Pharmacokinetics of liposomal amphotericin B (Ambisome) in critically ill patients

The liposomal formulation of amphotericin B (AmBisome) greatly reduces the acute and chronic side effects of the parent drug. The present study describes the pharmacokinetic characteristics of AmBisome applied to 10 patients at a dose of 2.8 to 3.0 mg/kg of body weight and compares them to the pharmacokinetics observed in 6 patients treated with amphotericin B deoxycholate at the standard dose of 1.0 mg/kg. Interpatient variabilities of amphotericin B peak concentrations (Cmax) and areas under concentration-time curves (AUC) were 8- to 10-fold greater for patients treated with AmBisome than for patients treated with amphotericin B deoxycholate. At the threefold greater dose of AmBisome, median Cmaxs were 8.4-fold higher (14.4 versus 1.7 microg/ml) and median AUCs exceeded those observed with amphotericin B deoxycholate by 9-fold. This was in part explained by a 5.7-fold lower volume of distribution (0.42 liters/kg) in AmBisome-treated patients. The elimination of amphotericin B from serum was biphasic for both formulations. However, the apparent half-life of elimination was twofold shorter for AmBisome (P = 0.03). Neither hemodialysis nor hemofiltration had a significant impact on AmBisome pharmacokinetics as analyzed in one patient. In conclusion, the liposomal formulation of amphotericin B significantly (P = 0.001) reduces the volume of drug distribution, thereby allowing for greater drug concentrations in serum. The low toxicity of AmBisome therefore cannot readily be explained by its serum pharmacokinetics.     

Activity of liposomal amphotericin B against experimental cutaneous leishmaniasis

The polyene antibiotic amphotericin B is currently a second-line treatment for visceral leishmaniasis (VL) and mucocutaneous leishmaniasis. Lipid-amphotericin B formulations with lower toxicity than the parent drug that were developed for the treatment of systemic mycoses have proved to be an effective treatment for VL, especially AmBisome, a small unilamellar negatively charged liposome. In vitro, free amphotericin B was three to six times more active than the liposomal formulation AmBisome against both Leishmania major promastigotes in culture and amastigotes in murine macrophages. In a BALB/c L. major model of cutaneous infection, liposomal amphotericin B administered once a day on six alternate days by the intravenous route produced a dose-response effect between 6.25 and 50 mg/kg. Liposomal amphotericin B administered subcutaneously close to a lesion had no significant activity. Free drug was ineffective at nontoxic doses. The results suggest that liposomal amphotericin B may be useful in the treatment of cutaneous leishmaniasis.     

Safety, tolerance, and pharmacokinetics of a small unilamellar liposomal formulation of amphotericin B (AmBisome) in neutropenic patients

The safety, tolerance, and pharmacokinetics of a small unilamellar liposomal formulation of amphotericin B (AmBisome) administered for empirical antifungal therapy were evaluated for 36 persistently febrile neutropenic adults receiving cancer chemotherapy and bone marrow transplantation. The protocol was an open-label, sequential-dose-escalation, multidose pharmacokinetic study which enrolled a total of 8 to 12 patients in each of the four dosage cohorts. Each cohort received daily doses of either 1.0, 2.5, 5.0, or 7.5 mg of amphotericin B in the form of AmBisome/kg of body weight. The study population consisted of patients between the ages of 13 and 80 years with neutropenia (absolute neutrophil count, <500/mm3) who were eligible to receive empirical antifungal therapy. Patients were monitored for safety and tolerance by frequent laboratory examinations and the monitoring of infusion-related reactions. Efficacy was assessed by monitoring for the development of invasive fungal infection. The pharmacokinetic parameters of AmBisome were measured as those of amphotericin B by high-performance liquid chromatography. Noncompartmental methods were used to calculate pharmacokinetic parameters. AmBisome administered as a 1-h infusion in this population was well tolerated and was seldom associated with infusion-related toxicity. Infusion-related side effects occurred in 15 (5%) of all 331 infusions, and only two patients (5%) required premedication. Serum creatinine, potassium, and magnesium levels were not significantly changed from baseline in any of the dosage cohorts, and there was no net increase in serum transaminase levels. AmBisome followed a nonlinear dosage relationship that was consistent with reticuloendothelial uptake and redistribution. There were no breakthrough fungal infections during empirical therapy with AmBisome. AmBisome administered to febrile neutropenic patients in this study was well tolerated, was seldom associated with infusion-related toxicity, was characterized by nonlinear saturation kinetics, and was effective in preventing breakthrough fungal infections.     

Reduction of amphotericin B nephrotoxicity with mannitol

Amphotericin B in combination with mannitol was given to a patient who had mucocutaneous candidiasis and moderate renal insufficiency. Previously, amphotericin B alone had induced an abrupt increase in serum creatinine and urea nitrogen, but when mannitol was given concurrently there was no worsening of renal function. Thus, amphotericin B with mannitol appears to offer a less nephrotoxic but equally candicidal therapeutic regimen in the renal compromised patient requiring parenteral candicidal therapy.     

Visceral leishmaniasis in the BALB/c mouse: a comparison of the efficacy of a nonionic surfactant formulation of sodium stibogluconate with those of three proprietary formulations of amphotericin B

In this study, treatment efficacies of a nonionic surfactant vesicle formulation of sodium stibogluconate (SSG-NIV) and of several formulations of amphotericin B were compared in a murine model of visceral leishmaniasis. Treatment with multiple doses of AmBisome, Abelcet, and Amphocil (total dose, 12.5 mg of amphotericin B/kg of body weight) resulted in a significant suppression of parasite burdens in liver (P < 0.0005) and spleen (P < 0.0005) compared with those of controls, with Abelcet having the lowest activity. Only AmBisome and Amphocil gave significant suppression of parasites in bone marrow (compared to control values, P < 0.005). In the acute-infection model, single-dose treatments of SSG-NIV (296 mg of SbV/kg), SSG solution (296 mg of SbV/kg), or AmBisome (8 mg of amphotericin B/kg) were equally effective against liver parasites (compared to control values, P < 0.0005). SSG-NIV and AmBisome treatment also significantly suppressed parasites in bone marrow and spleen (P < 0.005), with SSG-NIV treatment being more suppressive (>98% suppression in all three sites). Free-SSG treatment failed to suppress spleen or bone marrow parasites. Infection status influenced treatment outcome. In the chronic-infection model, the AmBisome single-dose treatment was less effective in all three infection sites and the SSG-NIV single-dose treatment was less effective in the spleen. The results of this study suggest that the antileishmanial efficacy of SSG-NIV compares favorably with those of the novel amphotericin B formulations.     

Assessment of antifungal activities of fluconazole and amphotericin B administered alone and in combination against Candida albicans by using a dynamic in vitro mycotic infection model

We evaluated the pharmacodynamic activities of fluconazole and amphotericin B given alone and in combination against Candida albicans by using an in vitro model of bloodstream infection that simulates human serum pharmacokinetic parameters for these antifungals. Fluconazole was administered as a bolus into the model to simulate regimens of 200 mg every 24 h (q24 h) and 400 mg q24 h. Amphotericin B was administered at doses producing the peak concentration (2.4 micrograms/ml) observed with a regimen of 1 mg/kg of body weight q24 h. A combination regimen of fluconazole (400 mg q24 h) and amphotericin B (1 mg/kg q24 h) administered simultaneously and as a staggered regimen (amphotericin B bolus given 8 h after fluconazole bolus) was also simulated in the model to characterize possible antagonism between these agents. Fluconazole alone and amphotericin B alone demonstrated fungistatic (< 99.9% reduction in numbers of CFU per milliliter from the starting inoculum) and fungicidal (> 99.9% reduction) activity, respectively. When fluconazole and amphotericin B were administered simultaneously, fungicidal activity similar to that observed with amphotericin B alone was observed. Staggered administration of fluconazole and amphotericin B, however, resulted in a substantial reduction of the fungicidal activity of amphotericin B, producing fungistatic activity similar to that observed with noncombination fluconazole regimens. These results demonstrate the usefulness of this model for comparing the in vitro pharmacodynamic characteristics of different antifungal regimens and support the theory of azole-polyene antagonism. The effects of this antagonism on the in vivo activity and clinical usefulness of combination antifungal therapy, however, remain to be determined.     

Quantitation of amphotericin B with use of high-pressure liquid chromatography

A chemical method for determination of concentrations of amphotericin B in serum and cerebrospinal fluid (CSF) is described. After extraction with methanol, the antibiotic was separated by reverse-phase, high-pressure liquid chromatography and quantitated by absorption at 405 nm. The lower limit of detection of this assay was 0.02 microng/ml. Relative standard deviations of less than 3.6% were noted for multiple determinations of sera containing 0.20 and 1.00 microng of amphotericin B/ml. No interfering peaks were found in extracts of serum or CSF from normal humans or in extracts of serum from patients treated with other drugs and antimicrobial agents, including 5-fluorocytosine. Comparison of the method with microbiological assays showed correlation coefficients of 0.90 and 0.83 for serum and CSF determinations, respectively. This chemical assay is very rapid (less than 30 min), sensitive, accurate, and specific and appears to be suitable for routine clinical use.     

Serum pharmacology of amphotericin B applied in lipid emulsions

Application of amphotericin B in lipid emulsions (AmB/L) reduced membrane toxicity in vitro and decreased amphotericin B-associated toxic side effects in vivo when compared to that of amphotericin B applied in 5% glucose (AmB/G). Therefore, a comparative analysis of the pharmacological parameters of AmB/L and AmB/G was performed. Thirteen patients were analyzed, and nine of these patients received a subsequent treatment with AmB/G and AmB/L. In patients in both treatment groups amphotericin B showed a biphasic elimination from serum, with a prolonged terminal half-life of approximately 27 h. Patients treated with AmB/L showed significantly lower peak concentrations (44.2%; P = 0.008) and correspondingly lower area under the drug concentration-time curve (AUC) values (64.3%; P = 0.015) compared to the values for the same patients treated with AmB/G at a dose range of 0.6 to 1.5 mg/kg of body weight. The enhanced clearance of AmB/L may be due to a faster initial elimination of amphotericin B-lipid aggregates by the reticuloendothelial system. Lower peak concentrations and AUC values in serum and a correspondingly faster deposition of AmB/L in tissues may at least partly explain the lower toxicity of AmB/L. A comparative pharmacokinetic analysis with data for a single patient treated with AmB/L demonstrated that hemodialysis did not significantly affect the disposition of amphotericin B.     

Must we be really concerned about amphotericin B toxicity in oncology patients?

BACKGROUND: Amphotericin B treatment in oncological patients is irrepaceable due to the high frequency of mycotic infections. From data in the literature ensues that the most serious undesirable effect of amphotericin B is nephrotoxicity, manifested by a reduced glomerular filtration and impaired tubular function (in particular the development of hypokalemia, and hypomagnesaemia). Prophylaxis of nephrotoxicity is despite major efforts unsatisfactory. In the submitted work the authors tested in a major group of patients their working hypothesis based on previous observations, that prophylactic replacement of the increasing ion losses in urine during amphotericin B treatment without waiting for a decline of serum concentrations of these ions, along with adequate hydration delays or eliminates the decline of glomerular functions. METHODS AND RESULTS: During amphotericin B therapy of 25 oncological patients renal functions, Na, K and Mg urinary excretion and the serum concentrations of these ions were followed up in detail. The urinary losses were replaced. No overall prophylaxis to prevent acute toxic reactions associated with administration of the drug was used. The mean dose of amphotericin B was 0.82 mg/kg, the mean diuresis 3662 ml/24 hours. Acute toxic reactions calling for hydrocortisone administration were observed only in 6% of the patients. During treatment the urinary K and Mg losses increased significantly and had to one replaced. There was also a significant increase of the excretory fractions of K and Na. However there were no significant changes of serum ions nor a rise of creatinine. The creatinine clearance even increased slightly though insignificantly (1.384 ml/s as compared with 1.392 ml/s). CONCLUSIONS: Consequential hydration of patients and prophylactic replacement of urinary ion losses during amphotericin B therapy are effective in preventing ion disbalances and a decline of glomerular functions. Acute toxic reactions associated with administration of amphotericin B are infrequent.     

A randomized trial comparing fluconazole with amphotericin B for the treatment of candidemia in patients without neutropenia. Candidemia Study Group and the National Institute

BACKGROUND: Amphotericin B has long been the standard treatment for candidemia, but its use is complicated by its toxicity. More recently, fluconazole, a water-soluble triazole with activity against candida species and little toxicity, has become available. We conducted a multicenter randomized trial that compared amphotericin B with fluconazole as treatment for candidemia. METHODS: To be eligible, patients had to have a positive blood culture for candida species, a neutrophil count > or = 500 per cubic millimeter, and no major immunodeficiency. Patients were randomly assigned to receive either amphotericin B (0.5 to 0.6 mg per kilogram of body weight per day) or fluconazole (400 mg per day), each continued for at least 14 days after the last positive blood culture. Outcomes were assessed by a group of investigators blinded to treatment assignment. RESULTS: Of the 237 patients enrolled, 206 met all entry criteria. The most common diagnoses were renal failure, nonhematologic cancer, and gastrointestinal disease. There was no statistically significant difference in outcome: of the 103 patients treated with amphotericin B, 81 (79 percent) were judged to have been treated successfully, as were 72 of the 103 patients treated with fluconazole (70 percent P = 0.22; 95 percent confidence interval for the difference, -5 to 23 percent). The bloodstream infection failed to clear in 12 patients in the amphotericin group and 15 in the fluconazole group; the species most commonly associated with failure was Candida albicans. There were 41 deaths in the amphotericin group and 34 deaths in the fluconazole group (P = 0.20). Intravascular catheters appeared to be the most frequent source of candidemia. There was less toxicity with fluconazole than with amphotericin B. CONCLUSIONS: In patients without neutropenia and without major immunodeficiency, fluconazole and amphotericin B are not significantly different in their effectiveness in treating candidemia.     

Activity of liposomal amphotericin B with prolonged circulation in blood versus those of AmBisome and fungizone against intracellular Candida albicans in murine peritoneal macrophages

Activity against intracellular Candida albicans was assessed in C. albicans-infected murine peritoneal macrophages exposed to long-circulating pegylated amphotericin B liposomes (PEG-AMB-LIP), AmBisome, or Fungizone. The level of antifungal activity of Fungizone is much higher than that of AmBisome or PEG-AMB-LIP, while PEG-AMB-LIP and AmBisome show equivalent activity levels. Previous exposure of uninfected macrophages to PEG-AMB-LIP or AmBisome is advantageous for intracellular antifungal activity.     

Superior efficacy of liposomal amphotericin B with prolonged circulation in blood in the treatment of severe candidiasis in leukopenic mice

In leukopenic mice with severe systemic candidiasis, single-dose treatment (5 mg of amphotericin B [AMB]/kg of body weight) with long-circulating polyethylene glycol-coated AMB liposomes (PEG-AMB-LIP) resulted in zero mortality and a significant reduction in the number of viable Candida albicans in the kidney, whereas 70% mortality was seen in mice treated with five daily doses of AmBisome (5 mg of AMB/kg . day). When the first of five daily doses of AmBisome was combined with a single low dose of Fungizone (0.1 mg of AMB/kg), the efficacy was equal to that of PEG-AMB-LIP.     

Chest discomfort associated with liposomal amphotericin B: report of three cases and review of the literature

Liposomal formulations of amphotericin B are designed to maintain therapeutic efficacy of amphotericin B deoxycholate while reducing its associated toxicities. In three patients chest discomfort occurred during planned 1-hour infusions of liposomal amphotericin B (AmBisome) 3 mg/kg/day during an open-label trial. The first patient experienced chest tightness and difficulty breathing and the second had dyspnea and acute hypoxia, both within 10 minutes of the start of the infusion. The third patient complained of chest pain 5 minutes after the start of two infusions. All symptoms resolved on terminating therapy. Two patients were later rechallenged with slower infusions and tolerated the drug well. A review of the English-language literature revealed only two other case reports of infusion-related chest or pulmonary reactions with the drug, although similar reactions were noted in several reports of clinical trials. Further review of the literature revealed reports of chest and pulmonary adverse events with other liposomal formulations of amphotericin B, liposomal daunorubicin, liposomal doxorubicin, and liposomes. The pathophysiology of such reactions remains unclear, and premedication with diphenhydramine did not completely prevent this reaction in one of our patients. We recommend infusing liposomal amphotericin B over at least 2 hours with careful monitoring for adverse reactions.     

Disposition of aerosolized liposomal amphotericin B

Amphotericin B (AmB) is an important drug for the treatment of fungal infection, but toxicity limits the lung tissue doses which may be achieved through intravenous administration. Although incorporation of AmB in liposomes reduces these effects and increases the therapeutic index for intravenous administration, targeted delivery to lung tissues via inhaled liposomal AmB aerosol may be a more effective approach. Aerosolization of liposomal amphotericin B targets the lungs, the organs first infested by many fungi. Development of optimal aerosolized liposomal AmB therapies requires a better understanding of the effect that liposome surface charge has on lung clearance kinetics. In this work we evaluated the clearance kinetics and organ distribution of inhaled liposomal AmB in male Balb/C mice. Mice were exposed via nose only to AmB-containing liposomal aerosols having positive, negative, or neutral surface charge characteristics. The formulations were aerosolized using a Collison nebulizer. Groups of animals were euthanized at predetermined times and the lungs and other organs were analyzed for AmB. AmB was not detected in serum and other organs such as kidneys, liver, and brain. The disposition of neutral and positive liposomal amphotericin B in lungs followed biexponential kinetics. The alpha and beta phase half-lives for positive liposomes were 1.3 and 15.1 days, respectively, and 2.3 and 22 days for neutral liposomes. AmB delivered via negative liposomes exhibited monoexponential clearance with a half-life of 4.5 days. These results suggest that toxic side effects in nontarget tissues are minimal and may indicate a potential for long term protection against fungal infections.     

Efficacy of NS-718, a novel lipid nanosphere-encapsulated amphotericin B, against Cryptococcus neoformans

In vitro and in vivo efficacies of NS-718, a lipid nanosphere-encapsulated amphotericin B (AMPH-B), have been studied. Of the tested AMPH-B formulations, NS-718 had the lowest MIC for Cryptococcus neoformans. In a murine model, low-dose therapy (0.8 mg/kg of body weight) with NS-718 showed higher efficacy than that with AmBisome. High-dose therapy (2.0 mg/kg) with NS-718 was much more effective than those with Fungizone and AmBisome. In mice treated with a high dose of NS-718, only a few yeast cells had grown in lung by 7 days after inoculation. A pharmacokinetic study showed higher concentrations of AMPH-B in lung following administration of NS-718 than after administration of AmBisome. Our results indicated that NS-718, a new AMPH-B formulation, is a promising antifungal agent for treatment of pulmonary cryptococcosis and could be the most effective antifungal agent against C. neoformans infections.     

Efficacy of low-dose dopamine in preventing amphotericin B nephrotoxicity in bone marrow transplant patients and leukemia patients

This study evaluated the efficacy of low-dose dopamine for prevention of amphotericin B-induced nephrotoxicity in autologous bone marrow transplant and leukemia patients. Seventy-one patients undergoing cytoreductive therapy who required amphotericin B were randomly assigned in an unblinded fashion to a group receiving continuous-infusion low-dose dopamine (3 microgram/kg/min) or a group receiving no dopamine. Amphotericin B was dosed at 0.5 or 1.0 mg/kg/day based on computerized tomography scan results or presence of positive blood cultures. No patient received saline boluses. The rate of nephrotoxicity, severity as graded by Southwest Oncology Group toxicity criteria, and time to each grade of nephrotoxicity were compared between the two groups. Eighty percent of the no-dopamine group and 66.7% of the dopamine group developed nephrotoxicity, defined as a 1.5-fold or greater increase in baseline serum creatinine level (P = 0.20). No statistical difference was noted at any grade of nephrotoxicity between the two groups. Thirty-four percent of patients in the no-dopamine group versus 17.6% in the dopamine group had a 2.5-fold or greater increase in serum creatinine level, which was not statistically significant (P = 0.0888). Ten patients developed grade IV nephrotoxicity and were withdrawn from the study, 7 in the no-dopamine group and 3 in the dopamine group (P = 0.19). The time to each grade of nephrotoxicity was also not significantly different for the two groups. Eleven adverse drug reactions were reported in the dopamine group in comparison to one in the no-dopamine group. Thus, dopamine offers little in the way of prevention of nephrotoxicity associated with amphotericin B therapy. Although the significance of drug reactions in the dopamine group is not clearly established due to lack of cardiac monitoring in the no-dopamine group, dopamine therapy is not without complications.     

Imipenem inhibits in vitro activity of amphotericin B directed against Aspergillus fumigatus

A decrease of the susceptibility of Aspergillus fumigatus strains to amphotericin B was found when tested in combination with high concentrations (128-2048 mg/l) of the antibacterial agent imipenem by checkerboard titration and agar diffusion assay. Only bacteriologically active imipenem showed the antagonism. The mechanism of action is unknown. However, imipenem and amphotericin B did not react directly, as shown by checkerboard titration with bacterial strains as well as by HPLC analysis. It is concluded that imipenem medication may influence the efficacy of amphotericin B treatment in aspergillosis.     

Determination of cyanide in whole blood by capillary gas chromatography with cryogenic oven trapping

Cyanide, one of the most important toxic substances, has been found measurable with high sensitivity by capillary gas chromatography (GC) with cryogenic oven trapping upon injection of headspace (HS) vapor samples. The entire amount of cyanide in the HS sample could be cryogenically trapped prior to on-line GC analysis. A 0.5-mL volume of blood in the presence or absence of cyanide and propionitrile (internal standard, IS) was added to a vial containing 0.25 mL of distilled water, 0.3 g of Na2-SO4, 0.2 mL of 50% H3PO4, and 0.1 g of ascorbic acid (when needed), and the mixture was heated at 70 degrees C for 15 min. A 5-mL volume of the HS vapor was introduced into a GC capillary column in the splitless mode at -30 degrees C oven temperature that was programmed up to 160 degrees C for GC analysis with nitrogen-phosphorus detection. A sharp peak was obtained for cyanide under the present conditions, and backgrounds were very clean. The extraction efficiencies of cyanide and IS were 2.89-3.22 (100 or 500 ng/mL) and 2.42%, respectively. The calibration curve showed good linearity in the range of 25-1000 ng/mL and the detection limit was approximately 2 ng/mL. The coefficients of intraday and interday variations were 2.9 and 11.8%, respectively. The mean blood cyanide level measured for actual fire victims was 687 +/- 597 ng/mL (mean +/- SD, n = 9). Endogenous blood cyanide concentration for healthy subjects was 8.41 +/- 3.09 ng/mL (mean +/- SD, n = 6).     

A high-performance liquid-chromatographic assay for amphotericin B in a hydrophilic colloidal paste base

A stability-indicating high-performance liquid-chromatographic (HPLC) assay has been developed for amphotericin B (AmB) in a paste, containing AmB, tobramycin (or gentamicin) sulphate, colistin sulphate, liquid paraffin and Orabase. Extraction of AmB was performed by partitioning the antibiotic between N,N-dimethylformamide (DMF) and cyclohexane, which led to precipitation of the polymeric materials and extraction of the liquid paraffin into the cyclohexane and AmB into the DMF. Analysis by HPLC of the latter layer gave a linear relationship between concentration and peak area response for the AmB over the range 5.0 x 10(-4) to 7.5 x 10(-3)% (w/v) (r = 0.9995) with a relative standard deviation of +/- 1.46% (n = 8). The efficiency of extraction was 1006 +/- 2.4% (n = 5).     

Nephrotoxicity of amphotericin B is attenuated by solubilizing with lipid emulsion

Nephrotoxicity is the major adverse effect of conventional amphotericin B (AMB/D), often limiting administration of full dosage. The new liposomal amphotericin B seems to be less toxic. The new liposomal amphotericin B seems to be less toxic. In this study, it is proposed that solubilizing the standard AMB/D preparation with 10% lipid emulsion will attenuate nephrotoxicity. Rats were injected with either AMB/D (Fungizone), AMB, AMB/D plus lipid emulsion (AMB/D/LE), or sodium deoxycholate (D). Renal function studies were performed on day 5. To assess a direct tubular toxic effect, isolated rat proximal tubule suspensions and inner medullary collecting duct cells in culture were exposed to AMB/D, AMB, AMB/D/LE, liposomal amphotericin B, and D for 60 min in normoxia. Lactate dehydrogenase (LDH) release was assessed as an index of cell injury. Creatinine clearance (ml/min per 100 g) averaged 0.79 +/- 0.04 in control rats, 0.29 +/- 0.09 in AMB rats (P < 0.001 versus control), 0.38 +/- 0.04 in AMB/D rats, 0.46 +/- 0.05 in D rats, and 0.78 +/- 0.03 in AMB/LE rats. Renal blood flow (ml/min per 100 g) was 3.45 +/- 0.31 in control, 1.29 +/- 0.28 in AMB, 1.42 +/- 0.23 in AMB/D, 3.03 +/- 0.39 in D, and 2.71 +/- 0.21 in AMB/D/LE rats. The fractional excretion of potassium (%) was 27.3 +/- 1.18 in control rats, 61.6 +/- 7.00 in AMB/D rats, 58.4 +/- 15.32 in AMB rats, and 37.9 +/- 2.06 in AMB/D/LE rats. LDH release (%) in proximal tubules incubated with AMB/D and D was 43.6 +/- 3.39 and 58.6 +/- 4.20, respectively. Addition of lipid emulsion decreased LDH release: 21.6 +/- 1.22 for AMB/D/LE and 26.4 +/- 3.03 for deoxycholate plus lipid emulsion. AMB did not demonstrate any toxic effect in proximal tubule suspensions. D was not toxic to inner medullary collecting duct cells at 0.16 mg/ml, whereas D at a higher dose and AMB induced a significant LDH release. Addition of lipid emulsion did not affect the antifungal activity as assessed by the Etest method. In conclusion, an alternative way of administering standard AMB with reduced nephrotoxicity is proposed.