Antihypertensive effects of low doses of hydrochlorothiazide in hypertensive black Zimbabweans

Pharmacotherapy for hypertension in Sub-Saharan Africa: a systematic review and network meta-analysis

BACKGROUND

The highest burden of hypertension is found in Sub-Saharan Africa (SSA) with a threefold greater mortality from stroke and other associated diseases. Ethnicity is known to influence the response to antihypertensives, especially in black populations living in North America and Europe. We sought to outline the impact of all commonly used pharmacological agents on both blood pressure reduction and cardiovascular morbidity and mortality in SSA.

METHODS

We used similar criteria to previous large meta-analyses of blood pressure agents but restricted results to populations in SSA. Quality of evidence was assessed using a risk of bias tool. Network meta-analysis with random effects was used to compare the effects across interventions and meta-regression to explore participant heterogeneity.

RESULTS

Thirty-two studies of 2860 participants were identified. Most were small studies from single, urban centres. Compared with placebo, any pharmacotherapy lowered SBP/DBP by 8.51/8.04 mmHg, and calcium channel blockers (CCBs) were the most efficacious first-line agent with 18.46/11.6 mmHg reduction. Fewer studies assessing combination therapy were available, but there was a trend towards superiority for CCBs plus ACE inhibitors or diuretics compared to other combinations. No studies examined the effect of antihypertensive therapy on morbidity or mortality outcomes.

CONCLUSION

Evidence broadly supports current guidelines and provides a clear rationale for promoting CCBs as first-line agents and early initiation of combination therapy. However, there is a clear requirement for more evidence to provide a nuanced understanding of stroke and other cardiovascular disease prevention amongst diverse populations on the continent.

TRIAL REGISTRATION

PROSPERO, CRD42019122490. This review was registered in January 2019.

Systematic review: antihypertensive drug therapy in patients of African and South Asian ethnicity

Despite the large differences in the epidemiology of hypertension across Europe, treatment strategies are similar for national populations of white European descent. However, hypertensive patients of African or South Asian ethnicity may require ethnic-specific approaches, as these population subgroups tend to have higher blood pressure at an earlier age that is more difficult to control, a higher occurrence of diabetes, and more target organ damage with earlier cardiovascular mortality. Therefore, we systematically reviewed the evidence on antihypertensive drug treatment in South Asian and African ethnicity patients. We used the Cochrane systematic review methodology to retrieve trials in electronic databases including CENTRAL, PubMed, and Embase from their inception through November 2015; and with handsearch. We retrieved 4596 reports that yielded 35 trials with 7 classes of antihypertensive drugs in 25,540 African ethnicity patients. Aside from the well-known blood pressure efficacy of calcium channel blockers and diuretics, with lesser effect of ACE inhibitors and beta-blockers, nebivolol was not more effective than placebo in reducing systolic blood pressure levels. Trials with morbidity and mortality outcomes indicated that lisinopril and losartan-based therapy were associated with a greater incidence of stroke and sudden death. Furthermore, 1581 reports yielded 16 randomized controlled trials with blood pressure outcomes in 1719 South Asian hypertensive patients. In contrast with the studies in African ethnicity patients, there were no significant differences in blood pressure lowering efficacy between drugs, and no trials available with mortality outcomes. In conclusion, in patients of African ethnicity, treatment initiated with ACE inhibitor or angiotensin II receptor blocker monotherapy was associated with adverse cardiovascular outcomes. We found no evidence of different efficacy of antihypertensive drugs in South Asians, but there is a need for trials with morbidity and mortality outcomes. Screening for cardiovascular risk at a younger age, treating hypertension at lower thresholds, and new delivery models to find, treat and follow hypertensives in the community may help reduce the excess cardiovascular mortality in these high-risk groups.

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.

Thiazides diuretics in the treatment of nephrolithiasis: are we using them in an evidence-based fashion?

In the 1980s a change occurred in hydrochlorothiazide prescribing practices for hypertension from high-dose (50 mg/day) to low-dose (12.5-25 mg/day) therapy. However, randomized controlled trials (RCT) for prevention of calcium-containing kidney stones (CCKS) employed only high doses (≥ 50 mg/day). We hypothesized that these practices have resulted in underdosing of hydrochlorothiazide for prevention of CCKS. Patients with a filled prescription for thiazide diuretics that underwent a 24-h urine stone risk factor analysis were eligible. Those with evidence that thiazide was prescribed for CCKS were further analyzed. Of 107 patients, 102 were treated with hydrochlorothiazide, 4 with indapamide, and one with chlorthalidone. Only 35% of hydrochlorothiazide-treated patients received 50 mg/day; a dose previously shown to reduce stone recurrence. Fifty-two percent were prescribed 25 mg and 13% 12.5 mg daily, doses that were not studied in RCT. Evidence-based hydrochlorothiazide use was suboptimal regardless of where the patient received care (Nephrology or Endocrinology clinic). In a small subset of patients (n = 6) with 24-h urinary calcium excretion measured at baseline and after 2 hydrochlorothiazide doses (25 and ≥ 50 mg), there was a trend toward decreased urinary calcium excretion as the dose was increased from 25 to ≥ 50 mg/day (p = 0.051). Low-dose hydrochlorothiazide was often used for prevention of CCKS despite the fact that there is no evidence that it is effective in this setting. This may have resulted from a practice pattern of using lower doses for hypertension therapy or a lack of knowledge of RCT results in treatment of CCKS.

WITHDRAWN: Effect of antihypertensive drugs on mortality, morbidity and blood pressure in blacks

BACKGROUND

Black people have a greater prevalence of elevated blood pressure leading to excess morbidity and mortality.

OBJECTIVES

To systematically review the effects of different antihypertensive drugs on mortality, morbidity and blood pressure black adults with elevated blood pressure.

SEARCH STRATEGY

Medline, Embase, LILACS, African Index Medicus, the Cochrane Library November 2003; Pubmed September 2003 to March 2004. Searches were conducted without language restriction.

SELECTION CRITERIA

Randomised controlled trials of drugs versus placebo (blood pressure outcomes) or versus placebo or other drugs (morbidity and mortality outcomes).

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data unblinded. Disagreements were resolved by discussion. Authors were contacted twice to obtain missing information.

MAIN RESULTS

Full reports or abstracts from more than 2900 references of papers yielded 30 trials considering 53 interventions with 8 classes of antihypertensive drugs in 20,006 black patients from Africa, the Caribbean, and the United States of America, aged 18 to >80 years. In one large trial the main morbidity and mortality outcomes did not differ significantly between initial treatment drug classes when drugs were added to reach goal blood pressures. However, the comparison ACE Inhibitors vs diuretic favoured the diuretic for stroke 1.40 [1.17 to 1.68]; combined CHD 1.15 [1.02 to 1.30] and combined CVD 1.19 [1.09 to 1.30] and the comparison alpha blocker vs diuretic favoured the diuretic for combined CVD 1.40 [1.25 to 1.57]. In addition, all comparisons for heart failure favoured diuretic (1.47 [1.24 to 1.74] vs calcium blocker; 1.32 [1.11 to 1.58] vs ACE Inhibitor; and 2.18 [1.73 to 2.74] vs alpha blocker. The results also showed a greater occurrence of diabetes with diuretics. No significant differences were detected between placebo and beta adrenergic blockers in the reduction of systolic blood pressure (weighted mean difference [95% CI], -3.52 [-7.50 to 0.46] mm Hg). In addition, ACE inhibitors did not significantly differ from placebo in achievement of goal diastolic blood pressure (risk difference [95% CI], 5% [-10% to 21%]). Calcium blockers, diuretics, centrally acting agents, alpha adrenergic blockers and angiotensin II antagonists were all more effective than placebo in reducing blood pressure in the pooled analyses. Only calcium blockers remained effective in all prespecified subgroups, including baseline diastolic blood pressure >109 mm Hg.

AUTHORS' CONCLUSIONS

When first-line drugs from different classes are compared in the treatment of black people, there is no evidence of differential effects on most mortality and morbidity outcomes. Those morbidity differences that were found favoured diuretics. Drugs differ in their ability to reduce blood pressure in black people. Calcium blockers were the only drug class that reduced blood pressure in all subgroups of black people including those with severe hypertension. Beta-blockers, angiotensin receptor blocker, alpha blockers and ACE Inhibitors were least good at reducing blood pressure in black adults.

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.