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PubMed2004

Effect of the calcimimetic NPS R-467 on furosemide-induced nephrocalcinosis in the young rat.

BACKGROUND: Furosemide induces nephrocalcinosis in both humans and animals. We showed previously that parathyroidectomy protected against the development of furosemide-induced nephrocalcinosis in young rats, indicating a possible role for parathyroid hormone (PTH) in its pathogenesis. Calcimimetic agents such as NPS R-467 are potent and selective agonists at the calcium-sensing receptor in parathyroid glands and inhibit PTH secretion. METHODS: To determine whether NPS R-467 could, like parathyroidectomy, prevent furosemide-induced nephrocalcinosis, we studied 35 6-week-old male Sprague-Dawley rats, divided into five groups. Group A served as control, group B received intraperitoneally furosemide (40 mg/kg), groups C, D, and E received furosemide and NPS R-467 intraperitoneally at doses of 10, 20, and 40 micromol/kg, respectively, daily for 8 days. During the last 3 days, animals were placed in metabolic cages for measurement of urine output, food, and water intake. Blood and kidneys were collected on day 8, 60 to 90 minutes after the last doses. Kidney calcium content was measured and nephrocalcinosis scoring (0 to 5) was assessed histologically. RESULTS: Furosemide increased urine output and fluid intake, and decreased body weight gain similarly in all groups. Serum PTH levels (mean +/- SD) were significantly higher in furosemide-treated control animals (276 +/- 226 pg/mL vs. 64 +/- 21 pg/mL); NPS R-467 induced a dose-dependent decrease in PTH levels (52 +/- 51 pg/mL, 18 +/- 7 pg/mL, and 13 +/- 3 pg/mL in groups C, D, and E, respectively). Plasma Ca(2+) was slightly, but significantly lower in all three NPS R-467 treated groups (5.1 +/- 0.4 mg/dL, 4.8 +/- 0.3 mg/dL, and 4.5 +/- 0.3 mg/dL in groups C, D, and E, respectively) compared to 5.7 +/- 0.1 mg/dL and 5.5 +/- 0.2 mg/dL in groups A and B, respectively. Furosemide treatment induced a substantial increase in kidney calcium content (1819 +/- 664 microg/g dry weight vs. 126 +/- 26 microg/g dry weight) and nephrocalcinosis scoring (5.0 +/- 0.0 vs. 0.0 +/- 0.0). Treatment with NPS R-467 ameliorated the furosemide-induced increase in kidney calcium content (673 +/- 312 microg/g, 361 +/- 188 microg/g, and 563 +/- 291 microg/g) and nephrocalcinosis scoring (2.2 +/- 1.2, 0.7 +/- 0.8, and 1.0 +/- 1.2) in groups C, D, and E, respectively. CONCLUSION: The calcimimetic agent NPS R-467 prevents the development of hyperparathyroidism and attenuates nephrocalcinosis in the furosemide-treated young rat.

Aniline Compounds↗

PubMed1981

Effect of furosemide on parathyroid hormone stimulated guinea pig renal adenylate cyclase and thyrotrophin and fluoride stimulated human thyroid adenylate cyclase.

The effect of furosemide 8 X 10(-4) mol/l an 8 X 10(-5) mol/l on parathyroid hormone stimulated adenylate cyclase was studied in renal tissue slices from guinea pigs. Furosemide caused a dose-dependent inhibition of the effect of parathyroid hormone on production of cyclic AMP, without having any significant effect on the basal cyclic AMP production. Furosemide in similar concentrations did not inhibit the stimulatory effect of thyrotrophin and fluoride in human thyroid homogenates suggesting that furosemide is not an universal inhibitor of adenylate cyclase and that the inhibition is not caused by a direct action of furosemide on the adenylate cyclase enzyme. Furosemide did not interfere with binding of cyclic AMP to cyclic AMP binding protein kinase from rabbit muscle. The results indicate that furosemide exerts an inhibitory influence either upon binding of parathyroid hormone to renal receptors or upon transmission of impulse from receptor to adenylate cyclase. The inhibitory influence of furosemide on parathyroid hormone action in kidney could explain the value of furosemide in the acute treatment of hypercalcaemia, but also suggest that chronic treatment with furosemide might interfere with normal calcium metabolism.

Adenylyl Cyclases↗

PubMed1990

Activation of furosemide-sensitive K+ fluxes in myocytes by ouabain and recovery from metabolic inhibition.

Modulation of transsarcolemmal K+ flux mediated by the furosemide-sensitive K(+)-Cl- (or Na(+)-K(+)-Cl-) cotransport carrier was studied in cultured chick embryo ventricular cells. We defined at least three distinct K+ efflux pathways: 1) a Ba2(+)-sensitive efflux component, probably reflecting K+ movement through K+ channels; 2) a furosemide-sensitive component, reflecting K(+)-Cl- cotransport; and 3) a component insensitive to both Ba2+ and furosemide. With respect to K+ influx, there were 1) a ouabain-sensitive K+ uptake presumably mediated by Na(+)-K(+)-adenosinetriphosphatase and 2) a furosemide-sensitive K+ uptake. The effects of elevation of intracellular calcium concentration ([Ca2+]i) on Ba2+ and furosemide-sensitive K+ flux pathways were studied. Elevation of [Ca2+]i had minor effects on Ba2(+)-sensitive K+ flux. However, elevation of [Ca2+]i produced by exposure to ouabain for 60 min activated a furosemide-sensitive 42K+ efflux and a ouabain-resistant, furosemide-sensitive 42K+ influx. The activation of K+ influx, caused by an increase in [Ca2+]i, was completely inhibited by ATP depletion (produced by exposure to ouabain and metabolic inhibitors simultaneously) and was partially inhibited by the calmodulin inhibitor W7. Activation of the furosemide-sensitive K+ flux was also produced by washout of metabolic inhibitors, a condition in which ATP resynthesis occurs in the presence of an increased [Ca2+]i. Activation of furosemide-sensitive K+ fluxes by exposure to ouabain or washout of metabolic inhibitors caused a net K+ loss, which accounts in part for the cell shrinkage noted during recovery from metabolic inhibition in previous studies. These results suggest that [Ca2+]i and intracellular ATP concentration are important in the regulation of furosemide-sensitive K+ flux in these cells, perhaps via the involvement of a Ca2(+)-calmodulin-dependent protein kinase.

Adenosine Triphosphate↗

PubMed1993

Acute effects of furosemide on blood pressure in functionally anephric, volume-expanded rats.

The hypotensive effect of loop diuretics is primarily mediated by a decrease in extracellular fluid volume that follows the intense diuresis. In the present study we investigated whether furosemide (1.25 mg/kg i.v.) can acutely lower blood pressure independently of its diuretic action. The experiments were performed in four groups of male Wistar rats: (a) rats in which furosemide was administered after bilateral ligation of renal vessels and saline (0.9% NaCl at a rate of 0.25 ml/min to a final volume of 1% of body weight) infusion; (b) rats in which furosemide was injected after bilateral ligation of ureters and saline infusion; (c) rats pretreated with indomethacin (3 mg/kg i.p. for 4 days) in which furosemide was injected after bilateral ligation of ureters and saline infusion; (d) sham-operated rats with intact kidneys. All the groups were compared with appropriate time controls. After furosemide injection, heart rate and blood pressure were serially recorded for 30 min by plethysmography. Hematocrit, plasma 6-keto-prostaglandin F1 alpha levels and plasma renin activity were measured at baseline and 20 min after furosemide injection. No change in blood pressure followed furosemide administration in rats with ligation of the renal vessels. Conversely, furosemide induced a rapid and significant fall in blood pressure associated with a significant increase in heart rate in rats with ligation of the ureters and rats with intact kidneys. Indomethacin pretreatment prevented the furosemide-induced decrease in blood pressure in rats with ligation of the ureters. Hematocrit and plasma 6-keto-prostaglandin F1 alpha levels were not affected by furosemide in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

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

BACKGROUND: Ten chronic heart failure patients were studied on three occasions in randomized double-blind fashion to compare the acute hemodynamic, neurohormonal, and renal sodium-handling responses to 1 mg captopril versus 25 mg captopril, both in the absence of loop diuretic therapy and during furosemide-stimulated natriuresis. METHODS AND RESULTS: Compared with placebo, 1 mg captopril caused nonsignificant decreases in mean arterial pressure and circulating angiotensin II level and had no effect on glomerular filtration rate as determined by 51Cr-EDTA elimination. Captopril (25 mg) produced marked suppression of serum angiotensin II with or without oral furosemide (both p less than 0.002), a marked decrease in mean arterial pressure (p less than 0.001) that was accentuated by furosemide (p less than 0.00001), and a decrease in glomerular filtration rate (p = 0.0007). No difference from placebo in renal sodium excretion was noted with either 1 or 25 mg captopril in the absence of furosemide. In contrast, while 25 mg captopril caused slight attenuation of the natriuretic response to furosemide, 1 mg captopril significantly enhanced furosemide-induced natriuresis (p less than 0.05). No correlation was found in our patients between the natriuretic effect of furosemide and either absolute mean arterial pressure or change in mean arterial pressure during the furosemide phase of each study session. This suggests that blood pressure is not the important factor mediating the divergent renal responses to furosemide of the two captopril dosage regimens. CONCLUSIONS: We propose that in the face of furosemide-induced postglomerular vasodilatation in chronic heart failure, captopril at a starting dose of 1 mg (but not 25 mg) preserves enough circulating angiotensin II to maintain efferent arteriolar tone and thus glomerular filtration, while offsetting the antinatriuretic renal tubular effects of angiotensin II.

Aged↗

PubMed1997

Direct vascular effects of furosemide in humans.

BACKGROUND: In humans, hemodynamic changes observed within minutes after systemic administration of furosemide are often referred to as direct vasoactivity. However, these immediate changes do not per se imply a direct vascular effect. We examined the genuine direct vascular effects of furosemide on the human forearm vascular bed and dorsal hand vein. METHODS AND RESULTS: Forearm blood flow in response to infusion of increasing dosages of furosemide into the brachial artery was recorded by venous occlusion plethysmography. Local plasma concentrations of furosemide reached a maximum of 234+/-40 microg/mL during the highest infused dose but did not significantly affect the ratio of flow in the infused/noninfused arms. Venous distensibility of a dorsal hand vein was measured with a linear variable differential transformer. During precontraction with norepinephrine, five increasing dosages of furosemide (1 to 100 microg/min) were administered locally. Additional experiments using local administration of indomethacin or N(G)-monomethyl-L-arginine (L-NMMA) were carried out to determine whether effects were dependent on local prostaglandin or nitric oxide synthesis, respectively. Also, the effects of systemic administration of furosemide were examined. Local administration of furosemide led to a dose-dependent venorelaxation of 18+/-6% at the first to 72+/-16% at the last dose. Indomethacin almost completely abolished furosemide-induced venorelaxation, whereas L-NMMA had no effect. Systemic administration of furosemide resulted in a time-dependent increase of hand vein distensibility, reaching 45+/-11% after 8 minutes. CONCLUSIONS: Furosemide does not exert any direct arterial vasoactivity in the human forearm, even at supratherapeutic concentrations. In contrast, at concentrations estimated to be in the therapeutic range, we observed a dose-dependent direct venodilator effect on the dorsal hand vein that appears to be mediated by local vascular prostaglandin synthesis.

Adult↗

PubMed1974

A furosemide-sensitive cotransport of sodium plus potassium in the human red cell.

The influxes of Na(+) and K(+) into the human red cell appear to be interrelated. This relationship was investigated under conditions in which either Na(+) or K(+) concentration outside the cell was varied or one cation was replaced by Mg(2+), choline(+), or Li(+). The effects of furosemide on Na(+) and K(+) movements were studied in the presence of ouabain. When ouabain was present, Na(+) influx was higher with K(+) ions externally than with other cations externally. Furosemide inhibited this K(+)-stimulated Na(+) influx, but it had little effect when K(+) was absent. Ouabain-insensitive K(+) influx was stimulated two-fold by external Na(+) compared with other cations. Furosemide also inhibited this stimulation, but it had little effect when Mg(2+) or choline(+) replaced external Na(+). Thus it was confirmed that synergism exists between the ouabain-insensitive influxes of Na(+) and K(+) and it was demostrated that furosemide inhibits this cooperative effect. The ouabain-insensitive influx of both K(+) and Na(+) showed a hyperbolic "saturating" dependence on the external concentration of the transported cation. Furosemide therefore eliminates a saturable component of influx of each cation. The net uptake of Na(+) in the presence of ouabain was stimulated by K(+) ions. A similar effect was observed with red cells, in which Li(+) replaced nearly all the internal Na(+) plus K(+) ions. In these cells, net Na(+) uptake was stimulated by external K(+), and net K(+) uptake was stimulated by external Na(+). Furosemide inhibited this mutual stimulation of net cation entries. The inhibitory action of furosemide was not limited to inward flux and net movement of Na(+) and K(+). Furosemide also inhibited the efflux of Na(+) into Na(+)-free media and the efflux of K(+) into K(+)-free media. It appeared, therefore, that the action of furosemide was not explained by inhibition of exchange diffusion. These data are consistent with an ouabain-insensitive transport process that facilitates the inward cotransport of Na(+) plus K(+)-ions, and that can produce a net movement of both ions. Although this process under some conditions mediates an equal bidirectional flux of both Na(+) and K(+), it cannot be defined as exchange diffusion. The contransport process is inhibited by furosemide.

Biological Transport, Active↗

PubMed1980

The effect of chronic furosemide administration on urinary calcium excretion and calcium balance in growing rats.

The study was designed to determine the calciuretic effect of furosemide and its impact upon calcium balance during chronic (25 days) furosemide administration to growing rats. Experiments were performed on 18 six-wk-old rats. Nine animals received furosemide, and 9 served as controls. The administration of furosemide in a dose of 40 mg resulted in a significant increase in calcium excretion in the treated group; urinary calcium excretion almost doubled that of the controls during the first 24-hr collection (3.74 +/- 0.44 mg in the treated animals compared with 1.90 +/- 0.15 mg in the controls; P less than 0.05). The average daily urinary calcium excretion during each of four subsequent 6-day periods remained approximately three-fold higher in animals which received furosemide compared with controls (P less than 0.001 for each 6-day period). The furosemide-induced increase in urinary calcium excretion did not diminish with time. Sodium excretion did not significantly increase either acutely or chronically in response to furosemide. Daily urinary volume increased approximately 40 to 60% in the furosemide-treated group compared with that of the controls (P less than 0.001). The cumulative calcium balance in the control group exceeded by 7% that of the furosemide-treated animals [2696.3 +/- 20.8 mg versus 2518.6 +/- 20.1 mg (P less than .001]. The findings indicate that distal nephron compensatory mechanisms effecting sodium conservation following furosemide do not result in similar conservation of calcium. Calcium balance may be deleteriously affected.

Administration, Oral↗

PubMed2004

Aqueous solubilization of furosemide by supramolecular complexation with 4-sulphonic calix[n]arenes.

The solubilization of the practically water insoluble drug furosemide by guest:host inclusion complexation with 4-sulphonic calix[n]arenes has been reported. The 4-sulphonic calix[n]arenes are water-soluble phenolic cyclooligomers that form inclusion complexes with neutral molecules. The solubility of furosemide in acidic (pH < 4) aqueous solutions containing increasing concentrations of the calixarenes was determined at 30 degrees C and the concentration of furosemide in solution was determined by HPLC. Results showed that the molecular size of the 4-sulphonic calix[n]arenes and the concentration of the calix[n]arenes significantly influenced the increase in the solubility of furosemide. 4-Sulphonic calix[6]arene improved the solubility of furosemide the most (+/-104%) followed by 4-sulphonic calix[8]arene (+/-84-102%), while 4-sulphonic calix[4]arene increased the solubility of furosemide the least (+/-73-81%). The increase in furosemide solubility afforded by the calixarenes was most probably the result of the incorporation of the non-polar portions of the furosemide molecule into the non-polar cavities of the calixarenes similar to furosemide:cyclodextrin complexes. The driving force for this interaction was the reduction in the non-polar-water interfacial surface area when the furosemide (guest) molecules were inserted into the 4-sulphonic calix[n]arenes (host).

Benzenesulfonates↗

PubMed2001

Effects of albumin/furosemide mixtures on responses to furosemide in hypoalbuminemic patients.

Hypoalbuminemic patients often have sufficient fluid accumulation to mandate diuretic therapy but are often resistant to diuresis. Studies have suggested that hypoalbuminemia itself impairs delivery of effective amounts of diuretic agent into the urine, the site of action. Therefore, administration of mixtures of albumin and loop diuretics may enhance responses. Thirteen patients with biopsy-proven cirrhosis and ascites (age, 51.2 +/- 8.1 yr; Child-Pugh score, 8.5 +/- 1.0; serum albumin concentration, 3.0 +/- 0.6 g/dl) were studied in this randomized crossover study. Sodium balance was maintained throughout the study with a metabolic diet. All patients received spironolactone, but administration of all other diuretic agents was discontinued. Each patient received all of the following four treatments intravenously: (1) 40 mg of furosemide, (2) 25 g of albumin, (3) 40 mg of furosemide and 25 g of albumin premixed ex vivo, and (4) 40 mg of furosemide and 25 g of albumin infused simultaneously into different arms. Responses were assessed by measuring urinary sodium excretion and relating the urinary furosemide excretion rate to the sodium excretion rate. Additionally, the pharmacokinetics of furosemide were assessed. Furosemide pharmacokinetics were similar for all treatment arms. Albumin alone had negligible diuretic effects. Neither albumin regimen increased the response to furosemide. Moreover, the relationship between the urinary furosemide excretion rate and the sodium excretion rate was unaffected by albumin. In conclusion, albumin failed to enhance the diuretic effects of furosemide in cirrhotic patients with ascites. Therefore, the coadministration of albumin and furosemide for the treatment of cirrhosis, and likely other hypoalbuminemic conditions, should not be used clinically.

Adult↗

PubMed1996

Role of the kidneys in the metabolism of furosemide: its inhibition by probenecid.

The site where furosemide is metabolized and the location where probenecid reduces furosemide metabolism remain poorly defined. The liver appears to play a minor role, and there is indirect evidence suggesting that the kidneys could be responsible for the metabolism of furosemide. To assess the role of the kidneys in the metabolism of furosemide, its intravenous kinetics have been studied in control and anephric rabbits, after the ligation of the renal pedicles. Two additional groups of rabbits, control and anephric, have received probenecid before the administration of furosemide. In the control group, the total clearance of furosemide was 18.65 +/- 1.01 mL/ min per kg; urinary and metabolic clearances of furosemide were 7.95 +/- 0.65 and 10.70 +/- 1.11 mL/min per kg, respectively. In anephric rabbits, total clearance was reduced by 85% to 2.69 +/- 0.26 mL/min per kg (P < 0.001), secondary to the abolition of furosemide renal excretion and to the reduction in metabolic clearance from 10.70 +/- 1.11 to 2.69 +/- 0.26 mL/min per kg (P < 0.001). The pretreatment with probenecid reduced the total clearance of furosemide by 80%, to 3.62 +/- 0.24 mL/min per kg (P < 0.001), because of a reduction of 90 and 75% in urinary and metabolic clearances, respectively. The administration of probenecid to anephric rabbits did not reduce further the metabolic clearance. It is concluded that the kidneys are responsible for 85% of furosemide total clearance, either via excretion (43%) or biotransformation (42%), and that probenecid inhibits both processes.

Animals↗

PubMed2000

Healthcare costs of patients with heart failure treated with torasemide or furosemide.

OBJECTIVE: To compare the direct healthcare costs of patients with congestive heart failure (CHF) prescribed torasemide (torsemide) or furosemide (frusemide). DESIGN AND SETTING: As part of a prospective, randomised, nonblind study, we assessed the effects of torasemide and furosemide on readmission to hospital in 193 patients treated for CHF at a US urban public healthcare system. We also calculated total direct healthcare costs for the 2 drugs. The perspective of the analysis was that of the healthcare system. Healthcare charge and utilisation data, demographic information, and health status data were obtained from an electronic database containing data for all patients treated within the healthcare system. PATIENTS AND PARTICIPANTS: Upon admission to the hospital, patients were eligible if they had evidence of left ventricular systolic dysfunction, were at least 18 years old, and were receiving furosemide. INTERVENTION: Inpatients were randomised to either torasemide or furosemide treatment for 1 year. MAIN OUTCOME MEASURES AND RESULTS: Patients treated with torasemide had fewer hospital admissions than those treated with furosemide [18 vs 34% for CHF (p = 0.013) and 38 vs 58% for any cardiovascular cause (p = 0.005)]. In the torasemide group, expected annual hospital costs per patient were lower for CHF admissions (by $US1054; 1998 values) and for all cardiovascular admissions (by $US1545) than in the furosemide group. Because the annual acquisition cost of torasemide was $US518 per patient higher than that of furosemide, the resulting net cost saving per patient was $US536 for CHF and $US1027 for all cardiovascular causes. Outpatient costs did not differ between treatment groups regardless of whether drug costs were considered. Total direct costs were $US2124 lower with torasemide than with furosemide (not statistically significant). CONCLUSIONS: Owing largely to reduced readmission to the hospital, the cost of inpatient care for patients with CHF is significantly lower with torasemide than with furosemide, despite the higher acquisition cost of torasemide. Treatment with torasemide resulted in a nonsignificant reduction in total direct costs (outpatient plus inpatient) compared with furosemide.

Adult↗

PubMed1989

[Effect of furosemide on the obstructed kidney].

The effect of furosemide on the obstructed kidney was studied in dogs. In control kidneys (n = 4) the renal blood flow (RBF) was increased transiently after intravenous infusion of 20 mg of furosemide; from 12.9 +/- 1.2 to 14.8 +/- 1.4 ml/min/kg.B.W. No change in the renal pelvic pressure was observed. Urine flow increased from 0.47 +/- 0.12 to 4.98 +/- 1.15 ml/min at 20 minutes after furosemide administration. Increases in the fractional fluid excretion rate (V/GFR), the fractional sodium excretion rate (FENa) and the fractional potassium excretion rate (FEK) were observed and the maximum values were obtained at 20 minutes after furosemide administration. In two-week unilateral incompletely obstructed kidneys (incomplete UUO; n = 5), RBF was lower than that of the control kidney, whereas a tendency of transient increase was also noticed after furosemide administration; from 8.4 +/- 1.9 to 10.5 +/- 2.3 ml/min/kg.B.W. The renal pelvic pressure increased immediately and transiently after furosemide infusion. Increase in the urine flow was significant, but the value was lower than that of control, and the maximum value was marked at 20 minutes after furosemide administration. V/GFR, FENa and FEK were also increased in incomplete UUO, but the peak values were lower than those of control. In two-week unilateral completely obstructed kidneys (complete UUO; n = 5), RBF was markedly decreased (3.14 +/- 0.38 ml/min/kg.B.W.), and no significant increase was noticed after furosemide administration. The renal pelvic pressure was gradually and continuously increased after furosemide infusion. The fractional excretion rate of pelvic urine components was variable. In particular, V/GFR was significantly increased 60 minutes after furosemide administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1999

Effect of furosemide on performance of Thoroughbreds racing in the United States and Canada.

OBJECTIVE: To determine the effect of furosemide on performance of Thoroughbreds racing on dirt surfaces at tracks in the United States and Canada. DESIGN: Cross-sectional study. ANIMALS: All Thoroughbreds (n = 22,589) that finished a race on dirt surfaces at tracks in the United States and Canada between June 28 and July 13, 1997 in jurisdictions that allowed the use of furosemide. PROCEDURE: Race records were analyzed by use of multivariable ANOVA procedures and logistic regression analyses to determine the effect of furosemide on estimated 6-furlong race time, estimated racing speed, race earnings, and finish position. Principal component analysis was used to create orthogonal scores from multiple collinear variables for inclusion in the models. RESULTS: Furosemide was administered to 16,761 (74.2%) horses. Horses that received furosemide raced faster, earned more money, and were more likely to win or finish in the top 3 positions than horses that did not. The magnitude of the effect of furosemide on estimated 6-furlong race time varied with sex, with the greatest effect in males. When comparing horses of the same sex, horses receiving furosemide had an estimated 6-furlong race time that ranged from 0.56 +/- 0.04 seconds (least-squares mean +/- SE) to 1.09 +/- 0.07 seconds less than that for horses not receiving furosemide, a difference equivalent to 3 to 5.5 lengths. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the pervasive use of furosemide and its apparent association with superior performance in Thoroughbred racehorses, further consideration of the use of furosemide and investigation of its effects in horses is warranted.

Age Factors↗

PubMed1992

Quantitative contribution of endogenous compounds and hypoalbuminemia in reducing the binding of furosemide in the plasma of newborn infants.

The protein binding of furosemide was studied in the plasma of newborn infants and adult subjects. Plasma consisted of two pools obtained from 25 newborns and adult subjects. The concentrations of albumin were 36.8 (newborn) and 48.3 g/l (adult). The unbound fraction of furosemide was 1.38 +/- 0.15 (adult) and 2.03 +/- 0.13% (newborn; p < 0.001). After extensive dialysis of the plasma, the unbound fraction of furosemide was 1.12 +/- 0.15 (adult) and 1.39 +/- 0.09% (newborn; p < 0.0001), suggesting that dialyzable endogenous compounds interfere with the binding of furosemide. The addition of human albumin to the newborn plasma to give a final albumin concentration of 48.3 g/l yielded an unbound fraction of furosemide of 1.63 +/- 0.08 (nondialyzed plasma) and 1.17 +/- 0.08% (dialyzed plasma; p < 0.0001). The addition of albumin to the dialyzed newborn plasma, to give a final albumin concentration similar to that in adult plasma, decreased the unbound furosemide to the level of the dialyzed adult plasma. The binding defect of furosemide in newborn plasma reflects either the effects of the endogenous inhibitors or of hypoalbuminemia. The intrinsic binding properties for furosemide of newborn dialyzed plasma are similar to those of dialyzed adult plasma. This consideration corroborates our previous results on the binding of furosemide and diazepam, salicylic acid and digitoxin to newborn and adult albumin. The displacement of furosemide by salicylic acid, tolbutamide and azapropazone is 70% greater in newborn than in adult plasma. The greater displacing effect is largely due to hypoalbuminemia.

Aging↗

PubMedDate not supplied

Effectiveness of furosemide in patients on peritoneal dialysis.

BACKGROUND: Residual renal function (RRF) is a marker for a good index of health and is associated with improved survival for individuals with end stage renal disease on peritoneal dialysis. As RRF declines with time on dialysis, fluid balance is more difficult to achieve. Urine output plays a vital role in fluid removal and it has been postulated that loop diuretics improve diuresis in peritoneal dialysis (PD) patients. The aim of this study is to evaluate our use of furosemide and its effect on diuresis in a home peritoneal dialysis program. METHODS: Sixty-one patients met inclusion criteria of having been on PD continuously for one year from their start date with complete 24-hour urine kinetics. Twenty patients were on furosemide and 41 patients were in the control group. Data for urine volume (UV), serum creatinine (SCr), total and residual creatinine clearance (CrCl(total) and CrCl(residual)), total and residual urea clearance (Kt/V(total) and Kt/V(residual)) and dry body weight were collected at baseline, six months and one year. The average change in UV CrCl(total), and Kt/V(total) from baseline at six and 12 months and the proportion of patients who developed anuria at one year were determined. RESULTS: UV declined in the furosemide and control groups at six months by an average of 78.00 +/- 445.2 mL/day and 105.5 +/- 401.8 mL/day (p=0.8) and at 12 months by 85.00 +/- 481.7 mL/day and 110.7 +/- 455.4 mL/day (p=0.8), respectively. CrCl declined in the furosemide and control groups at six months by an average of 5.55 +/- 20.4 mL/min and 4.52 +/- 29.0 mL (p=0.9), and at 12 months by 3.95 +/- 35.5 mL/min and 9.05 +/- 28.4 mL/min (p = 0.5) respectively. Kt/V increased by 0.0850 +/- 0.890 in the furosemide group and declined by 0.0456 +/- 0.614 in the control group at six months (p=0.5), but after 12 months, Kt/V declined in both the furosemide and control groups by 0.00400 +/- 0.565 and 0.162 +/- 0.558 (p=0.5) respectively. Only one patient (five per cent) in the furosemide group developed anuria after one year on PD, whereas nine patients (22%) in the control group became anuric (p=0.1). CONCLUSION: Furosemide did not have a statistically significant effect in either improving UV or preserving RRF in patients on PD for one year, but this study was not adequately powered to show an association. Although not statistically significant, fewer patients were anuric at one year in the furosemide group (five per cent versus 22%). Furosemide was not shown to be detrimental to either RRF or UV.

Adult↗

PubMed1990

Intratubular albumin blunts the response to furosemide-A mechanism for diuretic resistance in the nephrotic syndrome.

An attenuated response to loop diuretics is a frequent observation in the nephrotic syndrome. To determine if the presence of albumin in renal tubular fluid attenuates diuretic response in normal rats, in vivo loop segment microperfusion was performed in normal rats at 20 nl/min with perfusates containing 6.0 microM furosemide in the presence and absence of 3.8 microM albumin. Compared to loop segments perfused without diuretic (control), furosemide reduced (P less than .001) fractional chloride uptake from 56 +/- 2 to 34 +/- 2%. After addition of albumin to furosemide perfusate, fractional loop chloride reabsorption was 45 +/- 1%; a value greater (P less than .01) than that observed in furosemide perfused loop segments, but less (P less than .05) than that observed in control loop segments. Albumin added to perfusate in the absence of furosemide had no effect on fractional loop segment chloride uptake. Addition of 1.7 microM immunoglobulin G to furosemide perfusate failed to attenuate furosemide response. Absolute loop segment chloride reabsorption demonstrated a similar pattern. Tubule fluid perfusion rates determined in vivo and loop segment fluid reabsorption were equivalent in all groups. Thus, albumin in renal tubule fluid attenuates the effect of furosemide on loop segment chloride reabsorption in the rat. This blunted response presumably occurs because of a reduction in the amount of pharmacologically active drug due to albumin-furosemide binding. Consequently, albumin-furosemide binding in the renal tubule may contribute to the diuretic resistance in nephrotic syndrome.

Absorption↗

PubMed1988

Effect of cyclooxygenase inhibition on the pulmonary vasodilator response to furosemide.

Furosemide is a potent vasodilator of the systemic arterial and venous systems. The mechanism of vasodilatation, however, remains unclear. We investigated the vasodilatory effect of furosemide and its relation to endogenous prostaglandins (PGs). In the isolated canine lung lobe, furosemide significantly decreased mean pulmonary artery pressure. This effect was inhibited by indomethacin. Furosemide also attenuated the pulmonary vasoconstrictor response to the endoperoxide analog U46619 and PGF2 alpha. The pulmonary pressor response to a submaximal constrictor dose of arachidonic acid was significantly enhanced by furosemide, however, the pressor response to a maximal constrictor dose of arachidonic acid was attenuated, although not significantly. In animals pretreated with indomethacin, furosemide had no effect on the vascular response to PGF2 alpha, but the response to U46619 was significantly increased. Prostacyclin reduced pulmonary perfusion pressure and inhibited the pressor response to PGF2 alpha and U46619. Furosemide failed to alter inactivation of PGE2 on pulmonary lobe transit. We conclude that: 1) the vasodilatory activity of furosemide is mediated by increased production and not decreased metabolism of an endogenous cyclooxygenase product; 2) the effect of prostacyclin on vascular reactivity is similar to that of furosemide; and 3) local formation of prostacyclin by vascular tissue most likely mediates the vascular activity of furosemide.

Animals↗