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

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.

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.

Amphotericin B loaded ethyl cellulose nanoparticles with magnified oral bioavailability for safe and effective treatment of fungal infection

Amphotericin B is a gold standard drug used in various fungal and parasitic infection treatment. Most of the marketed formulations are administered intravenously, but show dose-dependent adverse effects i.e., nephrotoxicity and hemolysis. Oral route eliminates the toxic concern but exhibits poor bioavailability. Therefore, ethylcellulose nanoparticles (EC-NPs) have been used for magnified oral delivery of AmB, where EC provides gastrointestinal stability. These nanoparticles were synthesized by high-pressure emulsification solvent evaporation (HPESE) method and evaluated for in vitro and in vivo studies. This method yields small, monodisperse AmB-EC-NPs along with smooth surface morphology and improved encapsulation efficiency. The developed formulation showed a sustained release pattern following Higuchi diffusion kinetics along with gastric and storage stability. Aggregation study revealed that AmB was present in its monomeric form inside the biocompatible EC matrix. The antifungal result demonstrated that the MIC of AmB-EC-NPs was reduced ∼1/3rd than AmB and Fungizone® at 24 h whereas it was observed ∼1/8th at 48 h. in vivo pharmacokinetic analysis demonstrated 1.3-fold higher AUC than Fungizone® even at a 4.5-time lesser dose via the oral route and a ∼15-fold rise in the bioavailability in contrast to the native AmB. The hemolytic study revealed that the developed formulation exhibited 8-fold lesser hemolysis than Fungizone®. Furthermore, the biosafety profile of AmB-EC-NPs was ensured by the significantly lesser level of blood urea nitrogen and plasma creatinine along with the normal pattern of renal tubules in comparison to AmB and Fungizone®. In conclusion, the results stipulated that the AmB-EC-NPs could be effective, viable and a better alternative to currently existing iv formulations, for magnified oral delivery of AmB in the treatment of fungal infection without associated adverse effects.

Exploiting knowledge on pharmacodynamics-pharmacokinetics for accelerated anti-leishmanial drug discovery/development

Introduction: Being on the top list of neglected tropical diseases, leishmaniasis has been marked for elimination by 2020. In the light of small armamentarium of drugs and their associated drawbacks, the understanding of pharmacodynamics and/or pharmacokinetics becomes a priority to achieve and sustain disease elimination. Areas covered: The authors have looked into pharmacological aspects of existing and emerging drugs for treatment of leishmaniasis. An in-depth understanding of pharmacodynamics and pharmacokinetics (PKPD) provides a rationale for drug designing and optimizing the treatment strategies. It forms a key to prevent drug resistance and avoid drug-associated adverse effects. The authors have compiled the researches on the PKPD of different anti-leishmanial formulations that have the potential for improved and/or effective disease intervention. Expert opinion: Understanding the pharmacological aspects of drugs forms the basis for the clinical application of novel drugs. Tailoring drug dosage and individualized treatment can avoid the adverse events and bridge gap between the in vitro models and their clinical application. An integrated approach, with pragmatic use of technological advances can improve phenotypic screening and physiochemical properties of novel drugs. Concomitantly, this can serve to improve clinical efficacies, reduce the incidence of relapse and accelerate the drug discovery/development process for leishmaniasis elimination.

Review and analysis of FDA approved drugs using lipid-based formulations

Lipid-based drug delivery systems (LBDDS) are one of the most studied bioavailability enhancement technologies and are utilized in a number of U.S. Food and Drug Administration (FDA) approved drugs. While researchers have used several general rules of thumb to predict which compounds are likely to benefit from LBDDS, formulation of lipid systems is primarily an empiric endeavor. One of the challenges is that these rules of thumb focus in different areas and are used independently of each other. The Developability Classification System attempts to link physicochemical characteristics with possible formulation strategies. Although it provides a starting point, the formulator still has to empirically develop the formulation. This article provides a review and quantitative analysis of the molecular properties of these approved drugs formulated as lipid systems and starts to build an approach that provides more directed guidance on which type of lipid system is likely to be the best for a particular drug molecule.

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

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

Design of amphotericin B oral formulation for antifungal therapy

Amphotericin B (AmB) remains the “gold standard” for systemic antifungal therapy, even though new drugs are emerging as the attractive antifungal agents. Since AmB has negligible oral absorption as a consequence of its unfavorable physicochemical characterizations, its use is restricted to parenteral administration which is accompanied by severe side effects. As greater understanding of the gastrointestinal tract has developed, the advanced drug delivery systems are emerging with the potential to overcome the barriers of AmB oral delivery. Much research has demonstrated that oral AmB formulations such as lipid formulations may have beneficial therapeutic efficacy with reduced adverse effects and suitable for clinical application. Here we reviewed the different formulation strategies to enhance oral drug efficacy, and discussed the current trends and future perspectives for AmB oral administration in the treatment of antifungal infections.

BCS class IV drugs: Highly notorious candidates for formulation development

BCS class IV drugs (e.g., amphotericin B, furosemide, acetazolamide, ritonavir, paclitaxel) exhibit many characteristics that are problematic for effective oral and per oral delivery. Some of the problems associated include low aqueous solubility, poor permeability, erratic and poor absorption, inter and intra subject variability and significant positive food effect which leads to low and variable bioavailability. Also, most of the class IV drugs are substrate for P-glycoprotein (low permeability) and substrate for CYP3A4 (extensive pre systemic metabolism) which further potentiates the problem of poor therapeutic potential of these drugs. A decade back, extreme examples of class IV compounds were an exception rather than the rule, yet today many drug candidates under development pipeline fall into this category. Formulation and development of an efficacious delivery system for BCS class IV drugs are herculean tasks for any formulator. The inherent hurdles posed by these drugs hamper their translation to actual market. The importance of the formulation composition and design to successful drug development is especially illustrated by the BCS class IV case. To be clinically effective these drugs require the development of a proper delivery system for both oral and per oral delivery. Ideal oral dosage forms should produce both a reasonably high bioavailability and low inter and intra subject variability in absorption. Also, ideal systems for BCS class IV should produce a therapeutic concentration of the drug at reasonable dose volumes for intravenous administration. This article highlights the various techniques and upcoming strategies which can be employed for the development of highly notorious BCS class IV drugs. Some of the techniques employed are lipid based delivery systems, polymer based nanocarriers, crystal engineering (nanocrystals and co-crystals), liquisolid technology, self-emulsifying solid dispersions and miscellaneous techniques addressing the P-gp efflux problem. The review also focuses on the roadblocks in the clinical development of the aforementioned strategies such as problems in scale up, manufacturing under cGMP guidelines, appropriate quality control tests, validation of various processes and variable therein etc. It also brings to forefront the current lack of regulatory guidelines which poses difficulties during preclinical and clinical testing for submission of NDA and subsequent marketing. Today, the pharmaceutical industry has as its disposal a series of reliable and scalable formulation strategies for BCS Class IV drugs. However, due to lack of understanding of the basic physical chemistry behind these strategies formulation development is still driven by trial and error.

Effect of Food Status on the Gastrointestinal Transit of Amphotericin B-Containing Solid Lipid Nanoparticles in Rats

Amphotericin B (AmB) is poorly absorbed from the gastrointestinal tract. Recent studies have suggested enhanced drug absorption from solid lipid nanoparticles (SLN). Little is known of the fate of AmB absorption within the gastrointestinal tract, and no gastrointestinal transit study has yet been performed on AmB-containing nano-formulations. We aimed to investigate the effect of food on the gastrointestinal transit properties of an AmB-containing SLN in rats. Three SLNs containing AmB, paracetamol, or sulfasalazine were formulated using cocoa butter and beeswax as lipid matrices and simultaneously administered orally to Sprague-Dawley rats. Paracetamol and sulfapyridine were used as marker drugs for estimating gastric emptying and cecal arrival, respectively. The pharmacokinetic data generated for paracetamol and sulfapyridine were used in estimating the absorption of the AmB SLNs in the small and large intestines, respectively. A delayed rate of AmB absorption was observed in the fed state; however, the extent of absorption was not affected by food. Specifically, the percentages of AmB absorption during the fasted state in the stomach, small intestine, and colon were not significantly different from absorption within the respective regions in the fed state. In both states, however, absorption was highest in the colon and appeared to be a combination of absorption from the small intestine plus absorption proper within the colon. The study suggests that AmB SLN, irrespective of food status, is slowly but predominantly taken up by the lymph, making the small intestine the most favorable site for the delivery of the AmB SLNs.

Physical characterization and in vivo pharmacokinetic study of self-assembling amphotericin B-loaded lecithin-based mixed polymeric micelles

To alleviate the inherent problems of amphotericin B (AmB), such as poor water solubility and nephrotoxicity, a novel self-assembling mixed polymeric micelle delivery system based on lecithin and combined with amphiphilic polymers, Pluronic^®, Kolliphor^®, d-alpha tocopheryl polyethylene glycol succinate, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy(poly(ethylene glycol)-2000 (DSPE-PEG2K) was developed. An optimal formulation (Ambicelles) composed of AmB:lecithin:DSPE-PEG2K in a 1:1:10 weight ratio was obtained. The particle size, polydispersion index, drug encapsulation efficiency, and drug loading were 187.20±10.55 nm, 0.51±0.017, 90.14%, and 7.51%, respectively, and the solubility was increased from 0.001 to 5 mg/mL. Compared with that of Fungizone^®, the bioavailability of Ambicelles administered intravenously and orally increased 2.18- and 1.50-fold, respectively. Regarding the in vitro cytotoxicity, Ambicelles had a higher cell viability than free AmB solution or Fungizone^® did. With pretreatment of 50 μg/mL ethanolic extract of Taiwanofungus camphoratus followed by AmB to HT29 colon cancer cells, the 50% inhibitory concentration of AmB solution was 12 μg/mL, whereas that of Ambicelles was 1 μg/mL, indicating that Ambicelles exerted a greater synergistic anticancer effect.

A gastrointestinal transit study on amphotericin B-loaded solid lipid nanoparticles in rats

The gastrointestinal (GI) transit behavior of and absorption from an amphotericin B (AmB) solid lipid nanoformulation (SLN) in rats was investigated. We aimed to estimate the gastric emptying time (GET) and cecal arrival time (CAT) of AmB SLN in rats as animal models. From these two parameters, an insight on the absorption window of AmB was ascertained. Three types of SLNs, AmB, paracetamol (PAR), and sulfasalazine (SSZ), were similarly formulated using beeswax/theobroma oil composite as the lipid matrix and characterized with regard to size, viscosity, density, migration propensity within agarose gel, in vitro drug release, morphology, gastrointestinal transit, and in vivo absorption. The GET and CAT were estimated indirectly using marker drugs: PAR and sulfapyridine (SP). All three types of SLNs exhibited identical properties with regard to z-average, viscosity, relative density, and propensity to migrate. PAR was absorbed rapidly from the small intestine following emptying of the SLNs giving the T50E (time for 50% absorption of PAR) to be 1.6 h. SP was absorbed after release and microbial degradation of SSZ from SLN in the colon with a lag time of 2 h post-administration, serving as the estimated cecal arrival time of the SLNs. AmB within SLN was favorably absorbed from the small intestine, albeit slowly.

Does P-glycoprotein contribute to amphotericin B epithelial transport in Caco-2 cells?

INTRODUCTION

Amphotericin B (AmB) is a highly efficacious therapeutic for invasive fungal infections and protozoal diseases. Increasing prevalence of these conditions warrants the development of an oral AmB formulation. Efflux transporters, such as the ABCB1 gene product P-glycoprotein, affect the oral bioavailability and disposition of a range of clinically relevant compounds. At present, it remains to be determined whether AmB is a substrate of P-glycoprotein mediated efflux. The objective of this study was to determine whether P-glycoprotein contributes to the epithelial transport of AmB in a Caco-2 cell model.

METHODS

Stimulation of P-glycoprotein ATPase activity was assessed using membranes containing human recombinant P-glycoprotein. An ABCB1 knockdown Caco-2 cell model was employed to determine non-toxic concentrations of AmB. AmB cellular association, following a 180 min incubation, was determined using an high performance liquid chromatography-ultraviolet (HPLC-UV) assay.

RESULTS

At the concentrations investigated, AmB did not stimulate P-glycoprotein ATPase activity. Non-toxic concentrations of AmB were 1 μg/mL-5 μg/mL; these were used in subsequent experiments. No significant difference in AmB cellular association was observed for ABCB1 small interfering ribonucleic acid transfected and non-transfected Caco-2 cells, following a 180 min incubation with 1 μg/mL and 2.5 μg/mL AmB. However, significantly greater AmB was associated with transfected cells as compared to non-transfected cells, when cells were incubated with 5 μg/mL AmB.

CONCLUSIONS

These results suggest that AmB is not a substrate of P-glycoprotein mediated efflux in this Caco-2 cell model. P-glycoprotein is not expected to be a major barrier to the oral absorption and disposition of AmB.

Evaluating the potential of cubosomal nanoparticles for oral delivery of amphotericin B in treating fungal infection

The oral administration of amphotericin B (AmB) has a major drawback of poor bioavailability. The aim of this study was to investigate the potential of glyceryl monoolein (GMO) cubosomes as lipid nanocarriers to improve the oral efficacy of AmB. Antifungal efficacy was determined in vivo in rats after oral administration, to investigate its therapeutic use. The human colon adenocarcinoma cell line (Caco-2) was used in vitro to evaluate transport across a model of the intestinal barrier. In vivo antifungal results showed that AmB, loaded in GMO cubosomes, could significantly enhance oral efficacy, compared against Fungizone®, and that during a 2 day course of dosage 10 mg/kg the drug reached effective therapeutic concentrations in renal tissue for treating fungal infections. In the Caco-2 transport studies, GMO cubosomes resulted in a significantly larger amount of AmB being transported into Caco-2 cells, via both clathrin- and caveolae-mediated endocytosis, but not macropinocytosis. These results suggest that GMO cubosomes, as lipid nanovectors, could facilitate the oral delivery of AmB.

Strategies for the design of orally bioavailable antileishmanial treatments

Leishmaniasis is one of the six major tropical diseases targeted by the World Health Organization. The most serious, life-threatening form is visceral leishmaniasis (VL). No vaccine is yet available for human use and chemotherapy is the main mean of dealing with this disease. This review focuses on the development of drug delivery systems (DDS) for treatment of leishmaniasis. After an overview of the significance of leishmaniasis in 2013, current chemotherapy and its limitations are considered, leading to possible strategies to improve the treatment of VL: new drugs, combinations of existing drugs and DDS, particularly for oral administration. Nanostructured biomaterials such as lipid-based or polymeric nanoparticles have unique physicochemical properties, ultra-small and controllable size, large surface area to mass ratio and the possibility of surface modification which can be used to advantage for the oral administration of antileishmanial drugs. They can improve the rate of dissolution of poorly water-soluble drugs, increase intestinal residence time by bioadhesion and, especially when lipid additives are used, influence the route and efficiency of absorption. These recent advances in this very active field should lead to better management of this serious disease.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Formulation strategies for drug delivery of tacrolimus: An overview

Tacrolimus (FK 506) is a potent macrolide lactone immunosuppressive agent used for prophylaxis of organ rejection after transplantation and graft-versus-host disease after bone marrow transplantation in patients. Moreover, tacrolimus is a drug of choice in the treatment of atopic dermatitis for decreasing side effects associated with the use of topical corticosteroids. In spite of its success in ensuring graft survival, therapeutic use of tacrolimus is complicated due to its narrow therapeutic index (between 5 and 15 ng/ml). Tacrolimus has a large inter-/intra-patient variability in pharmacokinetics profile and a poor oral bioavailability because of its poor solubility, P-gp efflux, marked pre-systemic metabolism by CYP3A in the enterocytes and liver first pass effect. Several formulation approaches such as oily solution, solid dispersions, complexation with cyclodextrins, liposomes etc., have been investigated to improve oral delivery of FK 506. In this review, we have discussed various formulation approaches that have been undertaken by various researchers to solve the problems related to the drug delivery of tacrolimus.

Development of amphotericin B-loaded cubosomes through the SolEmuls technology for enhancing the oral bioavailability

The oral administration of amphotericin B (AmB) has the major drawback of poor bioavailability. The aim of this work was to evaluate the potential of AmB-loaded cubosomes as an oral formulation with improved bioavailability. This manuscript firstly developed AmB-loaded cubosomes by using the SolEmuls technology. The encapsulation efficiency, the in vitro release, and stability studies in simulated gastrointestinal fluid were used to evaluate AmB-loaded cubosomes. The acute nephrotoxicity, bioavailability, and tissue distribution study of AmB-loaded cubosomes were assayed upon oral administration to rats. SAXS and cryo-TEM exhibited AmB-loaded cubosomes as a bicontinuous cubic liquid crystalline phase with Pn3m geometry. The encapsulation efficiency and the results of in vitro release and stability studies in simulated gastrointestinal fluid further demonstrated that AmB was successfully encapsulated in cubosomes. AmB-loaded cubosomal formulation orally administrated in rats did not show nephrotoxicity and its relative bioavailability was approximately 285% as compared to Fungizone®. The AmB-loaded cubosomal formulation presented an effective potential approach for enhancing the oral bioavailability of AmB.

Enhancement of oral bioavailability of the poorly water-soluble drug silybin by sodium cholate/phospholipid-mixed micelles

AIM

To evaluate a mixed micellar drug delivery system composed of sodium cholate and phospholipid for oral administration of silybin, a promising hepatoprotectants.

METHODS

The optimum formulation of sodium cholate/phospholipid-mixed micelles containing silybin was obtained based on the study of pseudo-ternary phase diagram. The dissolution of silybin-mixed micelles was investigated. The pharmacokinetic characteristics and bioavailability after oral administration of silybin-mixed micelles and silybin-N-methylglucamine were compared in dogs.

RESULTS

The mean particle size of prepared mixed micelles was 75.9+/-4.2 nm. The largest solubility of silybin was found to be 10.0+/-1.1 mg/mL in the optimum formulation of mixed micelles. The silybin-sodium cholate/phospholipid-mixed micelles showed a very slow release of silybin 17.5% (w/w) within 72 h in phosphate buffer (pH 7.4) and 15.6% (w/w) in HCl solution (pH 1.2). After oral administration to dogs, the relative bioavailability of mixed micelles versus silybin-N-methylglucamine in dogs was 252.0%.

CONCLUSION

Sodium cholate/phospholipid-mixed micelles are promising carriers in orally delivery of silybin, considering their capability of enhancing bioavailability and large-scale production.

A photophysical study on the role of bile salt hydrophobicity in solubilizing amphotericin B aggregates

Amphotericin B (AmB) is a highly effective antifungal agent and finds utility against a broad spectrum of fungal species. Bile salts are biocompatible biosurfactants, widely used as drug delivery media for many hydrophobic drugs. AmB in the colloidal suspension of sodium deoxycholate (NaDC) is a well-known commercial formulation of AmB. In the present work, the association of AmB with three bile salts, namely sodium cholate, sodium taurodeoxycholate and sodium taurocholate is studied using the photophysical properties of AmB. Selective excitation of monomeric AmB (lambda(ex) 414 nm, lambda(em) 560 nm) and dimeric AmB (lambda(ex) 335 nm, lambda(em) 472 nm) reveal that with increasing concentration of bile salts, the higher aggregates in water disaggregate to form both monomeric and dimeric forms of AmB. This is seen to be a general trend in all the bile salts studied. Results of steady state fluorescence anisotropy and fluorescence lifetimes studies suggest that the interaction between AmB (hydrophobic heptaene face) and bile salts (hydrophobic steroidal face) is essentially hydrophobic.

Enhanced oral bioavailability of griseofulvin via niosomes

The aim of the present report was to develop nonionic surfactant vesicles (niosomes) to improve poor and variable oral bioavailability of griseofulvin. Niosomes were prepared by using different nonionic surfactants span 20, span 40, and span 60. The lipid mixture consisted of surfactant, cholesterol, and dicetyl phosphate in the molar ratio of 125:25:1.5, 100:50:1.5, and 75:75:1.5, respectively. The niosomal formulations were prepared by thin film method and ether injection method. The influence of different formulation variables such as surfactant type, surfactant concentration, and cholesterol concentration was optimized for size distribution and entrapment efficiency for both methods. Result indicated that the niosomes prepared by thin film method with span 60 provided higher entrapment efficiency. The niosomal formulation exhibited significantly retarded in vitro release as compared with free drug. The in vivo study revealed that the niosomal dispersion significantly improved the oral bioavailability of griseofulvin in albino rats after a single oral dose. The maximum concentration (Cmax) achieved in case of niosomal formulation was approximately double (2.98 microg/ml) as compared to free drug (1.54 microg/ml). Plasma drug profile also suggested that the developed niosomal system also has the potential of maintaining therapeutic level of griseofulvin for a longer period of time as compared to free griseofulvin. The niosomal formulation showed significant increase in area under the curve0-24 (AUC; 41.56 microg/ml h) as compared to free griseofulvin (22.36 microg/ml h) reflecting sustained release characteristics. In conclusion, the niosomal formulation could be one of the promising delivery system for griseofulvin with improved oral bioavailability and prolonged drug release profiles.

Isolation and characterization of pcsB, the gene for a polyene carboxamide synthase that tailors pimaricin into AB-400

From cell-free extracts of Streptomyces RGU5.3, a tailoring activity of pimaricin, leading to the biosynthesis of its natural carboxamide derivative AB-400, was recently identified. The two polyene macrolides, pimaricin and AB-400, were produced in almost equal quantities and can be detected in the fermentation broth of the producer strain. This report concerns the isolation and partial characterization of the gene, polyene carboxamide synthase (pcsB), responsible for the bioconversion. The gene encoded an asparagine synthase-like protein, belonging to the type II glutamine amidotransferase family, and was named pcsB. The fermentation broth of a recombinant strain carrying the engineered pcsB gene under the control of the inducible tipA promoter within an integrative vector produces the carboxamide AB-400 as the main polyene macrolide.

Pharmacokinetics and biodistribution of amphotericin B in rats following oral administration in a novel lipid-based formulation

OBJECTIVES

To assess the pharmacokinetics and biodistribution of amphotericin B (AmB) following oral administration in a novel mono/diglyceride-phospholipid formulation and to compare with intravenous (iv) administrations using commercial formulations.

METHODS

Rats were allocated into the following treatment groups: oral gavage of AmB dispersed in mono/diglyceride-phospholipid formulation at doses of 4.5 and 10 mg/kg; iv bolus administration of 0.8 mg/kg Fungizone; iv bolus of 5 mg/kg Abelcet and iv bolus of 5 mg/kg AmBisome. Blood was sampled from jugular vein cannula at certain time points. The animals were sacrificed 72 h following administration of AmB and multiple tissues were harvested. The concentration of AmB in plasma and tissues was determined by means of HPLC. The plasma creatinine concentrations were determined using an enzymatic kit.

RESULTS

The pharmacokinetics and tissue distribution of AmB following iv administrations of the commercial formulations were found to be highly formulation dependent. The terminal half-life and biodistribution of orally administered AmB in a mono/diglyceride-phospholipid formulation resembled those of Fungizone. The larger volume of the co-administered lipid-based formulation in the case of the higher dose of orally administered AmB resulted in flip-flop kinetics and in preferential distribution into the kidneys. No nephrotoxicity was detected for any formulation and route of administration.

CONCLUSIONS

Oral administration of AmB in a mono/diglyceride-phospholipid formulation to rats resulted in significant intestinal absorption into the systemic circulation with pharmacokinetic and biodistribution properties similar to a micellar iv preparation.

The global access initiative at the University of British Columbia (UBC): Availability of UBC discoveries and technologies to the developing world

The University of British Columbia (UBC) became the first university in Canada to develop a strategy for enhancing global access to its technologies. UBC's University-Industry Liaison Office, in collaboration with the UBC chapter of Universities Allied for Essential Medicines (UAEM), established a mandate and developed principles that provide the developing world with access to UBC technologies. This commentary will discuss these principles and provide examples of where they have been applied to several UBC technologies.

Biodegradable nanoparticles improve oral bioavailability of amphotericin B and show reduced nephrotoxicity compared to intravenous Fungizone

PURPOSE

Amphotericin B (AMB), an effective antifungal and antileishmanial agent associated with low oral bioavailability (0.3%) and severe nephrotoxicity, was entrapped into poly(lactide-co-glycolide) (PLGA) nanoparticles to improve the oral bioavailability and to minimize the adverse effects associated with it.

MATERIALS AND METHODS

The AMB-nanoparticles (AMB-NP) were prepared by nanoprecipitation method employing Vitamin E-TPGS as a stabilizer. In vitro release was carried out using membrane dialysis method. The in vitro hemolytic activity of AMB-NP was evaluated by incubation with red blood cells (RBCs). The acute nephrotoxicity profile and oral bioavailability of AMB-NP were evaluated in rats.

RESULTS

The prepared AMB-NP formulation contained monodispersed particles in the size range of 165.6 +/- 2.9 nm with 34.5 +/- 2.1% entrapment at 10% w/w initial drug loading. AMB-NP formulation showed biphasic drug release, an initial rapid release followed by a sustained release. The AMB-NP formulation exerted lower hemolysis and nephrotoxicity as compared to Fungizone. The relative oral bioavailability of the AMB-NP was found to be approximately 800% as compared to Fungizone.

CONCLUSION

Together, these results offer a possibility of treating systemic fungal infection and leishmaniasis with oral AMB-NP, which could revolutionize the infectious disease treatment modalities.

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.

Enhancing drug absorption using lipids: a case study presenting the development and pharmacological evaluation of a novel lipid-based oral amphotericin B formulation for the treatment of systemic fungal infections

The development of a safe and efficacious drug involves a balance between bioavailability, toxicity and disposition within the body. If the drug is hydrophobic or acid labile, oral administration may lead to poor systemic exposure, necessitating a parenteral treatment regime. Amphotericin B (AmpB) is one example of a well established, highly efficacious drug that has a 50 year history of intravenous therapy. AmpB formulated as a micellar dispersion (Fungizone; FZ) for IV use, remains one of the most effective agents in the treatment of systemic fungal infections, yet no oral formulations are currently commercially available. Recently, our laboratory has developed new oral lipid-based AmpB formulations with enhanced gastrointestinal (GI) tract absorption and antifungal activity with minimum renal toxicity. This review article will discuss these findings and present data to support two potential mechanisms for the enhanced GI tract absorption of AmpB when formulated in this oral lipid-based delivery system, namely an increase in lymphatic drug transport and a decrease in pre-systemic transporter-mediated drug efflux.

Formulation and evaluation of microemulsion based delivery system for amphotericin B

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

Lipid Formulation Strategies for Enhancing Intestinal Transport and Absorption of P-Glycoprotein (P-gp) Substrate Drugs: In vitro/In vivo Case Studies

The intestinal efflux pump, P-glycoprotein (P-gp), located in the apical membranes of intestinal absorptive cells, can reduce the bioavailability of a wide range of drugs which are substrates for this membrane transporter. In addition to anticancer and anti-HIV drugs, NCEs for other disease indications are P-gp substrates and there is considerable interest in inhibiting P-gp and thus increasing the bioavailability of these molecules. In this review article, an overview of P-gp and its role in drug transport and absorption will be presented first and then formulation strategies to effectively inhibit P-gp will be discussed and compared. These strategies independently and in combination, are: (a) coadministration of another P-gp substrate/specific inhibitor, and (b) incorporation of a nonspecific lipid and/or polymer excipient in the formulation. The first approach, although very effective in inhibiting P-gp, utilizes a second active compound in the formulation and thus imposes regulatory constraints and long development timelines on such combination products. Excipient inhibitors appear to have minimal nonspecific pharmacological activity and thus potential side effects of specific active compound inhibitors can be avoided. Case studies will be presented where specific active compounds, surfactants, polymers, and formulations incorporating these molecules are shown to significantly improve the intestinal absorption of poorly soluble and absorbed drugs as a result of P-gp inhibition and enhanced drug transport in vitro.

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.