Thiazide‐Type Diuretics: Ongoing Considerations on Mechanism of Action

The Use of Thiazide Diuretics for the Treatment of Hypertension in Patients With Advanced Chronic Kidney Disease

The use of thiazide diuretics for the treatment of hypertension in patients with advance chronic kidney disease. Thiazides have been recommended as the first-line for the treatment of hypertension, yet their use has been discouraged in advanced chronic kidney disease (CKD), as they are suggested to be ineffective in advanced CKD. Recent data suggest that thiazide diuretics may be beneficial blood pressure control in addition to natriuresis in existing CKD. This review discusses the commercially available thiazides with a focus on thiazide pharmacology, most common adverse effects, clinical uses of thiazide diuretic, and the evidence for efficacy of thiazide use in advanced CKD.

Diuretic and Natriuretic Effects of Hesperidin, a Flavanone Glycoside, in Female and Male Hypertensive Rats

Hesperidin (HSP) is a major flavanone glycoside in citrus fruits, including sweet oranges and lemons. It demonstrates numerous pharmacological activities, such as antihypertensive effects and cardiac and kidney tissue protection. However, its effect on modulating renal function has yet to be properly explored. Female and male Wistar spontaneously hypertensive rats (SHR) were used to test the effect of HSP on renal function. The rats were divided into different groups, treated orally, and placed in metabolic cages for urine collection for 8 h. HSP, at doses of 0.3-3 mg/kg, led to an increase in urine volume in both female and male SHR. This effect was associated with increased Na⁺ elimination (3 mg/kg) without causing any change in K⁺ excretion or pH and conductivity values. When given HSP in combination with hydrochlorothiazide (HCTZ) or amiloride (AMLR), urine volume and Na⁺ elimination were significantly increased compared to the group that received only HSP. In relation to K⁺ excretion, the depleting effect of HCTZ and the sparing of AMLR prevailed in both groups. Pre-treatment with a non-selective cholinergic receptor antagonist, atropine, partially prevented HSP-induced diuresis and natriuresis in male SHR, but this effect was not demonstrated with the non-selective inhibitor of the enzyme cyclooxygenase, indomethacin. This study shows the diuretic action of HSP in hypertensive rats, an activity probably associated with the cholinergic pathway. Although various biological actions have already been defined for HSP, this pioneering research reveals its potential as a diuretic medicine.

Thiazide diuretics are back in CKD: the case of chlorthalidone

Sodium and volume excess is the fundamental risk factor underlying hypertension in chronic kidney disease (CKD) patients, who represent the prototypical population characterized by salt-sensitive hypertension. Low salt diets and diuretics constitute the centrepiece for blood pressure control in CKD. In patients with CKD stage 4, loop diuretics are generally preferred to thiazides. Furthermore, thiazide diuretics have long been held as being of limited efficacy in this population. In this review, by systematically appraising published randomized trials of thiazides in CKD, we show that this class of drugs may be useful even among people with advanced CKD. Thiazides cause a negative sodium balance and reduce body fluids by 1-2 l within the first 2-4 weeks and these effects go along with improvement in hypertension control. The recent CLICK trial has documented the antihypertensive efficacy of chlorthalidone, a long-acting thiazide-like diuretic, in stage 4 CKD patients with poorly controlled hypertension. Overall, chlorthalidone use could be considered in patients with treatment-resistant hypertension when spironolactone cannot be administered or must be withdrawn due to side effects. Hyponatremia, hypokalaemia, volume depletion and acute kidney injury are side effects that demand a vigilant attitude by physicians prescribing these drugs. Well-powered randomized trials assessing hard outcomes are still necessary to more confidently recommend the use of these drugs in advanced CKD.

Tagetes erecta L. flowers, a medicinal plant traditionally used to promote diuresis, induced diuretic and natriuretic effects in normotensive and hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tagetes erecta L., known as marigold, belongs to the Asteraceae family and is mainly found in South America. Despite reports that T. erecta flowers are used in folk medicine to treat cardiovascular and renal diseases, there is no study regarding its diuretic effect.

AIM

This study aimed to evaluate the chemical composition and the diuretic efficacy of the hydroethanolic extract from T. erecta (HETE) in normotensive (NTR) and hypertensive (SHR) rats.

MATERIAL AND METHODS

The HETE was analyzed by liquid chromatography coupled to diode array detector and mass spectrometry (LC-DAD-MS). Female and male NTR and SHR received the treatment with vehicle, HETE (0.01 mg/kg, 0.1 mg/kg, and 1 mg/kg) or hydrochlorothiazide (HCTZ; 5 mg/kg) orally. The urinary parameters were measured at the end of the 8-h experiment.

RESULTS

From HETE, saccharides and triterpenes were the main annotated compounds, such as erythrodiol and β-amyrin. The urine volume was significantly increased in the groups treated with HETE, in both male and female NTR and SHR rats, compared to the respective vehicle-treated groups. Regarding electrolytes elimination, the treatment with HETE did not reveal significant changes in the urine levels of K⁺ or Cl^-, but it showed a natriuretic and Ca²⁺-sparing effects. The HETE beneficial result in reducing Ca²⁺ excretion was confirmed through the protective effect found in front of the urinary calcium oxalate precipitation and crystallization. The combination with HCTZ, a classic diuretic and saluretic medicine, significantly enhanced HETE-induced diuresis, natriuresis, and the Ca²⁺-sparing effect. On the other hand, the K⁺-sparing action was improved in the combination of HETE with amiloride, a standard K⁺-sparing diuretic. In contrast, the combination of HETE with atropine (a non-selective muscarinic receptor antagonist) and indomethacin (an inhibitor of the cyclooxygenase enzyme), promoted an important reduction in urinary volume, but interestingly the natriuretic effect was maintained.

CONCLUSION

This study contributed to the preclinical validation of the diuretic efficacy of T. erecta, highlighting this species as promising for the development of new pharmacological strategies for the management of kidney disorders.

Effects of myricetin-3-O-α-rhamnoside (myricitrin) treatment on urinary parameters of Wistar rats

Objectives

This study aimed to investigate the diuretic efficacy of myricetin-3-O-α-rhamnoside (myricitrin), a common naturally occurring plant-derived flavonoid, obtained from Marlierea eugeniopsoides (D.Legrand & Kausel) D.Legrand leaves in rats.

Methods

For that, female Wistar rats were treated by oral route with the different treatments and kept in metaboloic cages for 8-h or 24-h experiment. The volume and urinary parameters were measured at the end of the period and compared between groups.

Key findings

When orally given to rats and compared to the vehicle-treated group, myricitrin (0.3 and 1 mg/kg) was able to stimulate rat diuresis, natriuresis and kaliuresis. The combination myricitrin plus hydrochlorothiazide, but not plus furosemide or amiloride, potentiated the urinary volume when compared to the effects of drugs alone. Besides, the 8-h renal effects of myricitrin were prevented in the presence of a cyclooxygenase inhibitor and a muscarinic receptor antagonist. However, all groups treated with myricitrin showed a significant reduction in Cl− excretion. In addition, a reduction in the urinary excretion of Cl− and HCO3− was detected on 24-h analysis, a result that showed to be associated with an increase of these anions in the blood samples from the myricitrin-treated group. Despite these alterations, no changes in urinary or blood pH were detected.

Conclusions

Taking together, although the results of this study point to the diuretic potential of myricitrin, the reduction in urinary Cl− and HCO3− excretion should be considered in future approaches, as well as for therapeutic applicability.

Effects of calcium channel blocker-based combinations on intra-individual blood pressure variability: post hoc analysis of the COPE trial

Visit-to-visit blood pressure (BP) variability is an important predictor of stroke. However, which antihypertensive drug combination is better at reducing visit-to-visit BP variability and therefore at reducing stroke incidence remains uncertain. We have previously reported that the dihydropyridine calcium channel blocker benidipine combined with a β-blocker appeared to be less beneficial in reducing the risk of stroke than a combination of benidipine and thiazide. Here, we further compare the visit-to-visit BP variability among three benidipine-based regimens, namely angiotensin receptor blocker (ARB), β-blocker and thiazide combinations. The present post hoc analysis included 2983 patients without cardiovascular events or death during the first 18 months after randomization. We compared the BP variability (defined as the s.d. and the coefficient of variation (CV)), maximum systolic BP (SBP) and diastolic BP (DBP) of the clinic mean on-treatment BPs obtained at 6-month intervals, starting 6 months after the treatment initiation, among the 3 treatments (ARB, n=1026; β-blocker, n=966; thiazide, n=991). During the first 6–36 months after randomization, both the s.d. and CV-BPs were lower in the benidipine–thiazide group than in the benidipine–β-blocker group (s.d.-SBP, P=0.019; s.d.-DBP, P=0.030; CV-SBP, P=0.012; CV-DBP, P=0.022). The s.d. and CV in the ARB group did not reach statistical significance compared with the other two groups. The maximum BPs did not differ among the three treatments. These findings suggest that the benidipine–thiazide combination may reduce visit-to-visit BP variability more than the benidipine–β-blocker combination.

The effects of angiotensinogen gene polymorphisms on cardiovascular disease outcomes during antihypertensive treatment in the GenHAT study

Previous studies have reported that risk of cardiovascular morbidity and mortality substantially increases in hypertensive patients, especially among those with inadequate blood pressure control. Two common antihypertensive drug classes including thiazide diuretics and angiotensin-converting enzyme (ACE) inhibitors affect different enzymes in the renin-angiotensin-aldosterone system (RAAS). In the RAAS, angiotensinogen is converted into angiotensin II which increases blood pressure through vasoconstriction. Using a case-only design with 3448 high-risk hypertensive individuals from the Genetics of Hypertension Associated Treatment (GenHAT) study, we examined whether seven single nucleotide polymorphisms (SNPs) in the angiotensinogen gene (AGT) interact with three classes of antihypertensive drugs including chlorthalidone (a thiazide diuretic), lisinopril (an ACE inhibitor), and amlodipine (a calcium channel blocker) to modify the risk of incident coronary heart disease (CHD) and heart failure (HF) among Caucasian and African American participants, separately. We found no gene by treatment interactions to be statistically significant after correction for multiple testing. However, some suggestive results were found. African American participants with the minor allele of rs11122576 had over two-fold higher risk of CHD when using chlorthalidone compared to using amlodipine, or lisinopril compared to amlodipine (p = 0.006 and p = 0.01, respectively). Other marginal associations are also reported among both race groups. The findings reported here suggest that rs11122576 could contribute to future personalization of antihypertensive treatment among African Americans though more studies are needed.

Clinical relevance of target identity and biology: implications for drug discovery and development

Many of the most commonly used drugs precede techniques for target identification and drug specificity and were developed on the basis of efficacy and safety, an approach referred to as classical pharmacology and, more recently, phenotypic drug discovery. Although substantial gains have been made during the period of focus on target-based approaches, particularly in oncology, these approaches have suffered a high overall failure rate and lower productivity in terms of new drugs when compared with phenotypic approaches. This review considers the importance of target identity and biology in clinical practice from the prescriber's viewpoint. In evaluating influences on prescribing behavior, studies suggest that target identity and mechanism of action are not significant factors in drug choice. Rather, patients and providers consistently value efficacy, safety, and tolerability. Similarly, the Food and Drug Administration requires evidence of safety and efficacy for new drugs but does not require knowledge of drug target identity or target biology. Prescribers do favor drugs with novel mechanisms, but this preference is limited to diseases for which treatments are either not available or suboptimal. Thus, while understanding of drug target and target biology is important from a scientific perspective, it is not particularly important to prescribers, who prioritize efficacy and safety.

Effects of a benidipine-based combination therapy on the risk of stroke according to stroke subtype: the COPE trial

The Combination Therapy of Hypertension to Prevent Cardiovascular Events (COPE) trial compared the dihydropyridine T/L-type calcium channel blocker benidipine-based therapies when combined with an angiotensin receptor blocker (ARB), a β-blocker (BB) or a thiazide diuretic (TD). The results suggested that benidipine combined with a BB appeared to be less beneficial in reducing the risk of stroke compared with the benidipine-TD combination (hazard ratio (HR): 2.31, P=0.0109). We further evaluated the treatment effects on different stroke subtypes among the three benidipine-based regimens. The COPE trial was an investigator-initiated, multicenter study with PROBE design. Patients with atrial fibrillation or flutter were excluded from the study. All stroke events were subclassified with the Trial of Org 10,172 in Acute Stroke Treatment (TOAST) criteria. The total incidence of stroke was 4.7, hemorrhagic stroke was 1.6 and ischemic stroke was 2.5 per 1000 person-years. The incidence of lacunar stroke was 1.1, large-artery stroke was 0.6, cardioembolic stroke was 0.3, unknown ischemic type was 0.6 and transient ischemic attack was 0.6 per 1000 person-years. Although few differences in stroke subtypes were observed among the three treatment groups, multi-adjusted HRs for the incidence rates of all types of stroke, hemorrhagic stroke and ischemic stroke were significantly higher with the benidipine-BB regimen than with the benidipine-TD regimen. The incidence of both hemorrhagic and ischemic stroke in the benidipine-ARB regimen was not different compared with the other two treatment regimens. This prespecified sub-analysis suggested that a blood pressure-lowering therapy with a benidipine-TD regimen might be beneficial for hypertensive patients to prevent both hemorrhagic and ischemic stroke.

Management of hypertension with fixed-dose triple-combination treatments

The objective of this review is to evaluate the role of fixed-dose triple-combination therapy for the management of hypertension. An assessment of clinical trials showed that half the patients with hypertension have uncontrolled blood pressure (BP), with underlying factors including therapeutic inertia and poor patient adherence. Many patients will require three antihypertensive agents to achieve BP goals, and current guidelines recommend combining drugs with complementary mechanisms of action. Three single-pill triple-combination treatments are available and each includes an agent affecting the renin-angiotensin-aldosterone pathway (either a direct renin inhibitor or an angiotensin II receptor blocker) in combination with a calcium channel blocker and diuretic. These triple-combination therapies consistently demonstrated significantly greater BP reduction relative to the component dual combinations, with BP reductions documented across a range of patient populations. Triple-combination treatments were well tolerated in all clinical trials reviewed. The use of single-pill, triple-combination antihypertensive therapy has been shown to be an effective, well-tolerated, and convenient treatment strategy that can help patients achieve BP control.

Single-pill triple-combination therapy: an alternative to multiple-drug treatment of hypertension

Hypertension (HTN) affects an estimated 76.4 million US adults. Despite improvements in blood pressure (BP) control rates and the availability of effective antihypertensive agents, only 50% of these individuals achieve BP control. It is now recognized that many patients will require ≥ 2 antihypertensive agents to achieve BP control. Both the current US and reappraisal of the 2007 European guidelines include dual-combination regimens among recommended treatments for initial HTN therapy. For patients requiring 3 drugs, the combination of agents with complementary mechanisms of action (ie, renin-angiotensin-aldosterone system blocker, calcium channel blocker, and diuretic) has been recognized as rational and effective. Three single-pill triple-drug combinations have recently been approved for use in HTN in the United States: valsartan (VAL)/amlodipine (AML)/hydrochlorothiazide (HCTZ); olmesartan medoxomil (OM)/AML/HCTZ; and aliskiren (ALI)/VAL/HCTZ. Triple-combination regimens have resulted in a greater proportion of patients achieving BP control compared with dual-combination regimens, with significantly lower BP levels documented after only 2 weeks at maximum doses. Single-pill combinations offer convenience to address barriers to BP control such as poor adherence to therapy and therapeutic inertia. Additional benefits of combining antihypertensive agents from different classes include improved efficacy, safety, and reduction of cardiovascular risk. In patients with essential HTN for whom dual therapy is inadequate, single-pill triple-drug therapy can offer a simplified and effective treatment strategy.

Diuretics in clinical practice. Part I: mechanisms of action, pharmacological effects and clinical indications of diuretic compounds

IMPORTANCE OF THE FIELD

Diuretics are among the most important drugs of our therapeutic armamentarium and have been broadly used for > 50 years, providing important help towards the treatment of several diseases. Although all diuretics act primarily by impairing sodium reabsorption in the renal tubules, they differ in their mechanism and site of action and, therefore, in their specific pharmacological properties and clinical indications. Loop diuretics are mainly used for oedematous disorders (i.e., cardiac failure, nephrotic syndrome) and for blood pressure and volume control in renal disease; thiazides and related agents are among the most prescribed drugs for hypertension treatment; aldosterone-blockers are traditionally used for primary or secondary aldosteronism; and other diuretic classes have more specific indications.

AREAS COVERED IN THIS REVIEW

This article discusses the mechanisms of action, pharmacological effects and clinical indications of the various diuretic classes used in everyday clinical practice, with emphasis on recent knowledge suggesting beneficial effects of certain diuretics on clinical conditions distinct from the traditional indications of these drugs (i.e., heart protection for aldosterone blockers).

WHAT THE READER WILL GAIN

Reader will gain insights into the effective use of diuretic agents for various medical conditions, representing their established or emerging therapeutic indications.

TAKE HOME MESSAGE

Knowledge of the pharmacologic properties and mechanisms of action of diuretic agents is a prerequisite for the successful choice and effective clinical use of these compounds.

Diuretics in clinical practice. Part II: electrolyte and acid-base disorders complicating diuretic therapy

IMPORTANCE OF THE FIELD

As with all potent therapeutic agents, the use of diuretic compounds has been linked with several adverse effects that may reduce quality of life and patient compliance and, in some cases, may be associated with considerable morbidity and mortality. Among the various types of adverse effects, disturbances of electrolyte and acid-base balance are perhaps the most common, and some of them are the aetiological factors of other side effects (i.e., hypokalaemia causing ventricular arrhythmias or glucose intolerance). The mechanism and site of action and, therefore, the pharmacological effects of each diuretic class largely determine the specific electrolyte or acid-base abnormalities that will accompany the use of each diuretic agent.

AREAS COVERED IN THE REVIEW

This article reviews the major electrolyte disturbances (hypokalaemia, hyperkalaemia, hyponatraemia, disorders of magnesium and calcium balance), as well as the acid-base abnormalities complicating the use of the various diuretic agents.

WHAT THE READER WILL GAIN

The reader will gain insights into the pathogenesis of the diuretic-induced electrolyte and acid-base disorders together with considerations for their prevention and treatment.

TAKE HOME MESSAGE

Knowledge of the pharmacologic properties of each diuretic class and appropriate monitoring of patients under diuretic treatment represent the most important strategies to prevent the development of diuretic-related adverse events and their consequences.

Calcium channel blockers: monotherapy and dual therapy considerations in the treatment of hypertension

The papers in this supplement speak to several of the issues pertinent to contemporary therapy with CCBs. The article by Dr Weir thoughtfully describes important pharmacokinetic and pharmacodynamic features of CCBs. In so doing he establishes the basis for combination CCB and ACE inhibitor therapy. Dr Frishman provides a scholarly description of the cardiovascular effects of CCBs and further elaborates on the distinctiveness of the various CCB subclasses. Finally, Dr Bakris et al. provides data from INVEST (INternational VErapamil-Trandolapril STudy), which shows the particular utility of a CCB and ACE inhibitor combination in bringing elderly hypertensive patients with CAD to goal BP when monotherapy

The influence of fluid and diuretic administration on the index of atrial contribution in sequentially paced patients

AIMS

To examine whether acute changes in patient hydration can change atrial contribution (AC) to circulatory function.

METHODS AND RESULTS

Atrial contribution was quantified by beat-to-beat changes in the amplitude of pulse oximetry signal in 24 paced outpatients. Changes in body weight were used for assessment of changes in total body water. The first measurement was performed at steady state. The second measurement was made after infusion of saline (5 mL/kg) and the third measurement was obtained 2 h after a bolus of furosemide (1 mg/kg). Changes found after furosemide administration (compared with steady state): a substantial decrease in body weight from median 78.6 (interquartile range 65.7-86.5) to 77.1 (64.4-85.6) kg (P < 0.001), accompanied by an increase in AC from 30.4 (20.2-47.1) up to 43.3 (30.6-80.9)% (P < 0.001). An increase in heart rate and shortening of the atrioventricular conduction time occurred during acute hypohydration in some of the subjects.

CONCLUSION

Administration of furosemide was followed by a decrease in body weight and an increase in AC to stroke volume. This suggests that in conditions where pre-load is reduced cardiac output is preserved by an increase in AC enforced by sympathetic activation.