Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “DIURETICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

Diuretics modify [Arg8]vasopressin-stimulated cAMP but not atrial natriuretic peptide-stimulated cGMP formation in renal cells.

The present study was undertaken to examine whether sulfonamide-derived diuretics affect [Arg8]vasopressin (AVP)-stimulated or atrial natriuretic peptide (ANP)-stimulated cyclic nucleotide formation in cells cultured from rat or dog kidney. In rat renal cells, all four sulfonamide-derived diuretics examined significantly suppressed 10(-9) M AVP-stimulated cAMP formation at concentrations of 10(-4) and 10(-3) M, while basal cAMP formation was unchanged by the diuretics. When cells were stimulated with 10(-7) M AVP, low ceiling diuretics (indapamide and trichlormethiazide) did not suppress cAMP formation, while high ceiling diuretics (furosemide and azosemide) significantly suppressed cAMP formation at concentrations of 10(-4) and 10(-3) M. The suppressive effect of the diuretics on AVP-stimulated cAMP formation in vitro paralleled the reported diuretic potency of the agents in vivo. In dog renal cells, all four diuretics significantly suppressed 10(-9) M AVP-stimulated cAMP formation at concentrations from 10(-6) to 10(-5) M, while these diuretics did not change basal cAMP levels. High ceiling diuretics suppressed 10(-7) M AVP-stimulated cAMP formation, whereas low ceiling diuretics did not. The difference in effective doses between rats and dogs seems to be consistent with the species difference observed in vivo. None of the diuretics affected basal levels of intracellular cGMP or ANP-stimulated cGMP formation in cultured rat renal cells. In addition to the inhibition of the Na/K/Cl co-transporter, it is suggested that most sulfonamide-derived diuretics act, at least in part, by inhibiting the actions of AVP.

Animals↗

[Diuretics and kidney diseases].

The main indications for diuretic treatment of renal patients are edema and hypertension. Pharmacokinetics and pharmacodynamics of diuretics are altered in patients with proteinuria and/or impaired renal function. These patients exhibit avid sodium retention. Diuretics are partially inactivated by binding to proteins in tubular fluid. The natriuretic response to diuretics is limited by counter-regulation, specifically increased proximal tubular reabsorption in response to hypovolemia and increased distal tubular sodium reabsorption in response to increased sodium load. At higher serum creatinine values, thiazides are no longer sufficiently effective in monotherapy. The diuretics of first choice are then loop diuretics, potentially in combination with thiazide diuretics. Potassium-sparing diuretics are contraindicated. The most important side effects of diuretics are hypovolemia with orthostatic hypotension, hypokalemia, metabolic alkalosis, increase of creatinine concentration and (rarely) hyponatremia. Diuretic treatment should be accompanied by reduction of dietary sodium intake. Important points are selection of an adequate dose (in problematic cases dose-finding via urine sodium measurements) and selection of proper dosing intervals. If cases do not respond to loop diuretic monotherapy, combination with thiazide diuretics or intravenous administration of loop diuretics should be considered.

Benzothiadiazines↗

Heart failure, chronic diuretic use, and increase in mortality and hospitalization: an observational study using propensity score methods.

AIMS: Non-potassium-sparing diuretics are commonly used in heart failure (HF). They activate the neurohormonal system, and are potentially harmful. Yet, the long-term effects of chronic diuretic use in HF are largely unknown. We retrospectively analysed the Digitalis Investigation Group (DIG) data to determine the effects of diuretics on HF outcomes. METHODS AND RESULTS: Propensity scores for diuretic use were calculated for each of the 7788 DIG participants using a non-parsimonious multivariable logistic regression model, and were used to match 1391 (81%) no-diuretic patients with 1391 diuretic patients. Effects of diuretics on mortality and hospitalization at 40 months of median follow-up were assessed using matched Cox regression models. All-cause mortality was 21% for no-diuretic patients and 29% for diuretic patients [hazard ratio (HR) 1.31; 95% confidence interval (CI) 1.11-1.55; P = 0.002]. HF hospitalizations occurred in 18% of no-diuretic patients and 23% of diuretic patients (HR 1.37; 95% CI 1.13-1.65; P = 0.001). CONCLUSION: Chronic diuretic use was associated with increased long-term mortality and hospitalizations in a wide spectrum of ambulatory chronic systolic and diastolic HF patients. The findings of the current study challenge the wisdom of routine chronic use of diuretics in HF patients who are asymptomatic or minimally symptomatic without fluid retention, and are on complete neurohormonal blockade. These findings, based on a non-randomized design, need to be further studied in randomized trials.

Adult↗

Renal excretory profiles of loop diuretics: consequences for therapeutic application.

In healthy subjects, 24-h natriuresis, kaliuresis, calciuresis, and magnesiuresis increase in response to the first oral dose of a standard (diuretic) formulation of a loop diuretic, such as furosemide 40 mg. However, low-dose formulations of loop diuretics, such as torasemide 2.5 mg, do not elevate 24-h natriuresis after the first dose is administered to normal individuals who are in steady-state habitual sodium balance; these formulations of loop diuretics are consequently labeled as nondiuretic formulations (of diuretic substances). Nondiuretic formulations of loop diuretics do not increase the 24-h urinary outputs of sodium, potassium, calcium, or magnesium after the first dose or in the course of repeated once-daily administration to healthy subjects. The 24-h natriuretic response to the first dose of standard (diuretic) formulations of loop diuretics wanes during repeated once-daily administration to healthy individuals, whereas the kaliuretic response becomes slightly attenuated, and calciuresis and magnesiuresis bear little change. Once-daily treatment with any formulation of a loop diuretic may result in an increase in plasma urate concentration. Nondiuretic formulations of loop diuretics, which are efficacious as once-daily monopharmacotherapy for high blood pressure, should be tried before standard (diuretic) formulations of diuretics are used in the treatment of uncomplicated essential hypertension. When loop diuretics are employed in the treatment of congestive heart failure, the minimal dose compatible with the attainment of clinical objectives should be used.

Diuresis↗

Diuretics and risk of arrhythmic death in patients with left ventricular dysfunction.

Background-Treatment with diuretics has been reported to increase the risk of arrhythmic death in patients with hypertension. The effect of diuretic therapy on arrhythmic death in patients with left ventricular dysfunction is unknown. Methods and Results-We conducted a retrospective analysis of 6797 patients with an ejection fraction <0.36 enrolled in the Studies Of Left Ventricular Dysfunction (SOLVD) to assess the relation between diuretic use at baseline and the subsequent risk of arrhythmic death. Participants receiving a diuretic at baseline were more likely to have an arrhythmic death than those not receiving a diuretic (3.1 vs 1.7 arrhythmic deaths per 100 person-years, P=0.001). On univariate analysis, diuretic use was associated with an increased risk of arrhythmic death (relative risk [RR] 1.85, P=0.0001). After controlling for important covariates, diuretic use remained significantly associated with an increased risk of arrhythmic death (RR 1.37, P=0.009). Only non-potassium-sparing diuretic use was independently associated with arrhythmic death (RR 1.33, P=0.02). Use of a potassium-sparing diuretic, alone or in combination with a non-potassium-sparing diuretic, was not independently associated with an increased risk of arrhythmic death (RR 0.90, P=0.6). Conclusions-In SOLVD, baseline use of a non-potassium-sparing diuretic was associated with an increased risk of arrhythmic death, whereas baseline use of a potassium-sparing diuretic was not. These data suggest that diuretic-induced electrolyte disturbances may result in fatal arrhythmias in patients with systolic left ventricular dysfunction.

Analysis of Variance↗

New insights into diuretic use in patients with chronic renal disease.

Patients with chronic renal insufficiency (CRI) or the nephrotic syndrome frequently manifest diuretic resistance. Factors limiting diuretic responsiveness in patients with CRI may include a reduced basal level of fractional Na(+) reabsorption that places an upper limit on diuretic response, and enhanced NaCl reabsorption in downstream segments, combined with a reduced delivery of diuretic to the kidney. Diuretics are secreted by the recently characterized organic anion transporters (OATs), which are expressed in proximal tubule cells. Secretion may be inhibited by retained organic anions, urate, or acidosis. These limitations necessitate an increased diuretic dosage, up to a defined ceiling level, and consideration of the use of a nonrenally metabolized loop diuretic rather than furosemide. Diuretic responsiveness in patients with the nephrotic syndrome is limited by avid Na(+) reabsorption by the terminal nephron. Experimental studies have shown that a reduced serum albumin concentration can increase the volume of distribution of loop diuretics, reduce their tubular secretion, and enhance the inactivation of furosemide within the kidney by glucuronidization. Binding of loop diuretics can curtail their action in the loop of Henle. Recent clinical investigations have challenged the importance of some of these mechanisms that were identified in animal models. Strategies to improve loop diuretic responsiveness include increasing diuretic dosage, concurrent use of a thiazide diuretic to inhibit downstream NaCl reabsorption and attempts to maximally reduce albumin excretion. Strategies to limit albumin excretion include the use of an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker and appropriate limitation of protein intake. These measures are more logical, effective, and less expensive than infusion of albumin solutions.

Animals↗

Diuretic therapy in elderly heart failure patients with and without left ventricular systolic dysfunction.

Long term prescription of diuretics for heart failure is very prevalent among elderly patients, although the rationale for such a treatment strategy is often unclear, as diuretics are not indicated if volume overload is absent. The concept of diastolic heart failure in the elderly might particularly change the role of diuretic therapy, since diuretics may have additional adverse effects in these patients. This paper reviews the effects of diuretic therapy in elderly patients with heart failure, emphasising the differences between patients with normal and decreased left ventricular systolic function. Studies on diuretic withdrawal in elderly patients with heart failure are discussed, with emphasis on issues involved in decision making such as diuretic dose reduction and withdrawal in elderly patients and factors that have been established to predict successful withdrawal. Existing guidelines on the prescription of diuretics in elderly patients with heart failure with normal and decreased left ventricular systolic function and in those with diastolic heart failure are also discussed. By reducing intravascular volume, diuretics may further impair ventricular diastolic filling in patients with diastolic heart failure and thus reduce stroke volume. Indeed, preliminary studies demonstrate that diuretics may provoke or aggravate hypotension on standing and after meals in these patients. Therefore, it is suggested that elderly patients with heart failure with intact left ventricular systolic function should not receive long term diuretic therapy, unless proven necessary to treat or prevent congestive heart failure. This implies that physicians should carefully evaluate the opportunities for diuretic dose tapering or withdrawal in all of these patients, and that a cautiously guided intermittent diuretic treatment modality may be critical in the care for older patients with heart failure with intact left ventricular systolic function.

Aged↗

Diuretic combinations in refractory oedema states: pharmacokinetic-pharmacodynamic relationships.

Diuretic resistance is encountered in a number of disease states, such as chronic renal failure, nephrotic syndrome, congestive heart failure (CHF) and cirrhosis. Diuretic stratagems which produce sequential nephron segment blockade, and thus a synergistic diuretic response, are frequently necessary and are regularly employed in these conditions. Pharmacokinetic determinants of diuretic response, including dose administered, absolute bioavailability, and tubular transport capacity and transport rate, are reviewed here. Pharmacodynamic factors are perhaps more important to overall response, and often result in modification of the dose-response relationship; these are also reviewed here. Stratagems used to maximise the diuretic response to loop diuretics include correcting abnormal haemodynamic parameters, utilising larger doses or constant intravenous infusions, and using albumin as a vehicle to deliver the loop diuretic to the site of tubular secretion. If these measures fail, then diuretic combinations are useful. Perhaps the most effective is the combination of metolazone (a thiazide-type diuretic) and a loop diuretic. The rationale for and use of various diuretic combinations, with particular emphasis on the metolazone-loop diuretic combination, is reviewed here and applied to the major disease states associated with diuretic resistance.

Diuretics↗

Diuretic drugs. Progress in clinical pharmacology.

Oral diuretics are amongst the most widely used drugs in clinical practice today. Their discovery close on thirty years ago remains a major milestone in therapeutic progress. Though originally designed for treating heart failure, diuretics are more commonly prescribed, worldwide, in hypertension than for relief of oedema. Since the introduction of chlorothiazide, diuretic development has passed through a series of distinct stages. The thiazide era was followed by the 'high-ceiling' diuretics, the antikaliuretics and, more recently, polyvalent agents that cause both saluresis and uricosuria. Alongside these synthetic achievements, major advances have occurred in the knowledge of nephron function and ion transport mechanisms. These have acted as stimulus to the design of novel categories of diuretics. The practising clinician thus has a wide range of available diuretics to choose from. The most appropriate choice of an agent aimed at the relief of symptoms with minimal adverse effects requires an understanding of where and how diuretics act within their primary target organ, the kidney. Whereas various procedures, ranging from micropuncture to the study of brush border membrane vesicles, have been utilised experimentally, investigation of the mode and sites of action of diuretics in man has largely depended on application of clearance methodology. Refinements in analytical chemistry have encouraged study of the pharmacokinetic and metabolic fate of diuretics. Taken together, available evidence shows that most diuretics exert their saluretic action from the intraluminal aspect of the renal tubules. The time-course of drug delivery, as well as total quantity of drug transported into the lumen determine the cumulative drug response. Exceptions are muzolimine and the aldosterone antagonists which act at the peritubular membrane. Distinctive stereospecific effects on luminal tubular ion transport occur with indacrinone and etozoline. The clinical use of diuretics often involves concurrent administration with other drugs. The mechanisms involved in a number of the resulting pharmacodynamic and pharmacokinetic interactions have considerable relevance in patient management. Notable examples of these interactions are the blunting of diuretic action by non-steroidal anti-inflammatory agents and the diuretic-induced diminution in the renal clearance of lithium salts.

Age Factors↗

The inhibitory effect of diuretics on carbonic anhydrases.

A classification of diuretics mainly comprises mercurials; carbonic anhydrase inhibitors, thiazide diuretics, loop diuretics, inhibitors of renal epithelial Na+ channels and antagonists of mineralocorticoid receptors. We studied in this paper the relationship between diuretics and carbonic anhydrase (CA). Our in vitro and in vivo results show that all diuretics inhibit carbonic anhydrase II and renal CA IV. Further, our data show that they also inhibit epithelial cell CA in the renal tubules. The changes in intracellular pH (pHi) induced by these diuretics through CA inhibition would influence: a) the coupling to their receptors affecting information transmission to the epithelial cells of renal tubules as well as diuretic response; b) the decrease of Na+ exchanger (thiazide), of Na+ - K+ - 2Cl- relation (loop diuretics), Na+ channel blocking in distal and collecting tubules (amiloride, triamterene), as well as the antagonism between spironolactone and aldosterone at the mineralocorticoid receptor level, suggest that this competition might also be produced on CA II and on renal CA IV, which, in turn, could be influenced by pH-induced changes, the binding of the diuretic to its membrane receptor as well as the activity of the brush membrane or cytosolic pump. Furosemide and indapamide, diuretics known to have vasodilating effects, induce the fall of blood pressure that parallels the decrease of CA I activity. These results show the involvement of CA in the mechanism of action of the diuretics and in their actions associated with vasodilating effects. pH changes resulting from the action of CA contribute to the action of diuretics. All diuretics inhibit CA isozymes.

Aged↗

[The significance of urine sodium measurement after furosemide administration in diuretics-unresponsive patients with liver cirrhosis].

BACKGROUND/AIMS: The diagnosis of refractory ascites means a poor prognosis for patients with liver cirrhosis. The definition of refractory ascites has already been established, but using the dosage of diuretics that correlates with the definition of refractory ascites in an out-patient department will lower the compliance of the patient, as well as causing serious complications, such as hepatic encephalopathy and hyponatremia, as the dosage of diuretics is increased. Due to this fact, it is very difficult to apply this definition of refractory ascites to patients in a domestic out-patient department. In this study, in situations where there are difficulties in applying the diuretics dosage according to definition of refractory ascites, we tried to find out whether measuring the value of urine sodium after the administration of intravenous furosemide can be the standard in early differentiation of the response to diuretics treatment. METHODS: We reviewed 16 cases of liver cirrhosis with ascites and classified them into two groups by the response to diuretics. The diuretics-responsive ascites group was 8 cases and the diuretics-unresponsive ascites group consisted of 8 cases. After admission, we examined the patients' CBC, biochemical liver function test, spot urine sodium, and 24 hour creatinine clearance. After the beginning of the experiment, all diuretic therapy was stopped for 3 days. Daily we examined the patients' CBC, biochemical liver function test, and in the 3rd experiment day, we measured 24-hour urine volume and sodium. In the 4th experiment day, after sampling for ADH, plasma renin activity and plasma aldosterone level, we administrated the furosemide 80 mg I.V, and measured the amount of 8 hour urine volume and sodium. RESULTS: The plasma aldosterone level was significantly higher in the diuretics- unresponsive ascites group than in the diuretics-responsive ascites group. In the 4th experiment day, the amount of urine volume and sodium was very significantly lower in the diuretics-unresponsive ascites group than in the diuretics-responsive ascites group (1297.5 +/-80.9 vs 2003.7 +/-114.6 ml, p<0.005, 77.3 +/-8.2 vs 211.8 +/-12.6 mEq, p<0.001). CONCLUSIONS: In out-patient departments, the measurement of urine sodium 8 hours after administrating 80 mg of intravenous furosemide, will help in differentiating ascites patients with lower treatment response to diuretics.

Adult↗

[Diuretics; their characteristics and future development].

We review the diuretics regarding the mechanism of action, way of clinical use and their adverse effects. Recent progress of molecular biology revealed the molecular target of diuretics and thereby, the molecular mechanism of diuretic action became clear to understand. Loop diuretics and thiazides are the most widely used diuretics and the physiologic adaptation to their prolonged use are mentioned. Carbonic anhydrase inhibitors are not used as diuretics but for correction of metabolic alkalosis and treatment of glaucoma. Potassium-sparing diuretics have modest natriuresis but the combination with loop diuretics or thiazides results in strong natriuresis. Adenosine type 1 receptor antagonist has been developed for treatment of edema in chronic heart failure. Vasopressin type 2 receptor antagonists are developed for a new type of diuretics to increase the free water clearance in cases of chronic heart failure and SIADH. The recombinant atrial natriuretic polypeptide is recently used as diuretics in acute heart failure. Knowledge of pharmacological action of diuretics could help the appropriately clinical use of diuretics, in particular the diuretics-resistant edema.

Diuretics↗

Approaches to diuretic therapy and electrolyte imbalance in congestive heart failure.

This review has summarized the current role of diuretic therapy in heart failure, emphasizing those aspects most relevant to this patient population. Recommended diuretic usage is as follows: Asymptomatic left ventricular dysfunction--establish moderate sodium intake, Mild sodium retention--thiazide-type diuretic or low-dose loop diuretic; continue moderate sodium intake; combine with an ACE inhibitor, Moderate sodium retention--loop diuretic, adjusting for renal function, if necessary; continue moderate sodium intake; combine with an ACE inhibitor, Severe sodium retention--large-dose loop diuretic combined with a thiazide-type diuretic; continue moderate sodium intake; ACE inhibitor, unless contraindicated; consider addition of a potassium-sparing diuretic Treatment measures for refractory sodium retention--intermittent intravenous loop diuretic; short-term infusion of a loop diuretic; intensified combination oral diuretic therapy; intravenous positive inotropic therapy; ultrafiltration or dialysis. In addition, the well-known adverse effect of electrolyte depletion and guidelines for electrolyte replacement have been discussed. It is evident that the diuretic class of pharmacologic therapy has not been as well assessed as both the positive inotrope and vasodilator classes. Limitations in this regard have been summarized recently. Even relatively simple parameters or instruments, such as the sodium retention score, when applied to clinical trials will yield a greater understanding of the utility and limitations of diuretic therapy for heart failure.

Animals↗

Discontinuation of chronic diuretic therapy in stable congestive heart failure secondary to coronary artery disease or to idiopathic dilated cardiomyopathy.

To assess the feasibility of diuretic discontinuation in patients with stable congestive heart failure (CHF) and to identify risk factors for subsequent development of congestion, a prospective, 12-week clinical trial of unmasked diuretic withdrawal was conducted with continuation of background CHF therapy and double-blind randomization to placebo or lisinopril. Forty-one patients with a history of CHF and continuous diuretic use for > or = 3 months had all diuretic therapy discontinued, and therapy with lisinopril 5 mg (target 20 mg)/day (n = 20) or placebo (n = 21) begun the next day. A diuretic was restarted if new or worsening CHF symptoms and signs developed. Twelve patients (29%) did not require diuretic reinitiation at any time during follow-up, whereas 29 (71%) restarted diuretic therapy after a median of 15 days (range 2 to 42). Fourteen patients taking lisinopril and 15 taking placebo required diuretic drugs (p = NS). The baseline daily furosemide dose of > 40 mg, a left ventricular ejection fraction < or = 0.27, and history of systemic hypertension were independently predictive of early diuretic reinitiation by Cox proportional-hazards analysis. The probability of remaining diuretic-free after 6 weeks was 71% if none of these criteria were present. This trial demonstrates the feasibility of discontinuing diuretic drugs in certain patients with stable CHF and predicts those patients likely to require reinitiation of therapy. Diuretic withdrawal may be warranted when the furosemide dose is < or = 40 mg/day, left ventricular ejection fraction is > 0.27 and when no history of systemic hypertension is present.

Adolescent↗

Beta-blockers and diuretics: to use or not to use.

The present review scrutinizes the recommendations of many guidelines to use beta-blockers and diuretics as first-line therapy in hypertension. These recommendations were ostensibly based on multiple prospective randomized trials attesting to a reduction of morbidity and mortality with both beta-blockers and diuretics in monotherapy as well as in combination. Although diuretic-based therapy has been shown to prevent strokes (and, to a lesser extent, heart attacks, and cardiovascular and all-cause mortality), no such data are available for beta-blockers. To the contrary, a recent metaanalysis documented that although blood pressure was lowered significantly by beta-blockers, this drug class was ineffective in preventing coronary heart disease, and cardiovascular and all-cause mortality (odds ratio 1.01, 0.98, and 1.05, respectively). Patients who received a combination of beta-blockers and diuretics fared consistently worse than those taking diuretics alone. Although diuretics have an unparalleled track record of safety and efficacy, the recent findings suggesting that long-term use increased the risk for renal cell carcinoma (RCC) is of concern. Over the past decade, an association between RCC and diuretic therapy has been documented in nine case control studies (odds ratio 1.55, confidence interval [CI] 1.42-1.71). In three cohort studies, diuretic therapy was associated with a greater than twofold increased risk of RCC. The risk of RCC increased with cumulative diuretic doses. In the elderly, a low-dose diuretic probably remains a good choice for antihypertensive therapy; however, in middle-aged patients, particularly in women, diuretics should be avoided for the long-term treatment of hypertension. Sweeping recommendations for the use of beta-blockers and diuretics as preferred therapeutic strategies are inappropriate and a more sophisticated drug therapy regimen is often needed.

Adrenergic beta-Antagonists↗

The effects of treatment with octreotide, diuretics, or both on portal hemodynamics in nonazotemic cirrhotic patients with ascites.

GOALS: To evaluate the effects of diuretic treatment, octreotide, or both on portal hemodynamics in nonazotemic cirrhotic patients with ascites. BACKGROUND: Diuretics and octreotide have been associated with a decrease in portal pressure in cirrhotic patients, suggested to be mediated by plasma volume depletion and splanchnic vasoconstriction, respectively. However, liver cirrhosis is characterized by activation of the renin-angiotensin-aldosterone axis, which increases hepatic vascular resistance and is augmented or suppressed by diuretics or octreotide, respectively. STUDY: Twenty nonazotemic cirrhotic patients with ascites were treated with furosemide and spironolactone. Of them, 10 (group 1) discontinued diuretic treatment for 7 days. Thereafter for 5 days, each patient received subcutaneous octreotide, 300 microg twice per day; ten of them (group 2) received the octreotide in addition to their usual diuretic treatment. Portal and systemic hemodynamics with Doppler ultrasound and endogenous vasoactive systems were evaluated while the patients received diuretics (both groups), after discontinuation of diuretics (group 1), and after octreotide administration (both groups). RESULTS: The withdrawal of diuretics did not alter portal hemodynamics, but it impaired systemic hemodynamics and suppressed the renin-aldosterone axis. The addition of octreotide to diuretic treatment but not octreotide alone improved portal and systemic hemodynamics. In both groups the initiation of octreotide administration suppressed the renin-aldosterone axis and plasma glucagon levels. CONCLUSIONS: In nonazotemic cirrhotic patients with ascites, the combination of diuretics and octreotide improves systemic hemodynamics and inhibits the diuretic-related component of the activated renin-aldosterone axis, which in turn augments the portal hypotensive effect of diuretic-induced plasma volume depletion.

Adult↗

Magnesium and potassium-sparing diuretics.

One of the most common and serious side effects of diuretic therapy is in increased urinary loss of K. Another, although less well publicized, side effect of diuretic therapy is excessive urinary loss of Mg. In examining the effects of diuretics on Mg and K metabolism, the following factors should be taken into account: site of action and duration of action of diuretics, duration of treatment and dosage used, concurrent drug therapy, underlying disease conditions and dietary intake of Mg. Diuretics acting in the proximal tubule tend to have only minor effects on Mg excretion. Loop-blocking diuretics, however, cause major urinary losses of Mg. The Mg-wasting effects of loop-blocking diuretics have been demonstrated in large numbers of experimental and clinical studies, and the findings are consistent with micropuncture studies in laboratory animals which indicate the loop of Henle as the major site of Mg reabsorption. The effects of thiazide diuretics on Mg excretion are less well established than those of loop-blocking diuretics. Experimental studies demonstrate that thiazides have little or no direct effect on Mg transport in the nephron. However, some clinical studies indicate that thiazide treatment may induce Mg loss. This may be secondary to alterations in the renin-angiotensin-aldosterone system and in the calcium and parathyroid hormone and may be contributed to by concurrent drug treatment and the underlying disease conditions. K-sparing diuretics are usually administered concomitantly with more potent diuretics to counteract diuretic-induced K depletion. These agents act in the late distal tubule and collecting duct. Evidence has accumulated in recent years indicating that these drugs may also exert some Mg-sparing properties. Experimental and clinical investigations from our own laboratories and from other investigators will be reviewed. In animal studies, a dose-response relationship has been established for the actions of amiloride in reducing fractional excretion of Mg and K during furosemide-induced diuresis. The effects of amiloride on Mg excretion are less than those on K excretion, and this is compatible with the different handling of K and Mg in the distal tubule and collecting duct. The effects of aldosterone antagonists on Mg excretion are less well established than those of amiloride. Some recent studies indicate that converting-enzyme inhibitors may also influence Mg and K metabolism. The Mg-sparing actions of drugs may have important therapeutic implications.

Amiloride↗

Diuretics. Clinical pharmacology and therapeutic use (Part II).

25 years have elapsed since the introduction of the first effective oral diuretic, chlorothiazide. Diuretics are now amongst the most widely prescribed drugs in clinical practice worldwide. Availability of these drugs has not only brought therapeutic benefit to countless numbers of patients but it has at the same time provided valuable research tools with which to investigate the functional behaviour of the kidney and other electrolyte-transporting tissues. Despite many remaining gaps in our knowledge of the biochemical processes involved in diuretic drug action, available compounds can be divided into 5 groups on the basis of their preferential effects on different segments of the nephron involved in tubular reabsorption of sodium chloride and water. Firstly, there is a heterogeneous group of chemicals that share the common property of powerful, short-lived diuretic effects that are complete within 4 to 6 hours. These agents act on the thick ascending limb of Henle's loop and are known as 'high ceiling' or 'loop' diuretics. The second group are the benzothiadiazines and their many related heterocyclic variants, all of which localise their effects to the early portion of the distal tubule. The third group comprises the potassium-sparing diuretics which act exclusively on the Na+-K+/H+ exchange mechanisms in the late distal tubule and cortical collecting duct. The action of drugs in groups 2 and 3 is prolonged to between 12 and 24 hours. The fourth group consists of diuretics that are chemically related to ethacrynic acid but have the unusual property of combining within the same molecule the property of saluresis and uricosuria. These compounds have actions, to different individual extents, in the proximal tubule, thick ascending limb, and early distal tubule and are known as 'polyvalent' diuretics. Finally, there is a mixed group of weak or adjunctive diuretics which includes the vasodilator xanthines such as aminophylline, and the osmotically active compounds such as mannitol. The metabolic consequences of continued diuretic usage are considered along with non-metabolic sequelae such as ototoxicity or interactions with other concurrent treatments. The relationships between the clinical benefits conferred and the potential harms generated by long term diuretic therapy are also discussed.

Amiloride↗