (p > 0.05, Wilcoxon test). The median dose of candesartan cilexetil was 12 mg/day (range: 4-24). The median total duration of therapy with candesartan (including the 6 weeks of the thirst study) was 12 months (range: 2-25). During candesartan cilexetil therapy, the number of concomitant anti-hypertensive drugs per patient fell significantly (median number of anti-hypertensive drugs before candesartan =2 (range: 1-6); during candesartan =1 (range: 1-5) (p < 0.02, Wilcoxon test). No anaphylactoid reactions occurred. A total of 161 episodes of hypotension (5%) occurred during 3074 hemodialysis sessions (including the 6 weeks of the thirst study) We conclude that, like angiotensin converting enzyme inhibitors and the other angiotensin receptor antagonists, candesartan cilexetil is unable to reduce interdialytic weight gain in hemodialysis patients. This study also shows that the irreversible angiotensin II receptor antagonist candesartan cilexetil is a safe and effective therapeutic option for hypertensive hemodialysis patients.

The Role of Angiotensin II Type 1 Receptor Antagonists in Elderly Patients with Hypertension

Hypertension is a major risk factor for stroke and coronary events in elderly people and clinical trials have shown that treatment of hypertension with various drugs can result in a substantial reduction in cerebrovascular and cardiovascular events. The angiotensin II type 1 (AT1) receptor antagonists are the newest class of antihypertensive agents to be used widely in clinical practice. AT1 receptor antagonists can generally be given once-daily. They are also extremely well tolerated with minimal first-dose hypotension and an incidence of adverse effects similar to that seen with placebo. Adverse event rates are significantly lower than with other classes of antihypertensive drugs including ACE inhibitors. These factors result in improved compliance and increased rates of continuance on therapy. AT1 receptor antagonists show similar efficacy in lowering blood pressure to other classes of antihypertensive agents and their antihypertensive effect is potentiated when they are given concomitantly with low-dose thiazide diuretics. AT1 receptor antagonists are eliminated predominantly by the hepatic route but most are not subject to extensive metabolism and interactions with other drugs are uncommon. This is an advantage in the elderly, who are often receiving multiple medications which increases the risk for adverse drug interactions. Dose adjustments are not usually required in the elderly unless there is plasma volume depletion. Although plasma AT1 receptor antagonist concentrations are generally higher in the elderly than in younger subjects, this pharmacokinetic difference may be balanced by decreased activation of the circulating renin-angiotensin-aldosterone system in the elderly. Recent clinical studies in high-risk hypertensive patients with left ventricular hypertrophy or in patients with diabetic nephropathy or heart failure have demonstrated that AT1 receptor antagonists can improve clinical outcomes to a similar or sometimes greater extent than other antihypertensive agents. Many of these studies have included large numbers of older patients and have confirmed the excellent tolerability profile of these drugs. Thus, AT1 receptor antagonists should be considered as a possible first-line treatment or as a component of combination therapy in patients with type 2 diabetes mellitus and microalbuminuria or nephropathy and as an alternative or additional treatment to ACE inhibitors in patients with heart failure or left ventricular dysfunction. AT1 receptor antagonists also appear to reduce the onset of new diabetes compared with some other antihypertensive drugs. The benefits in terms of organ protection have mainly been seen in studies using higher doses of particular AT1 receptor antagonists and it is not certain at present whether these results can be extrapolated to other members of the class. As the elderly are more likely to have developed organ damage related to hypertension or to have heart failure or diabetes as concomitant conditions, AT1 receptor antagonists represent an appropriate option for many elderly patients. The main disadvantage of these drugs is the cost of the medication but this may be offset by their improved tolerability with fewer adverse reactions and thus increased compliance, resulting in better blood pressure control and fewer clinical events. Overall, AT1 receptor antagonists are well tolerated and efficacious for blood pressure-lowering when given as a single daily dose in elderly patients and have many potential benefits in high-risk hypertensive subjects.

Drug therapy for hypertension in hemodialysis patients

The majority of end-stage renal disease (ESRD) patients are hypertensive. Drug therapy for hypertension in hemodialysis (HD) patients includes all classes of antihypertensive drugs, with the sole exception of diuretics. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers may decrease morbidity and mortality by reducing the mean arterial pressure (MAP), aortic pulse wave velocity, and aortic systolic pressure augmentation, as well as left ventricular hypertrophy (LVH) and probably reduction of C-reactive protein (CRP) and oxidant stress. Potential risk factors include hyperkalemia, anaphylactoid reaction with AN69 membranes (particularly ACE inhibitors), and aggravation of renal anemia. beta-blockers decrease not only mortality, blood pressure (BP), and ventricular arrhythmias, but also improve left ventricular function in ESRD patients. Nonselective beta-blockers can cause an increase in serum potassium (particularly during fasting or exercise). Lisinopril and atenolol have a predominant renal excretion and therefore a prolonged half life in ESRD patients. Thus thrice-weekly supervised administration of these drugs after HD can enhance BP control. The use of calcium channel blockers is also associated with lower total and cardiovascular-specific mortality in HD patients. Minoxidil is a very potent vasodilator that is generally reserved for dialysis patients with severe hypertension. Hypertensive dialysis patients who are noncompliant with their medications may benefit from transdermal clonidine therapy once a week. The majority of dialysis patients need a combination of several antihypertensive drugs for adequate BP control.

Renal handling of angiotensin receptor blockers: clinical relevance

Angiotensin receptor blockers (ARBs), like angiotensin-converting enzyme (ACE) inhibitors, are commonly used in the setting of chronic kidney disease. The use of drugs in this class, or for that matter any drug in the renally compromised patient, should raise consideration of the impact of renal disease on the systemic elimination of the compound. Unlike most of the drugs in the ACE inhibitor class, the compounds making up the ARB class undergo significant hepatic elimination; thus, in the renal failure patient, they are not prone to relevant degrees of systemic accumulation with repetitive dosing. ARBs do not require dose adjustment in renal failure on the basis of their pharmacokinetic pattern; rather, dose reduction should be an empiric process dictated by having reached or exceeded the goal established for blood pressure reduction.

The pharmacokinetics and pharmacodynamics of angiotensin-receptor blockers in end-stage renal disease

Angiotensin-converting enzyme (ACE) inhibitors and more recently angiotensin-receptor blockers (ARBs) have become popular therapies in the end-stage renal disease (ESRD) patient. The ability of either of these drug classes to reduce blood pressure in the ESRD patient is well accepted; however, there is considerably less information available to guide the clinician in the safe and effective use of these drugs in the ESRD patient with congestive heart failure and/or coronary artery disease. Head-to-head studies in the ESRD patient are lacking for both drug classes. Several pharmacokinetic factors can influence the selection of these drugs, including dialysability and the propensity for systemic accumulation. ACE inhibitors (ACE-Is) and ARBs are recognised as having a range of nonpressor effects that are pertinent to patients with ESRD. Such effects include their ability to decrease both thirst drive and erythropoiesis. These drug classes, though, are distinguishable by the unique adverse effect profile for ACE-Is. As is the case in patients without renal failure, ESRD patients can experience cough and, less frequently, angioneurotic oedema with ACE-Is. In the ESRD population, so-called anaphylactoid dialyser reactions can occur in conjunction with ACE-I use. The use of a drug from within the ARB class carries both less risk and permits a compound with a preferred pharmacokinetic profile limited dialysability and minimal systemic accumulation to be administered. These attributes would favour the increased use of ARBs in this population.