Angiotensin-converting enzyme inhibitors

Ramipril decreases chlorthalidone-induced loss of magnesium and potassium in hypertensive patients

A double-blind clinical trial was conducted to compare the efficacy of and electrolyte changes caused by ramipril-chlorthalidone combination treatment (5 mg + 25 mg) and chlorthalidone monotherapy (25 mg daily) in patients with hypertension. After a 4-week placebo period, 32 patients (mean age, 51 +/- 9 years) with essential hypertension (average blood pressure of 181.4/104.5 +/- 13.0/6.9 mmHg) were randomly assigned to receive combination therapy (group A, n = 17) or monotherapy (group B, n = 15). After 12 weeks of active treatment, systolic and diastolic blood pressure decreased by 16.1% and 13%, respectively, for patients taking combined therapy, and by 12.7% and 9.8%, respectively, for patients taking monotherapy. The difference was significant for between-group comparisons. There were no changes in serum sodium concentration, but a significant similar increase in 24-hour urinary sodium excretion was seen in both groups. Serum calcium levels increased slightly and 24-hour urinary calcium excretion decreased significantly in both groups, probably due to chlorthalidone administration. Serum potassium levels increased slightly in group A (from 4.16 +/- 0.39 mmol/L to 4.30 +/- 0.42 mmol/L) and decreased slightly in group B (from 4.18 +/- 0.32 mmol/L to 3.99 +/- 0.49 mmol/L). Urinary potassium excretion did not change significantly in group A, but increased by approximately 15% in group B. There was a decrease in 24-hour urinary magnesium excretion (from 4.01 +/- 1.24 mmol/24 hours to 3.50 +/- 0.93 mmol/24 hours) in group A and an increase (from 3.49 +/- 0.98 mmol/24 hours to 4.35 +/- 1.12 mmol/24 hours) in group B. At the end of the trial these changes were significant in between-group comparisons. Consistent with the previously shown amelioration by ramipril of thiazide-induced metabolic side-effects, ramipril appears to improve magnesium balance during cotreatment with chlorthalidone.

The safety and efficacy of quinapril in the treatment of mild to moderate essential hypertension

Major clinical trials are reviewed comparing the efficacy and safety of quinapril hydrochloride, a new nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor, with that of placebo, captopril, and enalapril in the treatment of mild to moderate essential hypertension. A randomized, double-blind 12-week study of 270 patients compared the efficacy of placebo with once or twice daily doses of quinapril (20, 40, 80 mg/day, with forced titration). Quinapril effectively lowered both diastolic blood pressure (DBP) and systolic blood pressure. Mean reductions in DBP of up to 13 mmHg from baseline were obtained. At full dosage, more than 65% of patients achieved a clinically significant reduction in DBP. Quinapril was similarly effective whether the total daily dose was given once or twice daily. In a multicenter, double-blind study involving more than 400 patients, the efficacy of quinapril (10-40 mg/day, given once or twice daily) was found to be similar to captopril (25 mg bid to 50 mg tid). Hydrochlorothiazide (HCTZ) safely provided additive effects when given to nonresponders in both treatment groups. In a 28-week double-blind study of 258 patients comparing the efficacy of quinapril or enalapril at doses of 10, 20, and 40 mg/day (with optional titration), quinapril was found to be of similar efficacy as enalapril. The large majority of patients on either regimen were controlled with monotherapy. HCTZ again safely provided additive effects. Quinapril was well tolerated in all trials, with the incidence of adverse events and withdrawals tending to be lower with quinapril than with enalapril or captopril.

Hypotensive action of DuP 753, an angiotensin II antagonist, in spontaneously hypertensive rats. Nonpeptide angiotensin II receptor antagonists: X

In conscious 18-21-week-old spontaneously hypertensive rats, DuP 753, a nonpeptide angiotensin II receptor antagonist, given orally at 3 and 10 mg/kg or intravenously at 3, 10, and 30 mg/kg, reduced blood pressure dose dependently. It did not alter heart rate at these doses. At 10 mg/kg i.v., DuP 753 decreased blood pressure significantly for at least 24 hours, suggesting a long duration of the antihypertensive effect. Unlike saralasin, DuP 753 did not cause a transient increase in blood pressure. The acute antihypertensive efficacy of DuP 753 was greater than that of captopril. Our data indicate that, for captopril to reduce blood pressure to a similar extent as that of DuP 753, it would need to be supplemented by a diuretic. DuP 753 did not have an acute diuretic effect. Bilateral nephrectomy, but not inhibition of prostaglandin synthesis, abolished the antihypertensive effect of DuP 753, suggesting that the antihypertensive effect of DuP 753 is dependent on an active renin-angiotensin system. Furthermore, DuP 753 inhibited the pressor response to angiotensin II but not the responses to norepinephrine, vasopressin, and Bay K 8644 (a calcium agonist). As neither DuP 753 nor captopril decreased blood pressure acutely in Wistar-Kyoto normotensive rats, our results suggest that the renin-angiotensin system plays a significant role in the control of blood pressure in spontaneously hypertensive rats.

Quinapril: a double-blind, placebo-controlled trial in essential hypertension

Quinapril HCl is a novel, nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor. The Study Group evaluated its efficacy (20, 40, 80 mg daily with forced dose titration determination at trough blood pressure) once daily versus twice daily versus placebo, as well as its tolerability and safety, in 270 patients with mild to moderate essential hypertension (WHO Stages I and II, sitting diastolic blood pressure [DPB] greater than or equal to 95 mm Hg), for twelve weeks. Reductions in DBP of up to 13 mm Hg were obtained, and in full dosage more than 65% of patients achieved a reduction in DBP of 10 mm Hg or more from baseline or reduced their DBP to 90 mm Hg or less. Quinapril was well tolerated, and reported adverse effects were scarcely more frequent than in the placebo group. Once daily doses of quinapril were as safe and effective as twice-daily doses. Quinapril is likely to exhibit good therapeutic utility in the management of essential hypertension.