Kinetic disposition and diuretic effect of frusemide in acute pulmonary oedema

Model based population PK-PD analysis of furosemide for BP lowering effect: A comparative study in primary and secondary hypertension

Though numerous reports have demonstrated multiple mechanisms by which furosemide can exert its anti-hypertensive response. However, lack of studies describing PK-PD relationship for furosemide featuring its anti-hypertensive property has limited its usage as a blood pressure (BP) lowering agent. Serum concentrations and mean arterial BP were monitored following 40 and 80mgkg^-1 multiple oral dose of furosemide in spontaneously hypertensive rats (SHR) and DOCA-salt induced hypertensive (DOCA-salt) rats. A simultaneous population PK-PD relationship using E_max model with effect compartment was developed to compare the anti-hypertensive efficacy of furosemide in these rat models. A two-compartment PK model with Weibull-type absorption and first-order elimination best described the serum concentration-time profile of furosemide. In the present study, post dose serum concentrations of furosemide were found to be lower than the EC₅₀. The EC₅₀ predicted in DOCA-salt rats was found to be lower (4.5-fold), whereas the tolerance development was higher than that in SHR model. The PK-PD parameter estimates, particularly lower values of EC₅₀, K_e and Q in DOCA-salt rats as compared to SHR, pinpointed the higher BP lowering efficacy of furosemide in volume overload induced hypertensive conditions. Insignificantly altered serum creatinine and electrolyte levels indicated a favorable side effect profile of furosemide. In conclusion, the final PK-PD model described the data well and provides detailed insights into the use of furosemide as an anti-hypertensive agent.

Adventures in drug disposition: pas seulement pâté de foie

Interindividual variability in drug disposition and effect has served to confound the optimization of drug therapy. Over my career, I have focused on delineating mechanisms that contribute to this variability, with the goal of improving the benefit : risk ratio when drug therapy is chosen as an intervention strategy. In this manuscript, I present some of our experimental findings that I believe have contributed to an increased understanding of variability in drug disposition and efficacy.

Risk Factors for Acute Renal Insufficiency Induced by Diuretics in Patients With Congestive Heart Failure

BACKGROUND

In patients with congestive heart failure (CHF), continuous diuretic therapy may result in acute renal insufficiency (ARI). This study examines factors contributing to this complication.

METHODS

We analyzed clinical data from 318 consecutive patients who were hospitalized for CHF. All were treated with diuretics and had echocardiography performed within 4 days of hospitalization. Systolic left ventricular (LV) dysfunction is defined as an ejection fraction less than 50%, and diastolic LV dysfunction, as an ejection fraction of 50% or greater in the presence of LV hypertrophy and a reversed E/A ratio.

RESULTS

ARI, defined as a 25% increase in serum creatinine level, occurred in 110 patients (35%) after diuretic therapy. Risk factors for ARI on univariate analyses were older age, higher baseline serum creatinine level, lower baseline serum sodium level, lower mean arterial pressure (MAP) during diuretic therapy, and greater doses and longer duration of diuretic therapy. In multivariate analyses, ARI occurred more frequently in patients with systolic (40%) than diastolic dysfunction (28%). The use of digoxin in patients with systolic LV dysfunction was observed to decrease the risk for ARI by 61%, independent of other agents used for the treatment of patients with CHF.

CONCLUSION

Age, baseline renal function and serum sodium concentration, MAP, and intensity of diuretic therapy can identify individuals at risk for ARI while receiving diuretic therapy for CHF. This complication is observed more often in individuals with systolic dysfunction, and its risk may be decreased with the use of digoxin.

Loop diuretics: from the Na-K-2Cl transporter to clinical use

The diuretic response to loop diuretics in various disease states has consistently been found to be subnormal. One of the key determinants of the degree of diuretic response is the functional integrity of the sodium-potassium-chloride transporter in the loop of Henle. Studies in animal models suggest that expression/activity of the transporter may be affected by factors such as altered natural splicing events of NKCC2 (the gene encoding for the renal transporter), renal prostanoids, vasopressin, and other autacoids. We have reviewed the pharmacokinetics and pharmacodynamics of loop diuretics in health and in edematous disorders for which they are used. On the basis of evidence reviewed in this paper, we propose that altered expression or activity of the sodium-potassium-chloride transporter in the loop of Henle, in conjunction with events occurring in other segments of the nephron, possibly accounts for the altered diuretic response to these agents. Thus the modulators of this altered expression/activity could serve as important therapeutic targets for alternative diuretic regimens in these conditions.

Treatment of edematous disorders with diuretics

Generalized edema results from alterations in renal sodium homeostasis that ultimately result in an expansion of extracellular fluid volume and accumulation of interstitial fluid. The common edematous disorders include congestive heart failure, cirrhosis, nephrotic syndrome, and renal insufficiency. The abnormalities of sodium homeostasis contributing to edema formation in each condition are discussed. Management of volume homeostasis, with an emphasis on the role of diuretic therapy, is reviewed.

Furosemide kinetics and dynamics in rats and humans

1. Increasing doses of furosemide (F) were given intravenously to rats and humans and initial pharmacokinetics and pharmacodynamics were compared. 2. Weight-related initial renal excretion rate of F was twice as high in rats and serum concentration at 30 min was twice as high in humans (P less than 0.01). 3. Volume of distribution for F was 44% larger in rats (P less than 0.01). 4. Maximal weight-related diuretic and natriuretic responses were, like the theoretical maximal efficiency, 5-6 times higher in the rat. The potency was 230 times lower in the rats. 5. On a molecular basis species differences in kinetics disappeared when standardization was based on ERPF and species differences in dynamics disappeared when standardization was based on GFR.

The effect of respiratory disorders on clinical pharmacokinetic variables

Respiratory disorders induce several pathophysiological changes involving gas exchange and acid-base balance, regional haemodynamics, and alterations of the alveolocapillary membrane. The consequences for the absorption, distribution and elimination of drugs are evaluated. Drug absorption after inhalation is not significantly impaired in patients. With drugs administered by this route, an average of 10% of the dose reaches the lungs. It is not completely clear whether changes in pulmonary endothelium in respiratory failure enhance lung absorption. The effects of changes in blood pH on plasma protein binding and volume of distribution are discussed, but relevant data are not available to explain the distribution changes observed in acutely ill patients. Lung diffusion of some antimicrobial agents is enhanced in patients with pulmonary infections. Decreased cardiac output and hepatic blood flow in patients under mechanical ventilation cause an increase in the plasma concentration of drugs with a high hepatic extraction ratio, such as lidocaine (lignocaine). On a theoretical basis, hypoxia should lead to decreased biotransformation of drugs with a low hepatic extraction ratio, but in vivo data with phenazone (antipyrine) or theophylline are conflicting. The effects of disease on the lung clearance of drugs are discussed but clinically relevant data are lacking. The pharmacokinetics of drugs in patients with asthma or chronic obstructive pulmonary disease are reviewed. Stable asthma and chronic obstructive pulmonary disease do not appear to affect the disposition of theophylline or beta 2-agonists such as salbutamol (albuterol) or terbutaline. Important variations in theophylline pharmacokinetics have been reported in critically ill patients, the causes of which are more likely to be linked to the poor condition of the patients than to a direct effect of hypoxia or hypercapnia. Little is known regarding the pharmacokinetics of cromoglycate, ipratropium, corticoids or antimicrobial agents in pulmonary disease. In patients under mechanical ventilation, the half-life of midazolam, a new benzodiazepine used as a sedative, has been found to be lengthened but the underlying mechanism is not well understood. Pulmonary absorption of pentamidine was found to be increased in patients under mechanical ventilation. Pharmacokinetic impairment does occur in patients with severe pulmonary disease but more work is needed to understand the exact mechanisms and to propose proper dosage regimens.

Effects of cardiovascular disease on pharmacokinetics

The pathophysiologic changes occurring in cardiovascular disease can affect the kinetics of drugs in several different ways. The present review examines these modifications and the underlying mechanisms. The kinetics of specific agents, such as antiarrhythmic, antihypertensive, cardiotonic, and other drugs are considered, and the clinical implications are outlined. The clinician should be aware of these modifications, because they require an adjustment of the dosage regimen. A rational basis for a correct therapeutic choice can be provided by adequate knowledge of these modifications.

Furosemide pharmacokinetics and pharmacodynamics in health and disease--an update

The literature on furosemide pharmacokinetics and pharmacodynamics is critically reviewed, concentrating on those papers published subsequent to the 1979 reviews of this topic. Intravenous and oral data are presented for healthy volunteers and for patients with various disease states. It is the latter populations about which the majority of the studies have been published since 1979. Inter- and intraindividual variations in bioavailability are discussed, as are data on the metabolism of furosemide to its glucuronide conjugate. Published studies examining the relationship between furosemide pharmacodynamics and pharmacokinetics are also evaluated. The literature is reviewed through June 1988.

The altered pharmacokinetics and pharmacodynamics of drugs commonly used in critically ill patients

The critically ill patient occupies an increasing amount of time and bed space in modern hospital practice, and also commands increasing expenditure. Drug therapy in these patients has, in the past, been based on data derived from healthy volunteers, fit anaesthetised patients undergoing minor operative procedures, or patients with single organ failure. Alterations in pharmacokinetics and pharmacodynamics have not been studied in depth in critically ill patients who often have multisystem failure. This paper reviews the currently available information on drugs in common usage in these patients. The studies that have been performed have usually shown delayed drug clearance, altered volumes of distribution and prolonged elimination half-lives. The sedative and analgesic drugs, in particular, have shown marked accumulation which may confuse the clinical picture, and prolonged periods of assisted ventilation may be required until the drugs are eliminated.

A decade of developments in diuretic drug therapy

New diuretics introduced into clinical medicine during the past decade include potent new loop diuretics such as bumetanide and piretanide, the uricosuric indanyloxyacetic acid derivative indacrinone, and a new generation of sulfamoyl diuretics such as indapamide and xipamide, which are recommended primarily for the treatment of hypertension. Pharmacokinetic studies of individual diuretics have demonstrated that the diuretic and natriuretic responses to the newer agents generally follow the plasma drug concentration-time curves and urinary drug excretion rates. Therapeutic monitoring can therefore be achieved in most patients with edema or hypertension by close clinical observation and laboratory analysis of plasma electrolyte and creatinine concentrations and urinary electrolyte excretion rates. Interest in the mechanisms involved in the renal and extrarenal vascular actions of the newer diuretics has led to a better understanding of how changes in venous compliance, peripheral vascular resistance, and renal blood flow distribution may contribute to the overall therapeutic response to these agents, especially in patients with severe congestive heart failure, renal insufficiency with low glomerular filtration rates, and hypertension with cardiorenal complications. Adverse reactions to modern diuretics, which are mainly an extension of their renal pharmacodynamic effects, have proved to be minimal, provided that the dosage is adjusted to meet but not exceed individual patient requirements. However, the long-term consequences of prolonged periods of diuretic-induced alterations in plasma potassium levels, and metabolic effects that include elevated blood lipids, are still under investigation.

Disposition and response to bumetanide and furosemide

Bumetanide and furosemide are potent loop diuretics; the former is 40 to 50 times more potent than the latter on a weight basis. Bumetanide is absorbed more quickly than furosemide and is twice as bioavailable. Both drugs exhibit changes in elimination in the presence of renal insufficiency as well as changes in the time course of absorption in congestive heart failure. More data are needed to assess potential differences between them in various clinical conditions.

Diuretics. Clinical pharmacology and therapeutic use (Part I)

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 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. Available evidence on the molecular mechanisms of action of diuretics in each group is reviewed. The haemodynamic, humoral and physical factors involved in control of electrolyte and fluid handling by the kidney in normal conditions and pathological states are discussed in relation to rational choices of different diuretics in the treatment of various oedematous and non-oedematous conditions.

The influence of age on renal and extrarenal effects of frusemide

The effect of frusemide 80 mg i.v. was compared during 24 h in 10 young and eight elderly healthy male volunteers following a 24 h control period in the ward. During the 30 min following the injection the increments in excretion of urine, sodium, potassium and frusemide were significantly smaller in the elderly. The 24 h increase in sodium excretion was significantly larger in the 0 young and eight elderly healthy male volunteers following a 24 h control period in the ward. During the 30 min following the injection the increments in excretion of urine, sodium, potassium and frusemide were significantly smaller in the elderly. The 24 h increase in sodium excretion was significantly larger in the 0 young and eight elderly healthy male volunteers following a 24 h control period in the ward. During the 30 min following the injection the increments in excretion of urine, sodium, potassium and frusemide were significantly smaller in the elderly. The 24 h increase in sodium excretion was significantly larger in the elderly. The endogenous 24 h creatinine clearance was reduced by 12% (P less than 0.01) in both age groups. The frusemide induced changes in the 8 h serum concentration curves for albumin differed significantly between the two groups (analysis of variance, P less than 0.01). The drug induced increase in albumin concentration became significant in the young 5 min after the injection. In the elderly it took more than 15 min before the increase in serum albumin reached significance. The average maximal increase in albumin concentration was 14.3% in the young and 9.7% in the elderly (P less than 0.05). No difference was seen between the two age groups in the significant frusemide induced increases in the 24 h albumin excretion but in the elderly a significantly larger decrease in the 24 h excretion of beta 2-microglobulin was observed (P less than 0.05). No significant age difference was observed in the initial significant increases in diastolic blood pressure observed in both age groups or between the later changes in systolic blood pressure which was significantly reduced in the young only. The slower haemoconcentration response in the elderly seemed associated with the slower secretion rate of frusemide to the tubular lumen. We found no evidence of an age related difference in tubular cell response to frusemide. It is emphasized that a maximal initial frusemide response in the elderly, in contrast to what was found in the young, probably was not achieved by the 80 mg i.v.

Absorption and disposition of furosemide in congestive heart failure

Changes in response to furosemide and other diuretics in patients with congestive heart failure (CHF) could occur because of disease-induced changes in absorption of the drug or changes in disposition which affect its access to its site of action. A difference was not found in the bioavailability of forosemide in patients with CHF compared to normal volunteers, 31 +/- 12 vs. 38 +/- 20% (mean +/- sd), respectively. Both groups showed considerable interindividual variability, though serial analyses within individuals revealed consistency. Amounts of furosemide delivered into the urine after an intravenous dose correlated significantly to that after an oral dose implying that the interindividual variability is not caused primarily by variability in absorption in either group. Overall, disposition kinetics of furosemide did not differ between groups. Because of heterogeneity of renal and cardiac function among the patients, we were able to demonstrate correlations of plasma and renal clearance of furosemide with renal function; in turn, renal function correlated with left ventricular ejection fraction. Consequently, some patients had changes in furosemide disposition, but, for the most part, differences in response to furosemide were caused by abnormal responses to, rather than changed handling of the diuretic.

In vitro studies on the hydrolysis of frusemide in gastrointestinal juices

To elucidate a possible explanation for a relatively low bioavailability, the hydrolysis of frusemide in gastrointestinal juices was studied in vitro at concentrations likely to be present in vivo. Between 1.0 and 4.4% of the frusemide molecules were hydrolyzed to 4-chloro-N-furfuryl-5-sulphamoyl-antranilic acid (CSA) after 1 h at 37 degrees C in gastric juices. The rate of hydrolysis was inversely connected to pH. No fall in frusemide concentration was observed and no CSA was found in duodenal juices after 4 h at 37 degrees C. In three buffer solutions with the same pH as three gastric juices frusemide was hydrolyzed to CSA at a lower rate than in the gastric juices (pH 1.2, P less than 0.15;pH 1.4, P less than 0.001; pH 1.6, P less than 0.001). The solubility of frusemide was significantly higher in gastric juice from two fasting subjects (83-104 mg l-1) than in buffer solutions with the same pH (52-58 mg 1-1). The solubility of frusemide was significantly increased (by 40-50%) in gastric juice obtained after pentagastrin stimulation compared with its solubility in the mixed gastric secretion obtained after fasting. The binding of frusemide to macromolecules was 28.0 +/- 9.7% in ventricular secretion after fasting while it was 1.4 +/- 2.6% in the fluid obtained after pentagastrin stimulation. It is concluded that a hydrolysis of frusemide in the stomach prior to absorption cannot explain the relatively low bioavailability of the drug observed after oral intake.

The individual variation in pharmacokinetics and pharmacodynamics of furosemide in young normal male subjects

Following a 24 h control period in the ward 80 mg furosemide was injected intravenously to ten young healthy, male volunteers. The serum clearance of furosemide (Cls) was between 140 and 201 ml min-1 and on the average the renal clearance was 60% of Cls. During the initial 30 min period a maximum additional excretion rate of sodium of 3.3 mmol min-1 was reached at an excretion rate of 0.8 mg furosemide min-1. A marked initial drop in creatinine clearance (Clcr) was noted and Clcr(24 h) showed an average decrease of 12% after the drug administration. The serum concentration of potassium was decreased at 1 and 2 h after the injection and of sodium from 2 h and on. The concentration of albumin in serum increased by 3% (P less than 0.05) already after 5 min. After 2 h a maximum increase of 14% was reached. After 8 min diastolic blood pressure was increased by 13% (P less than 0.05), whereas systolic blood pressure reached a significant decrease gradually (7% after 3 h).