Beta-Adrenergic Blocking Drugs in the Treatment of Hypertension
Abstract
The reduction in blood pressure seen with the use of beta-blocking drugs was an unexpected finding. Initially there was resistance to their use as the reduction of cardiac output and increase in peripheral resistance from beta-blockade was considered an undesirable pharmacological action for a drug in the treatment of hypertension. However, beta-blockers have now become established in the treatment of hypertension and have been recommended as a first line choice in various guidelines, although their exact mode of action remains a matter for debate. In broad terms beta-blocking drugs are at least of similar efficacy to the other major classes of antihypertensive drugs. They may be usefully combined with other anti-hypertensives, as is often required. There is some evidence that the beta- 1 selective agents are more efficacious than the non-selective beta-blockers. Notwithstanding some observations to the contrary beta-blockers are often effective antihypertensive agents in the elderly and in black patients; the combination of being elderly and black, however, appears to result in a reduced fall in blood pressure. If they are given early in pregnancy they lead to a low birth weight. Co-existant disease may influence the choice of a beta-blocker to treat hypertension. Beta-blockers are valuable agents in ischaemic heart disease, notably the control of chronic angina pectoris and to improve prognosis post-myocardial infarction. While initial dose titration has to be extremely careful, heart failure is now a strong indication for the use of a beta-blocker, as prognosis is much improved. Diabetes should no longer be regarded as a contra-indication to the use of a beta- 1 selective agent. Recent work confirms that beta-blockers should be given to patients undergoing surgery who have a high cardiac risk. Outcome studies suggest overall that in younger patients beta-blockers reduce the incidence of strokes and myocardial infarction. There is no convincing evidence of a difference between the ACE inhibitor captopril and the combination of diuretic and a beta-blocker. In high risk patients, i.e. those with diabetes, no difference was seen between captopril and atenolol. Diuretics may result in better outcome measurements in the elderly compared to beta-blockade but in combination, "conventional treatment" is as effective in terms of total mortality, strokes and myocardial infarction as ACE inhibitors or calcium antagonists. Co-existant asthma remains an important contra-indication to beta-blockade, but not chronic obstructive airways disease where a beta-blocker should be used with caution if it is indicated, e.g. post-infarction. Quality of life measurements, at least with beta- 1 selective agents compare favourably with other anti-hypertensive drugs. Beta-blockers, without partial agonist activity, should not be stopped abruptly, particularly in patients with, or at high risk of, co-existant ischaemic disease because of the danger of post-beta-blockade cardiac sympathetic hypersensitivity; alternatively bed rest should be instituted to reduce the risk of sympathetic stimulation.