Amphotericin B/emulsion admixture interactions: an approach concerning the reduction of amphotericin B toxicity

Potential lipid-based strategies of amphotericin B designed for oral administration in clinical application

Amphotericin B (AmB) is regarded as a first-line therapy against life-threatening invasive fungal infections. Due to its poor oral bioavailability, AmB is restricted to intravenous administration in clinical practice. As science continues to move forward, two lipid-based formulations are successfully developed for oral AmB administration, currently undergoing phase I clinical trials. Encouragingly, lipid-AmB conjugates with emulsions also exhibit a better bioavailability, which may be another strategy to design oral AmB formulation in clinical practice. Thus, this review mainly focused on the two lipid-based formulations in clinical trials, and discussed the potential perspectives of AmB-lipid conjugation-loaded nanocochleates and emulsions.

Exploring the permeability of Amphotericin B trough serum albumin dispersions and lipid nanocarriers for oral delivery

Amphotericin B (AmB) is a potent polyenic antifungal agent with leishmanicidal activity. Due to its low solubility and permeability in the gastrointestinal tract, AmB is usually administered intravenously. In this context, various approaches have been used to try to improve these properties. Some of the systems developed have shown proven successful, but there is still a lack of knowledge about the pathways AmB takes after oral administration. Therefore, the aim of this work was not only to obtain aqueous dispersions containing AmB at different aggregation states, but also to entrap this molecule in nanocarriers, and evaluate the influence of these conditions on the jejunal permeability of AmB. To observe the aggregation states of AmB, physicochemical characterization of AmB-albumin complexes and AmB-loaded formulations was performed. Different degrees of AmB aggregation states were obtained. Thus, permeability tests were performed in the Ussing chamber and a decrease in AmB concentration in the donor compartment was observed. Electrophysiological measurements showed different responses depending on the AmB formulation. In conclusion, although control of the AmB aggregation state was observed by physicochemical characterization, this approach does not seem to have a sufficient effect on AmB permeability, but on its toxicity. For a complete understanding of AmB-loaded nanocarriers, other pathways, such as lymphatic absorption, should also be investigated.

Enhancing Safety and Efficacy by Altering the Toxic Aggregated State of Amphotericin B in Lipidic Nanoformulations

The toxicity of Amphotericin B (AmB) is contributed by the small, water-soluble aggregates of the drug. Hence, AmB lipid polymer hybrid nanoparticles (LIPOMER), comprising stearate lipids with a hydrophilic polymer Gantrez (GZ), and solid lipid nanoparticles (SLN), comprising only stearates, were prepared with the objective of monomerizing AmB. While intercalation of stearates with the hydrophobic polyene chain could hinder AmB-AmB interactions, enabling monomerization, it was hypothesized that GZ could aid in the stabilization of the monomers through hydrophilic interactions. AmB LIPOMERs and SLNs, prepared by nanoprecipitation, exhibited an average size of 350-500 nm with negative ζ potential. Polyglyceryl-6-distearate (PGDS) SLN exhibited maximum monomerization, with the highest peak IV (410 nm) to peak I (350 nm) ratio in the UV-visible spectrum. In total contrast, LIPOMERs and GZ nanoparticles revealed a hypsochromic shifted peak I between 321 and 324 nm, indicative of AmB super-aggregate formation. Super-aggregates, which result due to condensation of multiple aggregates with monomers, were attributed to extensive GZ-AmB and GZ-GZ interactions and could provide advantages of enhanced thermodynamic stability, with safety and efficacy similar to the monomeric form. Safety was confirmed by low and comparable erythrocyte toxicity exhibited by the LIPOMERs and SLNs. An in vitro efficacy study of PGDS LIPOMER and SLN against intracellular amastigotes revealed significantly lower IC₅₀ values, which translated to a 7.1- and 6.1-fold enhancement in efficacy compared to commercial nanoformulations Amfocare (micellar AmB) and 1.79- and 1.54-fold enhancement in efficacy compared to Fungisome (liposomal AmB). High efficacy coupled with a higher selectivity index indicated the superiority of the developed AmB nanoformulations and substantiated that altering the toxic aggregated state of AmB can offer a promising approach for the design of safe and efficacious AmB lipidic nanoformulations.

Getting the Jump on the Development of Bullfrog Oil Microemulsions: a Nanocarrier for Amphotericin B Intended for Antifungal Treatment

Amphotericin B (AmB), a potent antifungal drug, presents physicochemical characteristics that impair the development of suitable dosage forms. In order to overcome the AmB insolubility, several lipid carriers such as microemulsions have been developed. In this context, the bullfrog oil stands out as an eligible oily phase component, since its cholesterol composition may favor the AmB incorporation. Thus, the aim of this study was to develop a microemulsion based on bullfrog oil containing AmB. Moreover, its thermal stability, antifungal activity, and cytotoxicity in vitro were evaluated. The microemulsion formulation was produced using the pseudo-ternary phase diagram (PTPD) approach and the AmB was incorporated based on the pH variation technique. The antifungal activity was evaluated by determination of minimal inhibitory concentration (MIC) against different species of Candida spp. and Trichosporon asahii. The bullfrog oil microemulsion, stabilized with 16.8% of a surfactant blend, presented an average droplet size of 26.50 ± 0.14 nm and a polydispersity index of 0.167 ± 0.006. This system was able to entrap AmB up to 2 mg mL^-1. The use of bullfrog oil as oily phase allowed an improvement of the thermal stability of the system. The MIC assay results revealed a growth inhibition for different strains of Candida spp. and were able to enhance the activity of AmB against T. asahii. The microemulsion was also able to reduce the AmB toxicity. Finally, the developed microemulsion showed to be a suitable system to incorporate AmB, improving the system's thermal stability, increasing the antifungal activity, and reducing the toxicity of this drug.

Amphotericin B-loaded solid lipid nanoparticles (SLNs) and nanostructured lipid carrier (NLCs): effect of drug loading and biopharmaceutical characterizations

The aim of this study was to further investigate the effect of drug loading, drug entrapment efficiency, the drug release profiles and biopharmaceutical point of views of amphotericin B (AmB) lipid formulations, that is, degree of aggregation by UV-spectroscopy, in vitro hemolytic and antifungal activities. The optimum drug loading was 2.5% by weight corresponded to lipid fraction in formulation. Increasing of the drug entrapment was achieved by blending small amount of phospholipid in solid lipid nanoparticle (SLN) dispersions. All AmB lipid dispersions were less aggregated species and hemolytic response than Fungizone^® indicating that lipid nanoparticles could reduce its toxicity. The sustained release profiles of AmB formulations depended on its aggregated form and entrapment efficiency. Too high AmB loaded (5% w/w) showed a biphasic drug release profile probably due to some amounts of drug deposited on the nanosphere surface including in continuous phase which promptly released. For in vitro antifungal testing, all AmB lipid formulations were equal and more effective than both AmB itself and Fungizone^®. These observations suggested that AmB loaded SLNs, nanostructured lipid carriers and modified SLNs by blending lecithin could enhance AmB solubility, prolong release characteristics, reduce toxicity and improve antifungal activity.

Efficacy of Intralipid infusion in reducing amphotericin-B-associated nephrotoxicity in head and neck invasive fungal infection: A randomized, controlled trial

Amphotericin B deoxycholate (ABD) is the best therapeutic agent available for the treatment of most systemic fungal infections. However, some untoward adverse effects such as nephrotoxicity may limit its appropriate therapeutic use. We conducted a randomized, controlled trial ofthe infusion of fat emulsion (Intralipid) shortly after the infusion of ABD to evaluate its effects on reducing ABD-associated nephrotoxicity. Our patient population was made up of 31 patients who were randomized into two groups: an intervention group (n = 16) and a control group (15 patients). There were no statistically significant differences between the two groups in demographic or clinical variables. All patients received 1mg/kg/day of ABD in dextrose 5%. In addition, the patients in the intervention arm received Intralipid 10%, which was started as soon as possible within 1 hour after the infusion of ABD. ABD-associated nephrotoxicity was defined as a minimum 50% increase in baseline serum creatinine to a minimum of 2mg/dl. We also measured daily serum creatinine changes during the first 2 weeks of treatment, and we compared some other relevant indices of renal function, as well as ABD-related hypokalemia. We found no statistically significant differences between the two treatments in terms of ABD-associated nephrotoxicity or any of the other indices. We conclude that the administration of Intralipid 10% early after infusion of ABD in dextrose 5% does not have any effect in decreasing ABD-associated nephrotoxicity or hypokalemia.

Nanoemulsions loaded with amphotericin B: a new approach for the treatment of leishmaniasis

This work aimed to develop nanoemulsions (NE) containing cholesterol and Amphotericin B (AmB) evaluating the influence of a lipophilic amine (stearylamine; STE) on drug encapsulation efficiency (EE), cytotoxicity on macrophages and in vitro antileishmanial activity. The EE of AmB in NE was nearly 100% regardless of STE concentration. Stability studies showed that AmB-loaded NE with or without STE were stable revealing that AmB content and EE remained constant after 180days. In significant contrast, the EE for AmB in NE without cholesterol drastically decreased showing that this co-surfactant significantly improved the retention of drug in NE. The electronic absorption and circular dichroism (CD) data revealed that the signal characteristic of self-associated free AmB, the most toxic form to the host cells, was virtually absent in the spectra of AmB-loaded NE. In agreement, NE-induced toxicity toward macrophages was significantly lower than that observed for the conventional AmB. STE enhanced both cytotoxicity and the activity against intracellular amastigotes of AmB-loaded NE. However, selectivity index values for AmB-loaded NE were considerably higher than that observed for conventional AmB. AmB-loaded and cholesterol-stabilized NE constitutes an attractive alternative for the treatment of leishmaniasis.

Influence of the freeze-drying process on the physicochemical and biological properties of pre-heated amphotericin B micellar systems

The moderate heat treatment of amphotericin B (AmB) in its micellar form (M-AmB) results in superaggregates (H-AmB) that present a substantially lower toxicity and similar activity. The aim of this work was to evaluate the H-AmB behavior after a freeze-drying process. H-AmB and M-AmB micelles were evaluated before and after freeze-drying concerning their physicochemical and biological properties by spectrophotometry and activity/toxicity assay, respectively. Four concentrations of M-AmB and H-AmB were studied aiming to correlate their aggregation state and the respective biological behavior: 50 mg L(-1), 5 mg L(-1), 0.5 mg L(-1), and 0.05 mg L(-1). Then, potassium leakage and hemoglobin leakage from red blood cells were used to evaluate the acute and chronic toxicity, respectively. The efficacy of M-AmB and H-AmB formulations was assessed by potassium leakage from Candida albicans and by the broth microdilution method. After heating, in addition to an evident turbidity, a slight blueshift from 327 to 323 nm was also observed at the concentrations of 50 and 5 mg L(-1) for H-AmB. Additionally, an increase in the absorbance at 323 nm at the concentration of 0.5 mg L(-1) was detected. Concerning the toxicity, H-AmB caused significantly lower hemoglobin leakage than M-AmB. These results were observed for H-AmB before and after freeze-drying. However, there was no difference between H-AmB and M-AmB concerning their activity. Accordingly, the freeze-drying cycle did not show any influence on the behavior of heated formulations, highlighting the suitability of such a method to produce a new AmB product with a long shelf life and with both greater efficiency and less toxicity.

Drug delivery systems for the topical treatment of cutaneous leishmaniasis

INTRODUCTION

The parenteral administration of pentavalent antimonials for the treatment of all forms of leishmaniasis, including cutaneous leishamniasis (CL), has several limitations. Therapy is long, requiring repeated doses and the adverse reactions are frequent. Topical treatment is an attractive alternative for CL, offering significant advantages over systemic therapy: fewer adverse effects, ease of administration, and lower costs.

AREAS COVERED

This review covers, from 1984 to the present, the progress achieved for the development of topical treatment for CL, using different drugs such as paromomycin (PA), imiquimod, amphotericin B (AmB), miltefosine, and buparvaquone. PA is the most commonly studied drug, followed by AmB and Imiquimod. These drugs were incorporated in conventional dosage forms or loaded in lipid nanocarries, which have been used mainly for improved skin delivery and antileishmanial activity.

EXPERT OPINION

Developing an effective topical treatment for CL using these antileishmanial drugs still remains a great challenge. Insights into the most promising delivery strategies to improve treatment of CL with PA and AmB using conventional dosage forms, lipid nanocarriers, and combined therapy are presented and discussed. The results obtained with combined therapy and alternative delivery systems are promising perspectives for improving topical treatment of CL.

How can micelle systems be rebuilt by a heating process?

The aim of this work was to evaluate how an aqueous micellar system containing Amphotericin B (AmB) and sodium deoxycholate (DOC) can be rebuilt after heating treatment. Also, a review of the literature on the physicochemical and biological properties of this new system was conducted. Heated (AmB-DOC-H) and unheated (AmB-DOC) micelles were then diluted at four different concentrations (50 mg · L(-1), 5 mg · L(-1), 0.5 mg · L(-1), and 0.05 mg · L(-1)) to perform physicochemical studies and a pharmacotoxicity assay, in which two cell models were used for the in vitro experiments: red blood cells (RBC) from human donors and Candida parapsilosis (Cp). While potassium (K(+)) and hemoglobin leakage from RBC were the parameters used to evaluate acute and chronic toxicity, respectively, the efficacy of AmB-DOC and AmB-DOC-H were assessed by K(+) leakage and cell survival rate from Cp. The spectral study revealed a slight change in the AmB-DOC aggregate peak from 327 nm to 323 nm, which is the peak for AmB-DOC-H. Although AmB-DOC and AmB-DOC-H exhibited different behavior for hemoglobin leakage, AmB-DOC produced higher leakage than AmB-DOC-H at high concentrations (from 5 mg · L(-1)). For K(+) leakage, both AmB-DOC and AmB-DOC-H showed a similar profile for both cell models, RBC and Cp (P < 0.05). AmB-DOC-H and AmB-DOC also revealed a similar profile of activity against Cp with an equivalent survival rate. In short, AmB-DOC-H showed much less toxicity than AmB-DOC, but remained as active as AmB-DOC against fungal cells. The results highlight the importance of this new procedure as a simple, inexpensive, and safe way to produce a new kind of micelle system for the treatment of systemic fungal infections.

Assessing the Antifungal Activity of a New Oral Lipid-Based Amphotericin B Formulation Following Administration to Rats Infected withAspergillus Fumigatus

The purpose of this study was to assess the antifungal activity of a new oral amphotericin B (AmpB) lipid-based formulation following administration to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (2.1-2.5 x 10(7) colony forming units [CFU]) were injected via the jugular vein; 48h later male albino Sprague-Dawley rats (350-400 g) were administered either a single oral dose of AmpB incorporated into Peceol (50 mg AmpB/kg), physiologic saline (nontreated controls) or Peceol alone (vehicle control) once daily for 4 days. To assess antifungal activity Brain, Lung, Heart, Liver, Spleen and Kidney sections were homogenized with normal saline (1 mL/g of tissue) and a 0.1-mL aliquot was spread plated onto a Sabourand dextrose agar plate. The plates were incubated for 48 hr at 37 degrees C, at which time the number of fungal CFU were determined and corrected for tissue weight. In addition, plasma galactomannan antigen concentrations were determined. Data was reported as mean +/- standard error of the mean. The AmpB-Peceol oral formulation significantly decreased total fungal CFU concentrations recovered in all the organs added together, brain CFU concentrations, spleen CFU concentrations and plasma galactomannan antigen concentrations compared to baseline. No significant differences in lung, heart, liver and kidney CFU concentrations between treatment and control groups were observed. Peceol vehicle control did not exhibit any antifungal activity. These findings suggest that a new oral lipid-based formulation of AmpB incorporated into Peceol can significantly decrease brain and spleen CFU concentrations and plasma galactomannan antigen concentrations compared to non-treated controls.

SolEmuls technology: a way to overcome the drawback of parenteral administration of insoluble drugs

In this article, a nanosuspension of AmB was prepared and mixed with the preformed parenteral emulsion Lipofundin and subjected to high-pressure homogenization (SolEmuls technology). Characterization was performed by photon correlation spectroscopy (PCS), laser diffractometry (LD), and zeta potential measurements. Drug incorporation was studied by using light microscopy. The produced emulsions were further investigated by comparing them with the commercially available Fungizone in regard to antifungal efficiency and toxicity. Results suggest that through the SolEmuls process the AmB forms a reservoir, out of which it is released in such a manner that it is more efficient and less toxic than Fungizone.

Physicochemical characterization of molecular assemblies of miltefosine and amphotericin B

This study describes the interactions between two amphiphilic molecules with antileishmanial activity, amphotericin B (AmB) and miltefosine [hexadecylphosphocholine (HePC)], the latter being effective by the oral route. The effect of HePC on the aggregation state of AmB in aqueous solution and the interactions between the two agents were monitored using absorption spectroscopy and circular dichroism. Structural characterization of the mixed aggregates formed in water by dynamic light scattering (DLS) and cryofracture electron microscopy was performed. At concentrations above its critical micelle concentration, HePC was shown to interact with AmB, leading to an increase in the proportion of AmB in its monomeric form as a result of a micellar solubilization mechanism with a capacity of 26 +/- 3 mmol of AmB solubilized/mol of HePC, that is, nearly 40 molecules of HePC per molecule of AmB in the mixed micelles. These were revealed as individual and spherical aggregates close to 10 nm in diameter by both electron microscopy and DLS. Such a micellar formulation provides a new AmB-based system which might be useful in delivering AmB orally for visceral leishmaniasis bitherapy.

Potential mechanisms by which Peceol increases the gastrointestinal absorption of amphotericin B

PURPOSE

The purpose of this study was to ascertain how the incorporation of AmpB into a glyceride-rich excipient Peceol significantly increased Amphotericin B's (AmpB) gastrointestinal absorption in white male Sprague-Dawley rats. Based on preliminary studies, our working hypothesis was that incorporation of AmpB into mixed micelles composed of Peceol would significantly enhance gastro-intestinal (GI) tract absorption by increasing lymphatic drug transport and decreasing P-glycoprotein (PGP)-mediated drug efflux.

METHODS

I. Lymphatic Transport

STUDIES

Following an overnight fast (12-16 hr) and 48 hr postsurgery, rats were divided into two treatment groups and received a single-dose oral gavage (1 mL total volume) at 0700 h of either desoxycholate (DOC)-AmpB (5 mg AmpB/kg; n = 6 at each time point) or AmpB incorporated into 100% Peceol (Peceol-AmpB; 5 mg AmpB/kg; n = 6 at each time point). Mesenteric lymph samples were obtained prior to and at 0-4-hr, 4-6-hr, and 6-8-hr intervals post oral gavage. An equal volume of normal saline (1 mL) was administered intravenously to the animal following each blood draw to prevent fluid depletion throughout the duration of the study. Lymph was immediately harvested by centrifugation and analyzed for drug by high-performance liquid chromatography (HPLC). II. Multidrug Resistance 1 (mdr-1) STUDIES: Caco-2 cells were seeded at 10,000 cells/cm2 in T-75 flasks. When the cells reached 80% confluency, they were treated for 1 day and 7 days with 0.1% to 1.0% (v/v) Peceol or media alone (control). Following treatment, total RNA was isolated using TRIzol reagent, followed by reverse transcription into single-stranded cDNA. Polymerase chain reactions (PCR) were performed with specific primers for mdr-1. The PGP protein was determined by Western Blot Analysis.

RESULTS

Mean weight of rats was not significantly different prior to and following drug administration. Similarly, kidney, liver, lung, spleen, and heart weights were not different between DOC-AmpB and Peceol-AmpB treatment group. A significantly greater amount of AmpB was transported through the mesenteric lymph duct for all the time intervals used following the administration of Peceol-AmpB treatment group compared to the administration of DOC-AmpB (suspension). A significant lower mdr-1 mRNA and PGP protein expression within Caco-2 cells was observed following 1 and 7 days treatment with Peceol 0.1% to 1.0% (v/v) compared to nontreated controls.

CONCLUSIONS

Taken together, these findings suggest that Peceol increases the gastrointestinal absorption of AmpB by increasing the amount of drug that is transported through the mesenteric lymph duct and by decreasing mdr-1 mRNA and PGP protein expression, resulting in lower PGP-mediated AmpB efflux.

Evaluation of the relationship of the molecular aggregation state of amphotericin B in medium to its genotoxic potential

This work analyzes the genotoxicity potential, in the G2 phase of the cellular cycle, of an amphotericin B (AmB) commercially available form (Fungizone), and correlates it with the physicochemical properties of this product in aqueous media. The genotoxic studies were performed using peripheral blood lymphocytes from human donors. The chromosome aberrations and mitotic index were determined. Absorption spectra of Fungizone were obtained by dispersion of the stock solution in water for injection at various AmB concentrations, and using different cuvette path lengths for spectrophotometric determination. The absorption spectra of Fungizone in water are concentration dependent. High concentrations of Fungizone present a spectrum with an intense band at 340 nm, characteristic of AmB self-association. Conversely, at low concentrations, the spectra are similar to those obtained with AmB in methanol, with a positive band at 409 nm, assigned to AmB monomeric form. Similarly, the cytogenetic analysis shows an important decrease on the mitotic index, which is also concentration dependent when compared with control. Furthermore, the chromosome aberrations present a small, not statistically significant, increase only at the highest concentration. The results suggest that the Fungizone presents a cytotoxicity similar to membrane pore formation in mammalian cells that depends on the existence of self-associated AmB. In the presence of only monomeric forms, this phenomenon disappears. However, no genotoxicity was observed in this study.

Similarity between the in vitro activity and toxicity of two different fungizone™ / lipofundin™ admixtures

PURPOSE: Amphotericin B (AmB), an antifungal agent that presents a broad spectrum of activity, remains the gold standard in the antifungal therapy. However, sometimes the high level of toxicity forbids its clinical use. The aim of this work was to evaluate and compare the efficacy and toxicity in vitro of Fungizon™ (AmB-D) and two new different AmB formulations. METHODS: three products were studied: Fungizon™, and two Fungizon™ /Lipofundin™ admixtures, which were diluted through two methods: in the first one, Fungizon™ was previously diluted with water for injection and then, in Lipofundin™ (AmB-DAL); the second method consisted of a primary dilution of AmB-D as a powder in the referred emulsion (AmB-DL). For the in vitro assay, two cell models were used: Red Blood Cells (RBC) from human donors and Candida tropicallis (Ct). The in vitro evaluation (K+ leakage, hemoglobin leakage and cell survival rate-CSR) was performed at four AmB concentrations (from 50 to 0.05mg.L-1). RESULTS: The results showed that the action of AmB was not only concentration dependent, but also cellular type and vehicle kind dependent. At AmB concentrations of 50 mg.L-1, although the hemoglobin leakage for AmB-D was almost complete (99.51), for AmB-DAL and AmB-DL this value tended to zero. The p = 0.000 showed that AmB-D was significantly more hemolytic. CONCLUSION: The Fungizon™-Lipofundin™ admixtures seem to be the more valuable AmB carrier systems due to their best therapeutic index presented.

Effects of lipid-based oral formulations on plasma and tissue amphotericin B concentrations and renal toxicity in male rats

The purpose of this study was to determine the effects of various lipid and mixed-micelle formulations on the oral absorption and renal toxicity of amphotericin B (AMB) in rats. The maximum concentration of AMB in plasma and the area under the concentration-time curve for 0 to 24 h for AMB were elevated in rats administered triglyceride (TG)-rich AMB formulations in comparison to those in rats given (i) AMB preformulated as a micelle containing sodium deoxycholate with sodium phosphate as a buffer (DOC-AMB), (ii) an AMB-lipid complex suspension, or (iii) AMB solubilized in methanol. Furthermore, our findings suggest that AMB incorporated into TG-based oral formulations has less renal toxicity than DOC-AMB.