A Cochrane review [Abstract] 1 included 20 studies with a total of 3 744 subjects evaluating the blood pressure (BP) lowering efficacy of beta-blockers as second-line drug (baseline BP of 158/102 mmHg; mean duration of 7 weeks). Beta-blocker was added to a thiazide diuretic (12 studies), a thiazide diuretic/potassium sparing diuretic combination pill (3 studies), or to a dihydropyridine calcium-channel blocker (5 studies). There were no studies that added a beta-blocker as second line drug to an angiotensin-receptor blocker, angiotensin-converting enzyme inhibitor, renin inhibitor or centrally acting antihypertensive drug.
The BP lowering efficacy of beta-blockers as a second drug was 6/4 mmHg at 1 times the manufacturer's recommended 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.
Based on an indirect comparison with a previously published review on thiazide diuretics as second-line therapy in patients with primary hypertension using similar methodology Diuretics as Second-Line Therapy for Primary Hypertension, 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. The authors hypothesize that this difference in the pattern of BP lowering with beta-blockers as compared to thiazides might explain why beta-blockers appear to be less effective at reducing adverse cardiovascular outcomes than thiazide diuretics, particularly in older individuals.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment).
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