Background: Hypomagnesemia can be caused by thiazide and thiazide-like diuretics that inhibit the renal NaCl cotransporter (NCC) expressed along the distal convoluted tubule (DCT). The mechanism is believed to be primarily induction of DCT atrophy that lowers Mg 2+ reabsorption through the TRPM6/7 channel. Inhibitors of the sodium-coupled glucose transporter 2 (SGLT2), normally used to treat diabetes, have been reported to increase plasma Mg 2+ in humans. We tested the hypothesis that the SGLT2 inhibitor empagliflozin (EMPA) suppresses hypomagnesemia induced by the thiazide-like diuretic metolazone (MET) and modulates expression of renal ion transport proteins. Methods: 64 male C57BL/6 mice were randomized into 4 groups of 16 mice (1: control, 2: MET, 3: EMPA, 4: MET+EMPA) and placed on a 0.08% Mg 2+ diet. For the entire study, mice in group 1 received no drugs, while mice in groups 3 & 4 were given MET (250 mg/kg diet) in their diet. From day 7 to day 28, EMPA (300 mg/kg diet) was added to the diets of the mice in groups 2 and 4 only. On day 28, 24-hour urine was collected and on day 29 mice were euthanized. Plasma and urine Mg 2+ and other electrolytes were measured. Kidneys were homogenized for Western blots for total NCC, phosphorylated NCC, and TRPM6 (expressed along DCT), and total NKCC2, phosphorylated NKCC2, γ-ENaC, α-ENaC, Calbindin, phosphorylated AQP2, total AQP2, NHE3, and NAPI2 (expressed in other segments). Results: Compared to controls, plasma Mg 2+ was significantly lower in MET mice and higher in EMPA mice; in MET+EMPA mice it was significantly higher than in MET mice and not different to controls, suggesting EMPA reversed MET-induced hypomagnesemia. Compared with control mice, plasma K + trended lower in MET mice. Plasma [TCO 2 ] was significantly higher in both MET mice and MET+EMPA mice than in controls and EMPA mice suggesting EMPA does not reverse MET-induced metabolic alkalosis. Consistent with strong diuretic effects, urine volume and urinary Na + , K + , and Mg 2+ excretion were higher in all drug groups compared with control. Compared with controls, abundances of total NCC, TRPM6, and calbindin were significantly lower in both MET and MET+EMPA mice but did not differ for EMPA mice, suggesting effects on other segments contribute to correction of hypomagnesemia. Abundance of total NKCC2 was significantly lower in MET mice compared with EMPA mice and controls, but did not differ from that of the MET+EMPA mice. Abundance of phosphorylated NKCC2 did not differ between groups. Uncleaved γ-ENaC was higher in EMPA mice but lower in MET and MET+EMPA mice. Abundance of phosphorylated AQP2 was significantly lower in MET-treated mice, and higher in EMPA mice; in MET+EMPA mice it did not differ from controls. Abundances of total AQP2, NHE3, and NAPI2 did not differ in any group compared with control mice. These data suggest that while EMPA may be a helpful approach to correct drug-induced hypomagnesemia in patients, it exerts complex effects on renal ion channels and transporters due to increased water and electrolyte excretion. American Heart Association 23EIA1037600 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Metolazone co-crystals-loaded oral fast dissolving films: Design, optimization, and in vivo evaluation

First-order derivative synchronous spectrofluorimetric determination of two antihypertensive drugs, metolazone and valsartan, in pharmaceutical and biological matrices

Synchronous spectrofluorimetry is utilized to carry out a rapid, sensitive and reliable method for determination of the binary mixture of metolazone (MTL) and losartan potassium (LSP). Under optimized experimental conditions, the synchronized fluorescence spectra of the two drugs were measured at Δλ=80nm in acidic methanolic solution and intensities were recorded at 260nm for MTL and 335nm for LSP. Linear correlation between fluorescence intensity and concentration were obtained through the ranges 0.02-0.2μg/mL and 0.2-2.0μg/mL for MTL and LSP, respectively. Limits of detection were 3.02 and 0.12ng/mL, whereas limits of quantification were 9.16 and 0.35ng/mL for MTL and LSP, respectively. The designated procedure was easily and successfully adopted to determine the two compounds in their single, as well as in co-formulated, tablets and the results showed high precision and accuracy without any significant interference from common tablet excipients. A comparison of the obtained results with a published reference method was carried out and both showed good agreement with respect to accuracy and precision.

Background: Thiazide diuretics are often utilized to overcome loop diuretic resistance when treating acute decompensated heart failure (ADHF). In addition to a large cost advantage, several pharmacokinetic advantages exist when administering oral metolazone (MTZ) compared with intravenous (IV) chlorothiazide (CTZ), yet many providers are reluctant to utilize an oral formulation to treat ADHF. The purpose of this study was to compare the increase in 24-hour total urine output (UOP) after adding MTZ or CTZ to IV loop diuretics (LD) in patients with heart failure with reduced ejection fraction (HFrEF). Methods and Results: From September 2013 to August 2016, 1002 patients admitted for ADHF received either MTZ or CTZ in addition to LD. Patients were excluded for heart failure with preserved ejection fraction (HFpEF) (n = 469), <24-hour LD or UOP data prior to drug initiation (n = 129), or low dose MTZ/CTZ (n = 91). A total of 168 patients were included with 64% receiving CTZ. No significant difference was observed between the increase in 24-hour total UOP after MTZ or CTZ initiation (1458 [514, 2401] mL vs 1820 [890, 2750] mL, P = .251). Conclusions: Both MTZ and CTZ similarly increased UOP when utilized as an adjunct to IV LD. These results suggest that while thiazide agents can substantially increase UOP in ADHF patients with HFrEF, MTZ and CTZ have comparable effects.

Thiazide diuretics are often utilized to overcome loop diuretic resistance when treating ADHF. In addition to a large cost advantage, several pharmacokinetic advantages exist when administering oral metolazone (MT) compared to IV chlorothiazide (CT); yet many providers are reluctant to utilize an oral formulation to treat ADHF. Several studies have found no difference in efficacy between the agents, however these studies had limited patients, utilized net UOP which can be misleading if patients are intubated or fluid restricted, and included HFpEF patients which may not have comparable UOP goals to HFrEF patients. The purpose of this study was to compare the increase in 24 hr total UOP after adding MT or CT to IV loop diuretics (LD) in patients with HFrEF. This was an IRB-approved, single-center retrospective chart review. Inclusion criteria were EF ≤40% and >24 hr use of LD with recorded UOP prior to administration of MT ≥ 5 mg or CT ≥ 500 mg. Patients with dialysis, no oral or per tube medications within 24 hr, or an overlap of MT/CT therapy were excluded. Baseline characteristics and safety data were collected in addition to 24 hr UOP prior and post drug administration. A subgroup analysis of patients receiving vasopressors was conducted a priori. From 9/2013-8/2016, 961 patients received either MT or CT in addition to LD. Most patients were excluded for HFpEF (n = 469), < 24 hr LD or UOP data prior to drug initiation (n = 129), or low dose MT/CT (n = 91). A total of 168 patients were included with 64% receiving CT. Baseline characteristics are listed in Table 1. No significant difference was observed between the increase in 24 hr total UOP after MT or CT initiation (1458 (514,2401) mL v. 1820 (890,2750) mL, P = .251). Net UOP and UOP for the entire course of MT or CT therapy are displayed in Figure. Additionally the vasopressor subgroup analysis (MT n = 16, CT n = 34) revealed no difference in increase in UOP between agents (1622 (60,3186) mL v. 1865 (302,3428) mL, P = .506). Both MT and CT similarly increased UOP when utilized as an adjunct to IV loop diuretics. These results may suggest that while thiazide agents can substantially increase UOP in ADHF patients with rEF and diuretic resistance, IV chlorothiazide may not offer benefit beyond oral metolazone 5 mg. A prospective RCT would be necessary to confirm.Table 1Baseline Characteristics for HFrEF Utilizing Thiazides for ADHF with Loop ResistanceBaseline CharacteristicIV Chlorothiazide (n = 108)Oral Metolazone (n = 60)PAge, yr64 (54,69)63 (54,74).558Male Sex, n(%)74 (69)41 (68).98White Race, n(%)68 (63)34 (57).621EF, %22 (15,30)23 (17,30).293BNP, pg/mL1371 (830,2230)1517 (825,3313).620SCr, mg/dL1.5 (1.0,2.1)1.6 (1.2,2.1).328cCrCl, mL/min47 (30,68)43 (30,61).390Total UOP, mL1693 (863,2388)1675 (1113,2591).330Net UOP, mL-350 (±1217)-552 (±1205).303Hospital LOS, days16 (9,28)13 (8,32).502Loop Continuous Infusion, n(%)67 (62)25 (42).011IV Inotropes, n(%)53 (49)24 (40).258ICU, n(%)77 (71)38 (63).287ICU LOS, days4 (0,10)2 (0,8).088Vasopressor, n(%)34 (32)16 (27).892Mechanical Ventilation, n(%)15 (14)2 (3).033APACHE II, score12 (9,15)10 (7,14).099Inhospital Morality, n(%)21 (19)1 (2).001 Open table in a new tab

In cases of loop diuretic resistance in the intensive care unit (ICU), recommendations for a specific second-line thiazide agent are lacking. To compare the effects of intravenous chlorothiazide (CTZ) and enteral metolazone (MET) on urine output (UOP) when added to furosemide monotherapy therapy in critically ill adults. This was a retrospective cohort study conducted in the medical, surgical, and cardiothoracic ICUs of a quaternary medical center. The primary outcome was change in UOP induced by the study interventions compared with furosemide alone. Secondary outcomes included onset of diuresis, eventual need for hemodialysis, and incidence of adverse events. A total of 122 patients (58 in CTZ, 64 in MET) were included. When added to furosemide monotherapy, CTZ induced a greater change in UOP at 24 hours compared with MET (2405 vs 1646 mL, respectively; P = 0.01). CTZ also caused a more rapid dieresis: 1463 mL total UOP in the first 6 hours compared with 796 mL in the MET group ( P < 0.01). There were no differences found regarding ICU length of stay, need for renal replacement therapy, or survival to discharge. The CTZ arm required more potassium supplementation to maintain normokalemia (median 100 vs 57 mEq in MET; P = 0.02) and carried a higher cost (mean $97 vs $8, P < 0.01). Both CTZ and MET induced significant increases in UOP. CTZ induced a greater and more rapid change and was associated with higher cost and greater need for potassium replacement. Randomized controlled trials are needed to establish whether a preferable thiazide diuretic exists in this setting.

This work represents the validation of a stability-indicating thin-layer chromatographic technique for the simultaneous estimation of metolazone (METO) and spironolactone (SPIRO) from marketed formulation (tablets). Thin-layer chromatography was performed using precoated silica gel plate 60 F254 using ethyl acetate—chloroform—GAA (5:5:0.1 v/v) as the mobile phase for the separation of METO and SPIRO. The stability study forms an integral part of the formulation development process, and its use is also encouraged by various guidelines. Stress study was performed on active pharmaceutical ingredients (APIs) as well as on formulation for establishing a stability-indicating thin-layer chromatographic method for both drugs. The APIs were subjected to change under various environmental conditions such as pH, temperature, oxidation, etc. to determine their effect on the stability of drugs. The developed method was able to resolve drugs and their degradation products formed under the aforementioned conditions. The...

For the first time, we developed and validated a highly sensitive, selective and rapid HPLC-ESI-MS-MS method for simultaneous quantification of metolazone (MET), losartan (LOS) and its metabolite losartan carboxylic acid (LCA) in rat plasma. After solid-phase extraction, the analytes and internal standard (irbesartan) were extracted from 100 µL plasma sample on an Agilent Poroshell 120, EC-C18 (50 × 4.6 mm, i.d., 2.7 µm) column using 5 µL injection volume with a total run time of 3 min. Acidified methanol/water mixture was used as a mobile phase. The parent → product ion transitions for MET (m/z 366.0 → 258.9), LOS (m/z 423.2 → 207.0), LCA (m/z 437.0 → 235.1) and IS (m/z 429.2 → 207.0) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ion mode. The method was found to be linear in the range of 0.05-250 for MET, 2-3,000 for LOS and 4-3,500 ng/mL for LCA. The method was validated with respect to selectivity, linearity, accuracy, precision, recovery and stability according to accepted regulatory guidelines. The described method was successfully applied to preclinical pharmacokinetic studies of analytes after an oral administration of mixture of MET (1 mg/kg) and LOS (10 mg/kg) in rats.

A simple, accurate and precise first order derivative spectrophotometric method was developed for simultaneous determination of Metolazone (MET) and Ramipril (RAM) in their combined pharmaceutical dosage form. MET and RAM were quantified using first derivative responses at 285nm and 212nm respectively. Methanol was taken as a common solvent. The calibration curve were linear in the concentration range of 5-25 μg/mL for MET and 8-24 μg/mL for RAM. The method was validated and found to be accurate and precise. Developed method was successfully applied for the estimation of MET and RAM in their combined dosage form

The monitoring of the plasmatic concentrations of cardiovascular drugs is crucial for understanding their pharmacokinetics and pharmacodynamics. A simple, sensitive, specific, and high-throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous estimation and pharmacokinetic study of losartan (LOS), losartan carboxylic acid (LCA), ramipril (RAM), ramiprilate (RPT), and hydrochlorothiazide (HCZ) in rat plasma using irbesartan (IBS) and metolazone (MET) as internal standards (ISs). After solid phase extraction (SPE), analytes and ISs were separated on an Agilent Poroshell 120, EC-C18 (50 mm × 4.6 mm, i.d., 2.7 μm) column with a mobile phase consisting of methanol/water (85:15, v/v) containing 5 mmol/L ammonium formate and 0.1% formic acid at a flow rate of 0.4 mL/min. The precursor → product ion transitions for the analytes and ISs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode and switching the electrospray ionization (ESI) mode during chromatography from positive (to detect LOS, LCA, RAM, RPT, and IBS) to negative (to detect HCZ and MET). The method was validated as per the FDA guidelines and it exhibited sufficient specificity, accuracy, and precision. The method was found to be linear in the range of 3–3000 ng/mL for LOS and LCA, 0.1–200 ng/mL for RAM and RPT, and 1–1500 ng/mL for HCZ. The described method was successfully applied to the preclinical pharmacokinetic study of analytes after oral administration of a mixture of LOS (10 mg/kg), RAM (1 mg/kg), and HCZ (2.5 mg/kg) in rats.

A highly sensitive, simple and rapid stability-indicating spectrofluorimetric method was developed for the determination of metolazone (MET) and xipamide (XPM) in their tablets. The proposed method is based on the measurement of the native fluorescence of MET in methanol at 437nm after excitation at 238nm and XPM in alkaline methanolic solution at 400nm after excitation at 255nm. The fluorescence-concentration plots were rectilinear over the range of 2.0- 20.0ng/mL for MET and 0.2- 2.0μg/mL for XPM, with lower detection limits (LOD) of 0.35ng/mL and 0.02μg/mL and a lower quantification limit (LOQ) of 1.05ng/mL and 0.07μg/mL for MET and XPM, respectively. The method was successfully applied to the analysis of MET and XPM in their commercial tablets and the results were in good agreement with those obtained using the official and comparison methods, respectively. Furthermore, content uniformity testing of the studied pharmaceutical tablets was also conducted. The application of the proposed method was extended to stability studies of MET and XPM after exposure to different forced degradation conditions, such as acidic, alkaline, oxidative and photolytic degradation conditions, according to ICH Guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and photolytic degradation of MET. The apparent first-order rate constants and half-life times were calculated. Proposals for the degradation pathways for both MET and XPM were postulated.

A new, specific and sensitive reversed-phase high-performance liquid chromatography method was developed for the simultaneous determination of metolazone (MET) and losartan potassium (LOS). Good chromatographic separation was achieved within 6.0 min on a 150 × 4.6 mm i.d., 5 µm Waters, Ireland and ProDIGY 5 ODS 3 100 A column. A mobile phase containing a mixture of methanol and 0.02 M phosphate buffer (65:35, v/v) at pH 3.0 was used. The analysis was performed at a flow rate of 1 mL/min with fluorescence detection at 410 nm after excitation at 230 nm. Aspirin (ASP) was used as an internal standard. The proposed method was rectilinear over 2.0-40.0 (MET) and 40.0-800.0 ng/mL (LOS), with limits of detection of 0.22 and 4.52 ng/mL and limits of quantification of 0.68 and 13.70 ng/mL for MET and LOS, respectively. The method was successfully applied for the simultaneous analysis of the studied drugs in their laboratory-prepared mixtures, single tablets and co-formulated tablets. Moreover, the method was applied to an in vitro drug release (dissolution) test. The method was further extended to the determination of LOS in spiked human plasma. Statistical evaluation and comparison of data obtained using the proposed and comparison methods revealed no significant difference between the two methods in addition to good accuracy and precision for the proposed method.

A new, specific and sensitive reversed-phase high performance liquid chromatographic method was developed for the simultaneous determination of two diuretic drugs; metolazone (MET) and spironolactone (SPL). Good chromatographic separation was achieved within 5.0 min on 150 mm × 4.6 mm i.d., 5 μm particle size Spherisorb-ODS 2 C18 column. A mobile phase containing a mixture of methanol and 0.02 M phosphate buffer (70 : 30) v/v at pH 3.0 was used. The analysis was performed at a flow rate of 1 mL min−1 with UV detection at 235 nm. Xipamide (XPM) was used as an internal standard (IS). The proposed method was rectilinear over the ranges of 0.05–1.0 μg mL−1 and 0.5–10.0 μg mL−1 with limits of detection (LOD) of 0.009, 0.04 ng mL−1 and limits of quantification (LOQ) of 0.03, 0.11 μg mL−1 for MET and SPL, respectively. The suggested method was successfully applied for the simultaneous analysis of the studied drugs in their laboratory prepared mixtures, single tablets and co-formulated tablets. The method was further extended to the determination of both drugs in spiked human urine. The mean percentage recoveries of MET and SPL in spiked human urine were 99.33 ± 2.37 and 99.72 ± 3.27, respectively. The proposed method was also applied for the determination of the studied drugs in the presence of some co-administered or co-formulated drugs without any interference. Statistical evaluation and comparison of the data obtained by the proposed and comparison methods revealed no significant difference between the two methods regarding accuracy and precision.

A sensitive and reproducible high performance liqui d chromatography (HPLC) method has been developed and validated for the quantification of metolazone in h uman plasma, after solid phase extraction (SPE). A Good reso- lution was achieved on a reverse-phase LichroCART Purospher ® C 18 column using the mobile phase acetoni- trile–0.5% triethylamine (35:65) in isocratic eluti on with a total run time of 15 min. The analyte, metolazone , was detected by using high performance liquid chromatog ra- phy with the support of photo diode array detector. Limit of detection and Lower limit of quantification was found to be 1 and 2.5 ng/mL. The present method was succe ss- fully applied in the pharmacokinetic study of metol azone in human plasma.

The effect of a number of ions on the binding of the thiazide-type diuretic metolazone (MTZ) to rat renal cortical membranes was studied to elucidate the mechanism of NaCl transport in the kidney distal tubule. Among the cations tested, Na+ significantly stimulated the binding up to 2.4-fold over control. The effective concentration of Na+ that produced half-maximal stimulation was 2-17 mM. Li+, K+, NH4+, Rb+, and Cs+ produced little stimulation of binding of MTZ. Several anions including Cl- inhibited binding. The inhibition of binding of MTZ by Cl- was enhanced by Na+ and Li+. Scatchard analyses revealed that 50 mM Na+ increased the affinity for binding of MTZ from a Kd = 3.56 +/- 0.15 nM to Kd = 1.32 +/- 0.11 nM. Chloride, in the presence of 50 mM Na+, competitively inhibited binding of MTZ by suppressing the affinity to Kd = 9.27 +/- 1.11 nM without changing the maximal number of binding sites (0.733 +/- 0.049 pmol/mg). A mechanism for the MTZ-sensitive NaCl transport is proposed, in which the transporter protein possesses a binding site for Na+ and a binding site for Cl-, which is also the binding site for MTZ. Na+ binds to its site and increases the affinity for Cl-/MTZ. The binding of Cl- to the transporter enables the import of Na+ and Cl- across the tubule membrane. MTZ, however, when present competes with Cl- for the binding site on the transporter and prevents the transport of Na+ and Cl-.

Neutropenia and metolazone.

Letter: Seizures and metolazone.