A Review of the Clinical Experience with the Angiotensin II Receptor Antagonist Irbesartan

AT1receptor antagonism in hypertension: what has been learned with irbesartan?

Irbesartan is a long-acting angiotensin II antagonist acting specifically at the level of the Type 1-receptor subtype (AT1-receptor). This compound lowers blood pressure dose-dependently in hypertensive patients and has a placebo-like tolerability. The antihypertensive efficacy of irbesartan is greatly enhanced by the coadministration of a diuretic, and fixed-dose combinations of irbesartan and hydrochlorothiazide are now available. Irbesartan-based treatment appears especially effective for high-risk patients, such as those with diabetes, renal disease and cardiac hypertrophy. In patients with Type 2 diabetes, irbesartan delays the development of nephropathy as well as the progression of renal failure. Irbesartan may have antiatherosclerotic properties beyond those expected from blood pressure lowering per se: this AT1-blocker decreases the vascular oxidative stress and prevents the procoagulant as well as the pro-inflammatory effects of angiotensin II. Irbesartan given alone or in combination with a diuretic therefore represents a rational approach to treat hypertensive patients.

Fraxinus excelsior L. evokes a hypotensive action in normal and spontaneously hypertensive rats

The hypotensive effect of an aqueous extract of Fraxinus excelsior L. was investigated in both normotensive (WKY) and spontaneously hypertensive rats (SHR). Daily oral administration of Fraxinus excelsior (20 mg/kg) aqueous extract for 3 weeks produced a significant decrease in systolic blood pressure (SBP) with variation coefficient (Delta%) of 13.5% in SHR (p<0.01) and 9% in WKY rats (p<0.05). The aqueous extract of Fraxinus excelsior significantly enhanced the urination in both SHR (p<0.05 compared to control) and WKY (p<0.05 compared to control). Irbesartan (Avapro), an angiotensin II antagonist, was used as reference drug. Furthermore, oral administration of aqueous Fraxinus excelsior extract at a dose of 20 mg/kg produced a significant increase in urinary excretion of sodium (p<0.01 compared to control), potassium (p<0.001 compared to control) and chlorides (p<0.01) in SHR rats. In normal rats, the aqueous Fraxinus excelsior extract administration induced a significant increase of the urinary elimination of sodium (p<0.05 compared to control), chlorides (p<0.01 compared to control) and potassium (p<0.01 versus control). While there were no significant changes in heart rate (HR) after Fraxinus excelsior treatment in both SHR and WKY rats, glomerular filtration rate (GFR) showed a significant increase in SH rats (p<0.001) after Fraxinus excelsior treatment. These results suggest that oral administration of aqueous extract of Fraxinus excelsior exhibited hypotensive and diuretic actions.

Fixed low-dose combination therapy for hypertension

Despite the availability of various classes of antihypertensive agents that lower blood pressure by different primary actions, the treatment of hypertension remains a difficult task. Essential hypertension has a highly heterogeneous character, so that monotherapies are often not sufficient to normalize blood pressure. This is especially true since the goal of treatment is currently to normalize both systolic and diastolic blood pressure. By combining medications acting by different mechanisms, it is possible to gain considerably in terms of antihypertensive efficacy because of synergistic impacts on the cardiovascular system. Furthermore, low doses of antihypertensive agents are generally sufficient when used in combination, which accounts for the excellent tolerability of combination products. Fixed low-dose combinations are very useful tools for treating hypertensive patients. Because of their simplicity of use, and the fact that they improve the blood pressure response rate while minimizing the incidence of adverse effects, such combinations are increasingly being considered as suitable for both second-line and first-line therapy.