Indomethacin, amiloride, or eplerenone for treating hypokalemia in Gitelman syndrome

Eplerenone for hypertension

BACKGROUND

Eplerenone is an aldosterone receptor blocker that is chemically derived from spironolactone. In Canada, it is indicated for use as adjunctive therapy to reduce mortality for heart failure patients with New York Heart Association (NYHA) class II systolic chronic heart failure and left ventricular systolic dysfunction. It is also used as adjunctive therapy for patients with heart failure following myocardial infarction. Additionally, it is indicated for the treatment of mild and moderate essential hypertension for patients who cannot be treated adequately with other agents. It is important to determine the clinical impact of all antihypertensive medications, including aldosterone antagonists, to support their continued use in essential hypertension. No previous systematic reviews have evaluated the effect of eplerenone on cardiovascular morbidity, mortality, and magnitude of blood pressure lowering in patients with hypertension.

OBJECTIVES

To assess the effects of eplerenone monotherapy versus placebo for primary hypertension in adults. Outcomes of interest were all-cause mortality, cardiovascular events (fatal or non-fatal myocardial infarction), cerebrovascular events (fatal or non fatal strokes), adverse events or withdrawals due to adverse events, and systolic and diastolic blood pressure.

SEARCH METHODS

We searched the Cochrane Hypertension Specialised Register, CENTRAL, MEDLINE, Embase, and two trials registers up to 3 March 2016. We handsearched references from retrieved studies to identify any studies missed in the initial search. We also searched for unpublished data by contacting the corresponding authors of the included studies and pharmaceutical companies involved in conducting studies on eplerenone monotherapy in primary hypertension. The search had no language restrictions.

SELECTION CRITERIA

We selected randomized placebo-controlled trials studying adult patients with primary hypertension. We excluded studies in people with secondary or gestational hypertension and studies where participants were receiving multiple antihypertensives.

DATA COLLECTION AND ANALYSIS

Three review authors independently reviewed the search results for studies meeting our criteria. Three review authors independently extracted data and assessed trial quality using a standardized data extraction form. A fourth independent review author resolved discrepancies or disagreements. We performed data extraction and synthesis using a standardized format on Covidence. We conducted data analysis using Review Manager 5.

MAIN RESULTS

A total of 1437 adult patients participated in the five randomized parallel group studies, with treatment durations ranging from 8 to 16 weeks. The daily doses of eplerenone ranged from 25 mg to 400 mg daily. Meta-analysis of these studies showed a reduction in systolic blood pressure of 9.21 mmHg (95% CI -11.08 to -7.34; I² = 58%) and a reduction of diastolic pressure of 4.18 mmHg (95% CI -5.03 to -3.33; I² = 0%) (moderate quality evidence).There may be a dose response effect for eplerenone in the reduction in systolic blood pressure at doses of 400 mg/day. However, this finding is uncertain, as it is based on a single included study with low quality evidence. Overall there does not appear to be a clinically important dose response in lowering systolic or diastolic blood pressure at eplerenone doses of 50 mg to 400 mg daily. There did not appear to be any differences in the number of patients who withdrew due to adverse events or the number of patients with at least one adverse event in the eplerenone group compared to placebo. However, only three of the five included studies reported adverse events. Most of the included studies were of moderate quality, as we judged multiple domains as being at unclear risk in the 'Risk of bias' assessment.

AUTHORS' CONCLUSIONS

Eplerenone 50 to 200 mg/day lowers blood pressure in people with primary hypertension by 9.21 mmHg systolic and 4.18 mmHg diastolic compared to placebo, with no difference of effect between doses of 50 mg/day to 200 mg/day. A dose of 25 mg/day did not produce a statistically significant reduction in systolic or diastolic blood pressure and there is insufficient evidence for doses above 200 mg/day. There is currently no available evidence to determine the effect of eplerenone on clinically meaningful outcomes such as mortality or morbidity in hypertensive patients. The evidence available on side effects is insufficient and of low quality, which makes it impossible to draw conclusions about potential harm associated with eplerenone treatment in hypertensive patients.

Management of uncommon disorders in pregnancy: Von Hippel-Lindau disease, Gitelman syndrome, and Nutcracker syndrome

Uncommon renal disorders in pregnancy can be challenging to manage given limited evidence in the literature to guide management. We present a series of three uncommon renal disorders in pregnancy: Von Hippel-Lindau disease, Gitelman syndrome, and Nutcracker syndrome. Previously published case reports with differing outcomes offer some guidance to the management of these disorders in pregnancy. In this case series, we address the management of these syndromes during pregnancy and discuss the maternal and fetal outcomes. All three of our patients had good maternal and fetal outcomes, which will contribute to current data on maternal and fetal outcomes in these rare diseases, which is limited.

Renal Toxicities of Targeted Therapies

With the incorporation of targeted therapies in routine cancer therapy, it is imperative that the array of toxicities associated with these agents be well-recognized and managed, especially since these toxicities are distinct from those seen with conventional cytotoxic agents. This review will focus on these renal toxicities from commonly used targeted agents. This review discusses the mechanisms of these side effects and management strategies. Anti-vascular endothelial growth factor (VEGF) agents including the monoclonal antibody bevacizumab, aflibercept (VEGF trap), and anti-VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) all cause hypertension, whereas some of them result in proteinuria. Monoclonal antibodies against the human epidermal growth factor receptor (HER) family of receptors, such as cetuximab and panitumumab, cause electrolyte imbalances including hypomagnesemia and hypokalemia due to the direct nephrotoxic effect of the drug on renal tubules. Cetuximab may also result in renal tubular acidosis. The TKIs, imatinib and dasatinib, can result in acute or chronic renal failure. Rituximab, an anti-CD20 monoclonal antibody, can cause acute renal failure following initiation of therapy because of the onset of acute tumor lysis syndrome. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, can result in proteinuria. Discerning the renal adverse effects resulting from these agents is essential for safe treatment strategies, particularly in those with pre-existing renal disease.

Mutation profile and treatment of Gitelman syndrome in Chinese patients

BACKGROUND

Gitelman syndrome (GS) is a rare autosomal recessive disease caused by loss-of-function mutations in the SLC12A3 gene, and is characterized by hypokalemia and metabolic alkalosis. In this study, we aimed to study the genotype, phenotype, and treatment in 42 GS patients, the largest sample size so far in mainland China.

METHOD

We retrospectively studied the clinical data and genetic characteristics of 42 patients diagnosed with GS in Peking Union Medical College Hospital from 2012 to 2015. Therapeutic efficacy of spironolactone and potassium supplements was also studied retrospectively.

RESULTS

Eighty-one mutation alleles were found in 42 patients, and total of 52 distinctly different mutation alleles were identified, of which 15 were new mutation alleles. p.Asp486Asn was a hotspot in our series, with the allele frequency being 19.7 % (16/81), and was found in 13 patients (31.0 %). Treatment with spironolactone or potassium supplements alone significantly increased serum potassium concentration by 0.36 ± 0.37 and 0.45 ± 0.35 mmol/l, respectively (both P < 0.05), and combined therapy with spironolactone and potassium increased serum potassium concentration by 0.69 ± 0.64 mmol/l (P < 0.05).

CONCLUSIONS

18.5 % (15/81) mutation sites identified in 42 Chinese GS patients are novel. p.Asp486Asn mutation is a hotspot, which is different from the reports from other countries. Spironolactone could moderately elevate serum potassium level, and spironolactone in combination with potassium supplements tended to be more effective.

Hydrochlorothiazide Potentiates Contractile Activity of Mouse Cavernosal Smooth Muscle

Introduction

Hydrochlorothiazide has a negative influence on penile erection but little is known about the mechanism(s) involved.

Aims

To characterize the effects of this diuretic on mouse corpus cavernosum (CC) smooth muscle in vitro and ex vivo.

Methods

CC strips of C57BL/6 mice (12–16 weeks old) were mounted in organ baths containing Krebs-Henseleit solution and tissue reactivity was evaluated. Expression of genes encoding diuretic targets and enzymes involved in penile erection were evaluated by polymerase chain reaction.

Main Outcome Measures

Stimulation-response curves to phenylephrine (10 nmol/L–100 μmol/L) or to electrical field stimulation (1–32 Hz) were constructed, with or without hydrochlorothiazide. Strips of CC from mice after long-term hydrochlorothiazide treatment (6 mg/kg/day for 4 weeks) with or without amiloride (0.6 mg/kg/day for 4 weeks) in vivo also were studied. Nitric oxide and Rho-kinase pathways were evaluated.

Results

Hydrochlorothiazide (100 μmol/L) increased the maximum response to phenylephrine by 64% in vitro. This effect was unaffected by the addition of indomethacin (5 μmol/L) but was abolished by N(^ω)-nitro-L-arginine methyl ester (100 μmol/L). Hydrochlorothiazide (100 μmol/L) potentiated electrical field stimulation-induced contraction in vitro, but not ex vivo. Long-term treatment with hydrochlorothiazide increased the maximum response to phenylephrine by 60% and resulted in a plasma concentration of 500 ± 180 nmol/L. Amiloride (100μmol/L) caused rightward shifts in concentration-response curves to phenylephrine in vitro. Long-term treatment with hydrochlorothiazide plus amiloride did not significantly increase the maximum response to phenylephrine (+13%). Reverse transcriptase polymerase chain reaction did not detect the NaCl cotransporter in mouse CC. Hydrochlorothiazide did not change Rho-kinase activity, whereas amiloride decreased it in vitro and ex vivo (approximately 18% and 24% respectively). A 40% decrease in Rock1 expression also was observed after long-term treatment with hydrochlorothiazide plus amiloride.

Conclusion

Hydrochlorothiazide potentiates contraction of smooth muscle from mouse CC. These findings could explain why diuretics such as hydrochlorothiazide are associated with erectile dysfunction.

Pathophysiology and clinical presentations of salt-losing tubulopathies

At least three renal tubular segments are involved in the pathophysiology of salt-losing tubulopathies (SLTs). Whether the pathogenesis starts either in the thick ascending limb of the loop of Henle (TAL) or in the distal convoluted tubule (DCT), it is the function of the downstream-localized aldosterone sensitive distal tubule (ASDT) to contribute to the adaptation process. In isolated TAL defects (loop disorders) ASDT adaptation is supported by upregulation of DCT, whereas in DCT disorders the ASDT is complemented by upregulation of TAL function. This upregulation has a major impact on the clinical presentation of SLT patients. Taking into account both the symptoms and signs of primary tubular defect and of the secondary reactions of adaptation, a clinical diagnosis can be made that eventually leads to an appropriate therapy. In addition to salt wasting, as occurs in all SLTs, characteristic features of loop disorders are hypo- or isosthenuric polyuria and hypercalciuria, whereas characteristics of DCT disorders are hypokalemia and (symptomatic) hypomagnesemia. In both SLT categories, replacement of urinary losses is the primary goal of treatment. In loop disorders COX inhibitors are also recommended to mitigate polyuria, and in DCT disorders magnesium supplementation is essential for effective treatment. Of note, the combination of a salt- and potassium-rich diet together with an adequate fluid intake is always the basis of long-term treatment in all SLTs.

Molecular pathophysiology of Bartter's and Gitelman's syndromes

BACKGROUND

In the last two decades, progress in cytogenetic and genome research has enabled investigators to unravel the underlying molecular mechanisms of inherited tubulopathies such as Bartter's and Gitelman's syndromes and helped physicians to better understand not only these two pathologic entities but also renal pathophysiology and salt sensitive hypertension.

DATA SOURCES

Articles collected from PubMed and open access journals included original articles, research articles, and comprehensive reviews. They were evaluated by the authors with an special emphasis on originality and up to date information about molecular pathophysiology.

RESULTS

Bartter's and Gitelman's syndromes are two different inherited salt loosing tubulopathies. They are characterized by various inability of distal nephron to reabsorb sodium chloride with resultant extarcellular volume contraction and increased activity of the renin angiotensin aldosterone system. Hypokalemic metabolic alkalosis is a common feature of these two forms of tubulopathies. Hypercalciuria characterizes the majority of Bartter's syndrome, and hypomagnesemia with hypocalciuria characterizes Gitelman's syndrome. Low blood pressure is a common feature among patients who suffered from these tubulopathies. Bartter's syndromes encompass a heterogeneous group of ion channels defects localized at the thick ascending limp of Henle's loop with resultant loss of function of sodium-potassium-2 chloride cotransporter. These defects result in the impairment of the countercurrent multiplication system of the kidney as well as calcium, potassium and acid base disturbances which in the majority of cases are proved lethal especially in the antenatal and/or immediate postnatal life period. The underlying pathology in Gitelman's syndrome is defined to the distal convoluted tubule and is related to loss of function of the sodium-chloride cotransporter. The results of this defect encompass the inability of extracellular volume homeostasis, magnesium and potassium conservation, and acid base disturbances which are generally mild and in the majority of cases are not life-threatening.

CONCLUSIONS

Recent advances in molecular pathophysiology of Bartter's and Gitelman's syndromes have helped physicians to better understand the underlying mechanisms of these pathologic entities which remain obscure. Data collected from experiments among genetically manipulated animals enable us to better understand the pathophysiology of mammalian kidney and the underlying mechanisms of salt sensitive hypertension and to lay a foundation for the future development of new drugs, especially diuretics and antihypertensive drugs.

Cisplatinum nephrotoxicity in oncology therapeutics: retrospective review of patients treated between 2005 and 2012

BACKGROUND

Cisplatinum (CP) is associated with acute kidney injury. The aim of this study was to define the spectrum of CP-induced nephrotoxicity in current practice.

CASE-DIAGNOSIS/TREATMENT

A single-center, retrospective chart review was performed on children who received CP for treatment of a malignancy at the Hassenfeld Children's Center for Blood and Cancer Disorders of NYU Langone Medical Center between 2005 and 2012. Patients were considered to have nephrotoxicity if they had: (1) a decrease in estimated glomerular filtration rate (eGFR) of ≥30 % or (2) a decline in serum magnesium of ≥0.2 meq/L or (3) a decline in serum potassium of ≥0.2 meq/L. Thirty-two patients (mean age 8.0 ± 7.0 years) were included in this review, of whom 21 had a brain tumor (BT) and 11 had an osteosarcoma (OS); 31 (97 %) of the patients had a disturbance in renal function. The mean reduction in eGFR, serum magnesium and potassium was 37 ± 17, 30 ± 16 and 25 ± 14 %, respectively. The decline in eGFR, hypomagnesemia and hypokalemia was persistent in 38, 60 and 40 % of cases, respectively, through the short-term follow-up period. No patients required dialysis.

CONCLUSIONS

Nearly all patients receiving CP in current care experience modest glomerular and tubular injury. The abnormalities persist in 40-60 % of cases during the short-term recovery period after CP treatment.