Alpha- and beta-receptor blocking drugs in the treatment of hypertension.

The wide variety of antihypertensive agents now available allows considerable flexibility in the pharmacologic management of hypertension. The newly available alpha- and beta-adrenergic blocking agents have added considerably to this flexibility. Their safety and efficacy insure that they will find increasing use in the treatment of hypertension. The new postsynaptic alpha-receptor blocker prazosin, is generally free of the side effects that precluded the use of alpha-blockers which affected both pre- and postsynaptic receptors. Is is moderately effective and, excepting the problem of "first-dose" hypotension, it is usually well tolerated. Labetalol, a compound possessing both alpha- and beta-receptor blocking properties, has been found to be effective both as an oral therapy for chronic hypertension and as an intravenous agent in treating hypertensive crisis. Further experience with labetolol will determine its safety and efficacy for the long-term management of hypertension. Although the usefulness of beta-adrenergic receptor blocking agents in hypertension is unquestionable, the mechanism by which they lower the blood pressure remains in question. Most of our experience has been with propranolol, but other beta-blockers, now used in England and Europe, are likely to become available in the United States. As of January, 1979 only metoprolol has been added to propranolol as approved beta-blockers for the treatment of hypertension. General guidelines for the use of propranolol are given in Table 6. Metoprolol will likely find increasing use since it seems to work as well as propranolol and probably causes fewer side effects. Nevertheless, the experiences with one beta-blocker, both good and bad, cannot be interpolated to another beta-blocker since there are obvious and subtle differences in their actions. Patients doing well on propranolol therapy should continue to receive that drug; patients being started on a beta-blocker therapy can be given the choice of metoprolol and, in the near future, other beta-blockers as well. Beyond their efficacy and freedom from side effects in about 80% of patients, beta-blockers may offer a special advantage in protecting from coronary heart disease. Such protection has been suggested in limited trials but needs further documentation. In the meantime, the known advantages of beta-blockers ensure their increasing use in the treatment of hypertension. Regardless of which alpha- or beta-blocker is chosen, a diuretic should be used concomitantly to enhance and preserve the effectiveness of the adrenergic blocker.