Pharmacokinetics of Tobramycin Administered at the Beginning of Intermittent Hemodialysis Session (ESRD Study).

BACKGROUND AND OBJECTIVES: There is a renewed interest in the successful use of aminoglycosides due to increasing resistance in gram-negative infections. Few studies to date have examined the pharmacokinetics (PK) of intradialytic infusions of tobramycin. This study sought to characterize the pharmacokinetic profile of intradialytically administered tobramycin in infected patients receiving chronic intermittent hemodialysis and to determine whether it is possible to achieve favorable PK targets. DESIGN SETTING PARTICIPANTS AND MEASUREMENTS: In this prospective pharmacokinetic study, a single dose (5 mg/kg) of tobramycin was administered intradialytically to 11 noncritically ill patients undergoing chronic intermittent hemodialysis. Blood samples were collected at selected time to determine tobramycin serum concentrations. The PK analysis was performed using Phoenix™ NLME. The efficacy exposure outcome for nonsevere gram-negative infections sensitive to tobramycin with a minimum inhibitory concentration ≤1 were maximum concentration (Cmax ≥ 10 mg/L) and area under the curve (AUC24 h > 30 mg⋅h/L). For toxicity, the goal was to identify plasma trough concentrations <2 mg/L. RESULTS: Tobramycin disposition was best described by a one-compartment model using a total clearance composed of the systemic clearance and a transitory hemodialysis clearance. Tobramycin mean (SD) Cmax, trough levels, and AUC24h were 13.1 (1.3) mg/L, 1.32 (0.47) mg/L, and 61 (23) mg⋅h/L, respectively. Monte Carlo simulation run with 1000 virtual patients showed that a 5 mg/kg dose of tobramycin administered intradialytically can outperformed the usual low-dose postdialysis dosing (80% meeting all targets versus <1%, respectively). CONCLUSIONS: A single high dose of tobramycin can achieve favorable PK outcome when administered using intradialytic infusions in hemodialysis patients. This practical dosing regimen may represent an effective and safer alternative to the usual dosing in the treatment of nonsevere gram-negative infections.

CONTEXTE ET OBJECTIFS: La résistance croissante des infections à Gram négatif suscite un regain d'intérêt pour l'utilisation efficace des aminoglycosides. À ce jour, peu d'études ont examiné la pharmacocinétique (PK) des infusions intradialytiques de tobramycine. La présente étude a tenté de caractériser le profil pharmacocinétique de la tobramycine administrée par infusion intradialytique chez des patients malades recevant des traitements intermittents d'hémodialyse de façon chronique. L'étude visait également à déterminer s'il est possible d'atteindre des objectifs de pharmacocinétique favorables. MÉTHODOLOGIE: Pour cette étude de pharmacocinétique prospective, une dose unique (5 mg/kg) de tobramycine a été administrée par infusion intradialytique à onze patients suivant des traitements d'hémodialyse intermittente de façon chronique ne nécessitant pas une admission aux soins intensifs. Des échantillons de sang ont été prélevés à des moments précis afin de mesurer les concentrations sériques de tobramycine. L'analyse de la PK a été effectuée à l'aide du PhoenixMC NLME. Les issues d'exposition d'efficacité avec une concentration minimale inhibitrice inférieure ou égale à 1 pour les infections à Gram négatifs non graves sensibles à la tobramycine étaient la concentration maximum (Cmax: ≥10 mg/L) et la surface sous la courbe (SSC24h: >30 mg⋅h/L). Quant à la toxicité, l'objectif était l'observation de concentrations plasmatiques inférieures à 2 mg/L. RÉSULTATS: La disponibilité de la tobramycine a été mieux décrite par un modèle à un compartiment utilisant une clairance totale composée de la clairance systémique et de la clairance transitoire de l'hémodialyse. La Cmax moyenne, la concentration minimale et la SSC24h de la tobramycine (écart-type) s'établissaient respectivement à 13,1 (1,3) mg/L, à 1,32 (0,47) mg/L et à 61 (23) mg⋅h/L. Une simulation de Monte Carlo réalisée avec 1 000 patients virtuels a montré qu'une dose unique de 5 mg/kg de tobramycine administrée par infusion intradialytique surpasse la faible dose normalement administrée après la dialyse (80 % des objectifs atteints pour la dose unique contre moins de 1 %, respectivement). CONCLUSIONS: Une dose unique élevée de tobramycine permet d'atteindre des paramètres pharmacocinétiques favorables si elle est administrée par infusion intradialytique chez les patients hémodialysés. Ce schéma posologique peut représenter une solution de remplacement efficace et plus sûre au dosage normalement administré pour le traitement des infections à Gram négatifs non graves.

Conversion of oral alfacalcidol to oral calcitriol in the treatment of secondary hyperparathyroidism in chronic hemodialysis patients.

PURPOSE: The optimal vitamin D3 therapy for the treatment of secondary hyperparathyroidism (SHPT) in chronic hemodialysis patients is still controversial. Recent studies suggest that uremia in end-stage renal disease is associated with enzymatic hepatic dysfunction altering 25-hydroxylation of vitamin D3. The goal of our study was to compare the efficacy of calcitriol, the fully hydroxylated active form of vitamin D3, to alfacalcidol which needs 25-hydroxylation to be effective, for the treatment of SHPT in chronic hemodialysis patients. METHODS: We retrospectively reviewed 45 chronic hemodialysis patients who were switched from oral alfacalcidol to oral calcitriol for the treatment of SHPT. Parathyroid hormone (PTH), serum calcium and serum phosphorus levels were compared pre- and post-conversion using paired Student's t tests. RESULTS: The mean dose of active vitamin D3 decreased from 3.50 mcg/week at baseline to 2.86 mcg (P < 0001) after the switch from alfacalcidol to calcitriol. PTH significantly decreased from 94.4 to 82.6 pmol/L (-11.8 pmol/L, P = 0.02). The mean corrected calcium increased from 2.17 to 2.25 mmol/L (+0.08 mmol/L, P < 0.001) without any clinically significant hypercalcemia, and phosphorus levels were stable. Results were similar in a subgroup of patients (n = 17) for whom the medication was administrated during the hemodialysis session, ensuring a complete compliance. CONCLUSIONS: According to our study, calcitriol in equal dosage is more effective than alfacalcidol in lowering serum PTH level in chronic hemodialysis patients. This suggests that calcitriol may be the optimal active vitamin D3 for the treatment of SHPT in chronic hemodialysis patients.

New drugs to prevent and treat hyperkalemia.

PURPOSE OF REVIEW: Hyperkalemia is frequent, but occurs mostly in patients with chronic kidney disease and is often the cause of discontinuation or omission of renin-angiotensin-aldosterone system inhibitors in patients with diabetes, chronic kidney disease and heart failure. RECENT FINDINGS: Without much evidence in the literature on its efficacy, sodium polystyrene sulfonate is being used frequently in the clinical setting to treat hyperkalemia. In the last few years, two new promising agents have been developed to treat hyperkalemia - patiromer and sodium zirconium cyclosilicate 9 (ZS-9). Both patiromer and ZS-9 have been shown to decrease potassium in patients with hyperkalemia and then to maintain normokalemia. Gastrointestinal adverse events were more frequent with patiromer, and edema occurred in patients using high doses of ZS-9, possibly due to its high sodium content. SUMMARY: Although patiromer and ZS-9 are very promising in terms of safety and efficacy, many questions remain, mostly in terms of selection of patients, long-term effects and costs.

Randomized Clinical Trial of Sodium Polystyrene Sulfonate for the Treatment of Mild Hyperkalemia in CKD.

BACKGROUND AND OBJECTIVES: Hyperkalemia affects up to 10% of patients with CKD. Sodium polystyrene sulfonate has long been prescribed for this condition, although evidence is lacking on its efficacy for the treatment of mild hyperkalemia over several days. This study aimed to evaluate the efficacy of sodium polystyrene sulfonate in the treatment of mild hyperkalemia. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In total, 33 outpatients with CKD and mild hyperkalemia (5.0-5.9 mEq/L) in a single teaching hospital were included in this double-blind randomized clinical trial. We randomly assigned these patients to receive either placebo or sodium polystyrene sulfonate of 30 g orally one time per day for 7 days. The primary outcome was the comparison between study groups of the mean difference of serum potassium levels between the day after the last dose of treatment and baseline. RESULTS: The mean duration of treatment was 6.9 days. Sodium polystyrene sulfonate was superior to placebo in the reduction of serum potassium levels (mean difference between groups, -1.04 mEq/L; 95% confidence interval, -1.37 to -0.71). A higher proportion of patients in the sodium polystyrene sulfonate group attained normokalemia at the end of their treatment compared with those in the placebo group, but the difference did not reach statistical significance (73% versus 38%; P=0.07). There was a trend toward higher rates of electrolytic disturbances and an increase in gastrointestinal side effects in the group receiving sodium polystyrene sulfonate. CONCLUSIONS: Sodium polystyrene sulfonate was superior to placebo in reducing serum potassium over 7 days in patients with mild hyperkalemia and CKD.