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Diuretics stimulate H+ secretion in turtle urinary bladder.

The effect of various diuretics on H+ secretion was studied in the isolated short-circuited urinary bladder of the turtle. Mucosal (urinary) chlorothiazide stimulated H+ secretion promptly, from 1.33 +/- 0.24 to 3.03 +/- 0.25 mueq/h (P less than 0.001). The effect was rapidly reversible upon washout of the drug, H+ returning to control levels, 1.37 +/- 0.26 mueq/h (P less than 0.001). Similar effects were observed with mucosal hydrochlorothiazide and mucosal ethacrynic acid/cysteine. Stimulation of H+ secretion occurred in the presence or the absence of exogenous CO2, in the presence or absence of mucosal Na+ and during inhibition of Na+ transport by ouabain. There was no stimulation of H+ secretion by uncomplexed ethacrynic acid or by mucosal furosemide. The nondiuretic sulfonamide, sulfasoxizole, and the nonsulfonamide buffer, borate, had no effect on H+ SECRETION. These observations indicate that the stimulatory effect of diuretics on H+ secretion is not related to active sodium transport, transepithelial electrical potential, or the buffering capacity of the drugs. Since the transepithelial pH gradient at which active H+ secretion was abolished was identical for chlorothiazide-treated tissues (2.68 pH U) as for control tissues (2.65 pH U, NS), the data suggest that the protonmotive force of the H+ pump was unaffected by the diuretic. This observation, plus the rapid onset and reversibility of the drugs, is consistent with an effect on the mucosal membrane to increase H+ conductance (K). The findings raise the possibility that direct enhancement of renal H+ secretion may play a role in the metabolic alkalosis induced by some diuretics.

Animals↗

Diuretic agents and glucose reabsorption.

Acetazolamide, chlorothiazide, ethacrynic acid and furosemide were infused to glucose loaded dogs. Glucose reasorption was unchanged after acetazolamide and chlorothiazide. Ethacrynic acid depressed glucose reabsorption significantly. Furosemide caused a modest decrease in glucose reabsorption which was not significant when the control values were compared with the last three experimental values, but which was significant when all experimental values are analyzed. These diuretics most likely depress glucose reabsorption by acting on the proximal tubule, though a distal effect cannot be excluded.

Absorption↗

Duration of effect of different diuretics.

Twenty-four patients with hypertension were treated with chlorothiazide, chlorthalidone, and frusemide. Each diuretic had a significant and similar antihypertensive effect. After cessation of the administration of diuretics, the antihypertensive effect persisted for a longer time with chlorthalidone than with the other two drugs. The full antihypertensive effect of chlorthalidone and chlorothiazide was still present 24 hours after the administration of the drugs was ceased, and the full effect of chlorthalidone was present 72 hours after the administration of the drug was ceased. Side effects related to a rapid diuresis were more common with frusemide. The study indicated that chlorthalidone could be given at 48-hour or 72-hour intervals, and that other diuretics may be given once daily to exert their full antihypertensive action.

Aged↗

Hyponatraemia and hypokalaemia due to indapamide.

OBJECTIVES: To review Australian adverse drug reaction reports describing hyponatraemia and hypokalaemia attributed to indapamide and compare the characteristics of the patients with those in Australian reports implicating two other diuretic products (hydrochlorothiazide and amiloride hydrochloride; chlorothiazide). DESIGN: Descriptive analysis using reports from the database of the Adverse Drug Reactions Advisory Committee (ADRAC). MAIN OUTCOME MEASURES: Numbers of reports of hyponatraemia and hypokalaemia; proportion of such reports in total reports of adverse reactions to each drug; severity of electrolyte disturbances. RESULTS: Between August 1984 and September 2000, 84 Australian reports of hyponatraemia and 87 reports of hypokalaemia, in which indapamide was the sole suspected drug, were submitted to ADRAC. Most reports involved an indapamide dose of 2.5 mg daily. There was a significantly greater proportion of reports of hyponatraemia with indapamide and with the hydrochlorothiazide and amiloride combination than with chlorothiazide; hypokalaemia was significantly more common for indapamide than for the other two drugs. Of the 87 reports of hypokalaemia with indapamide, 35 patients also had hyponatraemia. For all three drugs, at least 80% of reports of hyponatraemia were in people aged 65 or over, and electrolyte disturbance was most commonly reported in elderly women. CONCLUSIONS: Hyponatraemia and hypokalaemia have been described in 20.9% and 21.7%, respectively, of reports to ADRAC in which indapamide was the sole suspected drug. The electrolyte disturbances can be severe.

Amiloride↗

Tubular sodium handling in cold-exposed man during inhibition of distal tubular reabsorption of sodium.

In 8 healthy volunteers in stable water diuresis, exposed to cold at +15 degrees C for 60 min, changes in excretion and tubular reabsorption of sodium and osmoles were studied by the clearance technique during inhibition of distal tubular sodium reabsorption following chlorothiazide infusion at 2 mg/kg/hr. Inhibition of distal tubular sodium reabsorption by chlorothiazide increased fractional sodium excretion to 6.5% and fractional excretion of osmoles to 7.5% of the filtered amount. The superimposed cold exposure did not further increase these figures, despite a significant cold-induced increase in arterial blood pressure.

Adult↗

Pharmacological characterization of lithium reabsorption in the rat.

The effects of furosemide, chlorothiazide and acetazolamide upon fractional lithium excretion (FELi) were studied in acutely lithium-loaded rats. Changes in FELi were compared with the fractional excretions of sodium FENa and calcium FECa. Furosemide and acetazolamide, given separately, produced large and substantially equivalent increases in FELi. Responses of FENa and FECa to acetazolamide were much less than to furosemide. Chlorothiazide, alone or in combination with the other agents, produced moderate increases in FENa, modest increases in FECa and essentially no change in FELi. When furosemide was superimposed upon a previously established acetazolamide diuresis, the response in FELi was additive to that from acetazolamide alone. These results suggest that lithium reabsorption occurs at nephron sites primarily affected by acetazolamide and furosemide in the rat and that a significant amount of lithium reabsorption may take place in the loop of Henle. Acetazolamide, in combination with furosemide, appeared to depress renal tissue lithium accumulation.

Absorption↗

Pharmacologic probing of mercuric chloride-induced renal dysfunction in the neonatal rat.

Acetazolamide, furosemide, chlorothiazide and amiloride are pharmacologic agents that act primarily in the proximal tubule, loop of Henle, early distal tubule and late distal tubule and collecting duct, respectively. These diuretic agents were used to evaluate the functional integrity of discrete segments of the nephron in the neonatal rat following treatment with a known nephrotoxicant. Six-day old rats were treated s.c. with the proximal tubule toxicant mercuric chloride (1 or 3.2 mg/kg) or saline. Twenty-four hours later, when evidence of mercury nephrotoxicity is detectable, creatinine clearance and the fractional excretion of water and various components of the filtrate were determined using a 2-hr clearance period immediately after injection of a diuretic. The effects of mercury (3.2 mg/kg) were consistent with its ability to cause acute renal failure and proximal tubular necrosis and also indicated an apparent disruption of the cycling of urea in the nephron. A decrease in the fractional excretion of water, combined sodium and potassium and total osmotic solutes indicated that the diuretic response to acetazolamide was markedly attenuated in the mercuric chloride-treated pups whereas the responses to furosemide, chlorothiazide and amiloride were not altered by mercury treatment. Results from this study illustrate the specificity of these diuretics as pharmacologic probes of mercuric chloride induced renal dysfunction and, therefore, support their usefulness as tools in the investigation of renal developmental toxicity.

Acetazolamide↗

Profound pharmacologic inhibition of renal tubule sodium and water reabsorption in rats.

Vanadate, furosemide, chlorothiazide, acetazolamide, and amiloride were infused concomitantly into conscious rats to determine the extent to which renal sodium reabsorption can be inhibited. The animals were maintained in exact fluid balance despite exorbitant urine flow rates by intravenous infusion of an isotonic salt solution sufficient to keep body weight constant. In maximally effective doses vanadate, furosemide, chlorothiazide, acetazolamide, and amiloride increased sodium excretion to an amount equal to 69% of the filtered load. Together with isotonic extracellular fluid expansion equal to 7% of body weight, these pharmacologic agents increased sodium excretion to an amount equal to 83.7% of the filtered load, a level of sustained sodium excretion that has not been reported previously in mammals. These studies demonstrate that tubular sodium and water reabsorption can be profoundly inhibited in vivo by drugs that diminish sodium and water transport in proximal as well as in distal tubules.

Acetazolamide↗

Liquid chromatographic determination of methyldopa and methyldopa-thiazide combinations in tablets: collaborative study.

A reverse phase liquid chromatographic method for the determination of methyldopa, methyldopa-hydrochlorothiazide, and methyldopachlorothiazide in tablets was collaboratively studied by 8 laboratories. Each collaborator received 20 samples that included drug substance, synthetic and commercial tablet compositions. The overall repeatability and reproducibility standard deviations for commercial tablets were 1.11 and 1.75% for methyldopa, 0.96 and 1.62% for chlorothiazide, and 1.21 and 2.15% for hydrochlorothiazide, respectively. The overall recoveries of methyldopa, chlorothiazide, and hydrochlorothiazide added to synthetic tablets were 100.78, 100.70, and 101.34%, respectively. The method has been adopted official first action.

Chlorothiazide↗

Diuretics and small intestinal lymph flow in the dog.

Simultaneous measurements of thoracic duct lymph flow and small intestinal lymph flow were carried out in mongrel dogs after the administration of mannitol, ethacrynic acid, furosemide and chlorothiazide. Thoracic duct lymph flow increased only after injection of mannitol. Intestinal lymph flow increased after injection of all diuretics except chlorothiazide. Furthermore, mannitol produced simultaneous increases in thoracic duct and intestinal lymph flows. The durations of response of the increased lymph flows from each lymph channel produced by mannitol were statistically identical. The durations of increased intestinal lymph flows observed with each drug were: 40+/-3 (S.E.), 43+/-2 and 38+/-2 minutes for mannitol, ethacrynic acid and furosemide, respectively. Mean arterial blood pressures and inferior vena cava pressures did not change from the control to the experimental state in any animal studied. Similarly measurements of serum and lymph sodium, potassium and protein concentrations were unchanged from the control to the experimental state. These studies demonstrate that mannitol simultaneously increases thoracic duct lymph flow as well as intestinal lymph flow. Secondly, the results suggest that the increases in thoracic duct lymph flow after ethacrynic acid and furosemide administration, observed in previous studies arose primarily from the small intestine.

Animals↗

Pharmacologic probing of amphotericin B-induced renal dysfunction in the neonatal rat.

Acetazolamide, furosemide, chlorothiazide, and amiloride are pharmacologic agents that act primarily in the proximal tubule, loop of Henle, early distal tubule and late distal tubule and collecting duct, respectively. In order to investigate the renal pathophysiology induced by amphotericin B, these diuretic agents were used as probes of discrete segments of the nephron in the neonatal rat. Six-day-old rats were treated with amphotericin B (20 mg/kg, sc) or the vehicle. Twenty-four hours later, when evidence of amphotericin B-induced renal pathophysiology is detectable, the responses to the diuretic agents were assessed in a 2-hr clearance test, during which creatinine clearance (CCr) and the fractional excretion (FE) of water and various components of the filtrate were determined. Amphotericin B induced alterations in basal function including azotemia, hypostenuria, increases FE water and electrolytes, and a decreased FE urea (although CCr was normal). The diuretic responses to furosemide, chlorothiazide, and amiloride were not altered, indicating that the functional viability of the respective tubular segments was not affected by amphotericin B treatment. Although the maximal response to acetazolamide also remained unchanged in amphotericin B-treated pups, there was an attenuation in the half-maximal response, reflecting an apparent shift in the sensitivity to acetazolamide. All of the diuretic agents elicited an increase in urea excretion in amphotericin B-treated pups such that FE urea approached control values. Additionally, the magnitude of this increase was proportional to the magnitude of the increase in water excretion induced by each diuretic agent. These results indicate a disruption of urea recycling in the nephron and support the hypothesis that amphotericin B acts to increase the permeability of the distal tubule to urea. Thus, results from this study demonstrate the usefulness of pharmacologic agents as functional probes in the characterization of specific components of renal pathophysiology.

Amphotericin B↗

Solubility of drugs in the presence of gelatin: effect of drug lipophilicity and degree of ionization.

The solubility of seven drugs (nitrofurantoin, chlorothiazide, phenobarbital, prednisolone, griseofulvin, diazepam and piroxicam) in the absence and presence of gelatin was measured, at three different pH values (3.7, 5.0 and 7.0) at 37 degrees C. Drugs studied had different physicochemical properties (log P, pK(a), aqueous solubility) and their solubility in presence of 0.1 and 0.5% (w/v) hydrolyzed (and in some cases common) gelatin was estimated. Results show that the solubility of all drugs is significantly enhanced, especially in the presence of 0.5% gelatin. This gelatin-induced enhancement in drug solubility is higher in the pH in which acidic drugs are less ionized, especially for the less lipophilic acidic drugs (nitrofurantoin, chlorothiazide). In all cases, drug solubility in presence of gelatin is correlated with their aqueous solubility. Therefore, the established relationships between aqueous and gelatin solubility can be employed to derive an estimate of the drug solubility in presence of gelatin once its aqueous solubility is known. With the exception of piroxicam which is highly ionized and phenobarbital which is relatively soluble, there seems to be a tendency for larger gelatin-induced increases in solubility as drug lipophilicity increases or aqueous solubility decreases.

Chemistry, Pharmaceutical↗

Synthesis, saludiuretic, and antihypertensive activity of 6,7-disubstituted 1(2H)- and 3,4-dihydro-1(2H)-phthalazinones.

The synthesis of the isomeric series 6-chloro-7-sulfamoyl- and 7-chloro-6-sulfamoyl-1(2H)-phthalazinones (1 and 2) and 6-chloro-7-sulfamoyl- and 7-chloro-6-sulfamoyl-3,4-dihydo-1(2H)-phthalazinones (3 and 4), combining structural features characteristic to furosemide and hydralazine, is described, the mechanism of the formation of 1 and 2 is discussed, and their structure-activities relationships are studied. Preliminary screening in the rat shows that series 1 and 3 exhibit diuretic and saluretic activity similar to that of chlorothiazide with, however, Na+/K+ ratios more favorable than chlorothiazide and furosemide. The compounds of series 2 and 4 are practically inactive. All four series show initial antihypertensive activity lower than that of hydralazine. However, compounds 1a, 1c, and 4a show a higher activity at 8 and/or 24 h after administration and thus may offer a unique combination of a "loop" diuresis with direct long-acting peripheral vasodilating effects.

Animals↗

Interaction of benzothiadiazides with human serum albumin studied by dialysis and spectroscopic methods.

The interaction of a series of benzothiadiazides with human serum albumin (HSA) was investigated by equilibrium dialysis (ED) and spectroscopic methods including circular dichroism (CD). The primary binding site of benzothiadiazides was designated site II, the diazepam site on the HSA molecule, as indicated by displacement experiments using different site-selective probes. Tyrosine and lysine amino acid residues were probably involved in the binding site of these compounds to HSA. Both electrostatic and hydrophobic interactions were found to play a role in the binding of these compounds to HSA. Among the compounds tested, chlorothiazide had the highest affinity (K1 = 5.5 x 10(4) M-1, K2 = 5.8 x 10(3) M-1). The primary binding affinity of the compounds for HSA was of the order: chlorothiazide > cyclopenthiazide > polythiazide > ethiazide > trichlormethiazide = methyclothiazde > hydrochlorothiazide. Binding was insensitive to the N-B transition of HSA. The binding site is proposed to consist of a cationic site on the surface of the HSA molecular with a hydrophobic crevice to accommodate the aromatic ring of the compounds. Positions 3 and 7 of the benzothiadiazide molecule is thought to affect the binding affinity to HSA.

Benzothiadiazines↗

Renal magnesium handling: new insights in understanding old problems.

Recent research has provided new concepts in our understanding of renal magnesium handling. Although the majority of the filtered magnesium is reabsorbed within the loop of Henle, it is now recognized that the distal tubule also plays an important role in magnesium conservation. Magnesium absorption within the cTAL segment of the loop is passive and dependent on the transepithelial voltage. Magnesium transport in the DCT is active and transcellular in nature. Many of the hormonal (PTH, calcitonin, glucagon, AVP) and nonhormonal (magnesium-restriction, acid-base changes, potassium-depletion) influences that affect magnesium transport within the cTAL similarly alter magnesium absorption within the DCT. However, the cellular mechanisms are different. Actions within the loop affect either the transepithelial voltage or the paracellular permeability. Influences acting in the DCT involve changes in active transcellular transport either Mg2+ entry across the apical membrane or Mg2+ exit from the basolateral side. These transport processes are fruitful areas for future research. An additional regulatory control has recently been recognized that involves an extracellular Ca2+/Mg(2+)-sensing receptor. This receptor is present in the basolateral membrane of the TAL and DCT and modulates magnesium and calcium conservation with elevation in plasma divalent cation concentration. Further studies are warranted to determine the physiological role of the Ca2+/Mg(2+)-sensing receptor, but activating and inactivating mutations have been described that result in renal magnesium-wasting and hypermagnesemia, respectively. All of these receptor-mediated controls change calcium absorption in addition to magnesium transport. Selective magnesium control is through intrinsic control of Mg2+ entry into distal tubule cells. The cellular mechanisms that intrinsically regulate magnesium transport have yet to be described. Familial diseases associated with renal magnesium-wasting provide a unique opportunity to study these intrinsic controls. Loop diuretics such as furosemide increase magnesium excretion by virtue of its effects on the transepithelial voltage thereby inhibiting passive magnesium absorption. Distally acting diuretics, like amiloride and chlorothiazide, enhance Mg2+ entry into DCT cells. Amiloride may be used as a magnesium-conserving diuretic whereas chlorothiazide may lead to potassium-depletion that compromises renal magnesium absorption. Patients with Bartter's and Gitelman's syndromes, diseases of salt transport in the loop and distal tubule, respectively, are associated with disturbances in renal magnesium handling. These may provide useful lessons in understanding segmental control of magnesium reabsorption. Metabolic acidosis diminishes magnesium absorption in MDCT cells by protonation of the Mg2+ entry pathway. Metabolic alkalosis increases magnesium permeability across the cTAL paracellular pathway and stimulates Mg2+ entry into DCT cells. Again, these changes are likely due to protonation of charges along the paracellular pathway of the cTAL and the putative Mg2+ channel of the DCT. Cellular potassium-depletion diminishes the voltage-dependent magnesium absorption in the TAL and Mg2+ entry into MDCT cells. However, the relationship between potassium and magnesium balance is far from clear. For instance, magnesium-wasting is more commonly found in patients with Gitelman's disease than Bartter's but both have hypokalemia. Further studies are needed to sort out these discrepancies. Phosphate deficiency also decreases Mg2+ uptake in distal cells but it apparently does so by mechanisms other than those observed in potassium depletion. Accordingly, potassium depletion, phosphate deficiency, and metabolic acidosis may be additive. The means by which cellular potassium and phosphate alter magnesium handling are unclear. Research in the nineties has increased our understanding of renal magnesium transport and regulation, but there are many in

Absorption↗

Pulmonary function and electrolyte balance following spironolactone treatment in preterm infants with chronic lung disease: a double-blind, placebo-controlled, randomized trial.

OBJECTIVE: To study the effect of spironolactone on dietary electrolyte supplementation, pulmonary function, and electrolyte balance in premature infants with chronic lung disease. STUDY DESIGN: A double-blind, randomized, and placebo-controlled trial was designed to study two groups of low birth weight infants with chronic lung disease at Pennsylvania Hospital. The placebo group received chlorothiazide and a placebo, and the spironolactone group received chlorothiazide and spironolactone during the 2-week study period. A two-tailed t-test was used to determine equivalence between the two groups. RESULTS: Pulmonary compliance, resistance and tidal volume, serum sodium and potassium, and FIO2, were not statistically different between the two groups. The need for sodium and/or potassium chloride did not differ between the two groups, nor did the quantity of each salt. CONCLUSION: The addition of spironolactone did not reduce the requirement for supplemental electrolytes, nor did it improve pulmonary mechanics or electrolyte balance.

Chronic Disease↗

Chronic potassium depletion and sensitivity to tubocurarine.

The effect of low potassium diets with and without deoxycorticosterone (DOCA), furosemide, chlorothiazide, or ethacrynic acid on sensitivity of isolated guinea pig lumbrical nerve-muscle preparations to d-tubocurarine was examined. The ED50 of d-tubocurarine was found to fall as the potassium level was lowered by dietary restriction. Addition of DOCA or furosemide was without effect while chlorothiazide reduced and ethacrynic acid enhanced the effect of diet alone. Acute restoration of potassium levels of 5.9 mM reversed considerably, but not completely, the effect of chronic depletion. Thus, a patient suffering from chronic potassium depletion would be expected to require a decreased dose of d-tubocurarine, and although acute replacement of potassium preoperatively would tend to return the dose requirement toward normal, such reversal might not be complete.

Animals↗

Evidence against a contribution by Na(+)-Cl- cotransport to chloride accumulation in rat arterial smooth muscle.

1. Chloride accumulation into rat saphenous arterial smooth muscle has been examined using chloride-sensitive microelectrodes, to assess the contribution of Na(+)-Cl-cotransport. 2. Bumetanide (10 microM) produced a fall in intracellular chloride ([Cl-]i), and a hyperpolarization of membrane potential (Em). However, [Cl-]i remained above the equilibrium level predicted from the membrane potential, indicating a residual accumulation. 3. Replacement of extracellular sodium with N-methyl-D-glucamine or choline caused a fall in [Cl-]i similar to that observed with bumetanide, but the hyperpolarization of Em was larger. In Na(+)-free media, bumetanide had no effect. [Cl-]i remained significantly above equilibrium. 4. In the presence of bumetanide, chlorothiazide produced a further dose-dependent fall in [Cl-]i, and hyperpolarization of Em. However, although [Cl-]i fell more than with bumetanide alone, it remained significantly above equilibrium. Metolazone was without effect at 100 microM. 5. In the presence of bumetanide, ethacrynic acid and N-ethyl maleimide caused a dose-dependent hyperpolarization of Em and a fall in [Cl-]i to equilibrium. 6. The third inward chloride pump in rat saphenous arterial smooth muscle appears not to be a form of Na(+)-Cl- cotransport. The potency series of thiazide diuretic action (acetazolamide > chlorothiazide > metolazone) differed significantly from that published for Na(+)-Cl- cotransport, and there is no sodium dependence.

Animals↗