Pharmacological parameters of intravenously administered amphotericin B in rats: comparison of the conventional formulation with amphotericin B associated with a triglyceride-rich emulsion

Lipid nanoparticles for amphotericin delivery in the treatment of American tegumentary leishmaniasis

Leishmaniasis occurs in the five continents and represents a serious public health challenge, but is still a neglected disease, and the current pharmacological weaponry is far from satisfactory. Triglyceride-rich nanoparticles mimicking chylomicrons (TGNP) behave metabolically like native chylomicrons when injected into the bloodstream. Previously we have shown that TGNP as vehicle to amphothericin B (AB) for treatment of fungi infection showed reduced renal toxicity and lower animal death rates compared to conventional AB. The aim of the current study was to test the tolerability and effectiveness of the TGNP-AB preparation in a murine model of Leishmania amazonensis infection. The in vitro assays determined the cytotoxicity of TGNP-AB, AB, and TGNP in macrophages and promastigote forms and the leishmanicidal activity in infected macrophages. The in vivo toxicity tests were performed in healthy mice with increasing doses of TGPN-AB and AB. Then, animals were treated with 2.5 mg/kg/day of AB, 17.5 mg/kg/day of TGNP-AB, or TGNP three times a week for 4 weeks. TGNP-AB formulation was less cytotoxic for macrophages than AB. TGNP-AB was more effective than AB against the promastigotes forms of the parasite and more effective in reducing the number of infected macrophages and the number of amastigotes forms per cell. TGNP-AB-treated animals showed lower hepatotoxicity. In addition, TGNP-AB group showed a marked reduction in lesion size on the paws and parasitic load. The TGNP-AB preparation attained excellent leishmanicidal activity with remarkable lower drug toxicity at very high doses that, due to the toxicity-buffering properties of the nanocarrier, become fully tolerable.

Lipid peroxidation: Its effects on the formulation and use of pharmaceutical emulsions

Pharmaceutical delivery systems are developed to improve the physicochemical properties of therapeutic compounds. Emulsions are one of these drug delivering systems formulated using water, oils and lipids as main ingredients. Extensive data are usually generated on the physical and chemical characteristics of these oil-in-water and lipid emulsions. However, the oxidative tendency of emulsions is often overlooked. Oxidation impacts the overall quality and safety of these pharmaceutical emulsions. Additionally, introducing oxidatively unstable emulsions into biological systems further promotes oxidation in situ. Products of these reactions then continue to pose serious harm to cells and fuel other physiological oxidation reactions. Consequently, the increase of oxidation products leads to oxidative damage to biological systems. Thus, emulsions with lower lipid peroxidation are more stable and will reduce the negative effects of oxidation in situ. Preventive measures during the formulation of emulsions are important. Many naturally occurring and cost effective substances possess low oxidation tendencies and confer oxidative protection when used in emulsions. Additionally, certain preparatory methods should be employed to reduce or better control lipid peroxidation. Finally, emulsions must be evaluated for their oxidation susceptibility using the various techniques available. Careful attention to the preparation of emulsions and assessment of their oxidative stability will help produce safer emulsions without compromising efficacy.

ESTRATÉGIAS TECNOLÓGICAS PARA FORMULAÇÕES DE ANFOTERICINA B EM SISTEMAS LIPÍDICOS DISPONÍVEIS NO MERCADO FARMACÊUTICO E OUTROS PROMISSORES SISTEMAS DE ADMINISTRAÇÃO

A anfotericina B (AmB) é um fármaco antifúngico utilizado no tratamento de micoses sistêmicas desde sua descoberta nos anos de 1950. O objetivo deste trabalho foi estabelecer o estado da arte das estratégias tecnológicas envolvidas nas formas de administração da AmB, nas intervenções diretas nos aspectos de melhoria de solubilidade do fármaco, que possibilitem sua administração por via intravenosa (iv) e minimizem sua toxicidade. Devido à limitada utilidade clínica do sal de desoxicolato (Fungizon®) em razão de sua alta toxicidade, sistemas de liberação mais eficientes foram desenvolvidos. Neste trabalho, são apresentadas as principais formulações disponíveis no mercado farmacêutico e outras formulações lipídicas promissoras, as quais se mostraram mais eficazes como veículos de solubilização e menos tóxicas quando comparadas com a AmB esoxicolato, mas ainda não fazem parte da rotina hospitalar para o tratamento de micoses profundas.

Optimizing therapy for vancomycin-resistant enterococcal bacteremia in children

PURPOSE OF REVIEW

Uncertainties exist regarding the optimal treatment for vancomycin-resistant enterococcal (VRE) bloodstream infections, particularly in settings in which ampicillin cannot be used.

RECENT FINDINGS

Quinupristin-dalfopristin, linezolid, and daptomycin, all approved between 1999 and 2003, represent the mainstays of therapy for VRE bacteremia, although only linezolid has been specifically approved by the United States Food and Drug Administration for this indication. The main objective of this review is to compare the relative efficacies, dosing strategies, and side-effect profiles of quinupristin-dalfopristin, linezolid, and daptomycin for VRE bacteremia in the pediatric population. A brief description of recently approved broad-spectrum Gram-positive agents that may have a role in the management of VRE bacteremia in upcoming years is also provided.

SUMMARY

Linezolid, despite its bacteriostatic activity against VRE, may be the most versatile of the available drugs. It has activity against both Enterococcus faecalis and E. faecium, can be administered orally, and resistance appears to be less of a concern with linezolid compared with the other agents. Additionally, the results of two recent meta-analyses demonstrate more favorable outcomes with linezolid compared with daptomycin for the treatment of VRE bacteremia. The clinical pharmacokinetics of linezolid have been well described in children. The most notable concern with linezolid, however, is toxicities associated with prolonged use. Until more prospective data are available, we favor linezolid as first-line therapy for the treatment of VRE bacteremia in children.

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.

Low nephrotoxicity of an effective amphotericin B formulation with cationic bilayer fragments

OBJECTIVES

Evaluation of nephrotoxicity of a novel amphotericin B (AMB) formulation with dioctadecyldimethylammonium bromide (DODAB) bilayer fragments (DOD/AMB).

METHODS

Dose-dependent cytotoxicity of DOD/AMB was evaluated in vitro against cultured kidney epithelial cells in culture. For in vivo experiments, Swiss Webster female mice were injected intraperitoneally for 10 consecutive days with 0.4 mg/kg/day AMB in the form of traditional bile salt desoxycholate (DOC)/AMB or DOD/AMB. Body and spleen weight, and biochemical and histopathological data were obtained at days 11 and 180 after injection.

RESULTS

Nephrotoxicity of the novel formulation was lower than that of Fungizone (DOC/AMB), which is the traditional AMB formulation using DOC. Dose-dependent cytotoxicity of DOD/AMB was lower than that exhibited by DOC/AMB. At day 11, DODAB and DOD/AMB caused loss of body weight and increase in spleen weight, which were not observed for DOC/AMB, although the changes were reversible and weights returned to control values at day 180. Ten days after injection, biochemical parameters for hepatic and renal function remained unaltered. At day 180, renal cortex histopathology revealed leucocytic infiltration and moderate hydropic degeneration of the renal tubules in the DODAB and DOD/AMB groups, in contrast to more severe lesions observed for the DOC/AMB group such as tubular cystic degeneration and glomerular injury, which were absent for the former groups.

CONCLUSIONS

The DOD/AMB formulation exhibited differential cytotoxicity and low nephrotoxicity, but there were also important aspects of general toxicity that will require evaluation with full-scale toxicity protocols.

Amphotericin B

Invasive fungal infections are a major cause of morbidity and mortality in immunodeficient individuals (such as AIDS patients) and in transplant recipients or tumor patients undergoing immunosuppressive chemotherapy. Amphotericin B is one of the oldest, yet most efficient antimycotic agents. However, its usefulness is limited due to dose-dependent side-effects, notably nephrotoxicity. In order to improve its safety margin, new pharmaceutical formulations of amphotericin B have been designed especially to reduce its detrimental effects on the kidneys. Since the 1980s, a wide variety of new amphotericin B formulations have been brought forward for clinical testing, many of which were approved and reached market value in the 1990s. This review describes and discusses the molecular genetics, pharmacological, toxicological, and clinical aspects of amphotericin B itself and many of its innovative formulations.

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.

Indomethacin-loaded methoxy poly(ethylene glycol)/poly(D,L-lactide) amphiphilic diblock copolymeric nanospheres: Pharmacokinetic and toxicity studies in rodents

Biodegradable methoxy poly(ethylene glycol)/poly(D,L-lactide) amphiphilic block copolymeric nanospheres were prepared for application as a particulate drug carrier. Drug-loaded nanospheres (ML50) showed a narrow size distribution with the average diameter of <200 nm. When the feed weight ratio of indomethacin (IMC) to polymer was 1:1, the ML50 nanosphere having a relatively high drug-loading efficiency of about 33.0% could be obtained. To investigate pharmacokinetic characteristics of IMC in rats, the IMC concentration in plasma was analyzed using a high-performance liquid chromatography system after intravenous bolus injection of free IMC and IMC-loaded ML50 nanospheres. ML50 nanosphere system exhibited a significant potential for sustained release of drug and showed slow clearance of IMC, but there was no significant effect on metabolism of IMC in the rats. Median lethal dose (LD50) and major organs (e.g., heart, lung, liver, and kidney) toxicities were determined using ICR mice to estimate the acute toxicity of ML50 nanospheres. The LD50 of ML50 nanospheres determined by Litchfield-Wilcoxon method was about 1.54 g/kg. After the mice were intraperitoneally administered with a half dose of LD50 for 7 days, no significant histopathologic changes were observed in ML50-treated mice compared with normal mice in the light and electron microscopic observations of major organs. This indicates that ML50 nanospheres might be a useful candidate as a novel sustained drug carrier for hydrophobic drugs.

Treatment of experimental visceral leishmaniasis with amphotericin B in stable albumin microspheres

Hydrophilic albumin microspheres are proposed as a new delivery system for amphotericin B (AMB; AMB microspheres). The acute toxicity of AMB microspheres was lower than that of the AMB-deoxycholate (AMB-Doc) reference formulation in hamsters. Lethal doses in healthy and infected animals were improved at least eight times. Intravenous bolus administration of doses of AMB microspheres up to 40 mg/kg of body weight did not produce acute symptoms of toxicity. The efficacy of this new formulation was tested against Leishmania infantum-infected hamsters at doses of 2, 10, 20, and 40 mg/kg. With the 2-mg/kg dose, the activity of AMB, as assessed through the parasite load reductions in the liver and spleen and the evolution of antibody levels, was also improved (P < 0.05) by use of the AMB microsphere system. At the higher doses of 10, 20, and 40 mg/kg, reductions in parasite levels of more than 99% were achieved in the liver and spleen after the administration of AMB microspheres. A pharmacokinetic study was performed to study the serum, liver, and spleen AMB concentrations after administration of AMB microspheres and the reference formulation. Interestingly, a significant accumulation of AMB in the spleen and liver was observed after AMB microsphere administration. Our results suggest that this new formulation is a promising alternative to the conventional AMB-Doc formulation for the treatment of visceral leishmaniasis.

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.

Toxic characteristics of methoxy poly(ethylene glycol)/poly(epsilon-caprolactone) nanospheres; in vitro and in vivo studies in the normal mice

Amphiphilic diblock polymeric nanospheres composed of methoxy poly(ethylene glycol) (MePEG) and poly(epsilon-caprolactone)(PCL) was prepared for application as a novel drug carrier. We could obtain the MePEG/PCL nanospheres that exhibited an average diameter of less than 200 nm with narrow size distribution and a relatively high drug-loading efficiency of about 41.98% and 20.8% for indomethacin and paclitaxel, respectively. To estimate the toxicity of nanospheres, we investigated cytotoxicity using the normal human fibroblast, the median lethal dose (LD(50)) and various organ toxicities using male ICR mice. The indomethacin-loaded nanosphere showed higher cell viability than indomethacin in the cytotoxicity test using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The LD(50) of MePEG/PCL nanospheres determined by Litchfield-Wilcoxon method was 1.47 g/kg. After the mice were intraperitoneally injected with MePEG/PCL nanospheres as a half-dose level of LD(50) for 7 days, no significant histopathologic changes were observed in MePEG/PCL nanospheres-treated mice compared with normal mice in the light and electron microscopic observations of various organs such as heart, lung, liver and kidney. It was suggested that MePEG/PCL nanospheres might be useful candidate as a novel injectable drug carrier for hydrophobic drugs such as indomethacin and paclitaxel.

Efficacy of TAK-457, a novel intravenous triazole, against invasive pulmonary Aspergillosis in neutropenic mice

TAK-457 is an injectable prodrug of TAK-456, which is a novel oral triazole compound with potent antifungal activity. The in vivo efficacy of TAK-457 was evaluated in two models of invasive pulmonary aspergillosis with CDF(1) mice and CBA/J mice with transient neutropenia induced by cyclophosphamide. Against the infection in CDF(1) mice, treatment with 10 mg of TAK-457 and 1 mg of amphotericin B/kg reduced the fungal burden in lungs and rescued all mice. In the infection model with CBA/J mice, TAK-457 at a dose of 10 mg/kg significantly prolonged the survival time of mice, showing significant reduction of lung chitin levels and the plasma beta-D-glucan levels. On the other hand, amphotericin B at 1 mg/kg which was a maximum tolerable dose showed slight but not significant prolongation of survival time of mice, although it also reduced the lung chitin levels and the plasma beta-D-glucan levels to a lower extent but still significantly. These results suggest that TAK-457 is a promising candidate for development for the treatment of invasive aspergillosis in humans.

Treatment of vancomycin-resistant Enterococcus faecium infections with quinupristin/dalfopristin

Clinicians caring for patients with vancomycin-resistant Enterococcus faecium (VREF) infections face severe constraints in the selection of treatment. Quinupristin/dalfopristin (Synercid) is active in vitro against VREF, with a MIC(90) of 1.0 microg/mL. We investigated the clinical efficacy and safety of this agent in a multicenter, prospective, noncomparative, emergency-use study of 396 patients. Patients were included if they had signs and symptoms of active infection, including bacteremia of unknown origin, intra-abdominal infection, and skin and skin-structure infection, with no alternative antibiotic therapy available. The mean duration of treatment was 20 days (range, 4-40 days). The clinical response rate was 68.8% in the evaluable subset, and the overall response rate was 65.6%. The most common adverse events related to quinupristin/dalfopristin were arthralgias and myalgias. Related laboratory abnormalities were rare. In this severely ill patient population, quinupristin/dalfopristin was efficacious and demonstrated an acceptable safety profile in the treatment of VREF infection.

Taxol-loaded block copolymer nanospheres composed of methoxy poly(ethylene glycol) and poly(epsilon-caprolactone) as novel anticancer drug carriers

We prepared the methoxy poly(ethylene glycol) (MePEG)/poly(epsilon-caprolactone) (PCL) amphiphilic block copolymeric nanospheres containing taxol which has promising anticancer activity. MePEG/PCL block copolymeric nanospheres (MEP50) showed a narrow size distribution and an average diameter of less than 100 nm. When the initial weight ratio of taxol to polymer was 0.5:1.0, we could obtain the nanospheres having a relatively high drug-loading of more than about 20%. The size of the MePEG/PCL nanospheres also increased according to the taxol loading. However, the nanospheres did not exhibit a significant change in the size distribution and also showed a size of less than 100 nm for even that with drug-loading content (DLC) of about 20%. From the 1H NMR analysis, we identified that the MePEG/PCL nanospheres prepared by dialysis procedure have core-shell structure consisting of the hydrophilic outer shell of MePEG and the hydrophobic inner core of PCL. We confirmed the low toxicity of MePEG/PCL nanospheres (MEP70) in the acute toxicity study using male ICR mice. In addition, considering the extremely lipophilic characteristics of taxol, this MePEG/PCL, nanosphere system with high taxol loading content and suspended properties in water could be useful for the delivery of taxol.

[New lipid formulations of amphotericin B. Review of the literature]

INTRODUCTION

Amphotericin B (amB) remains the gold standard for treatment of invasive fungal infections. Lipid formulations of amB have been developed in an attempt to improve both efficacy and tolerability (especially renal toxicity): amB lipid complex (ABLC), liposomal amB (AmBisome), amB colloidal dispersion (ABCD) and amB in lipid emulsion (Intralipid). This review analyzes the data available in the literature.

CURRENT KNOWLEDGE AND KEY POINTS

ABLC, AmBisome and ABCD are effective in various fungal infections, including invasive aspergillosis, systemic candidiasis, cryptococcal meningitis, mucormycosis and fusariosis. These formulations are also effective in persistent febrile neutropenia and in leishmaniosis. The three formulations show little renal toxicity and are safer than conventional amB in this respect. Preliminary data are available on amB in Intralipid: infusion-related adverse effects are reduced, but few data are available on efficacy in documented mycoses.

FUTURE PROSPECTS AND PROJECTS

Large-scale comparative clinical trials may clarify issues of relative efficacy in various forms of fungal infections.

Novelties in the field of anti-infective compounds in 1999

In 1999 the number of new compounds reported in the anti-infective field decreased significantly in comparison with previous years, especially for antifungals. The reported new compounds are mainly directed against Staphylococcus aureus isolates resistant to methicillin. Few derivatives were reported in the field of anti-infectives for gram-negative bacteria. At the moment, we are in a period of discovery as we await novel compounds that could issue from new engineering.

Lipid emulsion reduces subacute toxicity of amphotericin B: a histopathological study

In previous work acute toxic effects of amphotericin B (AB) were reduced in both in vitro and in vivo tests when AB was associated with a triglyceride-rich emulsion (AB-emulsion). The present paper compares the severity of the histopathological alterations as determined by morphometry produced in the target tissues (kidneys, liver, and lungs) by AB-emulsion with those produced by the conventional formulation AB-deoxycholate (DOC) following subacute AB treatment. No morphological alterations were seen in the spleen and heart following both AB-DOC and AB-emulsion treatment. Although the alterations in the liver, kidneys and lungs are basically the same for both formulations, the intensity of the changes varies considerably. AB-emulsion always caused statistically decreased severity of morphologic alterations, compared to AB-DOC by stereological measurements, for the three treatment regimes of AB-administration. These three treatment regimens consisted of 1 mg AB/kg of body weight every 48 hours for 20 days, 2 mg AB/kg of body weight every 48 hours for 12 days, and 2 mg AB/kg of body weight for 4 consecutive days. Thus, these regimens consisted of total doses varying from 8-12 mg/kg of body weight. Specifically, these morphological changes included proximal and distal tubular edema, inflammation and tubular cell degeneration in the kidney and a moderate inflammation of the portal region in the liver. Vacuolization of hepatocytes only occurred for AB-DOC treatment. In addition, acute interstitial inflammation was observed in the lungs prior to interstitial and alveolar edema. The intensity of the histopathological damage increase with the dose and with the reduction in the time interval between AB administrations. Abnormal serum biochemical parameters were observed for serum urea which was higher for both treated AB-groups, as compared to control, and for iron which was lower for the AB-DOC group. In conclusion, the decreased severity of the morphological alterations in the kidneys, liver, and lungs following subacute treatment with AB-emulsion, as compared to AB-DOC formulation, confirms our previous results consisting of acute toxic effects induced by in vitro and in vivo tests with AB-emulsion treatment.