Valsartan in heart failure patients previously untreated with an ACE inhibitor

Spectrum of use for the angiotensin-receptor blocking drugs

The renin-angiotensin system (RAS) plays an important role in regulating blood pressure, and maintaining fluid and electrolyte balance. Angiotensin II is the principal mediator of the RAS and has been implicated in the development of hypertension as well as other forms of cardiovascular and renal disease. Angiotensin II-receptor antagonists are a new class of drugs that inhibit the RAS by selectively blocking the AT(1) receptor. These compounds therefore provide more specific and thorough blockade of the RAS by inhibiting the deleterious actions of angiotensin II at the receptor level, irrespective of how this peptide is formed. The increased specificity of action of angiotensin II-receptor antagonists may also circumvent unwanted side-effects normally associated with angiotensin-converting enzyme (ACE) inhibitors (eg, cough and angioedema) as these agents do not interfere with the metabolism of other peptides (eg, bradykinin, substance P, etc.). There is still some concern with angiotensin II-receptor antagonists and the long-term effects of hyper-stimulation of the unopposed AT(2) receptor that is caused by elevated levels of angiotensin II. However, it appears that stimulation of the AT(2) receptor may actually contribute to the beneficial effects of angiotensin II-receptor antagonists by counteracting the effects mediated by the AT(1) receptor. Angiotensin II-receptor antagonists display great therapeutic promise in the field of cardiovascular medicine and are currently being exploited as new antihypertensive agents. These drugs have demonstrated safety, efficacy, and tolerability; however, morbidity and mortality data are still lacking. Nonetheless, it is likely that angiotensin II-receptor antagonists will become part of the medical arsenal against cardiovascular and renal disease, thus consideration should be given to their future use as first-line antihypertensive agents.

Recent insight into therapy of congestive heart failure: focus on ACE inhibition and angiotensin-II antagonism

One possible intervention to interrupt the deleterious effects of the renin-angiotensin system is suppression of angiotensin II (Ang II) formation by inhibition of angiotensin-converting enzyme (ACE). However, ACE inhibition incompletely suppresses Ang II formation and also leads to accumulation of bradykinin. Angiotensin II type 1 (AT1) receptors are believed to promote the known deleterious effects of Ang II. Therefore, AT1 receptor antagonists have been recently introduced into therapy for hypertension and congestive heart failure (CHF). Although there are significant differences between the effects of AT1 receptor antagonists and ACE inhibitors including the unopposed stimulation of angiotensin II type 2 (AT2) receptors by AT1 receptor antagonists, the discussion of whether ACE inhibitors, AT1 receptor antagonists or the combination of both are superior in the pharmacotherapy of CHF is still largely theoretical. Accordingly, AT1 receptor antagonists are still investigational. Angiotensin-converting enzyme inhibitors remain first line therapy in patients with CHF due to systolic dysfunction. However, in patients not able to tolerate ACE inhibitor induced side effects, in particular cough, AT1 receptor antagonism is a good alternative. In clinical practice, emphasis should be placed on increasing the utilization of ACE inhibitors, as more than 50% of patients with CHF do not receive ACE inhibitors. In addition, the majority of those on ACE inhibitors receive doses lower than the dosage used in the large clinical trials. Although not yet completely proved, it is likely that high doses of ACE inhibition are superior to low doses with respect to prognosis and symptoms.