STUDIES ON ETHACRYNIC ACID IN PATIENTS WITH REFRACTORY EDEMA

The clinical pharmacology of ethacrynic acid

Ethacrynic acid (Edecrin) is a loop diuretic that produces a prompt and profound diuresis. The primary action of ethacrynic acid is the inhibition of the activity of the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle. The onset of action is usually within 30 minutes after an oral dose and within 5 minutes after an intravenous injection. After oral administration, peak diuretic effect occurs in about 2 hours and the effect lasts about 6-8 hours. After intravenous administration, peak diuretic effect occurs within 30 minutes and the diuretic effect is virtually completed in 2-4 hours. The bioavailability of ethacrynic acid approximates 100%, with maximal blood level between 40 and 92 minutes. The elimination half-life has been reported to be less than 1 hour, but highly variable (average 30 minutes with a range of 12-160 minutes). Intravenous ethacrynic acid has a prompt venous dilatory effect and immediately relieves symptoms of pulmonary congestion, before a diuresis can occur. Ethacrynic acid is effective in all types of edema whether there is clinical acidosis, alkalosis, or electrolyte imbalance. Most side effects of ethacrynic acid can be attributed to its effectiveness (volume depletion); however, it may cause metabolic alkalosis that is preventable by KCl replacement. Ethacrynic acid has ototoxic effect that occasionally results in temporally or permanent deafness. Despite limitations, ethacrynic acid has been employed in the treatment of congestive heart failure and other edematous states, especially in patients allergic to sulfa-containing drugs because all the other loop diuretics have a sulfa moiety.

Ethacrynic acid butyl-ester induces apoptosis in leukemia cells through a hydrogen peroxide mediated pathway independent of glutathione S-transferase P1-1 inhibition

Ethacrynic acid (EA), a glutathione S-transferase inhibitor and diuretic agent, inhibits cell growth and induces apoptosis in cancer cells. To improve the activities, the structure of EA has been modified, and it has been shown that EA esters had an increased cell growth inhibitory ability compared with nonesterified analogue. EA butyl-ester (EABE) was synthesized, and its apoptosis induction ability was studied. The efficacy of EABE was compared with that of EA, and the mechanisms of action were studied in HL-60 leukemia cells. EABE exhibited greater cell growth inhibitory and apoptosis induction abilities than did EA. EABE-induced apoptosis in HL-60 cells correlated with increased levels of reactive oxygen species, the death receptor 5 (DR5), and caspase activation and decreased levels of the mitochondrial membrane potential. Pretreatment with antioxidants, either N-acetylcysteine or catalase, completely blocked EABE-induced apoptosis, H2O2 accumulation, and up-regulation of DR5 levels. RG19, a subclone of Raji cells stably transfected with a GSTpi expression vector, and K562 cells with high endogenous GSTP1-1 activity were less sensitive to EABE-induced apoptosis. EABE was more rapidly taken up than EA by HL-60 cells as determined by high-performance liquid chromatography (HPLC) measurements of intracellular concentrations. These results suggest that (a) H2O2 production is a mediator of EABE and EA-induced apoptosis; (b) GSTP1-1 plays a negative role in EABE and EA-induced apoptosis; and (c) the activity of EABE is greater than EA due to its more rapid entry into cells.

Gene-Based Deafness Research: Ion Transport and Hearing

The cochlea is a sensory organ that converts physical (sound) stimulation into electrical signals. This process is fundamentally and substantially based upon the ion transport system. Here, I summarize the physiological and molecular biological aspects of transporters, channels and receptors expressed in the cochlea. With reference to these findings, recent advances in genetic research on hereditary deafness are discussed.

Molecular and clinical implications of loop diuretic ototoxicity

Recent advances in molecular biology have been applied to inner ear research. Loop diuretic ototoxicity has been suggested, but not proven, to share a common mechanism with diuretic effects on renal tubules. The discovery of the molecular nature of the Na-K-2Cl cotransporter in the cochlea provided a better understanding of loop diuretic ototoxicity. In this review, we describe clinical reports of loop diuretic ototoxicity and other information obtained by physiological, biochemical and morphological investigations related to the mechanism sensitive to loop diuretics. Based on recent evidence for the molecular nature of the Na-K-2Cl cotransporter expressed in the mammalian cochlea, the underlying mechanisms of ototoxicity induced by loop diuretics are described.

Acute renal failure

Acute renal failure (ARF) is common among critically ill patients and renal dysfunction is often associated with the multisystem organ failure syndrome. The mortality of ARF remains high but animal data indicate that prevention and early treatment may decrease the morbidity and mortality. This review defines ARF based on urine volume, laboratory parameters, and clinical presentation. The pathophysiology of prerenal, postrenal, and intrinsic ART are differentiated and diagnostic criteria provided. Preventive therapy, supportive care, and proposed treatments are outlined. Studies examining the prevention and treatment of ARF in animal models and trials in humans are evaluated. Mannitol 0.5-1 g/kg, furosemide 0.5-1 mg/kg initially, and dopamine 1-5 micrograms/kg/min are effective in preventing or decreasing the severity of ARF in animal models. In humans these drugs are effective at maintaining urine output in various clinical situations and converting oliguria to nonoliguria in some patients; however, increased survival has not been adequately proven as of yet. Dialysis and experimental therapy are briefly discussed.

Comparative ototoxicity of furosemide and piretanide

The purpose of these studies was to compare the ototoxicity of piretanide to that of furosemide in the chinchilla. Chinchillas weighing 400 to 700 g were anesthetized with ketamine plus pentobarbital. Endocochlear potential (EP) was measured continuously by the round window approach using glass microelectrodes. Piretanide or furosemide injected through a jugular vein catheter in adults range from 10-100 mg/kg. Little or no change in EP was noted with doses below 15 mg/kg of either diuretic. The overall pattern of decline of EP was rather similar in piretanide-treated and furosemide-injected animals, and it was interesting to find that the dose-ototoxicity response curve for piretanide was similar to that for furosemide. The diuretic effect of equal ototoxic doses of either diuretic was equivalent. Both diuretics cause a decrease of endocochlear potential when applied locally to the round window membrane of the chinchilla as well as by systemic administration. These findings suggest that piretanide and furosemide have approximately the same propensity for ototoxicity.

Oral piretanide in chronic renal failure

1 The effects of high doses of piretanide, a new diuretic agent chemically related to frusemide and bumetanide were evaluated in twelve patients with severe chronic renal insufficiency (creatinine clearance below 25 ml/min). 2 Patients received either 30 mg or 60 mg piretanide orally after a water load of 11. Urine volume and the excretion of electrolytes, creatinine, urea and uric acid were measured over the subsequent 24 h. 3 Piretanide produced an effective diuresis and natriuresis in these patients, its action being broadly similar to those of bumetanide and frusemide observed in previous studies.

A survey of the effects of loop diuretics on the zonulae occludentes of the perilymph-endolymph barrier by freeze fracture

The acute (30 min) effects of the loop diuretics piretanide, ethacrynic acid, bumetanide, furosemide, and azosemide, and the chronic (8 days) effects of furosemide and bumetanide on the zonulae occludentes (tight junctions) of the perilymph-endolymph barrier in the stria vascularis and in Reissner's membrane of the basal cochlear turns were studied by freeze-fracture. Quantitative analysis of their effects indicated that the structural integrity of the barrier was modified by either as increase or a decrease in the number, depth, and density of the strands of the tight junctions of the strial marginal cells. Only azosemide appeared to modify the tight junctions between the epithelial cells of Reissner's membrane, but it had little effect on the strial junctions. The tight junctions between the basal cells of the stria appeared to be the least affected by the various loop diuretics, although piretanide appeared to increase randomly the intercellular spaces lying between the strands.

The pharmacology of ototoxic drugs

This article briefly reviews the nature of the toxic effects of drugs on the inner ear and the incidence of ototoxic side effects in man. There follows a more detailed discussion of the most important groups of ototoxic drugs which are identified as the aminoglycoside antibiotics, the "loop" diuretics, quinine and chloroquine, the salicylates and some antitumour drugs. Attention is drawn to the synergistic interaction between aminoglycoside antibiotics and "loop" diuretics and the predisposition to ototoxicity if the drugs are given to subjects with renal impairment. The comparative ototoxicological potential of individual aminoglycosides is discussed and their toxic effects on the kidney and the neuromuscular junction summarized. The importance of an understanding of the pharmacokinetics of aminoglycosides both in relation to toxicity and the rational control of therapy is emphasized.

Ultrastructural histopathology in a case of human ototoxicity due to loop diuretics

The temporal bones of a patient who suffered sudden deafness and ataxia after administration of both furosemide and ethacrynic acid, were prepared for light and electron microscopy. There was no loss of hair or supporting cells. However, some hair cells, in both the vestibular neuroepithelium and the organ of Corti, particularly in the basal turn, were more densely staining and more granular than normal. Membrane whorls also were common within mitochondria of such cells. The endoplasmic reticulum of some spiral ganglion cells was dilated. The major cytologic changes were found in the stria vascularis of the cochlea and dark cell areas of the vestibular system. There was marked dilatation of the intercellular fluid spaces, consistent with the biochemical observation that loop diuretics interfere first with enzyme systems responsible for fluid transport within the inner ear.

Muzolimine: a new high-ceiling diuretic suitable for patients with advanced renal disease

Muzolimine was administered by mouth to 24 patients with creatinine clearances ranging from 4 to 28 ml/min to treat oedema or hypertension, or both. In four of these 24 patients muzolimine was given after intravenous high-dose frusemide had been unsuccessful. Muzolimine significantly increased urine volume and excretions of sodium, chloride, and potassium ions. Its diuretic efficacy was further shown by a mean reduction in body-weight of 8% and by the disappearance of oedema in all affected patients, even those refractory to intravenous frusemide. No rebound phenomenon was observed after the drug was stopped. Mean blood pressure was reduced in all hypertensive patients. Blood pressure was restored to normal in five out of seven patients treated with muzolimine alone and 10 out of 11 in whom muzolimine had been added to previously unsatisfactory antihypertensive treatment. Muzolimine was well tolerated by all patients. Muzolimine appears to be the diuretic of choice when treating patients with advanced renal disease.

Evidence for intracochlear impedance changes following ethacrynic acid administration

The effects of intra-arterial 30-, 40-, and 50-mg/kg doses of ethacrynic acid upon cochlear function in guinea pigs were studied for periods of three to five hours. Cochlear potentials recorded in the first turn included the endocochlear potential, whole nerve response, cochlear microphonics, and summating potentials in scala media, scala tympani, and scala vestibuli. Evidence of organ of Corti damage at 50 mg/kg was found in addition to electrical impedance changes in the cochlear membranes at all dose levels.

The effects of ethacrynic acid upon the potassium concentration in guinea pig cochlear fluids

After i.v. injection of 50 mg/kg ethacrynic acid (EA), potassium concentration in the endolymph (Ke+) measured with K+-specific microelectrodes decreases by 10 mM at the most and endocochlear potential falls to negative values. Potassium concentration in the perilymph (Kp+) generally does not change, but sometimes a transient decrease in Kp+ level of about 0.5 mM was observed, presumably due to the electrogenic effect of the time-related decrease of the endocochlear potential. When anoxia is induced approximately 120 min after EA administration Ke+ slowly decreases. The decrease in Ke+ 50 min after the arrest of ventilation is smaller when compared with the Ke+ anoxic decrease without preceding EA administration. The endocochlear potential, which falls to negative values during anoxia after EA administration, does not return to the zero level as in the case when only anoxia is applied. Similarly, during anoxia, which follows EA administration, the perilymphatic Ke+ concentration increases more slowly than in the case when only anoxia is introduced. It is assumed from the results that EA abolishes activity of the positive electrogenic K+ pump and reduces the passive permeability of the walls of the cochlear duct to the potassium ions.

Changes of the stria vascularis induced by ethacrynic acid

Histological changes in the stria vascularis of guinea pigs after the injection of ethacrynic acid (50 mg/kg) were investigated using a transmission electron microscope and a scanning electron microscope. The changes in permeability in the stria vascularis was also observed using horseradish peroxidase as a tracer. The pathological changes originating in endothelial cells of stria blood vessels and intermediate cells spread into the marginal cells and basal cells. The most remarkable changes were observed one hour after the injection of ethacrynic acid. Subsequently, recovery began in the cells around the blood capillaries and was most complete 3--4 hours after the injection. It is presumed that the strial damages by the ethacrynic acid are caused not only by the direct effect of this drug on the strial cells but also by the disturbances of blood flow and permeability of the capillaries.

Acute renal failure in the neonate

With advances in diagnostic technology, the diagnosis of renal failure from prerenal and renal causes is being made more frequently. With better clinical understanding of etiologic causes, early prevention and diagnostic and therapeutic measures can be taken. Proper and controlled use of fluids, calories, and drugs is essential. Because of its relative ease, peritoneal dialysis is usually preferred over hemodialysis when renal failure cannot be handled more conservatively. Although the incidence of renal failure has apparently increased with the advent of neonatal intensive care, survival rates are increasing and the potential for prevention is better.

Ototoxic interactions of ethacrynic acid and streptomycin

Various aminoglycoside antibiotics and potent diuretics are known to depress cochlear and vestibular function. Several clinical and research studies suggest that the drugs administered together produce enhanced ototoxicity. The present series of experiments determines the depressive effects of ethacrynic acid and streptomycin, alone or in combination, upon the vestibular system of the cat. The changes in function, when quantified, indicate an addition, rather than a potentiation of toxicity, and suggest different sites of action.

Diuretics: mechanism of action and clinical application

Despite the bewildering number of diuretics available to the physician, these drugs can be divided into 4 main groups, characterised by their site of action on sodium reabsorption in the kidney. Drugs acting on the ascending limb of the loop of Henle have a powerful but short acting diuretic effect; they include frusemide, ethacrynic acid and bumetanide. The benzothiadiazines and related compounds have a moderate diuretic action spread over a longer period, whilst the potassium-sparing diuretics, triamterene, amiloride and spironolactone, have only a weak diuretic effect but a marked ability to diminish urinary potassium excretion. The fourth group is made up of miscellaneous substances which function as vasodilator or osmotic agents. The pathogenesis of oedema formation in heart failure is outlined and a logical approach to treatment suggested. Duiretics are being increasingly used in the treatment of non-oedematous states, in particular hypertension, diabetes insipidus and hypercalciuria; their exact role in pregnancy and acute renal failure remains controversial. Side-effects can be related to their effect on electrolyte excretion and include hypokalaemia, hyponatraemia, hyperkalaemia and hyperuricaemia. The incidence of disturbed carbohydrate tolerance in previously normal individuals is low. Other less common side-effects are also discussed.

Ethacrynic acid, furosemide, and vestibular caloric responses

Ethacrynic acid and furosemide, saluretic diuretics of high potency, have been shown to be toxic to the auditory system. In the present study, it was found that the depressant effect of ethacrynic acid extends into the vestibular system. Cats, given a 20 mg/kg intravenous bolus of ethacrynic acid, exhibited a 50% greater reduction of the vestibular nystagmus response to a caloric irrigation than control animals receiving normal saline. This was true for all three major parameters of the recorded nystagmus response (degrees of slow phase displacement, frequency of beats and slow phase velocity). This effect was very rapid in onset (present at 30 seconds postinjection), and quite transient (approaching normal by 20 minutes postinjection). Furosemide did not produce the vestibular depression. Nystagmus responses observed after injection of furosemide (at 20 mg/kg) were not significantly different from those of control animals receiving normal saline. Possible mechanisms of action and therapeutic implications of the ethacrynic acid-induced vestibular depression are discussed.

High dosage metolazone in chronic renal failure

Metolazone is a modified quinazolinesulphonamide and in a dose of between 4 and 7.5 mg is an effective diuretic in man with normal renal function. Fourteen patients with non-oedematous stable chronic renal failure (creatinine clearance ranging from 1.2 to 12 ml/min) were given metolazone in doses ranging from 20-150 mg. A noticeable increase in urine flow and sodium excretion occurred, free water clearance increased, and there was a small but significant increase in potassium excretion. No side effects were noted.

Bumetanide: potent new "loop" diuretic

Bumetanide, a pharmacologically new diuretic, was evaluated in 27 subjects. Its onset of action was within 30 minutes with a peak at 90 minutes and a total duration of action of about 270 minutes. In a controlled study in oedematous patients it was equipotent with frusemide at one-fortieth the molar dosage and did not differ from frusemide with regard to its pattern of electrolyte excretion. On continuous oral administration for eight days it produced effective diuresis with minimal alteration in biochemical and haematological status. The only adverse effect was gastric discomfort in one patient.