Diuretics in the management of hypertension

Abstract

Thiazide diuretics have been in use for over 30 years in the treatment of hypertension. Their action results in a reduction in peripheral resistance without a significant decrease in cardiac output or a major shift in plasma volume. They are as or more effective than any of the other antihypertensive agents when used as monotherapy and can serve as baseline therapy in combination with any of the available adrenergic, converting enzyme-inhibiting agents, or calcium-entry blockers. There is a high degree of patient acceptance; titration to an effective dosage is relatively easy; and cost, relatively low. Although certain undesirable metabolic changes may occur following the use of these agents, most of them are controllable, and there is no evidence to date that they offset the benefits achieved by blood pressure lowering. Asymptomatic elevated uric acids have not been shown to be of great significance. If gout occurs, it can be managed. Alterations in glucose metabolism may occur, and in some patients, it appears that blood glucose levels are elevated over time. This is not a desirable metabolic change, but is one of doubtful prognostic significance. Changes in lipids are generally short-term, and in the major clinical trials, lipid levels have not remained elevated with a continuation of diuretic therapy. Although diuretics produce hypokalemia in a fairly high percentage of patients, this is not generally severe (less than 3.3 mEq per liter) and usually does not produce symptoms. There is no firm evidence that the hypokalemia produced by diuretics predisposes the patient to severe arrhythmias or sudden death, although this point has been emphasized repeatedly in recent publications. Diuretics can usually be given without potassium-maintenance therapy. However, hypokalemia should be prevented in the elderly, in patients with ischemic heart disease, left ventricular hypertrophy and those on digitalis, or with diabetes. We prefer potassium-sparing agents along with a diuretic over supplements to prevent hypokalemia; the number of pills is kept at a reasonable level, and cost is minimized. Physicians should continue to prescribe diuretics as first-step therapy in the majority of patients to maximize therapeutic outcome.