Pharmacodynamics and Pharmacokinetics of Irbesartan in Patients With Mild to Moderate Hypertension

Comprehensive overview: efficacy, tolerability, and cost-effectiveness of irbesartan

Background

Hypertension represents a major health problem, affecting more than one billion adults worldwide. Irbesartan, an angiotensin II receptor blocker, is considered to be a highly effective treatment in the management of hypertension. The purpose of this review is to evaluate the efficacy, safety and tolerability profile , and cost-effectiveness of treatment with irbesartan in hypertension.

Methods

A review of the literature was conducted using the electronic PubMed and Cochrane Library databases and the Health Economic Evaluations Database of search terms relating to irbesartan efficacy, tolerability, and cost-effectiveness, and the results were utilized.

Results

Findings from the present analysis show that irbesartan either as monotherapy or in combination with other antihypertensive agents can achieve significant reductions in blood pressure, both systolic and diastolic, compared with alternative treatment options. Irbesartan was also found to have a renoprotective effect independent of its blood pressure-lowering in patients with type 2 diabetes and nephropathy. Furthermore, irbesartan demonstrated an excellent safety and tolerability profile , with either lower or equal adverse events compared with placebo and other alternative treatments. In terms of economic analyses, compared with other antihypertensive therapy alternatives, irbesartan was found to be a preferred option, that is less costly and more effective.

Conclusion

The evidence indicates that treating patients with hypertension alone or with type 2 diabetes and nephropathy using irbesartan can control hypertension, prolong life, and reduce costs in relation to existing alternatives.

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.

Pharmacokinetics of irbesartan are not altered in special populations

Studies were conducted to determine whether pharmacokinetics of irbesartan (IRBE), a potent, long-acting angiotensin (AT)-II receptor antagonist selective for AT-II type 1 receptor subtype, are altered in patients with renal impairment (RI), hepatic impairment (HI), or heart failure (HF) or by patient gender, age, or race. IRBE pharmacokinetics and blood pressure (BP) response in hypertensive (HT) children and adolescents were also studied. HI or RI (including end-stage renal disease requiring hemodialysis) had no effect on IRBE pharmacokinetics after single or repeated dosing. IRBE was not removed by hemodialysis. In patients with New York Heart Association class II or III HF, IRBE single-dose pharmacokinetics were not altered following either oral or IV administration. There were no clinically significant differences in IRBE pharmacokinetics between men and women, elderly and young, or black and white patients. No accumulation of IRBE occurred with repeated dosing in RI or HI patients or in HT men or women. In a pediatric study, IRBE pharmacokinetics were comparable between 6- to 12-year and 13- to 16-year age groups and to that previously determined for adult subjects receiving the same dose; accumulation of IRBE was minimal during multiple dosing. IRBE lowered BP in the pediatric population. Adverse event profile with IRBE was similar in all patient groups. Based on these pharmacokinetic and safety data, no dosage adjustments of IRBE are necessary for patients with RI, HI, or HF, or based on patient age, gender, or race. IRBE may be a treatment option for pediatric HT patients. The pharmacokinetic profile of IRBE and lack of necessary dosage adjustments in special populations suggest that IRBE is an excellent choice for management of hypertension across all patient groups.

Irbesartan: an updated review of its use in cardiovascular disorders

Irbesartan interrupts the renin-angiotensin system via selective blockade of the angiotensin II subtype 1 receptor; the latter being responsible for the pressor related effects of angiotensin II. As treatment for mild to moderate hypertension, irbesartan 150 mg/day controlled diastolic BP in 56% of patients according to pooled data from several phase III studies and 77% of patients in a large phase IV study. in comparative trials, irbesartan was significantly more effective than losartan and valsartan as treatment for mild to moderate essential hypertension and as effective as enalapril or atenolol. Results from many studies show an additive antihypertensive effect when hydrochlorothiazide is added to irbesartan monotherapy. The drug also induces statistically significant regression of left ventricular mass in patients with hypertension and left ventricular hypertrophy, and preliminary evidence suggests it has beneficial haemodynamic effects in patients with heart failure. Irbesartan is very well tolerated, exhibiting an adverse event profile similar to that seen with placebo in comparative trials. In conclusion, although the role of irbesartan as a treatment for heart failure is little clearer than it was 2 years ago, the place of the drug in the management of hypertension is now better established. There is evidence to suggest the drug may have a role as initial therapy for hypertension, although formal recommendation in management guidelines will almost certainly not occur until long term morbidity and mortality benefits are established.