Renin-angiotensin system inhibitors versus other types of medicine for hypertension

What is hypertension?

Hypertension is a long-lasting medical condition in which a person's blood pressure is high. Hypertension can contribute to other health problems such as heart disease, stroke, and kidney problems, and so reduces quality of life.

What medicines can be used to treat hypertension?

There are a number of types of medicines that can be used to treat hypertension. These include three types of renin-angiotensin system (RAS) inhibitors: angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and renin inhibitors. Other types of medicine include thiazide diuretics, beta-blockers, and calcium channel blockers (CCBs).

The first medicine that a person is prescribed for treating hypertension is called the 'first-line' medicine. Frequently, over time, other medicines are added to this in an attempt to reduce blood pressure in the long-term.

The purpose of this research

Researchers from the Cochrane Collaboration tried to determine how RAS inhibitors compare as first-line medicines for treating hypertension with other types of first-line medicines (thiazide diuretics, beta-blockers, CCBs, alpha-blockers, or central nervous system (CNS) active drugs) for hypertension.

What this research discovered

The researchers searched the medical literature up to November 2014 to identify all the relevant medical research. They identified a total of 42 medical studies that had included a total of 65,733 participants, with an average age of 66 years.

Nine of these studies did not include people who had suffered heart attacks or strokes, but 14 studies did include them if the heart attack or stroke had happened more than three or six months before the study began. Twelve studies included diabetic participants, and seven included people with kidney problems.

Twenty-six of the 42 studies were sponsored by pharmaceutical companies that manufactured the medicines being studied. The researchers did not investigate how this might have affected the results.

The results of the research showed moderate quality evidence that:

1. thiazides caused less heart failure and stroke than RAS inhibitors;

2. RAS inhibitors caused less heart failure but more stroke than CCBs, however the reduction in heart failure was considerably bigger than the increase in stroke.

Less robust results showed that RAS inhibitors reduced heart attacks and stroke compared to beta-blockers.

The different medicines produced small differences in effect on blood pressure, but these did not seem to be related to the number of heart attacks, strokes and kidney problems.

More trials are needed to strengthen the findings of this review.

Authors' conclusions: 

We found predominantly moderate quality evidence that all-cause mortality is similar when first-line RAS inhibitors are compared to other first-line antihypertensive agents. First-line thiazides caused less HF and stroke than first-line RAS inhibitors. The quality of the evidence comparing first-line beta-blockers and first-line RAS inhibitors was low and the lower risk of total CV events and stroke seen with RAS inhibitors may change with the publication of additional trials. Compared with first-line CCBs, first-line RAS inhibitors reduced HF but increased stroke. The magnitude of the reduction in HF exceeded the increase in stroke. The small differences in effect on blood pressure between the different classes of drugs did not correlate with the differences in the primary outcomes.

Read the full abstract...
Background: 

Renin-angiotensin system (RAS) inhibitors are widely prescribed for treatment of hypertension, especially for diabetic patients on the basis of postulated advantages for the reduction of diabetic nephropathy and cardiovascular morbidity and mortality. Despite widespread use of angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) for hypertension in both diabetic and non-diabetic patients, the efficacy and safety of RAS inhibitors compared to other antihypertensive drug classes remains unclear.

Objectives: 

To evaluate the benefits and harms of first-line RAS inhibitors compared to other first-line antihypertensive drugs in patients with hypertension.

Search strategy: 

We searched the Cochrane Hypertension Group's Specialised Register, MEDLINE, MEDLINE In-Process, EMBASE and ClinicalTrials.gov for randomized controlled trials up to November 19, 2014 and the Cochrane Central Register of Controlled Trials (CENTRAL) up to October 19, 2014. The WHO International Clinical Trials Registry Platform (ICTRP) is searched for inclusion in the Cochrane Hypertension Group's Specialised Register.

Selection criteria: 

We included randomized, active-controlled, double-blinded studies with at least six months follow-up in people with primary elevated blood pressure (≥130/85 mmHg), which compared first-line RAS inhibitors with other first-line antihypertensive drug classes and reported morbidity and mortality or blood pressure outcomes. Patients with proven secondary hypertension were excluded.

Data collection and analysis: 

Two authors independently selected the included trials, evaluated the risk of bias and entered the data for analysis.

Main results: 

We included 42 studies, involving 65,733 participants, with a mean age of 66 years. Much of the evidence for our key outcomes is dominated by a small number of large studies at a low risk of bias for most sources of bias. Imbalances in the added second-line antihypertensive drugs in some of the studies were important enough for us to downgrade the quality of the evidence.

Primary outcomes were all-cause death, fatal and non-fatal stroke, fatal and non-fatal myocardial infarction (MI), fatal and non-fatal congestive heart failure (CHF) requiring hospitalization, total cardiovascular (CV) events (consisted of fatal and non-fatal stroke, fatal and non-fatal MI and fatal and non-fatal CHF requiring hospitalizations), and ESRF. Secondary outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR).

Compared with first-line calcium channel blockers (CCBs), we found moderate quality evidence that first-line RAS inhibitors decreased heart failure (HF) (35,143 participants in 5 RCTs, RR 0.83, 95% CI 0.77 to 0.90, ARR 1.2%), and moderate quality evidence that they increased stroke (34,673 participants in 4 RCTs, RR 1.19, 95% CI 1.08 to 1.32, ARI 0.7%). They had similar effects on all-cause death (35,226 participants in 5 RCTs, RR 1.03, 95% CI 0.98 to 1.09; moderate quality evidence), total CV events (35,223 participants in 6 RCTs, RR 0.98, 95% CI 0.93 to 1.02; moderate quality evidence), total MI (35,043 participants in 5 RCTs, RR 1.01, 95% CI 0.93 to 1.09; moderate quality evidence). The results for ESRF do not exclude potentially important differences (19,551 participants in 4 RCTs, RR 0.88, 95% CI 0.74 to 1.05; low quality evidence).

Compared with first-line thiazides, we found moderate quality evidence that first-line RAS inhibitors increased HF (24,309 participants in 1 RCT, RR 1.19, 95% CI 1.07 to 1.31, ARI 1.0%), and increased stroke (24,309 participants in 1 RCT, RR 1.14, 95% CI 1.02 to 1.28, ARI 0.6%). They had similar effects on all-cause death (24,309 participants in 1 RCT, RR 1.00, 95% CI 0.94 to 1.07; moderate quality evidence), total CV events (24,379 participants in 2 RCTs, RR 1.05, 95% CI 1.00 to 1.11; moderate quality evidence), and total MI (24,379 participants in 2 RCTs, RR 0.93, 95% CI 0.86 to 1.01; moderate quality evidence). Results for ESRF do not exclude potentially important differences (24,309 participants in 1 RCT, RR 1.10, 95% CI 0.88 to 1.37; low quality evidence).

Compared with first-line beta-blockers, we found low quality evidence that first-line RAS inhibitors decreased total CV events (9239 participants in 2 RCTs, RR 0.88, 95% CI 0.80 to 0.98, ARR 1.7%), and low quality evidence that they decreased stroke (9193 participants in 1 RCT, RR 0.75, 95% CI 0.63 to 0.88, ARR 1.7% ). Our analyses do not exclude potentially important differences between first-line RAS inhibitors and beta-blockers on all-cause death (9193 participants in 1 RCT, RR 0.89, 95% CI 0.78 to 1.01; low quality evidence), HF (9193 participants in 1 RCT, RR 0.95, 95% CI 0.76 to 1.18; low quality evidence), and total MI (9239 participants in 2 RCTs, RR 1.05, 95% CI 0.86 to 1.27; low quality evidence).

Blood pressure comparisons between RAS inhibitors and other classes showed either no differences or small differences that did not necessarily correlate with the differences in the morbidity outcomes.

In the protocol, we identified non-fatal serious adverse events (SAE) as a primary outcome. However, when we extracted the data from included studies, none of them reported total SAE in a manner that could be used in the review. Therefore, there is no information about SAE in the review.

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