Furosemide-induced natriuresis is augmented by ultra-low-dose captopril but not by standard doses of captopril in chronic heart failure

Angiotensin Receptor Neprilysin Inhibitors in HFrEF: Is This the First Disease Modifying Therapy Drug Class Leading to a Substantial Reduction in Diuretic Need?

Despite significant advances in disease modifying therapy in heart failure (HF), diuretics have remained the cornerstone of volume management in all HF phenotypes. Diuretics, alongside their definite acute haemodynamic and symptomatic benefits, also possess many possible deleterious side effects. Moreover, questions remain regarding the prognostic impact of chronic diuretic use. To date, few data exist pertaining to diuretic reduction as a result of individual traditional guideline directed medical therapy in HF with reduced ejection fraction (HFrEF). However, diuretic reduction has been demonstrated with sacubitril/valsartan (angiotensin receptor-neprilysin inhibitor [ARNi]) from the PARADIGM study, as well as, post-marketing reports from our own group and others. Whether the ARNi compound represents the dawn of a new era, where effective therapies will have a more noticeable reduction on diuretic need, remains to be seen. The emergence of sodium glucose transport 2 inhibitors and guanylate cyclase stimulators may further exemplify this issue and potentially extend this benefit to HF patients outside of the HFrEF phenotype. In conclusion, emerging new therapies in HFrEF could reduce the reliance on diuretics in the management of this phenotype of HF. These developments further highlight the clinical importance to continually assess an individual's diuretic requirements through careful volume assessment.

Oral Treatment of Spontaneously Hypertensive Rats with Captopril-Surface Functionalized Furosemide-Loaded Multi-Wall Lipid-Core Nanocapsules

Multi-wall lipid-core nanocapsule (MLNC) functionalized with captopril and nanoencapsulating furosemide within the core was developed as a liquid formulation for oral administration. The nanocapsules had mean particle size below 200 nm, showing unimodal and narrow size distributions with moderate dispersity (laser diffraction and dynamic light scattering). Zeta potential was inverted from −14.3 mV [LNC-Fur(0,5)] to +18.3 mV after chitosan coating. Transmission electron microscopy and atomic force microscopy showed spherical structures corroborating the nanometric diameter of the nanocapsules. Regarding the systolic pressure, on the first day, the formulations showed antihypertensive effect and a longer effect than the respective drug solutions. When both drugs were associated, the anti-hypertensive effect was prolonged. On the fifth day, a time effect reduction was observed for all treatments, except for the nanocapsule formulation containing both drugs [Capt(0.5)-Zn(25)-MLNC-Fur(0.45)]. For diastolic pressure, only Capt(0.5)-Zn(25)-MLNC-Fur(0.45) presented a significant difference (p < 0.05) on the first day. On the fifth day, both Capt(0.5)-MLNC-Fur(0.45) and Capt(0.5)-Zn(25)-MLNC-Fur(0.45) had an effect lasting up to 24 h. The analysis of early kidney damage marker showed a potential protection in renal function by Capt(0.5)-Zn(25)-MLNC-Fur(0.45). In conclusion, the formulation Capt(0.5)-Zn(25)-MLNC-Fur(0.45) proved to be suitable for hypertension treatment envisaging an important innovation.

Determinants of Diuretic Responsiveness and Associated Outcomes During Acute Heart Failure Hospitalization: An Analysis From the NHLBI Heart Failure Network Clinical Trials

BACKGROUND

Poor response to loop diuretic therapy is a marker of risk during heart failure hospitalization. We sought to describe baseline determinants of diuretic response and to further explore the relationship between this response and clinical outcomes.

METHODS AND RESULTS

Patient data from the National Heart, Lung, and Blood Institute Heart Failure Network ROSE-AHF and CARRESS-HF clinical trials were analyzed to determine baseline determinants of diuretic response. Diuretic efficiency (DE) was defined as total 72-hour fluid output per total equivalent loop diuretic dose. Data from DOSE-AHF was then used to determine if these predictors of DE correlated with response to a high- versus low-dose diuretic strategy. At 72 hours, the high-DE group had median fluid output of 9071 ml (interquartile range: 7240-11775) with median furosemide dose of 320 mg (220-480) compared with 8030 ml (6300-9915) and 840 mg (600-1215) respectively for the low DE group. Cystatin C was independently associated with DE (odds ratio 0.36 per 1mg/L increase; 95% confidence interval: 0.24-0.56; P < 0.001). Independently from baseline characteristics, reduced fluid output, weight loss and DE were each associated with increased 60 day mortality. Among patients with estimated glomerular filtration rate below the median, those randomized to a high-dose strategy had improved symptoms compared with those randomized to a low-dose strategy.

CONCLUSIONS

Elevated baseline cystatin C, as a biomarker of renal dysfunction, is associated with reduced diuretic response during heart failure hospitalization. Higher loop diuretic doses are required for therapeutic decongestion in patients with renal insufficiency. Poor response identifies a high-risk population.

WITHDRAWN: Diuretics for heart failure

This protocol was withdrawn in April 2016 as the author team was unable to progress to the final review stage. An editorial decision was taken not to pursue this title.

The editorial group responsible for this previously published document have withdrawn it from publication.

Everything we always wanted to know about furosemide but were afraid to ask

Furosemide is a widely used, potent natriuretic drug, which inhibits the Na(+)-K(+)-2Cl(-) cotransporter (NKCC)-2 in the ascending limb of the loop of Henle applied to reduce extracellular fluid volume expansion in heart and kidney disease. Undesirable consequences of furosemide, such as worsening of kidney function and unpredictable effects on sodium balance, led to this critical evaluation of how inhibition of NKCC affects renal and cardiovascular physiology. This evaluation reveals important knowledge gaps, involving furosemide as a drug, the function of NKCC2 (and NKCC1), and renal and systemic indirect effects of NKCC inhibition. Regarding renal effects, renal blood flow and glomerular filtration rate could become compromised by activation of tubuloglomerular feedback or by renin release, particularly if renal function is already compromised. Modulation of the intrarenal renin angiotensin system, however, is ill-defined. Regarding systemic effects, vasodilation followed by nonspecific NKCC inhibition and changes in venous compliance are not well understood. Repetitive administration of furosemide induces short-term (braking phenomenon, acute diuretic resistance) and long-term (chronic diuretic resistance) adaptations, of which the mechanisms are not well known. Modulation of NKCC2 expression and activity in kidney and heart failure is ill-defined. Lastly, furosemide's effects on cutaneous sodium stores and on uric acid levels could be beneficial or detrimental. Concluding, a considerable knowledge gap is identified regarding a potent drug with a relatively specific renal target, NKCC2, and renal and systemic actions. Resolving these questions would increase the understanding of NKCCs and their actions and improve rational use of furosemide in pathophysiology of fluid volume expansion.

Effective use of loop diuretics in heart failure exacerbation: a nephrologist's view

Unfortunately, patients with congestive heart failure suffer frequent admissions for the management of fluid overload. Loop diuretics are pivotal in the management of this common clinical problem. Although loop diuretics have been in clinical use since the 1960s, we still do not understand how to optimally administer these drugs. It is unknown why some decompensated heart failure patients exhibit improvements in renal function with diuresis, whereas others display renal function deterioration, limiting attainment of euvolemia. Here the physiologic interactions between the failing heart and kidneys are reviewed. A conceptual framework is presented that emphasizes the balance between tubuloglomerular feedback and venous congestion in determining renal function during loop diuretic use in heart failure. Within this framework, guidelines are derived that seek to maximize the chance for achieving adequate volume removal while maintaining stable or improved renal function during the treatment of acute decompensated heart failure.

Ace inhibitor therapy for heart failure in patients with impaired renal function: a review of the literature

Heart failure syndromes are often associated with multi-organ dysfunction, and concomitant liver, renal, and neurologic involvement is very common. Neuro-hormonal antagonism plays a key role in the management of this syndrome, and angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are one of the cornerstones of therapy. Cardiorenal physiology is becoming more recognized in these patients with advanced heart failure, and the role of neuro-hormonal blockade in this setting is vaguely defined in the literature. Often, angiotensin-converting enzyme inhibitors are decreased or even withheld in these circumstances. The purpose of this article is to review the role and pathophysiology of ace inhibition and angiotensin receptor blockade in patients with acute and chronic heart failure syndromes and concomitant cardiorenal physiology.

Systemic arterial and venous determinants of renal hemodynamics in congestive heart failure

Heart and kidney interactions are fascinating, in the sense that failure of the one organ strongly affects the function of the other. In this review paper, we analyze how principal driving forces for glomerular filtration and renal blood flow are changed in heart failure. Moreover, renal autoregulation and modulation of neurohumoral factors, which can both have repercussions on renal function, are analyzed. Two paradigms seem to apply. One is that the renin-angiotensin system (RAS), the sympathetic nervous system (SNS), and extracellular volume control are the three main determinants of renal function in heart failure. The other is that the classical paradigm to analyze renal dysfunction that is widely applied in nephrology also applies to the pathophysiology of heart failure: pre-renal, intra-renal, and post-renal alterations together determine glomerular filtration. At variance with the classical paradigm is that the most important post-renal factor in heart failure seems renal venous hypertension that, by increasing renal tubular pressure, decreases GFR. When different pharmacological strategies to inhibit the RAS and SNS and to assist renal volume control are considered, there is a painful lack in knowledge about how widely applied drugs affect primary driving forces for ultrafiltration, renal autoregulation, and neurohumoral control. We call for more clinical physiological studies.

Diuretics for heart failure

BACKGROUND

Chronic heart failure is a major cause of morbidity and mortality worldwide. Diuretics are regarded as the first-line treatment for patients with congestive heart failure since they provide symptomatic relief. The effects of diuretics on disease progression and survival remain unclear.

OBJECTIVES

To assess the harms and benefits of diuretics for chronic heart failure

SEARCH METHODS

Updated searches were run in the Cochrane Central Register of Controlled Trials in The Cochrane Library (CENTRAL Issue 1 of 4, 2011), MEDLINE (1966 to 22 February 2011), EMBASE (1980 to 2011 Week 07) and HERDIN database (1990 to February 2011). We hand searched pertinent journals and reference lists of papers were inspected. We also contacted manufacturers and researchers in the field. No language restrictions were applied.

SELECTION CRITERIA

Double-blinded randomised controlled trials of diuretic therapy comparing one diuretic with placebo, or one diuretic with another active agent (e.g. ACE inhibitors, digoxin) in patients with chronic heart failure.

DATA COLLECTION AND ANALYSIS

Two authors independently abstracted the data and assessed the eligibility and methodological quality of each trial. Extracted data were analysed by determining the odds ratio for dichotomous data, and difference in means for continuous data, of the treated group compared with controls. The likelihood of heterogeneity of the study population was assessed by the Chi-square test. If there was no evidence of statistical heterogeneity and pooling of results was clinically appropriate, a combined estimate was obtained using the fixed-effects model.

MAIN RESULTS

This update has not identified any new studies for inclusion. The review includes 14 trials (525 participants), 7 were placebo-controlled, and 7 compared diuretics against other agents such as ACE inhibitors or digoxin. We analysed the data for mortality and for worsening heart failure. Mortality data were available in 3 of the placebo-controlled trials (202 participants). Mortality was lower for participants treated with diuretics than for placebo, odds ratio (OR) for death 0.24, 95% confidence interval (CI) 0.07 to 0.83; P = 0.02. Admission for worsening heart failure was reduced in those taking diuretics in two trials (169 participants), OR 0.07 (95% CI 0.01 to 0.52; P = 0.01). In four trials comparing diuretics to active control (91 participants), diuretics improved exercise capacity in participants with CHF, difference in means WMD 0.72 , 95% CI 0.40 to 1.04; P < 0.0001.

AUTHORS' CONCLUSIONS

The available data from several small trials show that in patients with chronic heart failure, conventional diuretics appear to reduce the risk of death and worsening heart failure compared to placebo. Compared to active control, diuretics appear to improve exercise capacity.

Drug Absorption in the Management of Congestive Heart Failure: Loop Diuretics

Congestive heart failure is a disease state distinguished by the regular presence of both renal and hepatic abnormalities in drug handling. One such abnormality involves flaws in the process of drug absorption. In most instances, congestive heart failure-related abnormalities in drug absorption are of inconsequential significance. However, this is not the case with loop diuretics. Loop diuretic action ordinarily tracks the rate and extent of absorption if a sufficient amount of diuretic has been given to exceed the threshold for diuretic effect. In congestive heart failure, both the rate and absolute amount of loop diuretic absorbed can be reduced as a function of the heart failure state itself. In this setting, drug dissolution characteristics can assume added significance. Furosemide is the loop diuretic with the widest intra- and interpatient variability of absorption. Alternatively, the loop diuretic torsemide is rapidly and fairly completely absorbed independent of the heart failure state. This pattern of absorption establishes it as the preferred loop diuretic in the otherwise diuretic-resistant heart failure patient. However, the exact role of torsemide in the outpatient management of congestive heart failure remains to be determined.

Diuretics for heart failure

BACKGROUND

Chronic heart failure is a major cause of morbidity and mortality world-wide. Diuretics are regarded as the first-line treatment for patients with congestive heart failure since they provide symptomatic relief. The effects of diuretics on disease progression and survival remain unclear.

OBJECTIVES

To assess the harms and benefits of diuretics for chronic heart failure

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (Issue 2 2004), MEDLINE 1966-2004, EMBASE 1980-2004 and HERDIN database. We hand searched pertinent journals and reference lists of papers were inspected. We also contacted manufacturers and researchers in the field.

SELECTION CRITERIA

Only double-blinded randomised controlled trials of diuretic therapy comparing one diuretic with placebo, or one diuretic with another active agent (e.g. ACE inhibitors, digoxin) in patients with chronic heart failure were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two reviewers independently abstracted the data and assessed the eligibility and methodological quality of each trial. Extracted data were entered into the Review Manager 4.2 computer software, and analysed by determining the odds ratio for dichotomous data, and difference in means for continuous data, of the treated group compared with controls. The likelihood of heterogeneity of the study population was assessed by the Chi-square test. If there was no evidence of statistical heterogeneity and pooling of results was clinically appropriate, a combined estimate was obtained using the fixed-effects model.

MAIN RESULTS

We included 14 trials (525 participants), 7 were placebo-controlled, and 7 compared diuretics against other agents such as ACE inhibitors or digoxin. We analysed the data for mortality and for worsening heart failure. Mortality data were available in 3 of the placebo-controlled trials (202 participants). Mortality was lower for participants treated with diuretics than for placebo, odds ratio (OR) for death 0.24, 95% confidence interval (CI) 0.07 to 0.83; P = 0.02. Admission for worsening heart failure was reduced in those taking diuretics in two trials (169 participants), OR 0.07 (95% CI 0.01 to 0.52; P = 0.01). In four trials comparing diuretics to active control (91 participants), diuretics improved exercise capacity in participants with CHF, difference in means WMD 0.72 , 95% CI 0.40 to 1.04; P < 0.0001.

AUTHORS' CONCLUSIONS

The available data from several small trials show that in patients with chronic heart failure, conventional diuretics appear to reduce the risk of death and worsening heart failure compared to placebo. Compared to active control, diuretics appear to improve exercise capacity.

Combining renin-angiotensin-aldosterone system blockade with diuretic therapy for treatment of hypertension

The rationale for using angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARBs) in combination with thiazide diuretic therapy has centred formerly around antihypertensive synergy and counter-balancing adverse metabolic effects, particularly on potassium homeostasis. However, two recent landmark clinical trials that included high-risk hypertensive patients have now provided an evidence base for this form of combination therapy by demonstrating the efficacy of perindopril/indapamide and losartan/ hydrochlorothiazide in reducing vascular morbidity and mortality, a proportion of the benefit being unaccounted for by blood pressure reduction alone. Several unresolved issues remain concerning class effects versus specific drug effects, optimal dosing, potential differences in efficacy between ACE-I and ARBs, whether elderly mild hypertensives benefit from this form of combination therapy, and the possibility that the optimal regimen may be a triple combination of ACE-I, ARB and thiazide diuretic. These issues will be resolved by ongoing and future major endpoint trials in hypertension.

Diuretic treatment and diuretic resistance in heart failure

Diuretic therapy decreases capillary wedge pressure and improves New York Heart Association (NYHA) functional class both in acute and chronic heart failure. In advanced symptomatic heart failure, loop diuretics are generally necessary to improve symptoms of congestion. Diuretic resistance in the edematous patient has been defined as a clinical state in which diuretic response is diminished or lost before the therapeutic goal of relief from edema has been reached. The major causes of diuretic resistance are functional renal failure (prerenal azotemia), hyponatremia, altered diuretic pharmacokinetics, and sodium retention caused by counterregulatory mechanisms intended to reestablish the effective arterial blood volume. Therapeutic approaches to combat diuretic resistance include restriction of fluid and sodium intake, use of angiotensin-converting-enzyme (ACE) inhibitors, changes in route (oral, intravenous) and timing (single dose, multiple doses, continuous infusion) of diuretic therapy, and use of diuretic combinations.

Increased toxicity of high-dose furosemide versus low-dose dopamine in the treatment of refractory congestive heart failure

OBJECTIVE

To evaluate the safety and efficacy of low-dose dopamine, high-dose furosemide, and their combination in the treatment of refractory congestive heart failure.

METHODS

Twenty consecutive patients with refractory congestive heart failure were randomized to receive intravenous low-dose (4 micrograms/kg/min) dopamine combined with low-dose (80 mg/day) oral furosemide (group A; n = 7), intravenous low-dose dopamine with medium-dose furosemide (5 mg/kg/day through continuous intravenous administration; group B; n = 7), or high-dose furosemide (10 mg/kg/day through continuous intravenous administration; group C; n = 6).

RESULTS

The three groups showed similar improvement in signs and symptoms of congestive heart failure, urinary output (2506 +/- 671 ml/24 hr, mean +/- SD) and weight loss (3.3 +/- 2.3 kg) after 72 hours of therapy. Mean arterial blood pressure (MAP) decreased by 14% +/- 8% and 15% +/- 6% in groups B and C, respectively, but increased by 4% +/- 15% in group A (p = 0.017). Renal function deteriorated significantly in groups B and C: creatinine clearance decreased by 41% +/- 23% and 42% +/- 23%, respectively, but increased by 14% +/- 35% in group A (p = 0.0074). MAP decrease was positively correlated with the decrease in creatinine clearance (r = 0.7; p = 0.0007). Patients in group B and C had more hypokalemia than group A. Two patients in group C sustained acute oliguric renal failure and one patient in group B died suddenly while sustaining severe hypokalemia.

CONCLUSION

Combined low-dose intravenous dopamine and oral furosemide have similar efficacy but induce less renal impairment and hypokalemia than higher doses of intravenous furosemide taken either alone or with low-dose dopamine. The renal impairment induced by intravenous furosemide is probably related to its hypotensive effect in patients with refractory congestive heart failure.

Enalapril reduces QTc dispersion in mild congestive heart failure secondary to coronary artery disease

This study was designed to investigate the possible mechanisms whereby enalapril improves cardiac function and mortality in chronic heart failure. We explored potential mechanisms by following 41 patients with early heart failure over the course of 1 year. These patients were randomized in a prospective triple-blind manner to receive either enalapril or placebo. Over the 1 year, repeated measurements were obtained of echocardiographic parameters, glomerular filtration rate, renal blood flow, hematocrit, plasma neurohormones, and QTc dispersion. Echocardiographic parameters improved with enalapril but deteriorated with placebo (cardiac output 4.6 +/- 1.6 to 3.7 +/- 1.5 L/min with placebo, and 4.5 +/- 1.3 to 5.8 +/- 2.0 L/min with enalapril; p <0.01). In contrast, there were no significant changes in renal blood flow (518 +/- 185 to 509 +/- 180 ml/min/1.73 m2 with placebo, and 541 +/- 142 to 504 +/- 162 ml/min/1.73 m2 with enalapril). Glomerular filtration rate changed from 79 +/- 20 to 78 +/- 19 ml/min/1.73 m2 with placebo, and from 85 +/- 21 to 73 +/- 27 ml/min/1.73 m2 with enalapril (p = 0.051). Enalapril reduced hematocrit (0.414 +/- 0.041 to 0.377 +/- 0.040%) significantly more than placebo (0.420 +/- 0.029 to 0.411 +/- 0.023 l/l; p <0.01). In addition, enalapril produced a marked reduction in QTc dispersion (93 +/- 36 to 88 +/- 28 ms with placebo and 93 +/- 35 to 60 +/- 22 ms with enalapril; p <0.05). Thus, enalapril significantly reduced hematocrit and reduced QTc dispersion in early heart failure. Both of these effects, but especially the latter, could be an important mechanism for the reduced mortality seen with angiotensin-converting enzyme inhibitors in heart failure. In contrast, renal hemodynamics did not parallel either the placebo-induced deterioration in cardiac function or the enalapril-induced improvements in cardiac function.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Furosemide dynamics in conscious rabbits: modulation by angiotensin II

The aim of this study was to investigate the effects of an infusion of angiotensin II (50 ng/kg/min) on furosemide pharmacodynamics and kinetics in the conscious rabbit. The protocol included a 90-minute phase to estimate the glomerular filtration rate and the renal plasma flow, followed by a 60-minute phase where 5 mg/kg (n = 12) or 10 mg/kg (n = 9) of furosemide were administered. During the pre-furosemide phase, compared to control rabbits, angiotensin II increased natriuresis and diuresis. In the presence of angiotensin II, the furosemide-induced natriuresis decreased, that is, it was 174 +/- 14 versus 95 +/- 25 mumol/min (p < 0.05) and 187 +/- 17 versus 89 +/- 21 mumol/min (p < 0.05) for the 5 and the 10 mg/kg doses, respectively. The infusion of angiotensin II decreased renal plasma flow without modifying the glomerular filtration rate, thus the filtration fraction was increased. Angiotensin II increased the area under the furosemide plasma concentrations as a function of time since it decreased its systemic clearance. However, furosemide urinary excretion rate was not altered and its renal clearance decreased slightly without reaching statistical significance. It is concluded that angiotensin II decreases the response to furosemide and the mechanism underlying this effect is related to the pharmacodynamics rather than the kinetics of the diuretic.

Heart failure: lessons learned over the past 25 years

Over the past 25 years, a great deal has been learned about the pathophysiology and management of heart failure--a major health problem whose prevalence and incidence have not declined, unlike other cardiovascular disorders. Several of these lessons are reviewed herein. However, despite these advances, important issues remain to challenge both the practicing physician and the research scientist.

The renin angiotensin aldosterone system and frusemide response in congestive heart failure

1. To test the hypothesis that basal renin angiotensin aldosterone system (RAAS) activity impairs the acute natriuretic response to frusemide in patients with mild or moderate congestive heart failure (CHF), we studied eight adult volunteers with preserved renal function, stable New York Heart Association Class II or III CHF, and echocardiographic evidence of left ventricular dysfunction due to myocardial infarction, hypertension, or both causes. 2. All patients received three dosing regimens administered in random order: (a) intravenous frusemide: 40 mg bolus then 40 mg h-1 for 3 h, (b) captopril: two 12.5 mg oral doses separated by 2 h, (c) combined dosing: the first captopril dose preceded the frusemide bolus by 30 min. Sodium balance on an 80 mmol day-1 sodium diet was documented prior to each dosing regimen. Sodium excretion was quantitated in urine collected at intervals until 3.5 h after initiating drug administration. During this time, urine output was replaced intravenously with an equivalent volume of 0.45% saline. 3. Captopril significantly lowered plasma angiotensin converting enzyme (ACE) activity and plasma aldosterone concentration, and raised inulin clearance. The drug had essentially no effect on the time course of magnitude of frusemide's natriuretic effect. Maximal fractional sodium excretion during frusemide infused by itself and in combination with captopril was 24.7 +/- 1.9% vs 28.2 +/- 3.8%, respectively (difference 3.5%; 95% CI, -4.0 to 11.0%; P > 0.05). Cumulative sodium excretion ending at 3.5 h was 429 +/- 53 mmol when frusemide was given alone and 455 +/- 69 mmol when captopril was added (difference, 26 mmol; CI, -121 to 174 mmol; P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of intrarenal ACE-inhibition estimated from the renal response to angiotensin I and II in humans

Recent studies on the nature of the renin-angiotensin system (RAS) in animals have led to the concept that systemic and intrarenal RAS can be influenced to different degrees by angiotensin converting enzyme (ACE) inhibitors. Assessment of efficacy of intrarenal ACE inhibition by ACE inhibitors in humans is necessarily indirect and has not been reported. We therefore monitored the renal response to acute angiotensin (Ang) I infusion in volunteers taking 20 mg enalapril twice daily, and related the responses to the obtained increments in plasma Ang II levels. Ang I infusion rates of 4, 8, 16, and 32 pmol/kg/min caused gradual increments in plasma Ang I (maximal change from 26 +/- 18 to 578 +/- 120 pmol/liter, P < 0.05) and, despite treatment with enalapril, also of Ang II (from 3 +/- 1 to 29 +/- 5 pmol/liter, P < 0.05). This was associated with large reductions in renal plasma flow (paraaminohippurate clearance), filtration fraction, maximal urine flow, sodium excretion, lithium and uric acid clearance, and increments in mean arterial pressure and plasma aldosterone (P < 0.05 for each variable). Strong correlations existed between the changes in either variable and the increment in plasma Ang II. Infusions of Ang II at 1 and 4 pmol/kg/min in the same subjects caused comparable increments in plasma Ang II and had similar physiological effects as found during the Ang I infusion. Analysis of covariance of the changes in plasma Ang II and each of the measured variables revealed no differences between Ang I and Ang II infusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of the initial effects of captopril on blood pressure, glomerular filtration rate, and natriuresis in mild-to-moderate chronic congestive heart failure secondary to coronary artery disease

Whereas angiotensin-converting enzyme inhibitors are now indicated for all grades of chronic heart failure, the 2 adverse effects that limit use of these drugs are systemic hypotension and renal dysfunction. The recognized clinical correlates such as hyponatremia and high diuretic dose, which predict occurrence of these adverse effects in severe chronic congestive heart failure (CHF), are rarely evident in patients with mild-to-moderate CHF. Accordingly, we studied 36 patients with stable, moderate CHF in a double-blind, placebo-controlled, crossover fashion to evaluate by multiple discriminate regression analysis the pathophysiologic determinants of changes in blood pressure, glomerular filtration rate, and urinary sodium excretion after initial converting enzyme inhibition with captopril 25 mg. A captopril-mediated decrease in mean arterial pressure was predicted by 3 factors (r2 = 0.74): the decrease in serum angiotensin II (F ratio = 10.3, p < 0.01), the decrease in plasma norepinephrine (F = 8, p = 0.02), and, inversely by pretreatment mean arterial pressure (F = 5.6, p = 0.04), patients with higher initial values exhibiting greater decreases in response to captopril. A captopril-mediated decline in glomerular filtration rate, determined by radioisotope elimination, was also predicted by 3 factors (r2 = 0.67): a decrease in renal plasma flow (F = 48.6, p < 0.01), low pretreatment glomerular filtration rate (F = 11.1, p < 0.01), and low absolute post-treatment serum angiotensin II (F = 5, p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Which diuretic to use?

The choice of a diuretic depends on knowledge of its efficacy in different disease states as well as the complications associated with its use. However, efficacy of the various diuretic agents as determined in healthy subjects may not always be applicable to the sick patient. The thiazide group appears to be the main offender with regard to hypokalemia and metabolic upsets; these complications seem to stem from long-term use and high dosages. Interest has been expressed on the influence of diuretic induced hypokalemia (and intracellular potassium deficiency) in inducing insulin resistance. The lipid abnormalities may arise as a result of this resistance or may be consequent on hyperinsulinemia from other as yet undetermined mechanisms. In addition, hypertension per se may be associated with insulin resistance. It is interesting to speculate that diuretics, which are commonly used in the treatment of hypertension, may, in some way, perhaps via the induction of hypokalemia, unmask this resistance.

Acute effects of captopril on the renal actions of furosemide in patients with chronic heart failure

This study examined the effects of conventional doses of oral captopril on the renal responses to oral furosemide in ambulant patients with stable chronic heart failure. Twenty-five men (mean age 63 years) were randomized to one of two groups. Group 1 received placebo on days 1 and 2 before furosemide. Group 2 received placebo on day 1 before furosemide and captopril thereafter (i.e., captopril before furosemide on day 2). Urine was collected after either placebo or captopril and after furosemide (taken after placebo or captopril pretreatment). Captopril by itself did not affect renal function. Captopril did, however, significantly affect the renal response to furosemide. The increase in urine flow rate after furosemide in group 2 was decreased from 225% with placebo to 128% with captopril (p < 0.02). The increase in sodium excretion after furosemide was decreased from 623% with placebo to 242% with captopril (p < 0.001). Pretreatment with captopril abolished the increase in creatine clearance after furosemide. The increase in urinary albumin excretion (used as a marker of glomerular function) after furosemide was also significantly blunted by captopril. Conventional doses of captopril acutely inhibit the natriuretic and diuretic responses to furosemide at the glomerular level in ambulant patients with stable chronic heart failure.

Relation of pathophysiologic mechanisms to outcome in heart failure

Advances in the treatment of heart failure with angiotensin-converting enzyme inhibitors have been accompanied by an improved understanding of the pathophysiology of heart failure. The inability of the heart to act as a pump is determined in some patients by alterations to the architecture of the heart and changes in the extracellular space, particularly fibrosis. The degree to which the failure of the heart as a pump can be attributed to a reduced ability of the myocyte to contract is contentious. The origin of symptoms is still uncertain but does relate to identified changes in the lung, increased peripheral resistance and atrophy of skeletal muscle. The mechanisms of action of angiotensin-converting enzyme inhibitors are numerous and do not yet account easily for the clinical benefits. Further epidemiologic studies are needed to ascertain the proportion of patients who manifest progressive heart failure rather than deterioration due to further cardiac events. Understanding the pathophysiology of heart failure will allow therapy to be tailored to the requirements of the individual patient.

Enalapril clinical pharmacokinetics and pharmacokinetic-pharmacodynamic relationships. An overview

The conventional pharmacokinetic profile of the angiotensin converting enzyme (ACE) inhibitor, enalapril, is a lipid-soluble and relatively inactive prodrug with good oral absorption (60 to 70%), a rapid peak plasma concentration (1 hour) and rapid clearance (undetectable by 4 hours) by de-esterification in the liver to a primary active diacid metabolite, enalaprilat. Peak plasma enalaprilat concentrations occur 2 to 4 hours after oral enalapril administration. Elimination thereafter is biphasic, with an initial phase which reflects renal filtration (elimination half-life 2 to 6 hours) and a subsequent prolonged phase (elimination half-life 36 hours), the latter representing equilibration of drug from tissue distribution sites. The prolonged phase does not contribute to drug accumulation on repeated administration but is thought to be of pharmacological significance in mediating drug effects. Renal impairment [particularly creatinine clearance < 20 ml/min (< 1.2 L/h)] results in significant accumulation of enalaprilat and necessitates dosage reduction. Accumulation is probably the cause of reduced elimination in healthy elderly individuals and in patients with concomitant diabetes, hypertension and heart failure. Conventional pharmacokinetic approaches have recently been extended by more detailed descriptions of the nonlinear binding of enalaprilat to ACE in plasma and tissue sites. As a result of these new approaches, there have been significant improvements in the characterisation of concentration-time profiles for single-dose administration and the translation to steady-state. Such improvements have further importance for the accurate integration of the pharmacokinetic and pharmacodynamic responses to enalapril(at) in a concentration-effect model.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical pharmacology of angiotensin converting enzyme inhibitors in chronic heart failure

ACE inhibitors (ACEIs) have now been shown to improve symptoms and survival in patients with mild, moderate and severe chronic heart failure. Their mechanism of action is thought to be a combination of RAAS suppression and augmentation of bradykinin and prostaglandins. Although ACE inhibitors improve hemodynamics post myocardial infarction, we do not yet have consistent data on their effects on symptoms or survival in these particular patients. One other potential benefit is their effects on reperfusion injury and free radicals. As yet only minor differences have been found to exist between different ACEIs but increasing attention is now being focussed in this direction.