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