RESUMO
STUDY OBJECTIVE: To assess the efficacy and safety of intravenous (IV) chlorothiazide versus oral metolazone when added to loop diuretics in patients with acute decompensated heart failure (ADHF) and loop diuretic resistance. DESIGN: Retrospective cohort study. SETTING: Large urban academic medical center. PATIENTS: Adults admitted with ADHF between 2005 and 2015 who had loop diuretic resistance, defined as administration of IV furosemide at a dose of 160 mg/day or higher (or an equivalent dose of IV bumetanide), during hospitalization, and who then received at least one dose of IV chlorothiazide (88 patients) or oral metolazone (89 patients) to augment diuresis. MEASUREMENTS AND MAIN RESULTS: The primary efficacy end point was a change in 24-hour net urine output (UOP) from before to after thiazide-type diuretic administration, and the study was designed to test for the noninferiority of metolazone. Safety end points included changes in renal function and electrolyte concentrations. The mean dose of IV loop diuretic therapy (in IV furosemide equivalents) at baseline (before thiazide-type diuretic administration) was higher in the chlorothiazide group (mean ± SD 318.9 ± 127.7 vs 268.4 ± 97.6 mg/day in the metolazone group, p=0.004), but net UOP was similar (mean ± SD 877.0 ± 1189.0 ml in the chlorothiazide group vs 710.6 ± 1145.9 ml in the metolazone group, p=0.344). Mean doses of chlorothiazide and metolazone were 491 ± 282 mg and 5.8 ± 3.5 mg, respectively. Following thiazide-type diuretic administration, net UOP improved to a similar degree (2274.6 ± 1443.0 ml vs 2030.2 ± 1725.0 ml in the chlorothiazide and metolazone groups, respectively, p=0.308). For the primary efficacy end point, metolazone met the threshold for noninferiority by producing a net UOP of 1319.6 ± 1517.4 ml versus 1397.6 ± 1370.7 ml for chlorothiazide (p=0.026 for noninferiority). No significant differences in renal function were observed between the groups. Although hypokalemia was more frequent in the chlorothiazide group (75% with chlorothiazide vs 60.7% with metolazone, p=0.045), no significant differences in the rates of severe hypokalemia or other electrolyte abnormalities were observed between the groups. CONCLUSION: Oral metolazone was noninferior to IV chlorothiazide for enhancing net UOP in patients with ADHF and loop diuretic resistance and was similarly safe with regard to renal function and electrolyte abnormalities. Given the significant cost disparity between the two agents, these findings suggest that oral metolazone may be considered a first-line option in this patient population.
Assuntos
Clorotiazida/uso terapêutico , Diuréticos/uso terapêutico , Insuficiência Cardíaca/tratamento farmacológico , Metolazona/uso terapêutico , Doença Aguda , Administração Intravenosa , Administração Oral , Adulto , Idoso , Clorotiazida/efeitos adversos , Estudos de Coortes , Resistência a Medicamentos , Feminino , Humanos , Masculino , Metolazona/efeitos adversos , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
Little is known about the residues that control the binding and affinity of thiazide-type diuretics for their protein target, the renal Na(+)-Cl(-) cotransporter (NCC). Previous studies from our group have shown that affinity for thiazides is higher in rat (rNCC) than in flounder (flNCC) and that the transmembrane region (TM) 8-12 contains the residues that produce this difference. Here, an alignment analysis of TM 8-12 revealed that there are only six nonconservative variations between flNCC and mammalian NCC. Two are located in TM9, three in TM11, and one in TM12. We used site-directed mutagenesis to generate rNCC containing flNCC residues, and thiazide affinity was assessed using Xenopus laevis oocytes. Wild-type or mutant NCC activity was measured using (22)Na(+) uptake in the presence of increasing concentrations of metolazone. Mutations in TM11 conferred rNCC an flNCC-like affinity, which was caused mostly by the substitution of a single residue, S575C. Supporting this observation, the substitution C576S conferred to flNCC an rNCC-like affinity. Interestingly, the S575C mutation also rendered rNCC more active. Substitution of S575 in rNCC for other residues, such as alanine, aspartate, and lysine, did not alter metolazone affinity, suggesting that reduced affinity in flNCC is due specifically to the presence of a cysteine. We conclude that the difference in metolazone affinity between rat and flounder NCC is caused mainly by a single residue and that this position in the protein is important for determining its functional properties.
Assuntos
Diuréticos/metabolismo , Linguado/metabolismo , Simportadores de Cloreto de Sódio/genética , Simportadores de Cloreto de Sódio/metabolismo , Tiazidas/metabolismo , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Western Blotting , Humanos , Metolazona/metabolismo , Camundongos , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação/fisiologia , Oócitos/metabolismo , Ligação Proteica , Biossíntese de Proteínas , Coelhos , Ratos , Simportadores de Cloreto de Sódio/química , Especificidade da Espécie , Xenopus laevisRESUMO
Most of the missense mutations that have been described in the human SLC12A3 gene encoding the thiazide-sensitive Na(+)-Cl(-) cotransporter (TSC, NCC, or NCCT), as the cause of Gitelman disease, block TSC function by interfering with normal protein processing and glycosylation. However, some mutations exhibit considerable activity. To investigate the pathogenesis of Gitelman disease mediated by such mutations and to gain insights into structure-function relationships on the cotransporter, five functional disease mutations were introduced into mouse TSC cDNA, and their expression was determined in Xenopus laevis oocytes. Western blot analysis revealed immunoreactive bands in all mutant TSCs that were undistinguishable from wild-type TSC. The activity profile was: wild-type TSC (100%) > G627V (66%) > R935Q (36%) = V995M (32%) > G610S (12%) > A585V (6%). Ion transport kinetics in all mutant clones were similar to wild-type TSC, except in G627V, in which a small but significant increase in affinity for extracellular Cl(-) was observed. In addition, G627V and G610S exhibited a small increase in metolazone affinity. The surface expression of wild-type and mutant TSCs was performed by laser-scanning confocal microscopy. All mutants exhibited a significant reduction in surface expression compared with wild-type TSC, with a profile similar to that observed in functional expression analysis. Our data show that biochemical and functional properties of the mutant TSCs are similar to wild-type TSC but that the surface expression is reduced, suggesting that these mutations impair the insertion of a functional protein into the plasma membrane. The small increase in Cl(-) and thiazide affinity in G610S and G627V suggests that the beginning of the COOH-terminal domain could be implicated in defining kinetic properties.
Assuntos
Alcalose/genética , Proteínas de Transporte/genética , Hipopotassemia/genética , Nefropatias/genética , Deficiência de Magnésio/sangue , Deficiência de Magnésio/genética , Mutação de Sentido Incorreto , Receptores de Droga/genética , Simportadores , Animais , Diuréticos/administração & dosagem , Relação Dose-Resposta a Droga , Feminino , Humanos , Transporte de Íons , Cinética , Metolazona/administração & dosagem , Camundongos , Mutagênese Sítio-Dirigida , Oócitos , Sódio/farmacocinética , Simportadores de Cloreto de Sódio , Membro 3 da Família 12 de Carreador de Soluto , Síndrome , Xenopus laevisRESUMO
The thiazide-sensitive Na(+)-Cl(-) cotransporter (TSC) is the major pathway for salt reabsorption in the apical membrane of the mammalian distal convoluted tubule. When expressed in Xenopus laevis oocytes, rat TSC exhibits high affinity for both cotransported ions, with the Michaelis-Menten constant (K(m)) for Na(+) of 7.6 +/- 1.6 mM and for Cl(-) of 6.3 +/- 1.1 mM, and Hill coefficients for Na(+) and Cl(-) consistent with electroneutrality. The affinities of both Na(+) and Cl(-) were increased by increasing concentration of the counterion. The IC(50) values for thiazides were affected by both extracellular Na(+) and Cl(-). The higher the Na(+) or Cl(-) concentration, the lower the inhibitory effect of thiazides. Finally, rTSC function is affected by extracellular osmolarity. We propose a transport model featuring a random order of binding in which the binding of each ion facilitates the binding of the counterion. Both ion binding sites alter thiazide-mediated inhibition of transport, indicating that the thiazide-binding site is either shared or modified by both Na(+) and Cl(-).
Assuntos
Proteínas de Transporte/metabolismo , Receptores de Droga/metabolismo , Inibidores de Simportadores de Cloreto de Sódio/metabolismo , Inibidores de Simportadores de Cloreto de Sódio/farmacologia , Sódio/metabolismo , Simportadores , Animais , Bendroflumetiazida/metabolismo , Bendroflumetiazida/farmacologia , Sítios de Ligação/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacos , Proteínas de Transporte/genética , Cloretos/metabolismo , Cloretos/farmacologia , Diuréticos , Hidroclorotiazida/metabolismo , Hidroclorotiazida/farmacologia , Concentração de Íons de Hidrogênio , Concentração Inibidora 50 , Cinética , Metolazona/metabolismo , Metolazona/farmacologia , Microinjeções , Modelos Biológicos , Oócitos/efeitos dos fármacos , Oócitos/metabolismo , Concentração Osmolar , Politiazida/metabolismo , Politiazida/farmacologia , Ratos , Receptores de Droga/genética , Sódio/farmacologia , Simportadores de Cloreto de Sódio , Membro 3 da Família 12 de Carreador de Soluto , XenopusRESUMO
A decreased response to the loop diuretic furosemide develops within a few doses in young infants. We tested the hypothesis that the use of the thiazide-like diuretic metolazone, in combination with furosemide, would inhibit water and electrolyte reabsorption and overcome pharmacologic tolerance to furosemide alone. Infants with bronchopulmonary dysplasia of similar gestational and postnatal ages were randomly assigned to one of three groups. Group 1 (n = 6) received furosemide (1 mg/kg per dose) intravenously every 24 hours for a total of five doses. Group 2 (n = 8) received the same treatment as group 1, but in addition metolazone (0.2 mg/kg per dose) was given enterally with doses 3 and 4 of furosemide. Group 3 (n = 8) received metolazone (0.2 mg/kg per dose) enterally every 24 hours for five doses. Urine was collected before the first diuretic dose and throughout the study for determination of the urine flow rate; urinary excretion of sodium, chloride, and potassium; and creatinine clearance. Urinary flow rate and urinary sodium and chloride excretion increased after the first dose in all groups. In the infants treated with either furosemide or metolazone, urinary flow rate and urinary and chloride excretion returned to baseline values after the last three doses. In contrast, when furosemide was administered with metolazone, urinary flow rate and urinary excretion of sodium, chloride, and potassium were greater than the values for baseline and for the previous dose, as well as for the corresponding doses of furosemide in group 1 and metolazone in group 3. Tolerance to furosemide (group 1) and metolazone (group 3) appeared to be explained by compensatory increased sodium and chloride reabsorption without changes in creatinine clearance. We conclude that the administration of metolazone with furosemide enhances diuresis, natriuresis, and chloruresis and overcomes the rapid development of tolerance to furosemide in infants with bronchopulmonary dysplasia by blocking the compensatory increase in renal sodium and chloride absorption.