ABSTRACT
In a multicentre, double-blind, crossover, placebo-controlled study, the antihypertensive effect of labetalol 100 mg and chlorthalidone 10 mg, given alone or in combination, has been assessed in 32 hypertensive patients. The combination had a greater effect in reducing blood pressure than did its separate components. This was particularly evident after exercise. Heart rate increased during chlorthalidone therapy, decreased during labetalol therapy, and a summation effect was observed during treatment with the combination. In most cases additivity was observed, as no interaction between the single components was observed, except for heart rate after exercise, and for diastolic blood pressure in the upright position. No interaction was observed either in the biochemical indices or in the clinical side-effects.
Subject(s)
Chlorthalidone/administration & dosage , Ethanolamines/administration & dosage , Hypertension/drug therapy , Labetalol/administration & dosage , Adult , Blood Pressure/drug effects , Chlorthalidone/adverse effects , Clinical Trials as Topic , Double-Blind Method , Drug Therapy, Combination , Female , Heart Rate/drug effects , Humans , Labetalol/adverse effects , Male , Middle AgedABSTRACT
2-Hydroxy-(1-hydroxy-[(1-methyl-3-phenylpropyl)amino]-2-ethyl)-5-benzamide (labetalol), a new alpha- and beta-adrenergic blocking agent, was employed in 21 patients with severe hypertension by slow (6 patients) and rapid (15 patients) i.v. infusion. A marked and significant fall of blood pressure was observed in both groups, though more gradual in patients treated by slow infusion. A rapid blood pressure fall with cardiac output decrease was observed by passing from supine to standing position in the first hours after infusion. Therefore, it is advisable to keep a supine position for a few hours. Plasma renin activity decreased after labetalol infusion, but basal plasma renin levels were not related to hypotensive effect of labetalol. In slow infusion patients, plasma noradrenaline levels increased and no changes of plasma adrenaline levels were observed during infusion. The most likely explanation of these variations is an increase of sympathetic activity secondary to hypotension, caused by labetalol, whereas a technical interference seems to be excluded. The simultaneous blockade of alpha- and beta-receptors can inhibit, in this case, the pressor effects of the sympathetic reflex.
Subject(s)
Ethanolamines/therapeutic use , Hypertension/drug therapy , Labetalol/therapeutic use , Adult , Blood Pressure/drug effects , Catecholamines/blood , Female , Humans , Hypertension/physiopathology , Infusions, Parenteral , Male , Middle Aged , Renin/blood , Time FactorsABSTRACT
1. Tienilic acid and hydrochlorothiazide were evaluated in a double-blind trial in order to investigate their antihypertensive and metabolic effects. 2. After 5 weeks, the decreases in blood pressure and the changes in plasma or serum electrolytes, urea, creatinine, glucose, cholesterol and triglycerides, and in creatinine clearance, did not differ in the two groups of patients. 3. In patients taking tienilic acid a significant decrease in serum uric acid and an increase in urate clearance was observed, whereas in patients receiving hydrochlorothiazide a slight increase in serum uric acid, with no modification of urate clearance, occurred. 4. The diuretic and antihypertensive actions of tienilic acid and hydrochlorothiazide are very similar. The uricosuric/hypouricaemic effect of tienilic acid could assume clinical relevance in long-term therapy of hypertensive patients.
