Mechanism of Thiazide Diuretic Arterial Pressure Reduction: The Search Continues

Thiazide diuretic (TZD)-mediated chronic reduction of arterial pressure is thought to occur through decreased total peripheral vascular resistance. Further, the decreased peripheral vascular resistance is accomplished through TZD activation of an extrarenal target, resulting in inhibition of vascular constriction. However, despite greater than five decades of investigation, little progress has been made into the identification of the TZD extrarenal target. Proposed mechanisms range from direct inhibition of constrictor and activation of relaxant signaling pathways in the vascular smooth muscle to indirect inhibition through decreased neurogenic and hormonal regulatory pathways. Surprisingly, particularly in view of this lack of progress, comprehensive reviews of the subject are absent. Moreover, even though it is well recognized that 1) several types of hypertension are insensitive to TZD reduction of arterial pressure and, further, TZD fail to reduce arterial pressure in normotensive subjects and animals, and 2) different mechanisms underlie acute and chronic TZD, findings derived from these models and parameters remain largely undifferentiated. This review 1) comprehensively describes findings associated with TZD reduction of arterial pressure; 2) differentiates between observations in TZD-sensitive and TZD-insensitive hypertension, normotensive subjects/animals, and acute and chronic effects of TZD; 3) critically evaluates proposed TZD extrarenal targets; 4) proposes guiding parameters for relevant investigations into extrarenal TZD target identification; and 5) proposes a working model for TZD chronic reduction of arterial pressure through vascular dilation.

Efficacy of zofenopril in combination with thiazide diuretics in patients with acute myocardial infarction: a pooled individual data analysis of four randomized, double-blind, controlled, prospective studies

Background

In the Survival of Myocardial Infarction Long-Term Evaluation (SMILE) studies, early administration of zofenopril after acute myocardial infarction (AMI) was prognostically beneficial as compared to placebo and other angiotensin-converting enzyme inhibitors (ACEIs), such as lisinopril and ramipril. Here, we investigated whether zofenopril efficacy could be affected by a concomitant use of thiazide diuretics (TDs).

Methods

This was a post hoc analysis of pooled individual patient data from the SMILE studies. Patients treated with other diuretics than TDs were excluded. The primary study endpoint was the 1-year combined occurrence of death or hospitalization for CV causes, with or without TD.

Results

Among 2,995 patients, 263 (8.8%) were treated with a combination including a TD (TD+), whereas 2,732 (91.2%) were not treated with any diuretic (TD−). Proportions of subjects who were treated with TD were equally distributed (p=0.774) within the placebo, zofenopril, and other ACEIs groups. The 1-year risk of major cardiovascular events was similar in TD+ (18.3%) and TD− (16.8%) patients (hazard ratio [HR] 1.04; 95% CI 0.74–1.45; p=0.838). After stratifying per concomitant treatment and TD, the 1-year risk of CV events was significantly lower with zofenopril than with placebo (HR 0.70; 95% CI 0.55–0.88; p=0.002) and other ACEIs (HR 0.58; 95% CI 0.46–0.74; p=0.0001). Treatment with ACEIs and TD as concomitant therapy was associated with a larger blood pressure (BP) reduction (p=0.0001 for systolic BP and p=0.045 for diastolic BP).

Conclusion

In post AMI patients, zofenopril maintained its positive impact on prognosis compared to placebo or other ACEIs, regardless concomitant TD administration. In this setting, TD shows advantages in managing the most difficult hypertensive patients.

Fixed-dose combination of zofenopril plus hydrochlorothiazide vs. irbesartan plus hydrochlorothiazide in hypertensive patients with established metabolic syndrome uncontrolled by previous monotherapy. The ZAMES study (Zofenopril in Advanced MEtabolic Syndrome)

OBJECTIVE

Whether all antihypertensive drugs are equally effective in patients with metabolic syndrome is still unclear. The goal of the Zofenopril in Advanced MEtabolic Syndrome (ZAMES) study was to investigate whether treatment with the fixed-dose combination of sulphydril-containing angiotensin-converting enzyme inhibitor zofenopril plus hydrochlorothiazide is at least as effective as that with the angiotensin receptor blocker irbesartan plus hydrochlorothiazide in patients with metabolic syndrome and essential hypertension, uncontrolled by a previous monotherapy.

METHODS

We enrolled 721 patients in a multicenter, international (Italy and Romania), randomized, double-blind, parallel group, phase III study. Following a 1-week screening withdrawal period, 482 patients (mean age 59 ± 10 years, 53% men) bearing a SBP at least 140 mmHg and/or DBP at least 90 mmHg plus metabolic syndrome (ATP-III criteria) were randomly allocated to a fixed-dose combination of zofenopril 30 mg plus hydrochlorothiazide 12.5 mg or irbesartan 150 mg plus hydrochlorothiazide 12.5 mg once daily for a cumulative period of 24 weeks. After 8 and 16 weeks, zofenopril and irbesartan doses were doubled in nonnormalized study participants. The study endpoint was the office DBP reduction at study end. In 20% of patients, an ambulatory blood pressure monitoring was performed.

RESULTS

The prevalence of diabetes at baseline was significantly (P < 0.05) greater in the zofenopril plus hydrochlorothiazide group (82%) than in the irbesartan plus hydrochlorothiazide (73%) group. Baseline-adjusted DBP reductions were superimposable (P = 0.370) with zofenopril plus hydrochlorothiazide [n = 231; 9.8 (95% confidence interval: 11.1, 8.4) mmHg] and irbesartan plus hydrochlorothiazide [n = 235; 10.4 (11.8, 9.0) mmHg]. The same was for SBP [17.0 (19.2, 14.8) mmHg zofenopril plus hydrochlorothiazide vs. 18.8 (21.0, 16.6) mmHg irbesartan plus hydrochlorothiazide, P = 0.113]. Rate of normalized and responder patients (SBP/DBP < 140/90 mmHg or SBP reduction more than 20 mmHg or DBP reduction more than 10 mmHg) did not differ at study end (65.8% and 77.5% zofenopril plus hydrochlorothiazide vs. 67.7% and 81.5% irbesartan plus hydrochlorothiazide; P = 0.695, P = 0.301). These results were confirmed in the 69 study participants undergoing ambulatory blood pressure monitoring (35 zofenopril plus hydrochlorothiazide; 34 irbesartan plus hydrochlorothiazide), with a comparable 24-h average BP reduction [BP difference between-treatment: SBP: 0.1 (-5.7, 5.9) mmHg, P = 0.975; DBP: -0.9 (-3.8, 2.0) mmHg, P = 0.541]. Both drugs attained similar BP reductions also in the last 6 h of the dosing interval [between-treatment difference SBP: 0.1 (-7.4, 7.5) mmHg P = 0.990; DBP: -0.9 (-4.4, 2.6) mmHg, P = 0.602]. Metabolic and renal indexes were not altered. Few patients were withdrawn for moderate adverse events (5% zofenopril plus hydrochlorothiazide; 5% irbesartan plus hydrochlorothiazide).

CONCLUSION

This is the first study supporting the comparable antihypertensive and metabolic response to fixed-dose combinations of sulphydril-containing angiotensin-converting enzyme inhibitors (zofenopril) or angiotensin receptor blockers (Irbesartan) with a diuretic in patients with advanced metabolic syndrome and nonresponders to monotherapy. The results of this study can further improve the clinical management of high cardiovascular risk patients with hypertension and metabolic syndrome, because these two drug combinations increase the number of available combinations, which may significantly improve patients' adherence in this special clinical condition that is frequently found in everyday practice.

Efficacy of Zofenopril vs. Irbesartan in Combination with a Thiazide Diuretic in Hypertensive Patients with Multiple Risk Factors not Controlled by a Previous Monotherapy: A Review of the Double-Blind, Randomized "Z" Studies

Combinations between an angiotensin converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker (ARB) and hydrochlorothiazide (HCTZ) are among the recommended treatments for hypertensive patients uncontrolled by monotherapy. Four randomized, double-blind, parallel group studies with a similar design, including 1469 hypertensive patients uncontrolled by a previous monotherapy and with ≥1 cardiovascular risk factor, compared the efficacy of a combination of a sulfhydryl ACE inhibitor (zofenopril at 30 or 60 mg) or an ARB (irbesartan at 150 or 300 mg) plus HCTZ 12.5 mg. The extent of blood pressure (BP)-lowering was assessed in the office and over 24 h. Pleiotropic features of the treatments were evaluated by studying their effect on systemic inflammation, organ damage, arterial stiffness, and metabolic biochemical parameters. Both treatments similarly reduced office and ambulatory BPs after 18-24 weeks. In the ZODIAC study a larger reduction in high sensitivity C reactive protein (hs-CRP) was observed under zofenopril (-0.52 vs. +0.97 mg/dL under irbesartan, p = 0.001), suggesting a potential protective effect against the development of atherosclerosis. In the ZENITH study the rate of carotid plaque regression was significantly larger under zofenopril (32% vs. 16%; p = 0.047). In the diabetic patients of the ZAMES study, no adverse effects of treatments on blood glucose and lipids as well as an improvement of renal function were observed. In patients with isolated systolic hypertension of the ZEUS study, a slight and similar improvement in renal function and small reductions in pulse wave velocity (PWV), augmentation index (AI), and central systolic BP were documented with both treatments. Thus, the fixed combination of zofenopril and HCTZ may have a relevant place in the treatment of high-risk or monotherapy-treated uncontrolled hypertensive patients requiring a more prompt, intensive, and sustained BP reduction, in line with the recommendations of current guidelines.

Zofenopril or irbesartan plus hydrochlorothiazide in elderly patients with isolated systolic hypertension untreated or uncontrolled by previous treatment: a double-blind, randomized study

OBJECTIVE

To compare zofenopril + hydrochlorothiazide (Z + H) vs. irbesartan + hydrochlorothiazide (I + H) efficacy on daytime SBP in elderly (>65 years) patients with isolated systolic hypertension (ISH), untreated or uncontrolled by a previous monotherapy.

METHODS

After a 1-week run-in, 230 ISH patients (office SBP ≥ 140  mmHg and DBP < 90  mmHg + daytime SBP ≥ 135  mmHg and daytime DBP < 85  mmHg) were randomized double-blind to 18-week treatment with Z + H (30 + 12.5  mg) or I + H (150 + 12.5  mg) once daily, in an international, multicenter study. Z and I doses could be doubled after 6 and 12 weeks, and nitrendipine 20  mg added at 12 weeks in nonnormalized patients.

RESULTS

In the full analysis set (n = 216) baseline-adjusted average (95% confidence interval) daytime SBP reductions after 6 weeks (primary study end point) were similar (P = 0.888) with Z + H [7.7 (10.7, 4.6)  mmHg, n = 107] and I + H [7.9 (10.7, 5.0)  mmHg, n = 109]. Daytime SBP reductions were sustained during the study, and larger (P = 0.028) with low-dose Z + H at study end [16.2 (20.0, 12.5)  mmHg vs. 11.2 (14.4, 7.9)  mmHg I + H]. Daytime SBP normalization (<135 mmHg) rate was similar under Z + H and I + H at 6 and 12 weeks, but more common under Z + H at 18 weeks (68.2 vs. 56.0%, P = 0.031). Both drugs equally reduced SBP in the last 6 h of the dosing interval and homogeneously reduced SBP throughout the 24 h. The proportion of patients reporting drug-related adverse events was low (Z + H: 4.4% vs. I + H: 6.0%; P = 0.574).

CONCLUSION

Elderly patients with ISH respond well to both low and high-dose Z or I combined with H.