Background
Beta-blockers are a class of drug commonly used to treat high blood pressure. Nonselective beta-blockers are a subclass of beta-blockers including propranolol (Inderal), nadolol (Corgard), etc. We asked how much this subclass of drugs lower blood pressure.
Study characteristics
We developed a comprehensive search strategy of all relevant scientific databases to identify all clinical trials to answer this question. Participants had to have a baseline systolic blood pressure (the top number of a blood pressure reading) of at least 140 mmHg or a diastolic blood pressure (the bottom number of a blood pressure reading) of at least 90 mmHg, or both of these. We did not restrict participants by age, gender, baseline risk or any other medical conditions.
Key results
We found 25 clinical trials that compared the blood pressure lowering effect of seven nonselective beta-blockers with placebo in 1264 people with high blood pressure. On average, nonselective beta-blockers lowered blood pressure by about 10 mmHg systolic and 7 mmHg diastolic, and reduced heart rate by 12 beats per minute. This estimate is likely greater than the true effect because of biases in the running and reporting of the trials. We did not find convincing evidence that higher doses of nonselective beta-blockers lowered blood pressure more than lower doses. However, higher doses of nonselective beta-blockers significantly lowered heart rate compared with lower doses, which could lead to more side effects. Since the blood pressure lowering effect for systolic is similar to the blood pressure lowering effect of diastolic, the effect of this subclass on pulse pressure (the difference between systolic and diastolic) was small at about 2 mmHg.
Quality of the evidence
The quality of the evidence is low due to the presence of extreme outliers and high risk of biases.
In people with mild-to-moderate hypertension, nonselective beta-blockers lowered peak BP by a mean of -10/-7 mmHg (systolic/diastolic) and reduced heart rate by 12 beats per minute. Propranolol and penbutolol were the two drugs that contributed to most of the data for nonselective beta-blockers. This estimate is likely exaggerated due to the presence of extreme outliers and other sources of bias. If we removed the extreme outliers from the analysis, the estimate for non-selective beta-blockers was lower (-8/-5 mmHg (systolic/diastolic)). Nonselective beta-blockers did not show a convincing graded dose-response in the recommended dose range for systolic BP and diastolic BP, while higher dose nonselective beta-blockers provided greater reduction of heart rate. Using higher dose nonselective beta-blockers might cause more side effects, such as bradycardia, without producing an additional BP lowering effect. The effect of nonselective beta-blockers on pulse pressure was likely small, at about 2 mmHg.
Beta-blockers are one of the classes of drugs frequently used to treat hypertension. Quantifying the blood pressure (BP) lowering effects of nonselective beta-blockers provides important information that aids clinical decision making.
To quantify the dose-related effects of nonselective beta-adrenergic receptor blockers (beta-blockers) on systolic blood pressure (SBP) and diastolic blood pressure (DBP) as compared with placebo in people with primary hypertension.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ClinicalTrials.gov for randomized controlled trials up to October 2013.
Randomized, double-blind, placebo-controlled, parallel or cross-over trials. Studies had to contain a nonselective beta-blocker monotherapy arm with a fixed dose. Participants enrolled into the studies had to have primary hypertension at baseline. Duration of studies had to be between three and 12 weeks.
Two review authors (GW and AL) independently confirmed the inclusion of studies and extracted the data.
We included 25 RCTs that evaluated the BP lowering effects of seven nonselective beta-blockers in 1264 people with hypertension. Among the 25 RCTs, four were parallel studies and 21 were cross-over studies. Overall, nonselective beta-blockers lowered systolic BP and diastolic BP compared with placebo. Nonselective beta-blockers, in the recommended dose range, did not showed a convincing dose-response relationship by direct comparison. The once (1x) and twice (2x) starting dose subgroups contained the largest sample size. The estimate of BP lowering efficacy for nonselective beta-blockers by combining the 1x and 2x starting dose subgroup was -10 mmHg (95% CI -11 to -8) for systolic BP and -7 mmHg (95% CI -8 to -6) for diastolic BP (low-quality evidence). Nonselective beta-blockers starting at the 1x recommended starting doses lowered heart rate by 12 beats per minute (95% CI 10 to 13) (low-quality evidence). The dose-response relationship in heart rate was evident by both direct and indirect comparison. Due to imprecision, there was no clear evidence of an effect of nonselective beta-blockers on pulse pressure in any dose subgroups except for a small reduction with the 2x starting dose (-2.2 mmHg, 95% CI -3.7 to -0.7) (very low quality evidence). The point estimates in the 1x, four times (4x) and eight times (8x) starting dose subgroups were similar to the 2x starting dose subgroup. Therefore, it would appear that if nonselective beta-blockers do lower pulse pressure, the magnitude is likely to be about 2 mmHg. There were very limited data (two studies) on withdrawals due to adverse effects (risk ratio (RR) 0.84; 95% CI 0.38 to 1.82).