The relative effectiveness of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) for lowering blood pressure is unknown.

To compare the benefits and harms of ACE inhibitors versus ARBs for treating essential hypertension in adults.

MEDLINE (1966 to May 2006), the Cochrane Central Register of Controlled Trials (Issue 2, 2006), and selected reference lists were searched for relevant English-language trials. The MEDLINE search was updated to August 2007 to identify head-to-head trials that reported blood pressure outcomes and major cardiovascular events.

61 clinical studies that directly compared ACE inhibitors versus ARBs in adult patients with essential hypertension, reported an outcome of interest, lasted at least 12 weeks, and included at least 20 patients.

A standardized protocol with predefined criteria was used to extract data on study design, interventions, population characteristics, and outcomes; evaluate study quality and applicability; and assess the strength of the body of evidence for key outcomes.

ACE inhibitors and ARBs had similar long-term effects on blood pressure (50 studies; strength of evidence, high). No consistent differential effects were observed for other outcomes (few studies reported long-term outcomes), including death, cardiovascular events, quality of life, rate of single antihypertensive agent use, lipid levels, progression to diabetes, left ventricular mass or function, and kidney disease. Consistent fair- to good-quality evidence showed that ACE inhibitors were associated with a greater risk for cough. There were fewer withdrawals due to adverse events and greater persistence with therapy for ARBs than for ACE inhibitors, although this evidence was not definitive. Patient subgroups for whom ACE inhibitors or ARBs were more effective, associated with fewer adverse events, or better tolerated were not identified.

Few studies involved a representative sample treated in a typical clinical setting over a long duration, treatment protocols had marked heterogeneity, and substantive amounts of data about important outcomes and patient subgroups were missing.

Available evidence shows that ACE inhibitors and ARBs have similar effects on blood pressure control, and that ACE inhibitors have higher rates of cough than ARBs. Data regarding other outcomes are limited.