Chlorthalidone Decreases Platelet Aggregation and Vascular Permeability and Promotes Angiogenesis

Chlorthalidone vs Hydrochlorothiazide for Hypertension Treatment After Myocardial Infarction or Stroke: A Secondary Analysis of a Randomized Clinical Trial

Importance

Patients with prior myocardial infarction (MI) or stroke have a greater risk of recurrent cardiovascular (CV) events.

Objective

To evaluate the association of chlorthalidone (CTD) vs hydrochlorothiazide (HCTZ) with CV outcomes and noncancer deaths in participants with and without prior MI or stroke.

Design, Setting, and Participants

This was a prespecified secondary analysis of the Diuretic Comparison Project (DCP), a pragmatic randomized clinical trial conducted within 72 participating Veterans Affairs health care systems from June 2016 to June 2021, in which patients aged 65 years or older with hypertension taking HCTZ at baseline were randomized to continue HCTZ or switch to CTD at pharmacologically comparable doses. This secondary analysis was performed from January 3, 2023, to February 29, 2024.

Exposures

Pharmacologically comparable daily dose of HCTZ or CTD and history of MI or stroke.

Main Outcomes and Measures

Outcome ascertainment was performed from randomization to the end of the study. The primary outcome consisted of a composite of stroke, MI, urgent coronary revascularization because of unstable angina, acute heart failure hospitalization, or noncancer death. Additional outcomes included achieved blood pressure and hypokalemia (potassium level <3.1 mEq/L; to convert to mmol/L, multiply by 1.0).

Results

The DCP randomized 13 523 participants to CTD or HCTZ, with a mean (SD) study duration of 2.4 (1.4) years. At baseline, median age was 72 years (IQR, 69-75 years), and 96.8% were male. Treatment effect was evaluated in subgroups of participants with (n = 1455) and without (n = 12 068) prior MI or stroke at baseline. There was a significant adjusted interaction between treatment group and history of MI or stroke. Participants with prior MI or stroke randomized to CTD had a lower risk of the primary outcome than those receiving HCTZ (105 of 733 [14.3%] vs 140 of 722 [19.4%]; hazard ratio [HR], 0.73; 95% CI, 0.57-0.94; P = .01) compared with participants without prior MI or stroke, among whom incidence of the primary outcome was slightly higher in the CTD arm compared with the HCTZ arm (597 of 6023 [9.9%] vs 535 of 6045 [8.9%]; HR, 1.12; 95% CI, 1.00-1.26; P = .054) (P = .01 for interaction). The incidence of a nadir potassium level less than 3.1 mEq/L and hospitalization for hypokalemia differed among those with and without prior MI or stroke when comparing those randomized to CTD vs HCTZ, with a difference only among those without prior MI or stroke (potassium level <3.1 mEq/L: prior MI or stroke, 43 of 733 [5.9%] vs 37 of 722 [5.1%] [P = .57]; no prior MI or stroke, 292 of 6023 [4.9%] vs 206 of 6045 [3.4%] [P < .001]; hospitalization for hypokalemia: prior MI or stroke, 14 of 733 [1.9%] vs 16 of 722 [2.2%] [P = .72]; no prior MI or stroke: 84 of 6023 [1.4%] vs 57 of 6045 [0.9%] [P = .02]).

Conclusions and Relevance

Results of this secondary analysis of the DCP trial suggest that CTD may be associated with reduced major adverse CV events and noncancer deaths in patients with prior MI or stroke compared with HCTZ.

Trial Registration

ClinicalTrials.gov Identifier: NCT02185417.

Chlorthalidone vs. Hydrochlorothiazide for Hypertension-Cardiovascular Events

BACKGROUND

Whether chlorthalidone is superior to hydrochlorothiazide for preventing major adverse cardiovascular events in patients with hypertension is unclear.

METHODS

In a pragmatic trial, we randomly assigned adults 65 years of age or older who were patients in the Department of Veterans Affairs health system and had been receiving hydrochlorothiazide at a daily dose of 25 or 50 mg to continue therapy with hydrochlorothiazide or to switch to chlorthalidone at a daily dose of 12.5 or 25 mg. The primary outcome was a composite of nonfatal myocardial infarction, stroke, heart failure resulting in hospitalization, urgent coronary revascularization for unstable angina, and non-cancer-related death. Safety was also assessed.

RESULTS

A total of 13,523 patients underwent randomization. The mean age was 72 years. At baseline, hydrochlorothiazide at a dose of 25 mg per day had been prescribed in 12,781 patients (94.5%). The mean baseline systolic blood pressure in each group was 139 mm Hg. At a median follow-up of 2.4 years, there was little difference in the occurrence of primary-outcome events between the chlorthalidone group (702 patients [10.4%]) and the hydrochlorothiazide group (675 patients [10.0%]) (hazard ratio, 1.04; 95% confidence interval, 0.94 to 1.16; P = 0.45). There were no between-group differences in the occurrence of any of the components of the primary outcome. The incidence of hypokalemia was higher in the chlorthalidone group than in the hydrochlorothiazide group (6.0% vs. 4.4%, P<0.001).

CONCLUSIONS

In this large pragmatic trial of thiazide diuretics at doses commonly used in clinical practice, patients who received chlorthalidone did not have a lower occurrence of major cardiovascular outcome events or non-cancer-related deaths than patients who received hydrochlorothiazide. (Funded by the Veterans Affairs Cooperative Studies Program; ClinicalTrials.gov number, NCT02185417.).

Thiazides in chronic kidney disease: "back to the future"

The thiazide class diuretics are first-line agents for managing hypertension either as monotherapy or as a fixed-dose combination with other antihypertensive drugs. However, despite the extensive experience with these drugs for >60 years, there is general reluctance to use these agents in patients with advanced chronic kidney disease (CKD) because of concerns about their efficacy and safety as kidney function declines. In this issue of Clinical Kidney Journal, Minutolo et al. performed an updated review of the pharmacological properties, efficacy and side effects and randomized controlled trials that tested these drugs in patients with CKD.

Comparative antiplatelet effects of chlorthalidone and hydrochlorothiazide

Chlorthalidone (CTD) may be superior to hydrochlorothiazide (HCTZ) in the reduction of adverse cardiovascular events in hypertensive patients. The mechanism of the potential benefit of CTD could be related to antiplatelet effects. The objective of this study was to determine if CTD or HCTZ have antiplatelet effects. This study was a prospective, double‐blind, randomized, three‐way crossover comparison evaluating the antiplatelet effects of CTD, HCTZ, and aspirin (ASA) in healthy volunteers. The effects of these treatments on platelet activation and aggregation were assessed using a well‐established method with five standard platelet agonists. Thirty‐four patients completed the three‐way crossover comparing pre‐ and post‐treatment changes in platelet activation and aggregation studies. There were statistically significant antiplatelet effects with ASA but not with CTD or HCTZ. Hypokalemia occurred in 0 (0%), 10 (30%), and 6 (18%) of the ASA, CTD, and HCTZ patients, respectively. The results of our study suggest that the benefits of CTD and HCTZ in reducing adverse cardiovascular events in patients with hypertension is not a result of an antiplatelet effect. In our study, hypokalemia with CTD was more prevalent than that reported in a large outcome trial in patients with hypertension. The clinical relevance of this finding is uncertain.

Thiazide and the Thiazide-Like Diuretics: Review of Hydrochlorothiazide, Chlorthalidone, and Indapamide

The term thiazide is universally understood to refer to diuretics that exert their principal action in the distal tubule. The thiazide class is heterogenous and can be further subdivided into compounds containing the benzothiadiazine ring structure-the thiazide-type (e.g., hydrochlorothiazide)-and those lacking the benzothiadiazine ring-the thiazide-like (e.g., chlorthalidone and indapamide) drugs. Thiazide-like agents are longer acting and constitute the diuretics used in most of the cardiovascular outcome trials that established benefits of treatment with diuretics, but pragmatic aspects, such as lack of availability in convenient formulations, limit their use. Regardless of class heterogeneity, thiazides have retained importance in the management of hypertension for over 60 years. They are reliably effective as monotherapy in a majority of hypertensive patients, and augment the efficacy of other classes of antihypertensives when used in combination. Importantly, a thiazide-based treatment regimen lowers cardiovascular events, and their sturdy effect reinforces their place among the recommended first-line agents to treat hypertension in major domestic and international hypertension guidelines. There are few head-to-head comparisons within the class, but potential differences have been explored indirectly as well as in non-blood pressure mechanisms and potential pleiotropic properties. Until proven otherwise, the importance of these differences remains speculative, and clinicians should assume that cardiovascular events will be lowered similarly across agents when equivalent blood pressure reduction occurs. Thiazides remain underutilized, with only about one-third of hypertensive patients receiving them. For many patients, however, a thiazide is an indispensable component of their regimen to achieve adequate blood pressure control.

Design of a pragmatic clinical trial embedded in the Electronic Health Record: The VA's Diuretic Comparison Project

BACKGROUND

Recent US guidelines recommend chlorthalidone over other thiazide-type diuretics for the treatment of hypertension based on its long half-life and proven ability to reduce CVD events. Despite recommendations most clinicians prescribe hydrochlorothiazide (HCTZ) over chlorthalidone (CTD). No randomized controlled data exist comparing these two diuretics on cardiovascular outcomes.

METHODS

The Diuretic Comparison Project (DCP) is a multicenter, two-arm, parallel, Prospective Randomized Open, Blinded End-point (PROBE) trial testing the primary hypothesis that CTD is superior to HCTZ in the prevention of non-fatal CVD events and non-cancer death. Patients with hypertension taking HCTZ 25 or 50 mg were randomly assigned to either continue their current HCTZ or switch to an equipotent dose of CTD. The primary outcome is time to the first occurrence of a composite outcome consisting of a non-fatal CVD event (stroke, myocardial infarction, urgent coronary revascularization because of unstable angina, or hospitalization for acute heart failure) or non-cancer death. The trial randomized 13,523 patients at 72 VA medical centers. The study is conducted by a centralized research team with site procedures embedded in the electronic health record and all data collected through administrative claims data, with no study related visits for participants. The trial will have 90% power to detect an absolute reduction in the composite event rate of 2.4%.

RESULTS

Enrollment ended in November 2021. There are 4128 participting primary care providers and 16,595 patients individually consented to participate, 13,523 of whom were randomized.

CONCLUSIONS

DCP should provide much needed evidence as to whether CTD is superior to HCTZ in preventing cardiovascular events in hypertensive patients.

CLINICAL TRIAL REGISTRATION

NCT02185417 [https://clinicaltrials.gov/ct2/show/NCT02185417].

Monosubstituted Coumarins Inhibit Epinephrine-Induced Platelet Aggregation Antiplatelet Effect of Monosubstituted Coumarins

Aim

The aim of this study was to evaluate the in vitro effect of coumarin and 15 monosubstituted  derivatives on  the inhibition  of human platelet  aggregation  induced by various  pro-aggregatory agonists, particularly by epinephrine.

Background

The emergence of residual platelet reactivity during the use of conventional antiplatelet agents (acetylsalicylic acid and clopidogrel) is one of the main causes of double therapy´s therapeutic failure. Platelet adrenoceptors participate in residual platelet reactivity. Therefore, it is necessary to develop new antiplatelet agents that inhibit epinephrine-induced platelet aggregation as a new therapeutic strategy. Information on the antiplatelet activity of coumarins in inhibiting epinephrine-induced aggregation is limited.

Objective

The objective of this study was to establish the structure-activity relationship (SAR) of coumarin derivatives with hydroxy, methoxy, and acetoxy groups in different positions of the coumarin nucleus to identify the most active molecules. Moreover, this study aimed to use in silico studies to suggest potential drug targets to which the molecules bind to produce antiplatelet effects.

Methods

The platelet aggregation was performed using a Lumi-aggregometer; the inhibitory activity of 16 compounds were evaluated by inducing the aggregation of human platelets (250 × 10³/μl) with epinephrine (10 µM), collagen (2 µg/ml) or ADP (10 µM). The aggregation of control platelets was considered 100% of the response for each pro-aggregatory agonist.

Results

Eleven molecules inhibited epinephrine-induced aggregation, with 3-acetoxycoumarin and 7-methoxycoumarin being the most active. Only coumarin inhibited collagen-induced platelet aggregation, but no molecule showed activity when using ADP as an inducer.

Conclusions

In silico studies suggest that most active molecules might have antagonistic interactions in the α₂ and β₂ adrenoceptors. The antiplatelet actions of these coumarins have the potential to reduce residual platelet reactivity and thus contribute to the development of future treatments for patients who do not respond adequately to conventional agents.

Network meta-analysis of efficacy and safety of chlorthalidone and hydrochlorothiazide in hypertensive patients

Hypertension is a chronic condition leading to increased stress on the heart and blood vessels, a critical risk factor for clinically significant events such as myocardial infarction heart failure, stroke and death. Chlorthalidone and hydrochlorothiazide are first-line antihypertensive agents for most patients with hypertension. The aim of our meta-analysis was to compare the efficacy and safety of both therapies in patients with hypertension. Searches of electronic databases PubMed, MEDLINE, Scopus, PsycInfo and eLIBRARY.ru, were performed. We used network meta-analysis to combine direct and indirect evidence. Forest plots and closed loops depict estimated results from studies included in our meta-analysis. Of 1289 identified sources, only 37 were included in our meta-analysis. Our analysis has demonstrated a slight superiority for chlorthalidone regarding SBP and not statistically significant differences regarding DBP. Simultaneously, hydrochlorothiazide seems to be a safer choice of therapy, as evidenced by the levels of serum potassium. The two diuretics can be used interchangeably.

Redefining diuretics use in hypertension: why select a thiazide-like diuretic?

Diuretics are listed in hypertension guidelines as one of three equally weighted first-line treatment options. In order to differentiate between antihypertensives, a lot of discussion has been directed at side effect profiles and as a result, has created a perhaps disproportionate fear of the metabolic effects that can be associated with diuretics. Data, however, show that the risk of a clinically meaningful change in laboratory parameters is very low, whereas the benefits of volume control and natriuresis are high and the reductions in morbidity and mortality are clinically significant. Moreover, as clinically significant differences in safety and efficacy profiles exist among diuretics, several international guidelines have started making a distinction between thiazides (hydrochlorothiazide) and thiazide-like (chlorthalidone, indapamide) diuretics; and some of them now recommend longer acting thiazide-like diuretics. In time, pending more data, chlorthalidone and indapamide may need to be subdivided further into separate classifications.

Comparative efficacy and safety of chlorthalidone and hydrochlorothiazide-meta-analysis

Hypertension is a complex syndrome of multiple hemodynamic, neuroendocrine, and metabolic abnormalities. The goals of treatment in hypertension are to optimally control high blood pressure and to reduce associated cardiovascular morbidity and mortality using the most suitable therapy available. Hydrochlorothiazide (HCTZ) and chlorthalidone (CTLD) are with proven hypertensive effects. The topic of our meta-analysis is to compare the efficacy of HCTZ and CTLD therapy in patient with hypertension. A search of electronic databases PubMed, MEDLINE, Scopus, PsyInfo, eLIBRARY.ru was performed. We chose the random-effects method for the analysis and depicted the results as forest plots. Sensitivity analyses were performed in order to evaluate the degree of significance of each study. Of the 1289 identified sources, only nine trials directly compared HCTZ and CTLD and were included in the meta-analysis. Changes in SBP lead to WMD (95% CI) equal to -3.26 mmHg showing a slight but statistically significant prevalence of CTLD. Results from analyzed studies referring to DBP lead to WMD (95% CI) equal to -2.41 mmHg, which is also statistically significant. During our analysis, we found that there were not enough studies presenting enough data on the effect of CTLD and HCTZ on levels of serum potassium and serum sodium. Our meta-analysis has demonstrated a slight superiority for CTLD regarding blood pressure control. At the same time, the two medications do not show significant differences in their safety profile.

Pharmacological Studies Pertaining to Smooth Muscle Relaxant, Platelet Aggregation Inhibitory and Hypotensive Effects of Ailanthus altissima

OBJECTIVE

This in vitro and in vivo study was conducted to rationalize some of traditional medicinal uses of Ailanthus altissima in gastrointestinal, respiratory, and cardiovascular systems.

MATERIALS

Crude extract of Ailanthus altissima (Aa.Cr) and its fractions were prepared and utilized in in vitro and in vivo studies. For in vitro studies, Aa.Cr was investigated on isolated rabbit jejunum, isolated tracheal strip, and isolated aorta of rat suspended in tissue organ bath. Platelet rich and platelet poor plasma were used to study platelet aggregation inhibitory activity. In vivo antidiarrheal effect of Aa.Cr was investigated on balb/c mice pretreated with castor oil to induce diarrhea and SD rats were used to study hypotensive activity.

RESULTS

Concentration dependent spasmolytic effects of Aa.Cr and its DCM fraction (Aa.DCM) were observed on spontaneous and spasmogen induced contractions in jejunum isolated from rabbit, but effect against high potassium (high-K+) induced contractions was more potent. Moreover Aa.Cr showed parallel shifting of calcium response curve to the right side. While its aqueous fraction (Aa.aq) caused spasmogenesis of isolated rabbit jejunum, this effect was blocked partially with prior administration of atropine (1μM). Concentration dependent protection against castor oil induced diarrhea was also observed. Relaxant effect was observed by the application of Aa.Cr and Aa.DCM against high-K+ and carbachol (CCh) induced contractions in tracheal strips isolated from SD rats, while Aa.Aq caused partial relaxation of high-K+ induced contractions, but no effect was observed against CCh induced contractions. Relaxation of rat aorta by the application of Aa.Cr and its fractions was also observed. Inhibition of force of contraction in rabbit atrium was also observed. Inhibition of platelet aggregation was observed against epinephrine and ADP induced aggregation.

CONCLUSION

Keeping in view the observed results, it is concluded that smooth muscle relaxant, platelet aggregation inhibitory and hypotensive effect may be due to the blockage of calcium channels.

Hydrochlorothiazide vs chlorthalidone, indapamide, and potassium-sparing/hydrochlorothiazide diuretics for reducing left ventricular hypertrophy: A systematic review and meta-analysis

Left ventricular hypertrophy develops in 36%-41% of hypertensive patients and independently predicts cardiovascular events and total mortality. Moreover, drug-induced reduction in left ventricular mass (LVM) correlates with improved prognosis. The optimal thiazide-type diuretic for reducing LVM is unknown. Evidence regarding potency, cardiovascular events, sodium, and potassium suggested the hypothesis that "CHIP" diuretics (CHlorthalidone, Indapamide, and Potassium-sparing diuretic/hydrochlorothiazide [PSD/HCTZ]) would reduce LVM more than HCTZ. Systematic searches of five databases were conducted. Among the 38 randomized trials, a 1% reduction in systolic blood pressure (SBP) predicted a 1% reduction in LVM, P = 0.00001. CHIP-HCTZ differences in reducing LVM differed across trials (ie, heterogeneity), making interpretation uncertain. However, among the 28 double-blind trials, heterogeneity was undetectable, and HCTZ reduced LVM (percent reduction [95% CI]) by -7.3 (-10.4, -4.2), P < 0.0001. CHIP diuretics surpassed HCTZ in reducing LVM: chlorthalidone -8.2 (-14.7, -1.6), P = 0.015; indapamide -7.5 (-12.7, -2.3), P = 0.005; and all CHIP diuretics combined -7.7 (-12.2, -3.1), P < 0.001. The comparison of PSD/HCTZ with HCTZ had low statistical power but favored PSD/HCTZ: -6.0 (-14.1, +2.1), P = 0.149. Thus, compared to HCTZ, CHIP diuretics had twice the effect on LVM. CHIP diuretics did not surpass HCTZ in reducing systolic or diastolic blood pressure: -0.3 (-5.0, +4.3) and -1.6 (-5.6, +2.4), respectively. The strength of evidence that CHIP diuretics surpass HCTZ for reducing LVM was high (GRADE criteria). In conclusion, these novel results have demonstrated that CHIP diuretics reduce LVM 2-fold more than HCTZ among hypertensive patients. Although generally related to LVM, blood pressure fails to explain the superiority of CHIP diuretics for reducing LVM.

The Human Carbonic Anhydrase II in Platelets: An Underestimated Field of Its Activity

Carbonic anhydrases constitute a group of enzymes that catalyse reversible hydration of carbon dioxide leading to the formation of bicarbonate and proton. The platelet carbonic anhydrase II (CAII) was described for the first time in the '80s of the last century. Nevertheless, its direct role in platelet physiology and pathology still remains poorly understood. The modulation of platelet CAII action as a therapeutic approach holds promise as a novel strategy to reduce the impact of cardiovascular diseases. This short review paper summarises the current knowledge regarding the role of human CAII in regulating platelet function. The potential future directions considering this enzyme as a potential drug target and important pathophysiological chain in platelet-related disorders are described.

Effect of hydrochlorothiazide on serum uric acid concentration: a genome-wide association study

AIM

To recognize genetic associations of hydrochlorothiazide-induced change in serum uric acid (SUA) concentration.

PATIENTS & METHODS

We conducted a genome-wide association study on hydrochlorothiazide-induced change in SUA in 214 Finnish men from the GENRES study. Replication analyses were performed in 465 Finns from the LIFE study.

RESULTS

In GENRES, we identified 31 loci associated with hydrochlorothiazide-induced change in SUA at p < 5 × 10^-5. rs1002976 near VEGFC associated with the change in GENRES and in LIFE. rs950569 near BRINP3 associated with the change in SUA in GENRES and LIFE. The analysis of previously reported SNPs and candidate genes provided some proof for PADI4 and ABCC4.

CONCLUSION

We report genetic markers that may predict the increase in SUA concentration during thiazide treatment.

Chlorthalidone, not hydrochlorothiazide, is the right diuretic for comparison

We have read the study design "Comparison of effects between calcium channel blocker and diuretics in combination with angiotensin II receptor blocker on 24-h central blood pressure and vascular hemodynamic parameters in hypertensive patients: study design for a multicenter, double-blinded, active controlled, phase 4, randomized trial" by Oh GC, et al. with interest. The authors aim to compare the efficacy of amlodipine or hydrochlorothiazide (HCTZ) with an ARB. However, we wish to highlight that chlorthalidone (CTD) is the evidence-based and recommended anti-hypertensive diuretic, and should replace HCTZ in the trial to effectively compare efficacy against the CCB amlodipine.

Platelet Carbonic Anhydrase II, a Forgotten Enzyme, May Be Responsible for Aspirin Resistance

Background

Thromboembolic events constitute a major health problem, despite the steadily expanding arsenal of antiplatelet drugs. Hence, there is still a need to optimize the antiplatelet therapy.

Objectives

The aim of our study was to verify a hypothesis that there are no differences in platelet proteome between two groups of healthy people representing different acetylsalicylic acid (aspirin) responses as assessed by the liquid chromatography/mass spectrometry (LC/MS) technique.

Patients/Methods

A total of 61 healthy volunteers were recruited for the study. Physical examination and blood collection were followed by platelet-rich plasma aggregation assays and platelet separation for proteomic LC/MS analysis. Arachidonic acid- (AA-) induced aggregation (in the presence of aspirin) allowed to divide study participants into two groups aspirin-resistant (AR) and aspirin-sensitive (AS) ones. Subsequently, platelet proteome was compared in groups using the LC/MS analysis.

Results

The LC/MS analysis of platelet proteome between groups revealed that out of all identified proteins, the only discriminatory protein, affecting aspirin responsiveness, is platelet carbonic anhydrase II (CA II).

Conclusions

CA II is a platelet function modulator and should be taken into consideration as a cardiovascular event risk factor or therapeutic target.

RAPIDSNPs: A new computational pipeline for rapidly identifying key genetic variants reveals previously unidentified SNPs that are significantly associated with individual platelet responses

Advances in omics technologies have led to the discovery of genetic markers, or single nucleotide polymorphisms (SNPs), that are associated with particular diseases or complex traits. Although there have been significant improvements in the approaches used to analyse associations of SNPs with disease, further optimised and rapid techniques are needed to keep up with the rate of SNP discovery, which has exacerbated the 'missing heritability' problem. Here, we have devised a novel, integrated, heuristic-based, hybrid analytical computational pipeline, for rapidly detecting novel or key genetic variants that are associated with diseases or complex traits. Our pipeline is particularly useful in genetic association studies where the genotyped SNP data are highly dimensional, and the complex trait phenotype involved is continuous. In particular, the pipeline is more efficient for investigating small sets of genotyped SNPs defined in high dimensional spaces that may be associated with continuous phenotypes, rather than for the investigation of whole genome variants. The pipeline, which employs a consensus approach based on the random forest, was able to rapidly identify previously unseen key SNPs, that are significantly associated with the platelet response phenotype, which was used as our complex trait case study. Several of these SNPs, such as rs6141803 of COMMD7 and rs41316468 in PKT2B, have independently confirmed associations with cardiovascular diseases (CVDs) according to other unrelated studies, suggesting that our pipeline is robust in identifying key genetic variants. Our new pipeline provides an important step towards addressing the problem of 'missing heritability' through enhanced detection of key genetic variants (SNPs) that are associated with continuous complex traits/disease phenotypes.

Hydrochlorothiazide is not the most useful nor versatile thiazide diuretic

PURPOSE OF REVIEW

To determine usefulness and versatility of hydrochlorothiazide (HCTZ) relative to other thiazide diuretics in the treatment of hypertension.

RECENT FINDINGS

HCTZ was found to be less potent in lowering blood pressure (BP) than other thiazide diuretics, including chlorthalidone (CTD) and bendroflumethiazide. A recent meta-analysis also suggested HCTZ (12.5-25 mg daily) to be less potent than antihypertensive agents from several other classes, including angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and calcium antagonists. The risk of hyponatremia, hypokalemia, and hyperuricemia associated with HCTZ was lower than with CTD, while the risk of gouty arthritis was similar. Despite lower risks of metabolic side-effects, meta-analysis of clinical trials showed that, for any given difference in achieved clinic SBP, HCTZ therapy was associated with 18% higher adverse cardiovascular events when compared with CTD.

SUMMARY

Increasing evidence suggests inferiority of HCTZ in lowering BP and cardiovascular outcomes in hypertensive patients when compared with other drugs in the same class, particularly CTD and indapamide. Thus, HCTZ is neither more useful nor more versatile than other thiazide diuretics. CTD and indapamide should be preferred over HCTZ in most hypertensive patients when diuretics are required for treatment of hypertension.

An association of losartan-hydrochlorothiazide, but not losartan-furosemide, completely arrests progressive injury in the remnant kidney

We have previously shown that an association of losartan and hydrochlorothiazide, initiated 1 mo after 5/6 nephrectomy (Nx), reversed hypertension and albuminuria and promoted lasting renoprotection. In this new study, we investigated whether equal or even better protection could be obtained by combining losartan and furosemide. Nx was performed in 58 Munich-Wistar rats. One month later, tail-cuff pressure and albuminuria were markedly elevated. At this time, Nx rats were distributed among the following four groups: untreated Nx rats, Nx rats that received losartan, Nx rats that received losartan + hydrochlorothiazide, and Nx rats that received losartan + furosemide. Seven months later, Nx rats exhibited high mortality, severe hypertension, albuminuria, glomerulosclerosis, and interstitial fibrosis. Losartan treatment limited mortality and attenuated the renal and hemodynamic abnormalities associated with Nx. As previously shown, the losartan + hydrochlorothiazide association normalized tail-cuff pressure and albumin, prevented renal injury, and reduced mortality to zero. The losartan + furosemide treatment failed to reduce tail-cuff pressure or albumin to normal and prevented renal injury less efficiently than the losartan and hydrochlorothiazide regimen. The reasons for the differing efficacies of the losartan + furosemide and losartan + hydrochlorothiazide schemes are unclear and may include beneficial nondiuretic actions of thiazides, such as vasorelaxation and antiproliferative activity. These results refute the established concept that thiazides and thiazide-like diuretics are ineffective at advanced chronic kidney disease stages. Rather, they suggest that, in view of their renoprotective action, these compounds may even be preferable to loop diuretics in the management of hypertension in advanced chronic kidney disease.

Not just chlorthalidone: evidence-based, single tablet, diuretic alternatives to hydrochlorothiazide for hypertension

Accounting for 15 % of deaths worldwide, hypertension is often treated with hydrochlorothiazide (HCTZ) (50 million prescriptions annually). HCTZ has a <24-h duration of action, is less potent than chlorthalidone and all major antihypertensive drug classes, and is inferior to four antihypertensive drugs for cardiovascular event (CVE) reduction. If there were alternative diuretics, why prescribe HCTZ? Chlorthalidone is often offered as an alternative to HCTZ, but has limited pharmaceutical formulations. However, there are seven evidence-based, single-tablet, alternative diuretics. For reducing CVE, the following are superior to their comparators: chlorthalidone versus four antihypertensives in multiple hypertensive populations; indapamide versus placebo in elderly Chinese (and versus enalapril for left ventricular hypertrophy), triamterene-HCTZ versus placebo in elderly Europeans, amiloride-HCTZ versus three antihypertensives, and indapamide-perindopril versus placebo in three populations. Additionally, chlorthalidone-azilsartan and spironolactone-HCTZ are potent combinations The aldosterone antagonist component of the latter combination has been shown to reduce total mortality by 30 % in heart failure. Five of these seven have multiple dose formulations. Six cost $4-$77 monthly. In conclusion, based on both scientific and practical grounds, new prescriptions for HCTZ are rarely justified.

Hypertension subtypes modify metabolic response to thiazide diuretics

BACKGROUND

Blood pressure (BP) and metabolic response to thiazide diuretics might be varied in patients with different hypertension subtypes and ethnicities. This study aimed to investigate the response of BP and metabolic profiles to short-term thiazide treatment in an Asian cohort with different hypertension subtypes.

DESIGN

Serial ethnic Chinese nondiabetic subjects with hypertension were evaluated. After diet instruction and lifestyle modification for 2 weeks, patients who still had elevated systolic BP (SBP≥140 mmHg) and/or diastolic BP (DBP≥90 mmHg) were given 50 mg of hydrochlorothiazide daily for 2 weeks. The responses of BP and metabolic profiles were evaluated before and after treatment according to the patient's baseline BP subtype - isolated systolic hypertension (ISH), systo-diastolic hypertension (SDH) and isolated diastolic hypertension (IDH).

RESULTS

Hydrochlorothiazide treatment significantly reduced the BP in all 92 patients (62 males, aged 45·7 ± 9·6 years), irrespective of their baseline BP subtypes. In patients with SDH (n = 39) or IDH (n = 40), hydrochlorothiazide treatment significantly increased serum adiponectin (P = 0·001 and 0·007, respectively) and reduced asymmetric dimethylarginine levels (P < 0·001, in both groups). Serum cholesterol (P = 0·027) and fasting blood sugar levels (P = 0·044) were significantly improved only in the IDH patients. Furthermore, IDH was independently associated with changes in fasting blood sugar (β = -11·178, P = 0·022) and cholesterol (β = -22·654, P = 0·027).

CONCLUSIONS

The characteristics of the Asian hypertensive patients with diastolic hypertension can present a favourable metabolic response to the short-term hydrochlorothiazide treatment. The potential positive effect on cardiovascular risk should be validated in long-term studies in this diastolic type of hypertension.

Evidence-based diuretics: focus on chlorthalidone and indapamide

Thiazide and thiazide-like diuretics are cornerstone treatments for hypertension. However, unlike chlorthalidone (CTD) and indapamide (IDP), hydrochlorothiazide (HCTZ) lacks evidence for reducing morbidity and mortality as monotherapy compared with placebo or control. Despite this fact, HCTZ is prescribed much more frequently than CTD or IDP. We believe that all hypertension guidelines should follow the National Institute for Health and Excellence (NICE) and make IDP and CTD first choice 'thiazide-like diuretics.' This article will focus on the available evidence pertaining to HCTZ versus CTD and IDP. We will review the pharmacological differences between these three diuretics, as well as the clinical trial data and important side effects.

New insights into carbonic anhydrase inhibition, vasodilation, and treatment of hypertensive-related diseases

Carbonic anhydrase (CA) and its inhibitors are relevant to many physiological processes and diseases. The enzyme is differentially expressed throughout the body, in concentration and subcellular location, and as 13 catalytically active isoforms. Blood vessels contain small amounts of CA, but the enzyme's role in vascular physiology and blood pressure regulation is uncertain. However, considerable recent evidence points to vasodilation by CA inhibitors. CA inhibition in vascular smooth muscle, endothelium, heart, blood cells, and nervous system could all contribute. It is equally plausible that other targets besides CA for all known CA inhibitors may account for their vascular effects. I will review this knowledge and important remaining gaps relating to treatment of hypertensive-related diseases with potent sulfonamide inhibitors, such as acetazolamide; but also the possibility that CA inhibition by thiazides and loop diuretics, although generally weaker, may have antihypertensive effects beyond their inhibition of renal sodium transporters.

Misconceptions and facts about treating hypertension

Hypertension is a powerful risk factor strongly linked to adverse cardiovascular outcomes. Because of its high prevalence, health care providers at many levels are involved in treating hypertension. Distinct progress has been made in improving the rates of hypertension awareness and treatment over years, but the overall control of hypertension remains inadequate. Several recent guidelines from different sources have been put forward in an attempt to bridge the gap between existing evidence and clinical practice. Despite this effort, several misconceptions about treating hypertensive cardiovascular disease continue to persist among clinicians. This review highlights some of the misconceptions regarding antihypertensive therapy.

Which thiazide to choose as add-on therapy for hypertension?

Combined therapy is required in the majority of patients with hypertension to achieve blood pressure (BP) targets. Although different antihypertensive drugs can be combined, not all combinations are equally effective and safe. In this context, the combination of a renin angiotensin system inhibitor with a diuretic, usually a thiazide, particularly hydrochlorothiazide (HCTZ) or thiazide-like diuretics, such as chlorthalidone or indapamide, is recommended. However, not all diuretics are equal. Although HCTZ, chlorthalidone, and indapamide as add-on therapy effectively reduce BP levels, the majority of studies have obtained greater BP reductions with chlorthalidone or indapamide than with HCTZ. Moreover, there are data showing benefits with chlorthalidone or indapamide beyond BP. Thus, chlorthalidone seems to have pleiotropic effects beyond BP reduction. Moreover, compared with placebo, chlorthalidone has small effects on fasting glucose and total cholesterol, and compared with HCTZ, chlorthalidone achieves significantly lower total cholesterol and low-density lipoprotein cholesterol levels. Similarly, indapamide has demonstrated no negative impact on glucose or lipid metabolism. More importantly, although head-to-head clinical trials comparing the effects of indapamide or chlorthalidone with HCTZ are not available, indirect comparisons and post hoc analyses suggest that the use of chlorthalidone or indapamide is associated with a reduction in cardiovascular events. Despite this, the most frequent diuretic used in clinical practice as add-on therapy for hypertension is HCTZ. The purpose of this review is to update the published data on the efficacy and safety of HCTZ, chlorthalidone, and indapamide as add-on therapy in patients with hypertension.

Which diuretic is the preferred agent for treating essential hypertension: hydrochlorothiazide or chlorthalidone?

Since their introduction over 50 years ago thiazide and thiazide-like diuretics have been a mainstay in the treatment of hypertension. Yet despite outcome evidence with chlorthalidone, the preponderance of usage has been with hydrochlorothiazide-either as monotherapy or in combination with other drugs. There is an increasing debate as to whether or not there are significant differences between hydrochlorothiazide and chlorthalidone. Early outcome studies, upon which the recommendations were made, utilized higher doses than those not only commonly employed in clinical practice, but also studied in more recent outcome trials. In addition, data suggests that chlorthalidone may be more potent, in equal doses, in its BP response than hydrochlorothiazide. A fundamental question asked in the debate is whether or not the benefits attributed to chlorthalidone as a thiazide-like diuretic may be reasonably ascribed to thiazides given differences in their pharmacokinetic properties and perhaps some other more recently noted differences.

Chlorthalidone: the forgotten diuretic

Chlorthalidone's safety and efficacy in the management of hypertension has been demonstrated in landmark trials. Despite understanding the effects of thiazides on urinary sodium excretion and intravascular volume, the exact mechanism of their antihypertensive effects is not clearly understood. Common compensatory mechanisms for decreases in circulating plasma volume include increased adrenergic tone and systemic vascular resistance, as well as increases in the renin-angiotensin-aldosterone system. Chlorthalidone has been shown to decrease platelet aggregation and vascular permeability and promote angiogenesis in vitro, which is thought to be, in part, the result of reductions in carbonic anhydrase-dependent pathways, including catecholamine-mediated platelet aggregation and downregulation of VEGF-C gene expression. This article reviews the comparative clinical data between chlorthalidone and hydrochlorothiazide, the pharmacologic properties that might explain some of their differences regarding half-life and efficacy, and what is known about the effect of chlorthalidone on intermediate endpoints.

Chlorthalidone compared with hydrochlorothiazide in reducing cardiovascular events: systematic review and network meta-analyses

Hydrochlorothiazide (HCTZ) is widely used for hypertension, and prescriptions for HCTZ outnumber those for chlorthalidone (CTDN) by >20-fold in 2 recent surveys. Some have recently expressed a preference for CTDN. However, head-to-head trials testing the effect of the 2 drugs on cardiovascular events (CVEs) are lacking. We conducted a systematic review of randomized trials in which 1 arm was based on either HCTZ or CTDN followed by 2 types of network meta-analyses, a drug-adjusted analysis and an office systolic blood pressure-adjusted analysis. Nine trials were identified: 3 based on HCTZ and 6 based on CTDN. In the drug-adjusted analysis (n = 50946), the percentage of risk reduction in congestive heart failure for CTDN versus HCTZ was 23 (95% CI, 2-39; P = 0.032); and in all CVEs was 21 (95% CI, 12-28; P<0.0001). In the office systolic blood pressure-adjusted analysis (n = 78350), the percentage of risk reduction in CVEs for CTDN versus HCTZ was 18 (95% CI, 3-30; P = 0.024). When the reduction in office systolic blood pressure was identical in the 2 arms, the risk for CVEs in HCTZ arms was 19% higher than in its nondiuretic comparator arms (P = 0.021). Relative to HCTZ, the number needed to treat with CTDN to prevent 1 CVE over 5 years was 27. In conclusion, CTDN is superior to HCTZ in preventing cardiovascular events. This cannot be attributed entirely to the lesser effect of HCTZ on office systolic blood pressure but may be attributed to the pleomorphic effects of alternative medications or to the short duration of action of HCTZ.

Half a century of hydrochlorothiazide: facts, fads, fiction, and follies

Hydrochlorothiazide (HCTZ) has become by far the most commonly prescribed antihypertensive drug in the US. In 2008, 47.8 million prescriptions were written for HCTZ alone and 87.1 million prescriptions for HCTZ combinations. However, there is no evidence that HCTZ in its usual dose of 12.5-25 mg daily reduces myocardial infarction, stroke, or death. In a meta-analysis of 19 randomized trials with over 1400 patients, the 24-hour decrease in blood pressure with HCTZ was inferior to angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and calcium channel blockers (P <.001 for all). Even in combination with an angiotensin-converting enzyme inhibitor, HCTZ was found to reduce morbidity and mortality less well than a calcium channel blocker. As measured by the adherence rate, thiazides are less well tolerated than any other drug class. Because outcome data at the usual daily dose of 12.5-25 mg are lacking, antihypertensive efficacy is paltry, and adherence is poor, HCTZ is an inappropriate first-line drug in hypertension. If a "thiazide-type" diuretic is indicated, either chlorthalidone or indapamide should be selected.

Older blood pressure medications-do they still have a place?

Hypertension is a major risk factor for cardiovascular disease, but control of hypertension remains inadequate, often because of poor patient adherence to prescribed medical regimens that are viewed as poorly tolerated and expensive. Physicians have largely stopped using some older blood pressure medications in favor of newer agents, mostly because of a presumed more favorable side effect profile. The investigators reviewed the pharmacologic properties and the evidence supporting the effectiveness and tolerability of several older blood pressure drugs: sympatholytic agents such as reserpine, methyldopa, and clonidine; diuretics such as chlorthalidone, ethacrynic acid and spironolactone; the vasodilators hydralazine and minoxidil; and others. In conclusion, some of these drugs are well studied and represent alternatives for patients who cannot afford or tolerate newer medications.