Have angiotensin receptor blockers lived up to expectations?

Angiotensin receptor blockers (ARBs) were introduced after clinical trials showed angiotensin-converting enzyme inhibitors (ACEIs) to have extensive clinical benefits in a wide range of diseases. Consequently, it has been more difficult for clinical trials to demonstrate similar, enhanced or additive benefits of ARBs. However, ARBs were introduced with the hypothesis that they were likely a more effective method of interrupting the renin-angiotensin system and would result in enhanced outcomes. Clinical trials in high-risk vascular patients (after myocardial infarction), patients with heart failure and patients with nephropathy show the benefits of ACE inhibition. ARBs likely have similar benefits as ACEIs when used after myocardial infarction, in patients with heart failure and for management of diabetic nephropathy. However, ARBs generally remain a second-line treatment because it has been more difficult to demonstrate that ARBs prevent acute vascular events, such as myocardial infarction, together with the greater clinical trial evidence for ACE inhibition. The primary application of ACEIs over ARBs is reflected in the Canadian clinical guidelines for the management of patients with diabetes, hypertension, heart failure and following myocardial infarction. Until the completion of clinical trials, such as the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), that examine whether ARBs have vascular protective properties similar to ACEIs, it is unlikely that the clinical guidelines will change.