Once-daily fixed combination of captopril and hydrochlorothiazide as first line therapy for mild to moderate hypertension

Association of Thiazide-Type Diuretics With Glycemic Changes in Hypertensive Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials

Patients receiving thiazide diuretics have a higher risk of impaired glucose tolerance or even incident diabetes, but the change of blood glucose level varies across different trials. The aim of this study was to investigate the glycemic changes in hypertensive patients with thiazide-type diuretics. Twenty-six randomized trials involving 16,162 participants were included. Thiazide-type diuretics were found to increase fasting plasma glucose (FPG) compared with nonthiazide agents or placebo or nontreatment (mean difference [MD], 0.27 mmol/L [4.86 mg/dL]; 95% confidence interval [CI], 0.15-0.39). Patients receiving lower doses of thiazides (hydrochlorothiazide or chlorthalidone ≤25 mg daily) had less change in FPG (MD, 0.15 mmol/L [2.7 mg/dL]; 95% CI, 0.03-0.27) than those receiving higher doses (MD, 0.60 mmol/L [10.8 mg/dL]; 95% CI, 0.39-0.82), revealed by the subgroup analysis of thiazides vs calcium channel blockers. Thiazide-type diuretics are associated with significant but small adverse glycemic effects in hypertensive patients. Treatment with a lower dose might reduce or avoid glycemic changes.

Blood pressure-lowering efficacy of monotherapy with thiazide diuretics for primary hypertension

BACKGROUND

Hypertension is a modifiable cardiovascular risk factor. Although it is established that low-dose thiazides reduce mortality as well as cardiovascular morbidity, the dose-related effect of thiazides in decreasing blood pressure has not been subject to a rigorous systematic review. It is not known whether individual drugs within the thiazide diuretic class differ in their blood pressure-lowering effects and adverse effects.

OBJECTIVES

To determine the dose-related decrease in systolic and/or diastolic blood pressure due to thiazide diuretics compared with placebo control in the treatment of patients with primary hypertension. Secondary outcomes included the dose-related adverse events leading to patient withdrawal and adverse biochemical effects on serum potassium, uric acid, creatinine, glucose and lipids.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 1), Ovid MEDLINE (1946 to February 2014), Ovid EMBASE (1974 to February 2014) and ClinicalTrials.gov.

SELECTION CRITERIA

We included double-blind, randomized controlled trials (RCTs) comparing fixed-dose thiazide diuretic monotherapy with placebo for a duration of 3 to 12 weeks in the treatment of adult patients with primary hypertension.

DATA COLLECTION AND ANALYSIS

Two authors independently screened articles, assessed trial eligibility, extracted data and determined risk of bias. We combined data for continuous variables using a mean difference (MD) and for dichotomous outcomes we calculated the relative risk ratio (RR) with 95% confidence interval (CI).

MAIN RESULTS

We included 60 randomized, double-blind trials that evaluated the dose-related trough blood pressure-lowering efficacy of six different thiazide diuretics in 11,282 participants treated for a mean duration of eight weeks. The mean age of the participants was 55 years and baseline blood pressure was 158/99 mmHg. Adequate blood pressure-lowering efficacy data were available for hydrochlorothiazide, chlorthalidone and indapamide. We judged 54 (90%) included trials to have unclear or high risk of bias, which impacted on our confidence in the results for some of our outcomes.In 33 trials with a baseline blood pressure of 155/100 mmHg, hydrochlorothiazide lowered blood pressure based on dose, with doses of 6.25 mg, 12.5 mg, 25 mg and 50 mg/day lowering blood pressure compared to placebo by 4 mmHg (95% CI 2 to 6, moderate-quality evidence)/2 mmHg (95% CI 1 to 4, moderate-quality evidence), 6 mmHg (95% CI 5 to 7, high-quality evidence)/3 mmHg (95% CI 3 to 4, high-quality evidence), 8 mmHg (95% CI 7 to 9, high-quality evidence)/3 mmHg (95% CI 3 to 4, high-quality evidence) and 11 mmHg (95% CI 6 to 15, low-quality evidence)/5 mmHg (95% CI 3 to 7, low-quality evidence), respectively.Direct comparison of doses did not show evidence of dose dependence for blood pressure-lowering for any of the other thiazides for which RCT data were available: bendrofluazide, chlorthalidone, cyclopenthiazide, metolazone or indapamide.In seven trials with a baseline blood pressure of 163/88 mmHg, chlorthalidone at doses of 12.5 mg to 75 mg/day reduced average blood pressure compared to placebo by 12.0 mmHg (95% CI 10 to 14, low-quality evidence)/4 mmHg (95% CI 3 to 5, low-quality evidence).In 10 trials with a baseline blood pressure of 161/98 mmHg, indapamide at doses of 1.0 mg to 5.0 mg/day reduced blood pressure compared to placebo by 9 mmHg (95% CI 7 to 10, low-quality evidence)/4 (95% CI 3 to 5, low-quality evidence).We judged the maximal blood pressure-lowering effect of the different thiazides to be similar. Overall, thiazides reduced average blood pressure compared to placebo by 9 mmHg (95% CI 9 to 10, high-quality evidence)/4 mmHg (95% CI 3 to 4, high-quality evidence).Thiazides as a class have a greater effect on systolic than on diastolic blood pressure, therefore thiazides lower pulse pressure by 4 mmHg to 6 mmHg, an amount that is greater than the 3 mmHg seen with angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and renin inhibitors, and the 2 mmHg seen with non-selective beta-blockers. This is based on an informal indirect comparison of results observed in other Cochrane reviews on ACE inhibitors, ARBs and renin inhibitors compared with placebo, which used similar inclusion/exclusion criteria to the present review.Thiazides reduced potassium, increased uric acid and increased total cholesterol and triglycerides. These effects were dose-related and were least for hydrochlorothiazide. Chlorthalidone increased serum glucose but the evidence was unclear for other thiazides. There is a high risk of bias in the metabolic data. This review does not provide a good assessment of the adverse effects of these drugs because there was a high risk of bias in the reporting of withdrawals due to adverse effects.

AUTHORS' CONCLUSIONS

This systematic review shows that hydrochlorothiazide has a dose-related blood pressure-lowering effect. The mean blood pressure-lowering effect over the dose range 6.25 mg, 12.5 mg, 25 mg and 50 mg/day is 4/2 mmHg, 6/3 mmHg, 8/3 mmHg and 11/5 mmHg, respectively. For other thiazide drugs, the lowest doses studied lowered blood pressure maximally and higher doses did not lower it more. Due to the greater effect on systolic than on diastolic blood pressure, thiazides lower pulse pressure by 4 mmHg to 6 mmHg. This exceeds the mean 3 mmHg pulse pressure reduction achieved by ACE inhibitors, ARBs and renin inhibitors, and the 2 mmHg pulse pressure reduction with non-selective beta-blockers as shown in other Cochrane reviews, which compared these antihypertensive drug classes with placebo and used similar inclusion/exclusion criteria.Thiazides did not increase withdrawals due to adverse effects in these short-term trials but there is a high risk of bias for that outcome. Thiazides reduced potassium, increased uric acid and increased total cholesterol and triglycerides.

Blood pressure lowering efficacy of diuretics as second-line therapy for primary hypertension

BACKGROUND

Diuretics are widely prescribed for hypertension not only as a first-line drug but also as a second-line drug. Therefore, it is essential to determine the effects of diuretics on blood pressure (BP), heart rate and withdrawals due to adverse effects (WDAEs) when given as a second-line drug.

OBJECTIVES

To quantify the additional reduction in systolic blood pressure (SBP) and diastolic blood pressure (DBP) of diuretic therapy as a second-line drug in patients with primary hypertension

SEARCH STRATEGY

CENTRAL (The Cochrane Library 2008, Issue 2), MEDLINE (1966-July 2008), EMBASE (1988-July 2008) and bibliographic citations of articles and reviews were searched.

SELECTION CRITERIA

Double-blind, randomized, controlled trials evaluating the BP lowering efficacy of a diuretic in combination therapy with another class of anti-hypertensive drugs compared with the respective monotherapy (without a diuretic) for a duration of 3 to 12 weeks in patients with primary hypertension.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data and assessed trial quality.

MAIN RESULTS

Fifty-three double-blind RCTs evaluating a thiazide in 15129 hypertensive patients (baseline BP of 156/101 mmHg) were included. Hydrochlorothiazide was the thiazide used in 49/53 (92%) of the included studies. The additional BP reduction caused by the thiazide as a second drug was estimated by comparing the difference in BP reduction between the combination and monotherapy groups. Thiazides as a second-line drug reduced BP by 6/3 and 8/4 mmHg at doses of 1 and 2 times the manufacturer's recommended starting dose respectively. The BP lowering effect was dose related. The effect was similar to that obtained when thiazides are used as a single agent. Only 3 double-blind RCTs evaluating loop diuretics were identified. These RCTs showed a BP lowering effect of a starting dose of about 6/3 mmHg.

AUTHORS' CONCLUSIONS

Thiazides when given as a second-line drug have a dose related effect to lower blood pressure that is similar to when they are added as a first-line drug. This means that the BP lowering effect of thiazides is additive. Loop diuretics appear to have a similar blood pressure lowering effect as thiazides at 1 times the recommended starting dose. Because of the short duration of the trials and lack of reporting of adverse events, this review does not provide a good estimate of the incidence of adverse effects of diuretics given as a second-line drug.

Evaluation of the efficacy and tolerability of the combination delapril plus indapamide in the treatment of mild to moderate essential hypertension: a randomised, multicentre, controlled study

The aim of the study was to evaluate efficacy and tolerability of two different fixed combinations of an angiotensin-converting enzyme inhibitor and a diuretic: delapril+indapamide (D+I) and captopril+hydrochlorothiazide (C+H) administered for 6 months to patients with mild to moderate essential hypertension. In all, 96 centres participated in this randomised, parallel groups, controlled study. A total of 829 patients with uncomplicated mild to moderate hypertension were randomised, and 790 were eligible for the analysis of efficacy (intention to treat). Patients of both sexes, aged 18-75 years, newly diagnosed or untreated during the last month were included in the study if their diastolic blood pressure (DBP) was > or =95 and < or =114 mmHg. The starting doses of the drugs were delapril 30 mg+indapamide 1.25 mg tablets o.d. or captopril 50 mg+hydrolchlorothiazide 15 mg tablets o.d. After a 1-month treatment period, nonresponders (DBP >90 mmHg, or decrease in DBP <10 mmHg) had the daily dose increased to either delapril 30 mg+indapamide 2.5 mg or captopril 50 mg+hydrochlorothiazide 25 mg tablets for a further 5 months. The primary assessment of antihypertensive efficacy was the percentage of patients who responded after a 6-month drug treatment. The responder rates were 72.6% with D+I and 62.9% with C+H (P=0.004 between treatments) after 60 days of treatment, and 92.6% in the D+I and 85.2% in the C+H (P<0.001 between treatments) at the end of the treatment period. The final value of systolic blood pressure was 134.5+/-13.1 mmHg with D+I and 138.3+/-14.0 mmHg with C+H (P<0.001 between treatments). At the final visit, DBP was 84.57+/-7.0 mmHg in the D+I group and 85.57+/-8.0 mmHg in the control group (P=0.017 between treatments). In all, 11 patients in the D+I group and 19 patients in the C+H group were withdrawn from the study because of adverse events. In all, 30 patients (7.6%) with D+I and 32 patients (8.1%) with C+H experienced adverse events. In conclusion, D+I was more effective than C+H in terms of overall reduction in blood pressure and response rate. Greater efficacy was obtained without any increase in adverse effects, since both treatments were equally well tolerated.

Tolerability, safety, and quality of life and hypertensive therapy: the case for low-dose diuretics

The safety and tolerability of antihypertensive therapies are an important clinical concern, because the demonstrated benefits of successful blood pressure-lowering depend on long-term compliance with pharmacologic treatments. Thiazide diuretics and beta blockers have been specifically recommended as preferred initial drug therapy by the Fifth Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNC-V), unless their use is contraindicated by concomitant disease, there is intolerance to these agents, or there is a specific indication for another drug class. These recommendations are a result of the lengthy clinical experience with these drugs and the results of long-term clinical trials that have demonstrated significant reductions in cardiovascular morbidity and mortality. However, data from these same clinical studies have also shown that diuretics (and beta blockers) can cause abnormalities in carbohydrate, electrolyte, and lipid metabolism and also may influence quality of life. The safety of diuretics was evaluated with regard to effects on carbohydrate, electrolyte, and lipid metabolism by seeking references from a MEDLINE search of documents published from 1966 to 1994 based on the search terms "hypertension," "human," and "hydrochlorothiazide" (HCTZ) dosed in a range of 12.5-25 mg daily. Two long-term clinical trials using low-dose (12.5-15 mg/day) chlorthalidone-the Systolic Hypertension in the Elderly Program (SHEP) and the Treatment of Mild Hypertension Study (TOMHS)-were also included. During the course of treatment with HCTZ in these studies, serum potassium was reduced and uric acid was increased in a dose-dependent manner. Although low doses of HCTZ elevated serum glucose, cholesterol, and triglycerides, the magnitude of effect was small in most cases and was probably of no clinical significance. Other laboratory parameters were not adversely affected, and subjective reporting of clinical adverse events was generally lower with low-dose HCTZ than with placebo or standard HCTZ dosing. The literature on the effects of low-dose diuretic therapy on quality of life is not large, although the results from the SHEP and TOMHS studies support the concept that diuretics either do not interfere with, or may actually improve, quality of life in hypertensive patients. Low-dose thiazide treatment is a well-tolerated, excellent first-line choice for hypertensive patients, especially older patients. However, diuretics should probably be avoided, whenever possible, in patients with preexisting diabetes, gout, and in men with erectile dysfunction.

Evidence for the efficacy of low-dose diuretic monotherapy

Diuretic monotherapy has been recommended by the fifth report of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (JNC-V) as a preferred initial treatment for hypertension. Thiazide diuretics are commonly used to treat hypertension because of their demonstrated efficacy, favorable safety profile, low acquisition cost, and their proven ability to reduce blood pressure-related morbidity and mortality. Once-daily low-dose hydrochlorothiazide (12.5 mg/ day) or chlorthalidone (15 mg/day) effectively reduces blood pressure in patients with stage 1 or stage 2 hypertension in comparison with placebo. Blood pressure reductions with low-dose hydrochlorothiazide and chlorthalidone are comparable to that achieved with higher doses (25 and 50 mg/day). Additional blood pressure reductions can be attained with concomitant use of once-daily low-dose hydrochlorothiazide or chlorthalidone with an angiotensin-converting enzyme (ACE) inhibitor, a beta blocker, or a calcium antagonist. Once-daily low-dose hydrochlorothiazide provides clinically meaningful blood pressure lowering while minimizing adverse effects, such as electrolyte disturbances, cholesterol elevations, and increases in serum uric acid levels.

Metabolic manifestations of low-dose diuretics

Hypertension has been defined and treated as a disease of abnormal systolic and diastolic blood pressure. Recent data have, however, demonstrated that effective blood-pressure control has not resulted in the expected decrease in coronary artery disease. These findings are probably a result of hypertension being a complex inherited syndrome of cardiovascular risk factors, all of which are genetically linked and all of which contribute to the development of cardiovascular disease in these patients. Included in the hypertension syndrome are abnormalities of lipid profile, insulin resistance, changes in renal function, left ventricular hypertrophy and reduced arterial compliance. In many patients, high blood pressure is a late manifestation of this disease process. Since all cardiovascular risk factors contribute to heart disease in these patients, they should all be considered in the management of this disease process. Diuretics and beta blockers, when used at high doses, negatively impact lipid metabolism and insulin sensitivity, while angiotensin converting enzyme (ACE) inhibitors and calcium antagonists tend to have a neutral effect on these metabolic risk factors. These findings have resulted in decreased use of diuretics and beta blockers in favor of newer agents such as ACE inhibitors and calcium antagonists. However, recent data have demonstrated that when used at low doses (6.25 or 12.5 mg of hydrochlorothiazide), diuretics lack significant metabolic side effects while bringing about significant reductions in blood pressure. Thus, at these doses, hydrochlorothiazide is a useful drug in the treatment of hypertension, both as monotherapy and in combination therapy.

Ramipril and felodipine: a comparison of the efficacy and safety of monotherapy versus combination therapy

A multinational, double-blind, randomised study was conducted to investigate the efficacy and safety of a low-dose combination of the angiotensin converting enzyme inhibitor, ramipril, and the calcium antagonist, felodipine ER, in 642 patients with mild to moderate hypertension [supine diastolic blood pressure (DBP) = 95-115 mm Hg]. After a 4-week single-blind placebo run-in, patients were randomly allocated to once-daily felodipine extended release (ER; 2.5 mg), ramipril (2.5 mg) or felodipine ER/ramipril (2.5/2.5 mg) for 12 weeks. In the intention-to-treat analysis, mean DBP decreased significantly (p < 0.0001) after felodipine ER, ramipril and the combination (-9.1, -9.8 and -11.4 mm Hg, respectively). The decrease was significantly greater with the combination than with felodipine ER monotherapy (p = 0.02). The number of responding patients (final DBP < or = 90 mm Hg or a decrease of > or = 10 mm Hg) was also higher with the combination than with felodipine ER or ramipril monotherapy (65.1%, 53.1%, 55.7%, respectively). There were no differences between the three groups with respect to the incidence of adverse events overall or those considered treatment-related. There were fewer cases of peripheral oedema with combination therapy than with felodipine ER monotherapy. Thirty-three patients (5.1%) withdrew from the study because of adverse events, but there was no clear pattern with regard to the specific events leading to withdrawal. There were no clinically relevant changes in laboratory or clinical safety variables. Ramipril/felodipine ER 2.5/2.5 mg is an appropriate starting dosage when initiating combination antihypertensive therapy.