Beta-blockers lower blood pressure when given as a second drug

Chen JMH, Heran BS, Perez MI, Wright JM

Published Online:

January 20, 2010

Beta-blockers are commonly used in the treatment for high blood pressure (BP). In this review, we asked how much do beta-blockers reduce BP when used as the second drug to treat hypertension. Twenty trials lasting an average of 7 weeks were found in the world scientific literature to answer this question. The data showed that the addition of a beta-blocker to thiazide diuretics or calcium channel blockers reduced BP by 8/6 mmHg when given at doses 2 times the recommended starting dose. When we compared these results with our previous review of the blood pressure lowering effect of thiazide diuretics as second line drug, we found that beta-blockers have a different pattern of BP lowering. This different pattern of effect on blood pressure might explain why first-line beta-blockers appear to be less effective at reducing adverse cardiovascular outcomes than first-line thiazide diuretics, particularly in older individuals.

Abstract (click to read)

Background:

Beta-blockers are one of the more commonly prescribed classes of anti-hypertensive drugs, both as first-line and second-line.

Objectives:

To quantify the effect on systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate and withdrawals due to adverse effects of beta-blocker therapy when given as a second-line drug in adult patients with primary hypertension.

Search strategy:

CENTRAL (The Cochrane Library 2009, Issue 2), MEDLINE (1966-Aug 2009), EMBASE (1988-Aug 2009) and bibliographic citations of articles and reviews were searched.

Selection criteria:

Double-blind, randomized controlled trials comparing a beta-blocker in combination with a drug from another class of anti-hypertensive drugs compared with that drug alone for a duration of 3 to 12 weeks in patients with primary hypertension were included.

Data collection and analysis:

Two reviewers independently extracted the data and assessed trial quality of each included study.

Main results:

20 double-blind RCTs evaluated the BP lowering efficacy of beta-blockers as second-line drug in 3744 hypertensive patients (baseline BP of 158/102 mmHg; mean duration of 7 weeks). The BP reduction from adding a beta-blocker as the second drug was estimated by comparing the difference in BP reduction between the combination and monotherapy groups. A reduction in BP was seen with adding a beta-blocker to thiazide diuretics or calcium channel blockers at doses as low as 0.25 times the manufacturer's recommended starting dose. The BP lowering efficacy of beta-blockers as a second drug was 6/4 mmHg at 1 times the starting dose and 8/6 mmHg at 2 times the starting dose. Beta-blockers reduced heart rate by 10 beats/min at 1 to 2 times the starting dose. Beta-blockers did not statistically significantly increase withdrawals due to adverse effects but this was likely due to the lack of reporting of this outcome in 35% of the included RCTs.

Authors' conclusions:

Addition of a beta-blocker to diuretics or calcium-channel blockers reduces BP by 6/4mmHg at 1 times the starting dose and by 8/6 mmHg at 2 times the starting dose. When the blood pressure lowering effect of beta-blockers from this review was compared to that of thiazide diuretics from our previous review (Chen 2009), second-line beta-blockers reduce systolic BP to the same extent as second-line thiazide diuretics, but reduce diastolic BP to a greater degree. The different effect on diastolic BP means that beta-blockers have little or no effect on pulse pressure whereas thiazides cause a significant dose-related decrease in pulse pressure. This difference in the pattern of BP lowering with beta-blockers as compared to thiazides might be the explanation for the fact that beta-blockers appear to be less effective at reducing adverse cardiovascular outcomes than thiazide diuretics, particularly in older individuals.

This record should be cited as:

Chen JMH, Heran BS, Perez MI, Wright JM. Blood pressure lowering efficacy of beta-blockers as second-line therapy for primary hypertension. Cochrane Database of Systematic Reviews 2010, Issue 1. Art. No.: CD007185. DOI: 10.1002/14651858.CD007185.pub2

Assessed as up to date:

November 11, 2009

Find the research

Get full text at The Cochrane Library

Primary Review Group:

Hypertension Group

PEARLS - Practical Evidence About Real Life Situations (click to read)

Clinical question:

How effective are beta-blockers as second-line therapy for primary hypertension?

Bottom line:

Addition of a beta-blocker to diuretics or calcium-channel blockers reduced blood pressure (BP) by 6/4 and 8/6mmHg at doses of 1 and 2 times the manufacturer’s recommended starting dose. Beta-blockers (at 1 to 2 times) the starting dose reduced heart rate by 10 beats/min. When the BP lowering effect of beta-blockers in this review was compared to that of thiazide diuretics from a previous review,¹ second-line beta-blockers reduced systolic BP to the same extent as second-line thiazide diuretics, but reduced diastolic BP to a greater degree. 1. Chen JMH et al. Cochrane Reviews 2009, Issue 4. Article No. CD007187. DOI:10.1002/14651858.CD007187.pub2.

Caveat:

There was not a statistically significant increase in withdrawals due to adverse effects shown for beta-blocker use but this was likely due to the lack of reporting of this outcome in 35% of the included randomised controlled trials. The duration of the trials was short, ranging from 3 to 12 weeks, with an average of 7 weeks.

Context:

The different effect on diastolic BP means beta-blockers have little or no effect on pulse pressure, whereas thiazides cause a significant dose-related decrease in pulse pressure. This difference in the pattern of BP lowering with beta-blockers as compared with thiazides might be the explanation for the fact that beta-blockers appear to be less effective at reducing adverse cardiovascular outcomes than thiazide diuretics, particularly in older individuals. Although factors independent of BP lowering may contribute to the reduction in mortality and morbidity associated with antihypertensive drugs, BP lowering ability remains an important factor. By combining antihypertensive agents that possess different mechanisms of action, each component drug can potentially neutralise or minimise counter-regulatory mechanisms triggered by the other, and thus help to further lower BP.

Cochrane Systematic Review:

Chen JMH et al. Blood pressure lowering efficacy of betablockers as second-line therapy for primary hypertension. Cochrane Reviews 2010, Issue 1. Article No. CD007185. DOI: 10.1002/14651858.CD007185.pub2. This review contains 20 studies involving 3744 participants

Authored by:

Brian R McAvoy

Cochrane Primary Health Care Field

Health topics:

Heart & circulation > Hypertension > Treatment: pharmacological

Kidney disease > Hypertension > Treatment: pharmacological

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

Beta-blockers lower blood pressure when given as a second drug

More like this

Copyright © 2012 - The Cochrane Collaboration