Contribution of Monocarboxylate Transporter 6 to the Pharmacokinetics and Pharmacodynamics of Bumetanide in Mice.

Bumetanide, a sulfamyl loop diuretic, is used for the treatment of edema in association with congestive heart failure. Being a polar, anionic compound at physiologic pH, bumetanide uptake and efflux into different tissues is largely transporter-mediated. Of note, organic anion transporters (SLC22A) have been extensively studied in terms of their importance in transporting bumetanide to its primary site of action in the kidney. The contribution of one of the less-studied bumetanide transporters, monocarboxylate transporter 6 (MCT6; SLC16A5), to bumetanide pharmacokinetics (PK) and pharmacodynamics (PD) has yet to be characterized. The affinity of bumetanide for murine Mct6 was evaluated using Mct6-transfected Xenopus laevis oocytes. Furthermore, bumetanide was intravenously and orally administered to wild-type mice (Mct6+/+) and homozygous Mct6 knockout mice (Mct6-/-) to elucidate the contribution of Mct6 to bumetanide PK/PD in vivo. We demonstrated that murine Mct6 transports bumetanide at a similar affinity compared with human MCT6 (78 and 84 µM, respectively, at pH 7.4). After bumetanide administration, there were no significant differences in plasma PK. Additionally, diuresis was significantly decreased by ∼55% after intravenous bumetanide administration in Mct6-/- mice. Kidney cortex concentrations of bumetanide were decreased, suggesting decreased Mct6-mediated bumetanide transport to its site of action in the kidney. Overall, these results suggest that Mct6 does not play a major role in the plasma PK of bumetanide in mice; however, it significantly contributes to bumetanide's pharmacodynamics due to changes in kidney concentrations. SIGNIFICANCE STATEMENT: Previous evidence suggested that MCT6 transports bumetanide in vitro; however, no studies to date have evaluated the in vivo contribution of this transporter. In vitro studies indicated that mouse and human MCT6 transport bumetanide with similar affinities. Using Mct6 knockout mice, we demonstrated that murine Mct6 does not play a major role in the plasma pharmacokinetics of bumetanide; however, the pharmacodynamic effect of diuresis was attenuated in the knockout mice, likely because of the decreased bumetanide concentrations in the kidney.

Effects of bumetanide on neurobehavioral function in children and adolescents with autism spectrum disorders.

In animal models of autism spectrum disorder (ASD), the NKCC1 chloride-importer inhibitor bumetanide restores physiological (Cl-)i levels, enhances GABAergic inhibition and attenuates electrical and behavioral symptoms of ASD. In an earlier phase 2 trial; bumetanide reduced the severity of ASD in children and adolescents (3-11 years old). Here we report the results of a multicenter phase 2B study primarily to assess dose/response and safety effects of bumetanide. Efficacy outcome measures included the Childhood Autism Rating Scale (CARS), the Social Responsive Scale (SRS) and the Clinical Global Impressions (CGI) Improvement scale (CGI-I). Eighty-eight patients with ASD spanning across the entire pediatric population (2-18 years old) were subdivided in four age groups and randomized to receive bumetanide (0.5, 1.0 or 2.0 mg twice daily) or placebo for 3 months. The mean CARS value was significantly improved in the completers group (P: 0.015). Also, 23 treated children had more than a six-point improvement in the CARS compared with only one placebo-treated individual. Bumetanide significantly improved CGI (P: 0.0043) and the SRS score by more than 10 points (P: 0.02). The most frequent adverse events were hypokalemia, increased urine elimination, loss of appetite, dehydration and asthenia. Hypokalemia occurred mainly at the beginning of the treatment at 1.0 and 2.0 mg twice-daily doses and improved gradually with oral potassium supplements. The frequency and incidence of adverse event were directly correlated with the dose of bumetanide. Therefore, bumetanide improves the core symptoms of ASD and presents a favorable benefit/risk ratio particularly at 1.0 mg twice daily.

[The immunomodulating properties of the diuretic bufenoks]. / Immunomoduliruiushchie svoistva diuretika bufenoksa.

Bufenox, a diuretic with a sodium-uretic and light potassium--uretic effect, has an immediate but short-term effect, stimulates IgM antibody production, depressed delayed-type hypersensitivity. The immunomodulating effect of bufenox may be due to changes in Na+ ions concentrations since sodium load abrogates immunoactive properties of the drug.

Comparative natriuretic and diuretic efficacy of theophylline ethylenediamine and of bendroflumethiazide during long-term treatment with the potent diuretic bumetanide. Permutation trial tests in patients with congestive heart failure.

The additive natriuretic and diuretic effects of theophylline ethylenediamine and of bendroflumethiazide have been compared in permutation trial tests in patients with advanced congestive heart failure receiving long-term treatment with the highly potent diuretic, bumetanide. Statistical analysis of renal water and electrolyte excretion revealed that theophylline ethylenediamine, 400 mg orally, and bendroflumethiazide, 5 mg orally, had very similar effects, both quantitatively and qualitatively. The mechanism of action of the supplementary diuretics is discussed. It is concluded that theophylline ethylenediamine represents a useful alternative to thiazide diuretics when supplementary natriuretic treatment is considered in patients with congestive heart failure during long-term treatment with potent diuretics. The significance of maintaining the potassium balance during such a combined regimen is stressed.

Patient acceptability of two diuretic/potassium supplement preparations.

In a random crossover study in general practice, sixty patients with heart failure were given one week's maintenance treatment with the recommended dosage of Burinex K or Lasix+K. Burinex K appeared to be easier to swallow than the supplement tablets of Lasix+K although the differences were not significant. Patients showed a highly significant preference to take two tablets on one occasion (Burinex K) rather than two different types of tablet on three separate occasions (Lasix+K). Despite pharmacological arguments in favour of stimultaneous versus separate administration of potassium supplement and diuretic, patient acceptibility is of over-riding importance in the long-term.

Patient tolerance of long-term diuretic/potassium supplement therapy.

Forty patients with congestive heart failure or hypertensive heart disease were given long-term maintenance treatment with a combined bumetanide/slow-release potassium supplement preparation ('Burinex K'). Stabilised doses ranged from 0.5 mg to 2 mg bumetanide with from 7.7 mmol to 30.8 mmol potassium. Patients took doses either at 9 a.m. or at 5 p.m. daily during a series of alternate 2 to 4-weekly treatment periods. Analysis of patient preference for morning or evening diuresis showed that the majority (72.5%), including all 18 patients who went out to work, preferred the evening regimen. Bumetanide proved to be a highly effective diuretic, irrespective of time of administration. Evening diuresis was associated with a statistically significant increase in the 24-hour excretion of sodium. Serial laboratory analyses showed no clinically significant changes in serum potassium or other parameters examined an in contrast to other diuretics bumetanide produced no significant hyperuricaemic effects.