Behavior of amphotericin B lipid complex in plasma in vitro and in the circulation of rats

Incidence of acute kidney injury in dogs with systemic mycotic infections treated with amphotericin B (1996-2020)

BACKGROUND

Amphotericin-B (AmB) is an essential medication for the treatment of life-threatening systemic mycoses but the incidence and risk factors for acute kidney injury (AKI) after its administration are not known in dogs.

OBJECTIVE

Determine the incidence of and risk factors for AKI in dogs receiving AmB.

ANIMALS

Fifty-one client owned dogs receiving AmB for the treatment of systemic mycoses.

METHODS

Retrospective study. Signalment, potential risk factors, AKI development (creatinine ≥0.3 mg/dL from baseline), drug formulation (deoxycholate [AmB-D] or lipid complex [ABLC]), dose, and treatment duration were recorded. The probability of an AKI diagnosis was evaluated using a log-rank test. The incidence of AKI and odds ratios were calculated for potential risk factors.

RESULTS

Incidence of AKI was 5/12 (42%) for dogs receiving AmB-D and 14/39 (36%) for dogs receiving ABLC. Of the 19 dogs that developed AKI, 16 (84%) continued treatment after a pause in the planned dosing protocol. Fifty percent of dogs received a cumulative dose of 6.9 mg/kg for AmB-D and 22.5 mg/kg for ABLC (P < .01) at time of AKI diagnosis. ICU hospitalization (odds ratio [OR] 0.21, 95% confidence interval [CI]: 0.58-0.87) and inpatient status (OR 0.25, 95% CI: 0.07-0.86) were associated with decreased odds of AKI.

CONCLUSIONS AND CLINICAL IMPORTANCE

Incidence of AKI with AmB is common but does not always preclude continued treatment. The incidence of AKI is similar between AmB-D and ABLC, but dogs receiving ABLC tolerated a higher cumulative total dose before AKI diagnosis.

Polyene Antibiotics Physical Chemistry and Their Effect on Lipid Membranes; Impacting Biological Processes and Medical Applications

This review examined a collection of studies regarding the molecular properties of some polyene antibiotic molecules as well as their properties in solution and in particular environmental conditions. We also looked into the proposed mechanism of action of polyenes, where membrane properties play a crucial role. Given the interest in polyene antibiotics as therapeutic agents, we looked into alternative ways of reducing their collateral toxicity, including semi-synthesis of derivatives and new formulations. We follow with studies on the role of membrane structure and, finally, recent developments regarding the most important clinical applications of these compounds.

Macrolides: From Toxins to Therapeutics

Macrolides are a diverse class of hydrophobic compounds characterized by a macrocyclic lactone ring and distinguished by variable side chains/groups. Some of the most well characterized macrolides are toxins produced by marine bacteria, sea sponges, and other species. Many marine macrolide toxins act as biomimetic molecules to natural actin-binding proteins, affecting actin polymerization, while other toxins act on different cytoskeletal components. The disruption of natural cytoskeletal processes affects cell motility and cytokinesis, and can result in cellular death. While many macrolides are toxic in nature, others have been shown to display therapeutic properties. Indeed, some of the most well known antibiotic compounds, including erythromycin, are macrolides. In addition to antibiotic properties, macrolides have been shown to display antiviral, antiparasitic, antifungal, and immunosuppressive actions. Here, we review each functional class of macrolides for their common structures, mechanisms of action, pharmacology, and human cellular targets.

Biodistribution and histopathology studies of amphotericin B sodium deoxycholate sulfate formulation following intratracheal instillation in rat models

Aerosol inhalation of amphotericin B (AmB) can be a clinically compliant way to administer the drug directly to the pulmonary route for treatment as well as prophylaxis of invasive pulmonary aspergillosis (IPA). We report aerosol formulation of AmB using sodium deoxycholate sulfate (SDCS), a lipid carrier synthesized in-house using natural precursor deoxycholic acid. In vitro toxicity was determined by MTT assay. Biodistribution and histopathology in rats were evaluated in targeted organs including the lungs, kidneys, spleen, and liver. No toxicity was observed when lung and kidney cells treated with AmB-SDCS formulations up to 8 μg/mL and minimal toxicity at higher concentration 16 μg/mL, while the Fungizone®-like formulation induced toxicity to lung and kidney cells with viability decreasing from 86 to 41% and 100 to 49%, respectively, when compared with an equivalent concentration of AmB-SDCS. Renal and hepatic markers were raised for Fungizone®-like formulation-treated rats but not for AmB-SDCS formulations following 7 days of regular dosing by intratracheal instillation. AmB concentrations were highest in the lungs (5.4-8.3 μg/g) which were well above minimum inhibitory concentration (MIC) of all Aspergillus species. Plasma concentration was also above MIC (> 2 μg/mL) for all AmB-SDCS formulations in comparison with Fungizone®-like formulation. No evidence of abnormal histopathology was observed in the lungs, liver, spleen, and kidneys for all AmB-SDCS formulations but was observed for the group treated with Fungizone®-like formulation. It is concluded that AmB-SDCS formulations can be efficiently administered via intratracheal instillation with no evidence of toxicity and may find great value in the treatment as well as prophylaxis of IPA through inhalation route.

Bioactivity, Safety, and Efficacy of Amphotericin B Nanomicellar Aerosols Using Sodium Deoxycholate Sulfate as the Lipid Carrier

We report nanomicelles of amphotericin B (AmB) using various molar ratios of AmB and sodium deoxycholate sulfate (SDCS) for inhalation with improved stability, solubility, bioactivity, and safety. The particle sizes of all aerosolized formulations are expressed as mass median aerodynamic diameter (0.9-1.6 μm), fine particle fraction (70.3-86.5%), and geometric standard deviation (1.4-2.1) which indicated their sizes are appropriate for use as an inhaler. In vitro cytotoxicity studies conducted using respiratory and kidney cell lines demonstrated that the marketed Fungizone^® was toxic to macrophage and embryonic kidney cells and cell viability decreased from 96 to 48% and from 97 to 67%, respectively when the AmB equivalent concentration was increased from 1 to 16 μg/mL. However, AmB-SDCS formulations showed no evidence of toxicity even up to 8 μg/mL compared to Fungizone^®. Minimum inhibitory and fungicidal concentrations were significantly reduced against Cryptococcus neoformans, and Candida albicans. Also, antileishmanial activity significantly improved for AmB-SDCS formulations. There was an evidence of phagocytosis of the AmB-SDCS formulation by alveolar macrophages NR 8383. Molecular modeling studies suggested the role of hydrogen bonding in stabilization of the AmB-SDCS complex. This study indicated that AmB-SDCS nanomicelles can be used to design a safe and cost-effective AmB for inhalation. Graphical abstract ᅟ.

Brain-Eating Amoebae: Silver Nanoparticle Conjugation Enhanced Efficacy of Anti-Amoebic Drugs against Naegleria fowleri

The overall aim of this study was to determine whether conjugation with silver nanoparticles enhances effects of available drugs against primary amoebic meningoencephalitis due to Naegleria fowleri. Amphotericin B, Nystatin, and Fluconazole were conjugated with silver nanoparticles, and synthesis was confirmed using UV-visible spectrophotometry. Atomic force microscopy determined their size in range of 20-100 nm. To determine amoebicidal effects, N. fowleri were incubated with drugs-conjugated silver nanoparticles, silver nanoparticles alone, and drugs alone. The findings revealed that silver nanoparticles conjugation significantly enhanced antiamoebic effects of Nystatin and Amphotericin B but not Fluconazole at micromolar concentrations, compared with the drugs alone. For the first time, our findings showed that silver nanoparticle conjugation enhances efficacy of antiamoebic drugs against N. fowleri. Given the rarity of the disease and challenges in developing new drugs, it is hoped that modifying existing drugs to enhance their antiamoebic effects is a useful avenue that holds promise in improving the treatment of brain-eating amoebae infection due to N. fowleri.

Amphotericin B lipid preparations: what are the differences?

To reduce the in-vivo toxicity of the broad-spectrum antifungal drug amphotericin B, various lipid formulations of amphotericin B, ranging from lipid complexes to small unilamellar liposomes, have been developed and subsequently commercialized. These structurally diverse formulations differ in their serum pharmacokinetics as well as their tissue localisation, tissue retention and toxicity. These differences can affect the choice of formulation for a given infection, the time of initiation of treatment, and the dosing regimen. Although preclinical studies have shown similarities in the in-vitro and in-vivo antifungal activity of the formulations with comparable dosing, their acute and chronic toxicity profiles are not the same, and this has a significant impact on their therapeutic indices, especially in high-risk, immunosuppressed patients. With the recent introduction of new antifungal drugs to treat the increasing numbers of infected patients, the amphotericin B lipid formulations are now being studied to evaluate their potential in combination drug regimens. With proven efficacy demonstrated during the past decade, it is expected that amphotericin B lipid formulations will remain an important part of antifungal drug therapy.

Assessing the antifungal activity, pharmacokinetics, and tissue distribution of amphotericin B following the administration of Abelcet® and AmBisome® in combination with caspofungin to rats infected with Aspergillus fumigatus

The purpose of this study was to assess the antifungal activity, pharmacokinetics, and tissue distribution of amphotericin B (AmpB) following the administration of Abelcet and AmBisome alone and in combination with Caspofungin to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (2.1-2.5 x 10(7) colony forming units [CFU]) was injected via the jugular vein; 48 h later male albino Sprague-Dawley rats (350-400 g) were administered either a single intravenous (i.v.) dose of Abelcet (5 mg AmpB/kg; n = 6), AmBisome (5 mg AmpB/kg; n = 6), Caspofungin (3 mg/kg; n = 5), Abelcet (5 mg AmpB/kg) plus Caspofungin (3 mg/kg) (n = 6), AmBisome (5 mg AmpB/kg) plus Caspofungin (3 mg/kg) (n = 7), or physiologic saline (non-treated controls; n = 6) once daily for 4 days. Antifungal activity was assessed by organ CFU concentrations and plasma galactomannan levels. Plasma and tissue samples were taken from each animal for AmpB pharmacokinetic analysis and tissue distribution determinations. Abelcet treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 73% compared to non-treated controls. Ambisome treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 69% compared to non-treated controls. Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 80% compared to non-treated controls. Abelcet plus Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 81% compared to non-treated controls. Ambisome plus Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 98% compared to non-treated controls. Abelcet treatment significantly decreased plasma galactomannan levels by 50 and 75% 96 h following the initiation of treatment in the absence and presence of Caspofungin co-therapy, respectively. AmBisome treatment significantly decreased plasma galactomannan levels by 73 and 78% 96 h following the initiation of treatment in the absence and presence of Caspofungin co-therapy, respectively. Co-administration of Caspofungin with Abelcet and AmBisome did not significantly alter the plasma concentration-time profile, pharmacokinetic parameters, and tissue distribution of AmpB. Taken together, our findings suggest that an alternative mechanism, possibly at the cellular level rather than altered AmpB disposition, may be an explanation for the differences in organ CFU concentrations following Abelcet plus Caspofungin versus AmBisome plus Caspofungin administration.

Population pharmacokinetics of amphotericin B lipid complex in neonates

The pharmacokinetics of amphotericin B lipid complex (ABLC) were investigated in neonates with invasive candidiasis enrolled in a phase II multicenter trial. Sparse blood (153 samples; 1 to 9 per patient, 1 to 254 h after the dose) and random urine and cerebrospinal fluid (CSF) samples of 28 neonates (median weight [WT], 1.06 kg; range, 0.48 to 4.9 kg; median gestational age, 27 weeks; range, 24 to 41 weeks) were analyzed. Patients received intravenous ABLC at 2.5 (n = 15) or 5 (n = 13) mg/kg of body weight once a day over 1 or 2 h, respectively, for a median of 21 days (range, 4 to 47 days). Concentrations of amphotericin B were quantified as total drug by high-performance liquid chromatography. Blood data for time after dose (TAD) of <24 h fitted best to a one-compartment model with an additive-error model for residual variability, WT0.75 (where 0.75 is an exponent) as a covariate of clearance (CL), and WT as a covariate of volume of distribution (V). Prior amphotericin B, postnatal age, and gestational age did not further improve the model. The final model equations were CL (liters/h) = 0.399 x WT(0.75) (interindividual variability, 35%) and V (liters) = 10.5 x WT (interindividual variability, 43%). Noncompartmental analysis of pooled data with a TAD of >24 h revealed a terminal half-life of 395 h. Mean concentrations in the urine after 1, 2, and 3 weeks ranged from 0.082 to 0.430 microg/ml, and those in CSF ranged from undetectable to 0.074 microg/ml. The disposition of ABLC in neonates was similar to that observed in other age groups: weight was the only factor that influenced clearance. Based on these results and previously published safety and efficacy data, we recommend a daily dosage between 2.5 and 5.0 mg/kg for treatment of invasive Candida infections in neonates.

Assessing the antifungal activity and toxicity profile of amphotericin B lipid complex (ABLC; Abelcet®) in combination with caspofungin in experimental systemic aspergillosis

The purpose of this study was to assess the antifungal activity and renal and hepatic toxicity of amphotericin B lipid complex (ABLC; Abelcet) following co-administration of Caspofungin to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (1.3-2.3 x 10(7) colony forming units [CFU]) was injected via the jugular vein; 48 h later male albino Sprague-Dawley rats (350-400 g) were administered either a single intravenous (i.v.) dose of Fungizone(R) (1 mg AmpB/kg), ABLC (1 or 5 mg AmpB/kg), or an equivalent volume of normal saline (NS) (vehicle control) once daily for 4 days. Rats were further randomized into groups to receive 3 mg/kg Caspofungin or physiologic saline i.v. once daily for 4 days. To assess antifungal activity, brain, lung, heart, liver, spleen, and kidney sections were homogenized with NS (2 mL; 1 g of each tissue/mL) and a 0.1-mL aliquot was spread plated onto a Sabouraud dextrose agar plate. The plates were incubated for 48 h at 37 degrees C, at which time the numbers of CFU were determined and corrected for tissue weight. To assess renal and hepatic toxicity, serum creatinine and aspartate aminotransferase levels were determined. Fungizone and ABLC at a dosing regimen of 1 mg/kg i.v. once daily for four consecutive days and Caspofungin at a dosing regimen of 3 mg/kg i.v. once daily for four consecutive days had similar effectiveness in decreasing the total number of Aspergillus fumigatus CFUs found in all organs analyzed compared to non-treated controls. A combination of ABLC (1 mg/kg i.v. x 4 days) and Caspofungin (3 mg/kg i.v. x 4 days) significantly decreased the total number of Aspergillus fumigatus CFUs found in all organs analyzed compared to Caspofungin alone and non-treated controls. ABLC at a dosing regiment of 5 mg/kg i.v. once daily for four consecutive days was more effective in decreasing the total number of Aspergillus fumigatus CFUs found in all organs analyzed compared to Fungizone or ABLC alone at 1 mg/kg and Caspofungin alone at 3 mg/kg. However, a combination of ABLC (5 mg/kg i.v. x 4 days) and Caspofungin (3 mg/kg i.v. x 4 days) was not more effective than ABLC at 5 mg/kg or the combination of ABLC at 1 mg/kg and Caspofungin 3 mg/kg in reducing the total number of Aspergillus fumigatus CFUs compared to controls. Except for non-treated infected control rats, none of the treatment groups tested displayed a greater than 50% increase in serum creatinine concentrations from baseline. In addition, only ABLC at a dosing regimen of 1 mg/kg i.v. once daily for four consecutive days displayed a greater than 50% increase in AST concentration from baseline. Taken together, these findings suggest that ABLC at 5 mg/kg once daily x 4 days appears to be the best therapeutic choice in this animal model.

Efficacy, safety and cost-effectiveness of Amphotericin B Lipid Complex (ABLC): a review of the literature

Amphotericin B Lipid Complex (ABLC) was the first lipid-based formulation of amphotericin B (AmB) to be developed, it was designed to provide a less toxic alternative to conventional AmB without compromising efficacy. Preclinical and early clinical data relating to ABLC have been presented in previous reviews. This paper reviews more recent published data on the efficacy, safety and cost-effectiveness of ABLC. All published manuscripts and conference abstracts were searched on MEDLINE, BIOL and SCIN for the period between January 1997 and August 2003. Comparative and non-comparative studies of ABLC are usually mild or moderate and are manageable were considered. Comparative studies and additional data from non-comparative studies suggest that ABLC 5 mg/kg/day is safe and effective for the treatment of documented or suspected systemic fungal infections in adults and children who are refractory to or intolerant of conventional AmB. ABLC is effective against a wide range of pathogens and efficacy is at least as good as conventional AmB or the other lipid-based formulations. The safety profile of ABLC is improved compared with conventional AmB; ABLC is less nephrotoxic than conventional AmB and can be given safely to patients with pre-existing renal impairment. The most commonly reported adverse effects are transient infusion-related events, including chills, fever, nausea and vomiting, which with premedication. Comparative studies suggest that ABLC is a cost-effective treatment option compared with conventional AmB or other lipid-based formulations of amphotericin B.

Comparison of LNS-AmB, a novel low-dose formulation of amphotericin B with lipid nano-sphere (LNS), with commercial lipid-based formulations

Three lipid-based delivery systems (AmBisome, Amphocil, and Abelcet) for amphotericin B (AmB) have been marketed to overcome the disadvantages associated with the clinical use of AmB. However, to show their efficacy, they need to be administered at higher doses than the conventional dosage form, Fungizone. In this study, we compared LNS-AmB, our new low-dose therapeutic system for AmB using lipid nano-sphere (LNS), with these commercial formulations in terms of their pharmacokinetics and efficacy. The plasma AmB levels yielded by LNS-AmB after intravenous administration to rats were much higher than those yielded by Amphocil or Abelcet, and similar to those yielded by AmBisome, but in dogs LNS-AmB yielded plasma AmB concentrations about three times higher than did AmBisome. In a carrageenin-induced pleurisy model in rats, LNS-AmB yielded AmB levels in the pleural exudate over 20 times those yielded by Amphocil or Abelcet, and similar to those yielded by AmBisome. From these pharmacokinetic results, it is clear that Amphocil and Abelcet are based on a quite distinct drug-delivery concept from LNS-AmB. In a rat model of localized candidiasis, LNS-AmB significantly inhibited the growth of Candida albicans in the pouch, whereas AmBisome did not, even though the AmB concentrations in the pouch were similar. This difference in antifungal activity between LNS-AmB and AmBisome was also found in vitro. That is, the antifungal activity of LNS-AmB against C. albicans was similar to that of Fungizone and dimethyl sulfoxide-solubilized AmB, while AmBisome showed weaker antifungal activity than did other formulations. Based on these results, the release of AmB from AmBisome was judged to be slow and slight. In a mouse model of systemic candidiasis, LNS-AmB (1.0mg/kg) was much more effective than AmBisome (8.0mg/kg) or Fungizone (1.0mg/kg). These results suggest that LNS-AmB maintained the potent activity of AmB against fungal cells even though the AmB was incorporated into LNS particles. We conclude that LNS-AmB may offer an improved therapeutic profile at lower doses than Fungizone and commercial lipid-based formulations.

Amphotericin B lipid complex or amphotericin B multiple-dose administration to rabbits with elevated plasma cholesterol levels: pharmacokinetics in plasma and blood, plasma lipoprotein levels, distribution in tissues, and renal toxicities

The purpose of the present study was to determine if a relationship exists between the plasma cholesterol concentration, the severity of amphotericin B (AmpB)-induced renal toxicity, and the pharmacokinetics of AmpB in plasma in hypercholesterolemic rabbits administered multiple doses of amphotericin B (AmB) deoxycholate (Doc-AmB) and AmB lipid complex (ABLC). After 7 days of administration of a cholesterol-enriched diet (0.50% [wt/vol]) or a regular rabbit diet, each rabbit was administered a single intravenous bolus of Doc-AmB (n = 8) or ABLC (n = 10) (1.0 mg/kg of body weight) daily for 7 consecutive days (a total of eight doses). Blood samples were obtained daily before and 24 h after the administration of each dose and serially thereafter following the administration of the last dose for the assessment of pharmacokinetics in plasma, kidney toxicity, plasma lipoprotein levels, and drug distribution in tissue. The pharmacokinetics of AmB in blood following the administration of ABLC were also determined in rabbits fed cholesterol-enriched and regular diets (n = 3 each group). Before drug treatment, cholesterol-fed rabbits demonstrated marked increases in total, low-density lipoprotein (LDL), and triglyceride-rich lipoprotein (TRL) cholesterol levels in plasma compared with the levels in rabbits on a regular diet. No significant differences in total plasma triglyceride levels were observed. Significant increases in plasma creatinine levels were observed in rabbits fed a cholesterol-enriched diet (P < 0.05) and rabbits fed a regular diet (P < 0.05) when administered AmB. However, the magnitude of this increase was twofold greater in rabbits fed a regular diet than in rabbits fed a cholesterol-enriched diet. An increase in plasma creatinine levels was observed only in rabbits on a cholesterol-enriched diet administered ABLC. The pharmacokinetics of AmB were significantly altered in rabbits on a cholesterol-enriched diet administered Doc-AmB or ABLC compared to those in rabbits on a regular diet administered each of these compounds. The pharmacokinetics of AmB in blood were significantly different following ABLC administration but not following Doc-AmB administration in both rabbits fed cholesterol-enriched diets and rabbits fed regular diets compared to their corresponding pharmacokinetics in plasma. An increased percentage of AmB was recovered in the TRL fraction when Doc-AmB was administered to rabbits fed a cholesterol-enriched diet than when it was administered to rabbits fed a regular diet. Furthermore, an increased percentage of AmB was recovered in the LDL and TRL fractions when ABLC was administered to rabbits fed a cholesterol-enriched diet rabbits fed a regular diet. These findings suggest that an increase in plasma cholesterol levels modifies the pharmacokinetics of AmB and renal toxicity following the administration of multiple intravenous doses of Doc-AmB and ABLC.

A pharmacokinetic study of amphotericin B lipid complex injection (Abelcet) in patients with definite or probable systemic fungal infections

This study describes a pharmacokinetic evaluation of amphotericin B (AMB) lipid complex injection (ABLC or Abelcet) in 17 patients with systemic fungal infection administered 5 mg/kg of body weight/day by infusion for 10 to 17 days. The results showed that AMB exhibited multiexponential disposition with high clearance, large volume of distribution at steady state, and long apparent elimination half-life but no evidence of accumulation in the blood after multiple daily doses. The results confirm previous observations and further reinforce the suggestion that ABLC may exist as a depot in the tissues from which free AMB is slowly released to limit exposure.

Dose-dependent pharmacokinetics of amphotericin B lipid complex in rabbits

Amphotericin B lipid complex (ABLC) was recently approved by the Food and Drug Administration for treatment of patients with invasive fungal infections who are intolerant of or refractory to conventional amphotericin B therapy. Little is known, however, about the pharmacokinetics of this new antifungal compound. We therefore investigated the pharmacokinetics of ABLC in comparison with those of conventional desoxycholate amphotericin B (DAmB) in rabbits. The pharmacokinetics of DAmB in a rabbit model were similar to those previously reported in humans. The pharmacokinetics of ABLC differed substantially from those of DAmB. Plasma amphotericin B levels following ABLC administration were 10 times lower than those following administration of an equal dosage of DAmB. The levels of ABLC in whole blood were approximately 40 times greater than those in plasma. The ABLC model differed from the DAmB model by (i) a dose- and time-dependent uptake and return between the plasma compartment and apparent cellular components of the blood-sediment compartment and (ii) time-dependent tissue uptake and return to plasma from serially connected compartments. Following infusion of ABLC, there was a nonlinear uptake into the apparent cellular components of the blood-sediment compartment. This uptake was related to the reciprocal of the integral of the total amount of drug infused (i.e., the more drug infused the greater the fractional uptake between 0.5 and 5 mg/kg of body weight for ABLC). The transfer of drug from plasma to the cellular components of the blood-sediment compartment resulted in initial uptake followed by rapid redistribution back to the plasma. The study describes a detailed model of the pharmacokinetics of ABLC and characterizes a potential role of the cellular components of the blood-sediment compartment in the distribution of this new antifungal compound in tissue.

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.

A comparison of the activities of three amphotericin B lipid formulations against experimental visceral and cutaneous leishmaniasis

The polyene antibiotic, amphotericin B, the gold standard for systemic fungal infections is also a recommended second line treatment for visceral, cutaneous and mucocutaneous leishmaniasis. Acute toxicity has limited the use of amphotericin B but less toxic lipid formulations, AmBisome, Amphocil and Abelcet, have shown potential for the treatment of clinical visceral and mucocutaneous leishmaniasis. This study compares the in vitro and in vivo anti-leishmanial activity of Fungizone and the three lipid formulations. AmBisome and Amphocil were more active (ED50 values 0.3 and 0.7 mg/kg, respectively) than Abelcet (ED50 2.7 mg/kg) against L. donovani in a mouse model. Against L. major in vivo, AmBisome at a dose of 25 mg/kg was the most successful at reducing lesion size, with Amphocil also showing activity while Abelcet was inactive. In the L. donovani--peritoneal macrophage (PEM) model Fungizone and Amphocil were significantly more active (ED50 values 0.013 and 0.02 microg/ml, respectively) than AmBisome and Abelcet (ED50 values 1.5 and 2.6 microg/ml). This trend was similar in the L. major--PEM model (Fungizone > Amphocil > AmBisome > Abelcet). THP-1 macrophages infected with L. donovani amastigotes showed a different profile with Amphocil = Abelcet > AmBisome > Fungizone. Differences could be due to the interaction of the formulations with the biological milieu and uptake into different cell types.

Absence in amphotericin B-spiked human plasma of the free monomeric drug, as detected by SERS

Using surface enhanced Raman spectroscopy (SERS) which enables us to specifically detect traces of monomeric amphotericin B (AmB), we were able to show that in a 10(-5) M AmB suspension, the concentration of free drug was below 10(-8) M in the presence of low density lipoproteins (LDL) or plasma. The affinity constant of AmB for LDL determined from electronic absorption data, was found to be 4 x 10(6) M(-1). Therefore, since AmB appears to be in the majority bound to lipoproteins under in vivo conditions, its toxicity should not result from the induction of host-cell transmembrane permeability but rather from the internalization of the AmB-LDL complex.

Pharmacokinetics, distribution in serum lipoproteins and tissues, and renal toxicities of amphotericin B and amphotericin B lipid complex in a hypercholesterolemic rabbit model: single-dose studies

The purpose of this study was to determine if a relationship exists among total serum and lipoprotein cholesterol concentration, the severity of amphotericin B (AmpB)-induced renal toxicity, and the serum pharmacokinetics of AmpB in hypercholesterolemic rabbits administered AmpB and AmpB lipid complex (ABLC). After 10 days of cholesterol-enriched diet (0.50% [wt/vol]) or regular rabbit diet (control), each rabbit was administered a single intravenous bolus of AmpB or ABLC (1.0 mg/kg of body weight). Blood samples were obtained before administration and serially thereafter for the assessment of serum pharmacokinetics, kidney toxicity, and serum lipoprotein distribution. Rabbits were humanely sacrificed after all blood samples were obtained, and tissues were harvested for drug analysis. Before drug treatment, cholesterol-fed rabbits demonstrated marked increases in total serum cholesterol and low-density lipoprotein (LDL) cholesterol levels compared with levels in rabbits on a regular diet. No significant differences in triglyceride levels were observed. A significant increase in serum creatinine levels was observed in cholesterol-fed and regular diet-fed rabbits administered AmpB. However, the magnitude of this increase was 2.5-fold greater in cholesterol-fed rabbits than in regular diet-fed rabbits. No significant differences in triglyceride levels were observed. A significant increase in serum creatinine levels was observed in cholesterol-fed and regular diet-fed rabbits administered ABLC. Whereas AmpB pharmacokinetics were significantly altered in cholesterol-fed rabbits administered free AmpB, similar AmpB pharmacokinetics were observed in both rabbit groups administered ABLC. Renal AmpB levels were significantly increased in cholesterol-fed rabbits administered AmpB compared with those in all other groups. Hepatic and lung AmpB levels were elevated in cholesterol-fed rabbits administered free AmpB compared to controls. In addition, hepatic, lung, and spleen AmpB levels were significantly decreased in cholesterol-fed rabbits administered ABLC compared to controls. An increased percentage of AmpB was recovered in LDL-very-low-density lipoprotein fraction when free AmpB was administered to cholesterol-fed rabbits compared with those in all other groups. These findings suggest that increases in cholesterol, specifically, LDL cholesterol levels, modify the disposition and renal toxicity of free AmpB. However, the pharmacokinetics and renal toxicity of ABLC were independent of elevations in total and LDL cholesterol levels.

AmBisome (liposomal amphotericin B): a comparative review

AmBisome (NeXstarPharmaceuticals, San Dimas, CA) is a unilamellar liposomal formulation of amphotericin B that was recently approved for use as empirical treatment for presumed fungal infections in febrile neutropenic patients and for aspergillosis, candidiasis, and cryptococcosis infections refractory to amphotericin B. It is a small closed microscopic sphere (<100 nm in diameter) with an inner aqueous core (i.e., a true liposome). AmBisome remains as an intact sphere in vitro and for prolonged periods of time in vivo during the processes of systemic transport and pharmacologic action. As a consequence of its size and in vivo stability, AmBisome has physiochemical properties and a pharmacokinetic profile that are considerably different from those of currently available lipid-complexed amphotericin B formulations, with greatly increased area under the plasma concentration-time curve and much lower clearance at equivalent doses. AmBisome liposomes can be seen to accumulate at sites of fungal infection. Disruption of AmBisome liposomes occurs after attachment to the fungal cell wall and results in amphotericin B binding to fungal cell membrane ergosterol with subsequent cell lysis. AmBisome has been shown to penetrate the cell wall of both extracellular and intracellular forms of susceptible fungi.

In vitro and in vivo antifungal activity of amphotericin B lipid complex: are phospholipases important?

Amphotericin B lipid complex for injection (ABLC) is a suspension of amphotericin B complexed with the lipids L-alpha-dimyristoylphosphatidylcholine (DMPC) and L-alpha-dimyristoylphosphatidylglycerol. ABLC is less toxic than amphotericin B deoxycholate (AmB-d), while it maintains the antifungal activity of AmB-d. Active amphotericin B can be released from ABLC by exogenously added (snake venom, bacteria, or Candida-derived) phospholipases or by phospholipases derived from activated mammalian vascular tissue (rat arteries). Such extracellular phospholipases are capable of hydrolyzing the major lipid in ABLC. Mutants of C. albicans that were resistant to ABLC but not AmB-d in vitro were deficient in extracellular phospholipase activity, as measured on egg yolk agar or as measured by their ability to hydrolyze DMPC in ABLC. ABLC was nevertheless effective in the treatment of experimental murine infections produced by these mutants. Isolates of Aspergillus species, apparently resistant to ABLC in vitro (but susceptible to AmB-d), were also susceptible to ABLC in vivo. We suggest that routine in vitro susceptibility tests with ABLC itself as the test material may not accurately predict the in vivo activity of ABLC and that the enhanced therapeutic index of ABLC relative to that of AmB-d in vivo may be due, in part, to the selective release of active amphotericin B from the complex at sites of fungal infection through the action of fungal or host cell-derived phospholipases.