Interaction of cyclosporine and FK506 with diuretics in transplant patients

Diuretic Treatment in Heart Failure: A Practical Guide for Clinicians

Congestion and fluid retention are the hallmarks of decompensated heart failure and the major reason for the hospitalization of patients with heart failure. Diuretics have been used in heart failure for decades, and they remain the backbone of the contemporary management of heart failure. Loop diuretics is the preferred diuretic, and it has been given a class I recommendation by clinical guidelines for the relief of congestion symptoms. Although loop diuretics have been used virtually among all patients with acute decompensated heart failure, there is still very limited clinical evidence to guide the optimized diuretics use. This is a sharp contrast to the rapidly growing evidence of the rest of the guideline-directed medical therapy of heart failure and calls for further studies. The loop diuretics possess a unique pharmacology and pharmacokinetics that lay the ground for different strategies to increase diuretic efficiency. However, many of these approaches have not been evaluated in randomized clinical trials. In recent years, a stepped and protocolized diuretics dosing has been suggested to have superior benefits over an individual clinician-based strategy. Diuretic resistance has been a major challenge to decongestion therapy for patients with heart failure and is associated with a poor clinical prognosis. Recently, therapy options have emerged to help overcome diuretic resistance to loop diuretics and have been evaluated in randomized clinical trials. In this review, we aim to provide a comprehensive review of the pharmacology and clinical use of loop diuretics in the context of heart failure, with attention to its side effects, and adjuncts, as well as the challenges and future direction.

Approach and Management of Hypertension After Kidney Transplantation

Hypertension is one of the most common cardiovascular co-morbidities after successful kidney transplantation. It commonly occurs in patients with other metabolic diseases, such as diabetes mellitus, hyperlipidemia, and obesity. The pathogenesis of post-transplant hypertension is complex and is a result of the interplay between immunological and non-immunological factors. Post-transplant hypertension can be divided into immediate, early, and late post-transplant periods. This classification can help clinicians determine the etiology and provide the appropriate management for these complex patients. Volume overload from intravenous fluid administration is common during the immediate post-transplant period and commonly contributes to hypertension seen early after transplantation. Immunosuppressive medications and donor kidneys are associated with post-transplant hypertension occurring at any time point after transplantation. Transplant renal artery stenosis (TRAS) and obstructive sleep apnea (OSA) are recognized but common and treatable causes of resistant hypertension post-transplantation. During late post-transplant period, chronic renal allograft dysfunction becomes an additional cause of hypertension. As these patients develop more substantial chronic kidney disease affecting their allografts, fibroblast growth factor 23 (FGF23) increases and is associated with increased cardiovascular and all-cause mortality in kidney transplant recipients. The exact relationship between increased FGF23 and post-transplant hypertension remains poorly understood. Blood pressure (BP) targets and management involve both non-pharmacologic and pharmacologic treatment and should be individualized. Until strong evidence in the kidney transplant population exists, a BP of <130/80 mmHg is a reasonable target. Similar to complete renal denervation in non-transplant patients, bilateral native nephrectomy is another treatment option for resistant post-transplant hypertension. Native renal denervation offers promising outcomes for controlling resistant hypertension with no significant procedure-related complications. This review addresses the epidemiology, pathogenesis, and specific etiologies of post-transplant hypertension including TRAS, calcineurin inhibitor effects, OSA, and failed native kidney. The cardiovascular and survival outcomes related to post-transplant hypertension and the utility of 24-h blood pressure monitoring will be briefly discussed. Antihypertensive medications and their mechanism of actions relevant to kidney transplantation will be highlighted. A summary of guidelines from different professional societies for BP targets and antihypertensive medications as well as non-pharmacological interventions, including bilateral native nephrectomy and native renal denervation, will be reviewed.

Magnesium Balance in Chronic and End-Stage Kidney Disease

This article explores the effects of CKD and end-stage kidney disease on magnesium balance. In CKD, there is decreased glomerular filtration of magnesium. Decreased tubular reabsorption can compensate to a degree, but once CKD stage 4 is reached there is a tendency toward hypermagnesemia. In dialysis, magnesium balance is dependent on the constituents of the dialysate that the blood is exposed to. The concentration of dialysate magnesium is just one of the factors that need to be considered. During transplantation, there are particular effects of immunosuppressants that can affect the magnesium balance and need to be considered by the clinician.

Different Effects of Tacrolimus on Innate and Adaptive Immune Cells in the Allograft Transplantation

While tacrolimus (FK506) is currently used as immunosuppression therapy in transplant recipient, the immunological mechanism remains unknown. Herein, the immunoregulatory effects of FK506 were investigated in the physiological status and allogeneic skin transplantation. FK506 cannot significantly alter the functions of innate immune cells (macrophages and neutrophils) and adaptive immune cells (T cells) in the physiological status. However, it can effectively delay allogeneic skin-graft rejection through ameliorating the T cell responses, but not myeloid-derived innate immune cell responses. Importantly, it did not affect the allograft recipient macrophage innate immune defence capacity to bacteria. In clinics, FK506 treatment can significantly control the cytokine production in T cells, but not non-T cells. This study shows targeting calcineurin signalling, FK506, to be essential in inducing allograft tolerance, but not to damage the innate defence capacity, validating the immune cell phenotypes as a potential marker in transplantation following FK506 treatment.

Impact of intravenous magnesium infusion rate during ambulatory replacements on serum magnesium concentrations after allogeneic stem cell transplant

PURPOSE

For an outpatient cancer center to operate efficiently, optimizing the use of chair time is essential. Allogeneic hematopoietic cell transplant (allo-HCT) recipients are seen frequently in this setting after hospital discharge and regularly for several months thereafter. Aggressive electrolyte replacement is commonly required in these patients, primarily due to renal wasting with calcineurin inhibitor use. Frequent intravenous (IV) magnesium repletion, requiring several hours of infusion time, is often needed in these patients to adequately manage their magnesium deficiencies. The purpose of this study is to explore the impact of extending the infusion rate of intravenous magnesium sulfate on the frequency and degree of IV magnesium replacements required in allo-HCT recipients.

METHODS

We conducted a retrospective study to compare two cohorts of patients administered IV magnesium sulfate at a rate of 4 g/1 h versus 4 g/2 h.

RESULTS

A total of 103 continuous patients were assessed in two groups as cohort 1 at the 4 g/1 h rate and cohort 2 at the 4 g/2 h rate. Cohort 1 required less IV magnesium per outpatient visit (median 2.2 vs. 2.9 g/visit, P = 0.0211) and less total IV magnesium replacement through day +100 (median 68 vs. 85 g, P = 0.0479) than cohort 2.

CONCLUSION

These data suggest that there is no apparent benefit of prolonging magnesium infusion from 1 to 2 h in our outpatient allo-HCT population.

Proton-pump inhibitors do not influence serum magnesium levels in renal transplant recipients

Severe hypomagnesemia has been reported with use of proton-pump inhibitors (PPIs). We assessed the effect, if any, of PPI use on serum magnesium level in a cross-sectional analysis of a large published cohort of renal transplant recipients (RTRs). Between February 2004 and February 2006, 512 consecutive prevalent RTRs were enrolled at two university hospitals in Belgium (Brussels and Ghent). Serum creatinine was 1.5 ± 0.7 mg/dl, and estimated glomerular filtration rate (eGFR) 53 ± 19 ml/min/1.73 m(2). Mean (and median) magnesium level was 1.91 ± 0.23 mg/dl. PPIs were prescribed in 20 % (n = 101) of cases. At multivariable analysis, PPI use was not an independent predictor of serum magnesium level or hypomagnesemia. The independent predictors of a lower serum magnesium level were the use of tacrolimus, cyclosporin and sirolimus, the absence of use of mycophenolate mofetil, lower levels of parathyroid hormone and higher eGFR. This study is the first to analyze the potential impact of PPIs on magnesium level in a large, representative cohort of RTR patients. Our results suggest that PPIs may be used without particular fear of favoring hypomagnesemia-related side effects in RTRs, an important finding in a population at high risk of hypomagnesemia.

Magnesium loss in cyclosporine-treated patients is related to renal epidermal growth factor downregulation

BACKGROUND

Cyclosporine (CsA) treatment is associated with hypomagnesaemia due to a renal Mg(2+) leak. In animal studies a role for the Mg(2+) channel TRPM6 localized in the distal convoluted tubule and stimulated by epidermal growth factor (EGF) is suggested. We hypothesize that CsA-induced hypomagnesaemia is due to a renal magnesium leak, also in patients, resulting from a downregulation of the renal EGF production, thereby inhibiting the activation of TRPM6.

METHODS

Renal transplant patients treated with CsA (n = 55) and 35 chronic kidney disease (CKD) patients were included. At three time points, with an interval of at least 1 month, blood and urine samples were taken to determine creatinine, Mg(2+), sodium and EGF.

RESULTS

Serum Mg(2+) was significantly lower in the CsA group versus the CKD group with significantly more CsA-treated patients developing hypomagnesaemia. Although the fractional excretion (FE) Mg(2+) did not differ significantly between the two groups, subanalysis of the patients with hypomagnesaemia showed a significantly higher FE Mg(2+) in CsA-treated patients compared with CKD patients (P = 0.05). The urinary EGF excretion was significantly decreased in the CsA group and was a predictor of the FE Mg(2+) in the two groups. Serum sodium was significantly decreased in the CsA group simultaneously with an increased FE Na(+).

CONCLUSIONS

In CsA-treated patients, the association of a low urinary EGF excretion and a decreased renal Mg(2+) reabsorption is in accordance with in vitro and animal studies. In the whole study population, log urinary EGF excretion is an independent predictor of the FE Mg(2+), supporting the role of EGF in magnesium reabsorption.

Are thiazide diuretics safe and effective antihypertensive therapy in kidney transplant recipients?

BACKGROUND/AIMS

There are no published studies assessing the safety and efficacy of thiazides as antihypertensives in kidney transplantation (KTX).

METHODS

This was a longitudinal retrospective cohort study conducted in adult KTX recipients. Patients were grouped based on receiving thiazides following KTX. Safety and efficacy comparisons were made between thiazide recipients and unexposed patients, as well as change in blood pressure (BP) within thiazide patients.

RESULTS

1,093 patients were included (thiazide group: 108, unexposed group: 985). Mean follow-up was 7.3 ± 4.5 years. Thiazide recipients were older (53 ± 11 vs. 48 ± 13 years, p < 0.001) and more likely to be female (52 vs. 41%, p = 0.023) and have pre-KTX hypertension (97 vs. 88%, p = 0.004) or diabetes (36 vs. 27%, p = 0.035). After controlling for baseline differences, safety analysis revealed thiazide recipients were not more likely to be readmitted to the hospital, but were at higher risk to develop hyperkalemia (56 vs. 38%, p < 0.001) or hypokalemia (28 vs. 18%, p = 0.010), with similar rates of hypotension, decreased estimated glomerular filtration rate, graft loss and death. Efficacy analysis demonstrated systolic (147 ± 17 to 139 ± 18 mm Hg, p < 0.001) and diastolic (79 ± 9 to 77 ± 11 mm Hg, p < 0.001) BPs were significantly reduced after thiazide initiation. Compared to unexposed patients, thiazide recipients had higher mean BPs during the entire follow-up (142/78 vs. 136/77, p < 0.001), with similar BPs while on thiazides and comparable rates of goal BPs (<130/80 mm Hg, 32 vs. 36%, p = 0.219).

CONCLUSIONS

In KTX, based on long-term outcomes, thiazides appear to be safe and effective antihypertensives; in the short-term, thiazides may increase the risk of developing potassium disturbances.

Effect of mycophenolate mofetil on plasma bioelements in renal transplant recipients

The proper concentrations of plasma bioelements may favorably reduce the incidence of metabolic disorders, which often occur during immunosuppressive therapy. Mycophenolate mofetil (MMF) is currently one of the most frequently administered immunosuppressive agents; however, MMF treatment is often related to gastrointestinal side effects. The aim of this study was thus to verify whether the MMF treatment itself, or its metabolite pharmacokinetics, has an effect on the concentrations of plasma bioelements. To determine this, the effect of MMF on the levels of both major (sodium [Na], potassium [K], calcium [Ca], magnesium [Mg]), and trace (iron [Fe], zinc [Zn], copper [Cu]) plasma bioelements in 61 renal transplant recipients was assessed in comparison to a control group (n = 45). The pharmacokinetic parameters of mycophenolic acid were determined by the high-performance liquid chromatography method. All patients filled out a 24-h diet history questionnaire. The results showed high plasma concentrations of Fe and low plasma concentrations of Mg and Zn as compared with diagnostic norms. The patients treated with MMF had significantly lower plasma Na (P < 0.001) and significantly higher plasma Zn (P = 0.030) and Cu concentrations (P < 0.001). In conclusion, MMF treatment was found to affect plasma Fe, Zn, and Cu levels by increasing their concentrations while decreasing the plasma Na concentration. Mg and Zn deficiencies, as well as excessive Fe levels, are frequently observed irrespective of the immunosuppressive regimen applied, which suggests that monitoring of these bioelements may be favorable.

The calcineurin inhibitor tacrolimus activates the renal sodium chloride cotransporter to cause hypertension

Calcineurin inhibitors (CNIs) are immunosuppressive drugs, which are used widely to prevent rejection of transplanted organs and treat autoimmune disease. Hypertension and renal tubule dysfunction, including hyperkalemia, hypercalciuria, and acidosis often complicate their use^1,2. These side effects resemble familial hyperkalemic hypertension (FHHt), a genetic disease characterized by overactivity of the renal sodium chloride co-transporter (NCC), and caused by mutations in WNK kinases. We hypothesized that CNIs induce hypertension by stimulating NCC. In wild-type mice, the CNI tacrolimus caused salt-sensitive hypertension and increased the abundance of phosphorylated NCC, and the NCC regulatory kinases WNK3, WNK4, and SPAK. The functional importance of NCC in this response was demonstrated by showing that tacrolimus did not affect blood pressure in NCC knockout mice, whereas the hypertensive response to tacrolimus was exaggerated in mice over-expressing NCC. Moreover, hydrochlorothiazide reversed tacrolimus-induced hypertension. In kidney transplant recipients treated with tacrolimus, fractional chloride excretion in response to bendroflumethiazide was greater than in controls, and renal NCC abundance was also greater, extending these observations to humans. Together, these findings indicate that tacrolimus-induced hypertension is mediated largely by NCC activation, and suggest that inexpensive and well-tolerated thiazide diuretics may be especially effective in preventing the complications of CNI treatment.

Hypertension following kidney transplantation

The majority of patients become hypertensive following kidney transplantation. Its occurrence is associated not only with increased fatal and nonfatal cardiovascular events but also with decreased allograft survival. This review summarizes the current knowledge of the epidemiology, etiology, pathophysiology, and management of post-transplant hypertension.

KDOQI US commentary on the 2009 KDIGO clinical practice guideline for the care of kidney transplant recipients

In response to recently published KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for the care of kidney transplant recipients (KTRs), the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) organized a working group of transplant nephrologists and surgeons to review these guidelines and comment on their relevance and applicability for US KTRs. The following commentaries on the KDIGO guidelines represent the consensus of our work group. The KDIGO transplant guidelines concentrated on aspects of transplant care most important to this population in the posttransplant period, such as immunosuppression, infection, malignancy, and cardiovascular care. Our KDOQI work group concurred with many of the KDIGO recommendations except in some important areas related to immunosuppression, in which decisions in the United States are largely made by transplant centers and are dependent in part on the specific patient population served. Most, but not all, KDIGO guidelines are relevant to US patients. However, implementation of many may remain a major challenge because of issues of limitation in resources needed to assist in the tasks of educating, counseling, and implementing and maintaining lifestyle changes. Although very few of the guidelines are based on evidence that is strong enough to justify their being used as the basis of policy or performance measures, they offer an excellent road map to navigate the complex care of KTRs.

Hypertension after pediatric cardiac transplantation: detection, etiology, implications and management

While it may rescue children with end-stage heart failure from impending catastrophe, cardiac transplantation leaves 50-70% of pediatric recipients with new-onset hypertension. Given the unique vulnerability of the heart and kidneys in these children, we can expect long-term uncontrolled hypertension to shorten both graft and patient survival. In this review we discuss the multi-factorial etiology of post-transplant hypertension, highlighting current uncertainties and emphasizing mechanisms specific to cardiac recipients. We consider the optimal means of monitoring BP and in particular, the advantages of 24 h-ABP over intermittent clinic measurements. We also review BP treatment after cardiac transplantation, drawing attention to specific cautions appropriate when prescribing antihypertensive agents in these circumstances.

Drug-induced hypomagnesaemia : scope and management

Nearly 50 medications have been implicated as inducing hypomagnesaemia, sometimes based on insufficient data regarding clinical significance and frequency of occurrence. In fact, clinical effects attributed to hypomagnaesemia have been reported in only 17 of these drugs. A considerable amount of literature relating to individual drugs has been published, yet a comprehensive overview of this issue is not available and the hypomagnesaemic effect of a drug could be either overemphasised or under-rated. In addition, there are neither guidelines regarding treatment, prevention and monitoring of drug-induced hypomagnesaemia nor agreement as to what serum level of magnesium may actually be defined as 'hypomagnesaemia'. By compiling data from published papers, electronic databases, textbooks and product information leaflets, we attempted to assess the clinical significance of hypomagnesaemia induced by each drug. A practical approach for managing drug-induced hypomagnesaemia, incorporating both published literature and personal experience of the physician, is proposed. When drugs classified as inducing 'significant' hypomagnesaemia (cisplatin, amphotericin B, ciclosporin) are administered, routine magnesium monitoring is warranted, preventive treatment should be considered and treatment of hypomagnesaemia should be initiated with or without overt clinical manifestations. In drugs belonging to the 'potentially significant' category, among which are amikacin, gentamicin, laxatives, pentamidine, tobramycin, tacrolimus and carboplatin, magnesium monitoring is justified when either of the following occurs: clinical manifestations are apparent; persistent hypokalaemia, hypocalcaemia or alkalosis are present; other precipitating factors for hypomagnesaemia coexist; or treatment is with more than one potentially hypomagnesaemic drug. No preventive treatment is required and treatment should be initiated only if hypomagnesaemia is accompanied by symptoms or clinically significant relevant laboratory findings. In those drugs whose hypomagnesaemic effect is labelled as 'questionable', including furosemide and hydrochlorothiazide, routine monitoring and treatment are not required.

Effects of Immunosuppressive Agents on Magnesium Metabolism Early after Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND

The calcineurin inhibitors, cyclosporine A (CSA) and tacrolimus, cause hypomagnesemia by suppressing reabsorption of magnesium (Mg) from renal tubules. To assess whether the effect on Mg metabolism after allogeneic hematopoietic stem cell transplantation (HSCT) differs among calcineurin inhibitors, we prospectively evaluated the Mg metabolism in recipients of allogeneic HSCT who received CSA or tacrolimus

METHODS

Patients who underwent allogeneic HSCT were enrolled. CSA and tacrolimus were given by continuous infusion starting from day -1. Serum Mg and the total amount of urinary Mg excretion were measured once before starting of CSA or tacrolimus, and once weekly after HSCT for 4 weeks. Mg was supplemented with magnesium l-aspartate by continuous infusion to maintain the serum Mg level >1.4 mEq/L.

RESULTS

Thirty-six patients were evaluated (12 in the CSA group, 24 in the tacrolimus group). The serum Mg level began to decrease in both groups at the first week after HSCT, and the mean serum Mg levels were significantly lower in the tacrolimus group than in the CSA group from the first to the third week. The total amount of urinary Mg excretion and Mg supplementation began to increase in both groups at the second week after HSCT, and the amounts in the tacrolimus group were significantly higher than those in the CSA group.

CONCLUSIONS

Although both calcineurin inhibitors increased urinary Mg excretion and caused hypomagnesemia shortly after HSCT, the effect was more significant with tacrolimus than with CSA. This observation may explain the higher incidence of renal impairment and encephalopathy in patients receiving tacrolimus.

Mechanisms of clinically relevant drug interactions associated with tacrolimus

The clinical management of tacrolimus, a macrolide used as immunosuppressant after transplantation, is complicated by its narrow therapeutic index in combination with inter- and intraindividually variable pharmacokinetics. As a substrate of cytochrome P450 (CYP) 3A enzymes and P-glycoprotein, tacrolimus interacts with several other drugs used in transplantation medicine, which also are known CYP3A and/or P-glycoprotein inhibitors and/or inducers. In clinical studies, CYP3A/P-glycoprotein inhibitors and inducers primarily affect oral bioavailability of tacrolimus rather than its clearance, indicating a key role of intestinal P-glycoprotein and CYP3A. There is an almost complete overlap between the reported clinical drug interactions of tacrolimus and those of cyclosporin. However, in comparison with cyclosporin, only few controlled drug interaction studies have been carried out, but tacrolimus drug interactions have been extensively studied in vitro. These results are inconsistent and are of poor predictive value for clinical drug interactions because of false negative results. P-glycoprotein regulates distribution of tacrolimus through the blood-brain barrier into the brain as well as distribution into lymphocytes. Interaction of other drugs with P-glycoprotein may change tacrolimus tissue distribution and modify its toxicity and immunosuppressive activity. There is evidence that ethnic and gender differences exist for tacrolimus drug interactions. Therapeutic drug monitoring to guide dosage adjustments of tacrolimus is an efficient tool to manage drug interactions. In the near future, progress can be expected from studies evaluating potential pharmacokinetic interactions caused by herbal preparations and food components, the exact biochemical mechanism underlying tacrolimus toxicity, and the potential of inhibition of CYP3A and P-glycoprotein to improve oral bioavailability and to decrease intraindividual variability of tacrolimus pharmacokinetics.