Comparison of nephrotoxicities of different polyoxyethyleneglycol formulations of amphotericin B in rats

Potential Usefulness of Early Potassium Supplementation for Preventing Severe Hypokalemia Induced by Liposomal Amphotericin B in Hematologic Patients: A Retrospective Study

PURPOSE

Liposomal amphotericin B (L-AMB) is an essential antifungal agent for patients with hematologic diseases; however, the drug causes severe hypokalemia at a high frequency. Meanwhile, there is little evidence regarding the risk factors for L-AMB-induced severe hypokalemia, and the prevention protocol has not been established. The goal of this study was to identify the risk factors related to severe hypokalemia induced by L-AMB in hematologic patients.

METHODS

Seventy-eight hematologic patients with a first administration of L-AMB were enrolled in the study. Eleven patients who had serum potassium levels <3.0 mmol/L before L-AMB administration and 12 patients who received L-AMB administration within 3 days were excluded. Patients who had a serum potassium level <3.0 mmol/L during L-AMB administration were classified into a hypokalemia group (n = 26), and those who had a serum potassium level ≥3.0 mmol/L were classified into a non-hypokalemia group (n = 29). The patient characteristics were analyzed retrospectively. In addition, the usefulness of potassium supplementation was analyzed for those patients who received potassium formulations (non-hypokalemia group, n = 15; hypokalemia group, n = 24).

FINDINGS

Twenty-six patients had hypolalemia after L-AMB administration. Hypokalemia with serum potassium levels <3.0 mmol/L was observed ~7 days after starting L-AMB administration. The patient characteristics, L-AMB dose, and L-AMB administration period did not differ between the 2 groups. In the patients who received potassium formulations, the period between starting L-AMB administration and starting potassium supplementation was significantly shorter in the non-hypokalemia group than in the hypokalemia group (median, 0 vs 4 days, respectively; P < 0.01); the potassium dose was not different between the 2 groups. A receiver-operating characteristic curve revealed that the cutoff time for the start of potassium supplementation to reduce the incidence of L-AMB-induced hypokalemia was 3 days. Multivariate logistic regression analysis revealed that beginning potassium supplementation within 2 days from the start of L-AMB administration was an independent factor reducing the risk of L-AMB-induced hypokalemia (odds ratio, 0.094 [95% CI, 0.019-0.47]).

IMPLICATIONS

This study showed that starting administration of a potassium formulation within 2 days from the start of L-AMB administration was a risk reduction factor for L-AMB-induced hypokalemia. This finding indicates that early potassium supplementation should be incorporated into the regimen of hypokalemia management when L-AMB is used.

Oral administration of amphotericin B nanoparticles: antifungal activity, bioavailability and toxicity in rats

Amphotericin B (AMB) is used most commonly in severe systemic life-threatening fungal infections. There is currently an unmet need for an efficacious (AMB) formulation amenable to oral administration with better bioavailability and lower nephrotoxicity. Novel PEGylated polylactic-polyglycolic acid copolymer (PLGA-PEG) nanoparticles (NPs) formulations of AMB were therefore studied for their ability to kill Candida albicans (C. albicans). The antifungal activity of AMB formulations was assessed in C. albicans. Its bioavalability was investigated in nine groups of rats (n = 6). Toxicity was examined by an in vitro blood hemolysis assay, and in vivo nephrotoxicity after single and multiple dosing for a week by blood urea nitrogen (BUN) and plasma creatinine (PCr) measurements. The MIC of AMB loaded to PLGA-PEG NPs against C. albicans was reduced two to threefold compared with free AMB. Novel oral AMB delivery loaded to PLGA-PEG NPs was markedly systemically available compared to Fungizone® in rats. The addition of 2% of GA to the AMB formulation significantly (p < 0.05) improved the bioavailability from 1.5 to 10.5% and the relative bioavailability was > 790% that of Fungizone®. The novel AMB formulations showed minimal toxicity and better efficacy compared to Fungizone®. No nephrotoxicity in rats was detected after a week of multiple dosing of AMB NPs based on BUN and PCr, which remained at normal levels. An oral delivery system of AMB-loaded to PLGA-PEG NPs with better efficacy and minimal toxicity was formulated. The addition of glycyrrhizic acid (GA) to AMB NPs formulation resulted in a significant oral absorption and improved bioavailability in rats.

Evaluation of hypokalemia and potassium supplementation during administration of liposomal-amphotericin B

Patients prescribed liposomal-amphotericin B (L-AMB) frequently require supplemental potassium to prevent hypokalemia. The aim of this retrospective study was to examine the appropriate potassium supplementation conditions to treat hypokalemia induced by L-AMB. The subjects were 100 hematological patients who received L-AMB for the first time between April 2012 and March 2013. A total of seven patients were excluded. Of the remaining 93 patients, 48 (51.6%) were assigned to the group receiving supplemental potassium (supplementation group), and 45 (48.4%) were assigned to the group without potassium supplementation (non-supplementation group). Hypokalemia greater than grade 3 was exhibited by 50 of the 93 (53.8%) patients. Multivariate analysis revealed that the minimum serum potassium levels during L-AMB administration (≤2.98 mEq/l) were an independent factor significantly contributing to the effectiveness of potassium supplementation [odds ratio (OR), 3.62; 95% confidence interval (CI), 1.44–9.59; P<0.01]. In addition, multivariate analysis revealed that the serum potassium levels (≥2.83 mEq/l) prior to the potassium supplementation were an independent factor significantly contributing to the development of proper potassium supplementation (OR, 14.21; 95% CI, 1.95–310.72; P=0.02), and no significant difference was observed in the dosage of the potassium supplementation administered to the patients who recovered from hypokalemia and those who did not. In conclusion, it is necessary to begin potassium supplementation prior to the reduction of the serum potassium levels to <2.83 mEq/l. Potassium supplementation at an early stage of L-AMB treatment is important to prevent severe electrolyte abnormalities.

Invasive fungal infection in children undergoing chemotherapy for cancer

BACKGROUND

In children with cancer, invasive fungal infection is a serious complication of anticancer therapy. Successful treatment is a major challenge for clinical oncologists.

METHODS

The records of all episodes of invasive fungal infection occurring in children with cancer undergoing chemotherapy at Mackay Memorial Hospital, Taipei between January 1987 and October 2005 were reviewed. The following were documented: general characteristics, clinical presentation, predisposing factors, pathogens, antifungal treatment, association with anticancer therapy and outcome. We endeavoured to preserve renal function by administration of new antifungal agents. Anticancer therapy was given as soon as possible after diagnosis and the dose of chemotherapeutic agents was adjusted as required to prevent unduly prolonged interruption of chemotherapy and minimise the risk of leukaemia relapse.

RESULTS

Twenty-six patients with 29 episodes of invasive fungal infection were reviewed. Candida species were the leading pathogens (14/29) followed by Aspergillus species (11/29). In six episodes there was both visceral dissemination and fungaemia. In 23/29 patients, antibiotic therapy preceded fungal infection with a median of 11 days. Three children died from extensive fungal infection and four from progression of malignancy; the remainder survived with a median follow-up of 40 months (range 12-233). The actuarial 12-month survival rate was 87%; in patients with invasive candidiasis and aspergillosis the rates were 75% and 100%, respectively.

CONCLUSIONS

In children with cancer, most invasive fungal infections can be treated successfully. Current antifungal prophylaxis should protect patients from fungal infection.

Cholesterol induces renal vasoconstriction and anti-natriuresis by inhibiting nitric oxide production in anesthetized rats

Although hypercholesterolemia is implicated in the pathophysiology of many renal disorders as well as hypertension, its direct actions in the kidney are not yet clearly understood. In the present study, we evaluated renal responses to administration of cholesterol (8 microg x min(-1).100 g body wt(-1); bound by polyethylene glycol) into the renal artery of anesthetized male Sprague-Dawley rats. Total renal blood flow (RBF) was measured by a Transonic flow probe, and glomerular filtration rate (GFR) was determined by Inulin clearance. In control rats (n = 8), cholesterol induced reductions of 10 +/- 2% in RBF [baseline (b) 7.6 +/- 0.3 microg x min(-1).100 g(-1)], 17 +/- 3% in urine flow (b, 10.6 +/- 0.9 microg x min(-1).100 g(-1)), 29 +/- 3% in sodium excretion (b, 0.96 +/- 0.05 mumol.min(-1).100 g(-1)) and 24 +/- 2% in nitrite/nitrate excretion (b, 0.22 +/- 0.01 nmol.min(-1).100 g(-1)) without an appreciable change in GFR (b, 0.87 +/- 0.03 ml.min(-1).100 g(-1)). These renal vasoconstrictor and anti-natriuretic responses to cholesterol were absent in rats pretreated with nitric oxide (NO) synthase inhibitor, nitro-l-arginine methylester (0.5 microg x min(-1).100 g(-1); n = 6). In rats pretreated with superoxide (O(2)(-)) scavenger tempol (50 microg x min(-1).100 g(-1); n = 6), the cholesterol-induced renal responses remained mostly unchanged, although there was a slight attenuation in anti-natriuretic response. This anti-natriuretic response to cholesterol was abolished in furosemide-pretreated rats (0.3 microg x min(-1).100 g(-1); n = 6) but remained unchanged in amiloride-pretreated rats (0.2 microg x min(-1).100 g(-1); n = 5), indicating that Na(+)/K(+)/2Cl(-) cotransport is the dominant mediator of this effect. These data demonstrate that cholesterol-induced acute renal vasoconstrictor and antinatriuretic responses are mediated by a decrease in NO production. These data also indicate that tubular effect of cholesterol on sodium reabsorption is mediated by the furosemide sensitive Na(+)/K(+)/2Cl(-) cotransporter.

Formulation and evaluation of microemulsion based delivery system for amphotericin B

The present studies were designed to develop a formulation of amphotericin B in a lipid-based preparation as a microemulsion and to compare its toxicity with the commercial formulation Fungizone. The final product developed is a lyophilized amphotericin B, oil and surfactant blend for reconstitution in water to yield a microemulsion containing 5 mg/ml of the drug. Pseudoternary phase diagrams were constructed to identify areas of existence of microemulsion composed of Peceol (glyceryl monooleate) as oil phase and Mys 40 (polyethylene glycol 40 stearate) and Solutol HS 15 (polyethylene glycol 15 hydroxy stearate) as surfactants. Amphotericin B was co-evaporated with oil - surfactant mixture to produce a microemulsion pre-concentrate. The co-evaporate was diluted in water, filtered for sterilization and lyophilized to obtain the final product. The lyophilized as well as the reconstituted products were separately studied for stability and the latter was also characterized for various physicochemical aspects including droplet size of the dispersed phase, osmolarity and aggregation state of drug. The dispersion showed no evidence of precipitation of drug for 48 h, and resisted destabilization due to freeze-thaw cycles or centrifugation. The dispersed phase globules measured a mean size of 84 nm and uv-spectrophotometric studies indicated the presence of self-aggregated amphotericin B. The present formulation showed a 92% decrease in haemolysis of human RBC in vitro when compared with the commercially available Fungizone. The LD(50) in mice was estimated to be 3.4 mg/kg. The results indicate that the formulation holds promise for development as a safer and efficacious alternative for amphotericin B therapy.

Proteinuria lowers the risk of amphotericin B-associated hypokalaemia

OBJECTIVES

Amphotericin B-induced nephrotoxicity is frequent, severe and associated with an increased risk of death. Patients with underlying renal disease are considered to be at high risk for amphotericin B nephrotoxicity. Amphotericin B is a molecule that is highly protein bound over a wide range of protein and drug concentrations, including those seen in patients with >or= 3 + proteinuria. We hypothesized that amphotericin B treatment in patients with proteinuria will be associated with less hypokalaemia than patients with non-proteinuric renal disease.

METHODS

Thirty-six subjects who received amphotericin B deoxycholate were studied retrospectively. Twenty-five patients with proteinuria < 3 g/L and 11 with proteinuria >or= 3 g/L were compared.

RESULTS

Hypokalaemia (K+ < 3.5 mmol/L) developed in 47.2% (17/36) of our cohort of patients. There was a 64% (16/25) incidence of hypokalaemia in the group with < 3 g/L of proteinuria in contrast to an incidence of 9.1% (1/11) in the other group.

CONCLUSIONS

In our study, heavy proteinuria appears to protect the tubular luminal membrane by decreasing the luminal concentration of free drug available to bind with the membrane. Our findings redefine the patient population deemed to be at risk of developing amphotericin B nephrotoxicity. This ensures the benefit of this important antifungal treatment option to patients with heavy proteinuria who might otherwise not be administered this drug due to the presence of pre-existing kidney disease.

Distribution and Transport of Cholesterol-rich Membrane Domains Monitored by a Membrane-impermeant Fluorescent Polyethylene Glycol-derivatized Cholesterol

Cholesterol-rich membrane domains function in various membrane events as diverse as signal transduction and membrane traffic. We studied the interaction of a fluorescein ester of polyethylene glycol-derivatized cholesterol (fPEG-Chol) with cholesterol-rich membranes both in cells and in model membranes. Unlike filipin and other cholesterol probes, this molecule could be applied as an aqueous dispersion to various samples. When added to live cells, fPEG-Chol distributed exclusively in the outer plasma membrane leaflet and was enriched in microdomains that dynamically clustered by the activation of receptor signaling. The surface-bound fPEG-Chol was slowly internalized via clathrin-independent pathway into endosomes together with lipid raft markers. Noteworthy, fPEG-Chol could be microinjected in the living cells in which we found Golgi apparatus as the sole major organelle to be labeled. PEG-Chol, thus, provides a novel, sensitive probe for unraveling the dynamics of cholesterol-rich microdomains in living cells.

A chemically modified tetracycline (CMT-3) is a new antifungal agent

Several chemically modified tetracycline analogs (CMTs), which were chemically modified to eliminate their antibacterial efficacy, were unexpectedly found to have antifungal properties. Of 10 CMTs screened in vitro, all exhibited antifungal activities, although their efficacies varied. Among these compounds, CMT-315, -3, and -308 were found to be the most potent as antifungal agents. The MICs of CMT-3 against 47 strains of fungi in vitro were determined by using amphotericin B (AMB) and doxycycline as positive and negative controls, respectively. The MICs of CMT-3 were generally found to be between 0.25 and 8.00 microg/ml, a range that approximates the blood levels of this drug when administrated orally to humans. Of all the yeast species tested to date, Candida albicans showed the greatest sensitivity to CMT-3. The filamentous species most susceptible to CMT-3 were found to be Epidermophyton floccosum, Microsporum gypseum, Pseudallescheria boydii, a Penicillium sp., Scedosporium apiospermum, a Tricothecium sp., and Trichophyton rubrum. Growth inhibition of C. albicans by CMT-3, determined by a turbidity assay, indicated a 50% inhibitory concentration of 1 microg/ml. Thirty-nine strains, including 20 yeasts and 19 molds, were used to measure viability (the ability to grow after treatment with a drug) inhibition by CMT-3 and AMB. CMT-3 exhibited fungicidal activity against most of these fungi, especially the filamentous fungi. Eighty-four percent (16 of 19) of the filamentous fungi tested showed more than 90% inhibition of viability by CMT-3. In contrast, AMB showed fungicidal activity against all yeasts tested. However, most of the filamentous fungi (16 of 19) showed less than 50% inhibition of viability by AMB, indicating that AMB is fungistatic against most of these filamentous fungi. To begin to identify the sites in fungal cells affected by CMT-3, C. albicans and a Penicillium sp. were incubated with the compound at 35 degrees C, and then the fluorescence of CMT-3 was observed by confocal laser scanning electron microscopy. CMT-3 appeared to have widespread intracellular distribution throughout C. albicans and the Penicillium sp. The mechanisms of the antifungal activity of CMT-3 are now being explored.

Comparative pharmacokinetics, tissue distributions, and effects on renal function of novel polymeric formulations of amphotericin B and amphotericin B-deoxycholate in rats

The pharmacokinetic profiles of a traditional formulation of amphotericin B (Fungizone) and novel nanosphere and mixed micelle delivery systems developed for amphotericin B were compared and described. Six groups of male Wistar rats received intravenous injections of the different formulations. Plasma and tissue samples were obtained at 11 different times after dosing, with three animals used each time. The amphotericin B concentrations in plasma and tissues were analyzed by high-performance liquid chromatography. The plasma drug concentration-time profiles were best described by a two-compartment model. Models that described the observed single or double peak disposition kinetics in kidney, liver, and spleen were also developed. Parameter estimates from those models show that components of the formulation such as poloxamer 188, which is present in all new formulations, seem to play an important role in the rate of drug uptake by the tissues; in general, the levels of amphotericin B in tissues were increased after the administration of the new formulations compared with those after the administration of Fungizone. The increment in the baseline plasma creatinine level was used as an index of renal function. All formulations increased this baseline value, but the novel formulations exhibited fewer renal effects than Fungizone did. However, a direct relationship between drug exposure in the kidneys and development of renal damage could not be found.