Angiotensin II receptor blockade: is there truly a benefit of adding an ACE inhibitor?

Long-Term Renoprotective Effects of Standard Versus High Doses of Telmisartan in Hypertensive Nondiabetic Nephropathies

BACKGROUND

This report describes an open randomized study intended to evaluate the long-term renoprotective effects of "standard" (80 mg once daily) versus "high" (80 mg twice daily) doses of telmisartan in hypertensive patients without diabetes with biopsy-proven chronic proteinuric nephropathies.

METHODS

We included 78 patients (age, 43.5 +/- 13.2 years; 71.8% men). After a 4-week wash-out period, patients were randomly assigned to telmisartan, 80 mg once daily (n = 40) or 80 mg twice daily (n = 38), during a mean follow-up of 24.6 +/- 2.2 months.

RESULTS

Baseline characteristics were similar in both groups, including blood pressure, renal function, and proteinuria. Blood pressure control did not differ between groups during follow-up. In the group administered telmisartan, 80 mg once daily, serum creatinine level increased from 1.6 +/- 0.6 to 2.7 +/- 0.9 mg/dL (141 +/- 52 to 239 +/- 80 micromol/L), and estimated creatinine clearance declined from 68 +/- 30 to 50 +/- 34 mL/min (1.13 +/- 0.50 to 0.83 +/- 0.57 mL/s), whereas in those administered 80 mg twice daily, serum creatinine (1.6 +/- 0.7 to 1.6 +/- 0.8 mg/dL [141 +/- 62 to 141 +/- 71 micromol/L]) and estimated creatinine clearance values (67 +/- 38 to 74 +/- 38 mL/min [1.12 +/- 0.63 to 1.23 +/- 0.63 mL/s]) did not change during the study. The decrease in proteinuria was more pronounced (P < 0.01) in patients administered the high dose of telmisartan compared with those treated with the standard dose. Serum potassium levels and lipid profiles did not change significantly in either group.

CONCLUSION

Long-term administration of high doses of telmisartan seems to improve the efficacy of the drug to decrease proteinuria and slow the progression to end-stage renal failure in nondiabetic hypertensive renal disease.

Addition of an angiotensin receptor blocker to full-dose ACE-inhibition: controversial or common sense?

Both angiotensin-converting enzyme (ACE)-inhibitors and angiotensin receptor blockers (ARBs) interfere with the activity of the renin-angiotensin system (RAS) in a different way. Theoretically, one might expect beneficial effects when they are used in combination, as a more complete suppression of the RAS can be achieved. But can this additional effect still be seen in patients on full-dose ACE-inhibition? Several controlled trials demonstrated that combination therapy can have additional benefits in hypertensive patients, in chronic heart failure patients, and in both diabetic and non-diabetic nephropathy patients. However, the clinical benefit was not always as pronounced as expected and not every patient will benefit from dual blockade of the RAS. There is some evidence of a less pronounced effect of combination therapy when a full dose of the ACE-inhibitor is given. However, it is well known that ACE-inhibitors cannot completely suppress the formation of angiotensin II, in particular, when the RAS is activated. Indeed, clinical trials indicated that add-on therapy with an ARB was especially of use when the RAS remained activated despite full-dose ACE-inhibitor treatment. In summary, combination of a full-dose ACE-inhibitor and an ARB can be a rational choice in selected patients.

Aliskiren, a novel, orally effective renin inhibitor, lowers blood pressure in marmosets and spontaneously hypertensive rats

OBJECTIVES

Aliskiren is a new renin inhibitor of a novel structural class that has recently been shown to be efficacious in hypertensive patients after once-daily oral dosing. We report the results of animal experiments performed in marmosets and rats in order to characterize aliskiren before its recent investigation in humans.

METHODS

The effects of aliskiren were investigated in sodium-depleted marmosets (oral dosing) and in spontaneously hypertensive rats (dosing via subcutaneous osmotic minipumps). Blood pressure (BP) and heart rate were measured by radiotelemetry.

RESULTS

In sodium-depleted marmosets, single oral doses of aliskiren (1-30 mg/kg) dose-dependently lowered BP. At a dose of 3 mg/kg, peak effects were observed 1 h after dosing (-30 +/- 4 mmHg, n = 6) and the response persisted for more than 12 h. A single oral dose of 3 mg/kg aliskiren was more effective than the same dose of either remikiren or zankiren, two orally active renin inhibitors previously tested in humans. Aliskiren (10 mg/kg) was at least as effective as equal doses of the AT1-receptor blocker valsartan or the angiotensin-converting enzyme inhibitor benazepril. In spontaneously hypertensive rats, aliskiren dose-dependently (10-100 mg/kg per day) decreased BP. Aliskiren also potentiated the antihypertensive effects of low doses of valsartan or benazeprilat (1 or 3 mg/kg per day).

CONCLUSIONS

Aliskiren is an orally effective, long-lasting renin inhibitor that shows antihypertensive efficacy in animals superior to previous renin inhibitors and at least equivalent to angiotensin-converting enzyme inhibitors and AT1-receptor blockers. Aliskiren may therefore represent an effective, novel approach to the treatment of hypertension and related disorders, alone or in combination with other antihypertensive agents.

Systematic Review of Combined Angiotensin-Converting Enzyme Inhibition and Angiotensin Receptor Blockade in Hypertension

Some evidence suggests that long-term angiotensin-converting enzyme (ACE) inhibition may become less effective, thereby increasing angiotensin II levels, which could be inhibited by the addition of an angiotensin receptor blocker. We conducted a meta-analysis of randomized trials with searches of MEDLINE, EMBASE, and Cochrane databases. Overall, the combination of an ACE inhibitor and an angiotensin receptor blocker reduced ambulatory blood pressure by 4.7/3.0 mm Hg (95% confidence interval [CI], 2.9 to 6.5/1.6 to 4.3) compared with ACE inhibitor monotherapy and 3.8/2.9 mm Hg (2.4 to 5.3/0.4 to 5.4) compared with angiotensin receptor blocker monotherapy. Clinic blood pressure was reduced by 3.8/2.7 mm Hg (0.9 to 6.7/0.8 to 4.6) and 3.7/2.3 mm Hg (0.4 to 6.9/0.2 to 4.4) compared with ACE inhibitor and angiotensin receptor blocker, respectively. However, the majority of these studies used submaximal doses or once-daily dosing of shorter-acting ACE inhibitors and, when a larger dose of shorter-acting ACE inhibitor was given or a longer-acting ACE inhibitor was used, there was generally no additive effect of the angiotensin receptor blocker on blood pressure. Proteinuria was reduced by the combination compared with ACE inhibitor and angiotensin receptor blocker monotherapy, an effect that was independent of blood pressure in several studies, suggesting that the combination could have benefits in proteinuric nephropathies. None of the studies was of sufficient size and duration to determine whether there may be safety concerns. In conclusion, although there is a small additive effect on blood pressure with an ACE inhibitor-angiotensin receptor blocker combination, the routine use of this combination in uncomplicated hypertension is not recommended until more carefully controlled studies are performed.

Comparison of antihypertensive effects of an angiotensin-converting enzyme inhibitor, a calcium antagonist and a diuretic in patients with hypertension not controlled by angiotensin receptor blocker monotherapy

OBJECTIVE

To compare the additional antihypertensive effects of an angiotensin-converting enzyme inhibitor (ACEI), a dihydropyridine calcium antagonist and a diuretic in patients whose hypertension is not controlled by full-dose angiotensin receptor blocker (ARB) monotherapy.

DESIGN AND METHODS

Individuals with an ambulatory blood pressure (ABP) that was not controlled by valsartan 160 mg once daily were allocated randomly to two groups: those in group A (n = 35) were assigned randomly to treatment with benazepril 20 mg once daily or chlorthalidone 12.5 mg once daily, whereas patients in group B (n = 29) were assigned randomly to benazepril 20 mg once daily or amlodipine 5 mg once daily. All individuals continued to receive background valsartan 160 mg once daily. After 5 weeks, patients crossed over to the alternative valsartan-based combination treatment of each group for a second 5-week period. Twenty-four-hour ABP monitoring was performed before the random allocation to groups and at the end of each randomized combination pharmacotherapy period.

RESULTS

Sixty-four individuals completed the study: 32 men and 32 women (mean +/- SD age 48.2 +/- 7.9 years, average 24-h ABP on valsartan monotherapy 143.4 +/- 12.6/87.7 +/- 7.8 mmHg). Significant additional antihypertensive effects on the average 24-h ABP were obtained with benazepril (8.6 +/- 8.8/6.3 +/- 6.7 mmHg), amlodipine (15.2 +/- 12.9/9.9 +/- 6.8 mmHg) and chlorthalidone (13.5 +/- 11.6/9.5 +/- 7.7 mmHg) (P < 0.001 for all additional antihypertensive effects). The additional effects of amlodipine and chlorthalidone added to valsartan were approximately 6/3.5 mmHg (P < 0.05) greater than that of benazepril.

CONCLUSIONS

In patients in whom hypertension was not controlled by full-dose ARB monotherapy, a diuretic, a calcium antagonist or an ACE inhibitor provided significant additional antihypertensive effect. The antihypertensive effects of the ARB-diuretic and the ARB-calcium antagonist combinations were superior to that of the ARB-ACE inhibitor combination.

Circadian variations in blood pressure : implications for chronotherapeutics

The management of hypertensive patients usually ignores or gives little credit to the biologic rhythms inherent to the disease process and their potential clinical implications. The development of ambulatory blood pressure monitoring and the rapidly growing popularity of home blood pressure measurements by patients have now generated a series of new clinical questions that are directly linked to the chronobiology of the cardiovascular system, such as the clinical interpretation of a blunted nocturnal fall in blood pressure or the difficulty of achieving adequate blood pressure control in the morning. Today, there is growing evidence that night-time blood pressure, and particularly the absence of a decrease in sleep blood pressure, contributes to the occurrence of target organ damages, and that the early morning rise in blood pressure increases the risk of developing cardiovascular events, including stroke, perhaps independently of 24-hour blood pressure levels. On the basis of these observations, it may be necessary to reconsider the way antihypertensive drugs are prescribed in order to obtain smooth, 24-hour blood pressure control, respecting the circadian pattern of blood pressure. Several approaches exist, including the use of drugs that lower blood pressure around the clock and respect the diurnal rhythm. Preliminary studies performed with such agents have provided interesting results. However, there is a clear need for large clinical trials demonstrating the clinical superiority of this approach. In any case, a better understanding of the importance of the circadian variations of blood pressure could certainly have a major impact on our view of the therapeutic management of hypertensive patients.

Integrating Drug Pharmacokinetics for Phenotyping Individual Renin Response to Angiotensin II Blockade in Humans

Renin release into plasma has been used to investigate the drug dose-dependence of renin-angiotensin system inhibition because it is proportional to the interruption of the permanent negative feedback loop of angiotensin II on renin secretion. We investigated the 24-hour between-subject differences in renin profiles by analyzing the time-dependence of individual renin responses in 16 mildly sodium-depleted normotensive subjects exposed in a 4-period crossover study to single oral doses of 8- and 16-mg (C8 and C16) candesartan cilexetil and 80- and 160-mg (V80 and V160) valsartan. C8 had a similar effect to V160 in terms of the increase in active renin concentration and decrease in blood pressure. C16 had the strongest effect and V80 the weakest effect on renin release. Within- and between-subject variability was more marked for valsartan pharmacokinetics than for candesartan pharmacokinetics and influenced variability in renin response. To eliminate some of the variability caused by the pharmacokinetics of each drug, we corrected the area under time curve of plasma renin levels by that of plasma drug levels to obtain an individual normalized index of renin release or “renin/pharmacokinetic index”. In these experimental conditions, this index was found to be a reproducible individual characteristic affecting renin response, in addition to the pharmacokinetics and pharmacological properties of angiotensin II type-1 receptor antagonists. The pharmacokinetic–pharmacodynamic model of renin release described here could be of value for the identification and investigation of renin release abnormalities in patients with hypertension and for the comparison of renin-angiotensin system blockers.

Telmisartan/hydrochlorothiazide: in the treatment of essential hypertension

Oral telmisartan/hydrochlorothiazide (HCTZ) combines two antihypertensive agents, a selective angiotensin II receptor antagonist with a long half-life and once-daily administration, and a thiazide diuretic. In two large, 8-week, double-blind trials, patients with hypertension unresponsive to monotherapy who received combined telmisartan/HCTZ 80/12.5 or 40/12.5 mg/day, achieved significantly larger reductions in diastolic and systolic blood pressure (BP), than recipients of continued telmisartan monotherapy (p < 0.05 for all). Compliance with telmisartan/HCTZ 80/12.5 mg/day was 98.9%. In patients with hypertension, telmisartan/HCTZ resulted in similar BP reductions to oral enalapril/HCTZ and atenolol/HCTZ in 26-week double-blind trials and greater reductions than oral losartan/HCTZ 50/12.5 mg/day in a 6-week randomised open-label trial (p < 0.001). Up to one-third of patients with hypertension initially responsive to telmisartan 40 or 80 mg/day in a 4-year study required the eventual addition of HCTZ 12.5 or 25 mg/day and/or another agent to maintain BP control. BP was controlled in about 75% of these by adding only HCTZ. In clinical trials of up to 4 years, including elderly patients, telmisartan/HCTZ had similar tolerability to placebo, with few reports of hypokalaemia. Most adverse events were mild to moderate.

Dual renin???angiotensin system blockade restores blood pressure???renin dependency in individuals with low renin concentrations

BACKGROUND

The prevailing sodium intake and renin-angiotensin system status influence the blood pressure response to an angiotensin II type 1 (AT1) receptor antagonist or an angiotensin I converting enzyme inhibitor, which is known to be reinforced by a low sodium intake or administration of a diuretic.

OBJECTIVE

To investigate the possibility that combining both drugs might be more effective in conditions of high sodium intake than blocking the renin-angiotensin system in a single step.

METHODS

In a placebo-controlled, four-period crossover study in 12 normotensive volunteers who received a high sodium chloride intake (more than 250 mmol/day for 6 days), the haemodynamic and renin effects of a single oral dose of irbesartan 150 mg combined with fosinopril 20 mg were compared with those of a usual daily dose of fosinopril (20 mg) and a high dose of irbesartan (300 mg).

RESULTS

The changes in blood pressure induced by fosinopril and irbesartan alone were not different from those of placebo, whereas the combination significantly decreased blood pressure. Simultaneously, it increased plasma active renin and prorenin concentrations to a greater extent than did each single-site blocker.

CONCLUSION

In low-renin conditions, combined renin-angiotensin system blockade enables the demonstration of a persistent renin-dependency of the blood pressure. Through its more efficient blockade of the renin-angiotensin system, demonstrated by the increase in renin and prorenin, combined renin-angiotensin system blockade is more effective than doubling the usual dose of an AT1 receptor antagonist. This may offer an alternative strategy for treating patients with a range of renin concentrations, and may potentially increase the cardio- and nephrotective benefits through a more complete blockade of the renin-angiotensin system.

How high should an ACE inhibitor or angiotensin receptor blocker be dosed in patients with diabetic nephropathy?

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), two drug classes that effectively block the actions of the renin-angiotensin system (RAS), have unique capabilities as antihypertensive agents. Recent landmark clinical trials have demonstrated their important roles as primary therapy for the prevention of renal disease in diabetes. The optimal dosage of these RAS blockers required to slow the progression of renal disease or impair the development of cardiovascular risk is not known. However, data from many studies strongly support the use of the higher doses of ACE inhibitors or ARBs to reduce proteinuria. All studies of kidney disease progression demonstrate benefit on slowing only when blood pressure is reduced when using higher doses. In order to accrue the optimum benefit from ACE inhibitors and ARBs, the dose-response relationship for diabetic renal disease will have to be determined. The best strategy, ie, supramaximal doses of ACE inhibitors or ARBs or combining them, is still a matter of debate but may be resolved soon by results of ongoing studies.

Combination is better than monotherapy with ACE inhibitor or angiotensin receptor antagonist at recommended doses

OBJECTIVE

The combination of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II (Ang II) receptor antagonist (ARB) could provide a higher degree of blockade of the renin-angiotensin system(RAS) than either agent alone. The primary aim of this study was to look at the effect of three therapeutic regimens (titrated ACE inhibitor (ACE-I) versus titrated ARB versus the combination of an ACE-I and an ARB) on the attainment of adequate blood pressure (BP) control and antiproteinuric effect. Both ACE-I and ARB were titrated as monotherapy up to the maximal recommended dose.

METHODS

A pilot randomised, parallel group open-label study was conducted in 36 patients with primary renal disease, proteinuria above 1.5 g/day and BP >140/90 mmHg while on therapy with an ACE-I. Patients were randomly assigned to (1) benazepril, n=12; (2) valsartan, n=12; or (3) benazepril plus valsartan, n=12. Other antihypertensive therapies could also be added to attain goal BP (<140/90 mmHg). The primary endpoint was the change in proteinuria during six months of follow-up.

RESULTS

In the presence of similar BP decreases and stable creatinine clearance values, mean proteinuria decreases were 0.5+1.7, 1.2+2.0 and 2.5+1.8 g/day in groups 1, 2 and 3, respectively. When compared with baseline values, only the fall induced by the combination of ARB and ACE-I attained statistical significance (p<0.05).

CONCLUSION

The antiproteinuric capacity of monotherapy at recommended doses with either an ACE-I or an ARB is lower than that obtained with the combination of the two drugs.