Pharmacokinetics of Benznidazole in Healthy Volunteers and Implications in Future Clinical Trials.

Despite its toxicity and low efficacy in the chronic phase, benznidazole is the drug of choice in Chagas disease. Scarce information about pharmacokinetics and pharmacodynamics of benznidazole has been published. We performed a phase I, open-label, nonrandomized pharmacokinetic study of benznidazole (Abarax) conducted with 8 healthy adult volunteers at the Infectious Diseases Department of the Vall d'Hebron University Hospital (Barcelona, Spain). The separation and detection of benznidazole were performed on a Waters Acquity ultraperformance liquid chromatography system (UPLC) coupled with a Waters Xevo TQ MS triple quadrupole mass spectrometer. The pharmacokinetic parameters were calculated based on a noncompartmental body model using Phoenix WinNonlin version 6.3 software. Furthermore, computational simulations were calculated for the multiple-dose administration at two dose regimens: 100 mg of benznidazole administered every 8 h and 150 mg of benznidazole administered every 12 h. After benznidazole administration, the median area under the concentration-time curve from time zero to time t (AUC0-t ) and extrapolated to infinity (AUC0-∞) were about 46.4 µg · h/ml and 48.4 µg · h/ml, respectively. Plasma benznidazole concentrations peaked at 3.5 h, with maximal concentrations of 2.2 µg/ml, and benznidazole exhibited a terminal half-life of 12.1 h. The median maximum concentration (Cmax) of benznidazole was lower in men than in women (1.6 versus 2.9 µg/ml), and median volume of distribution (V) as a function of bioavailability (F) was higher in men than in women (125.9 versus 88.6 liters). In conclusion, dose regimens (150 mg/12 h or 100 mg/8 h) reached a steady-state range concentration above of the minimum experimental therapeutic dose. Sex differences in the benznidazole pharmacokinetics were observed; mainly, men had lower Cmax and higher V/F than women.

Stability study of sodium colistimethate-loaded lipid nanoparticles.

In the last decades, the encapsulation of antibiotics into nanoparticulate carriers has gained increasing attention for the treatment of infectious diseases. Sodium colistimethate-loaded solid lipid nanoparticles (Colist-SLNs) and nanostructured lipid carriers (Colist-NLCs) were designed aiming to treat the pulmonary infection associated to cystic fibrosis patients. The nanoparticles were freeze-dried using trehalose as cryoprotectant. The stability of both nanoparticles was analysed over one year according to the International Conference of Harmonisation (ICH) guidelines by determining the minimum inhibitory concentration (MIC) against clinically isolated Pseudomonas aeruginosa strains and by studying their physico-chemical characteristics. The results showed that Colist-SLNs lost their antimicrobial activity at the third month; on the contrary, the antibacterial activity of Colist-NLCs was maintained throughout the study within an adequate range (MIC ≤16 µg/mL). In addition, Colist-NLCs exhibited suitable physico-chemical properties at 5 °C and 25 °C/60% relative humidity over one year. Altogether, Colist-NLCs proved to have better stability than Colist-SLNs.

Killing effect of nanoencapsulated colistin sulfate on Pseudomonas aeruginosa from cystic fibrosis patients.

Pseudomonas aeruginosa frequently infects the respiratory tract of cystic fibrosis (CF) patients. Multidrug-resistant phenotypes and high capacity to form stable biofilms are common. Recent studies have described the emergence of colistin-resistant isolates in CF patients treated with long-term inhaled colistin. The use of nanoparticles containing antimicrobials can contribute to overcome drug resistance mechanisms. The aim of this study was to explore antimicrobial activity of nanoencapsulated colistin (SLN-NLC) versus free colistin against P. aeruginosa clinical isolates from CF patients and to investigate their efficacy in biofilm eradication. Susceptibility of planktonic bacteria to antimicrobials was examined by using the broth microdilution method and growth curve assay. Minimal biofilm eradication concentration (MBEC) and biofilm prevention concentration (BPC) were determined to assess antimicrobial susceptibility of sessile bacteria. We used atomic force microscopy (AFM) to visualize treated and untreated biofilms and to determine surface roughness and other relevant parameters. Colistin nanoparticles had the same antimicrobial activity as free drug against planktonic bacteria. However, nanoencapsulated colistin was much more efficient in the eradication of biofilms than free colistin. Thus, these formulations have to be considered as a good alternative therapeutic option to treat P. aeruginosa infections.

Pulmonary drug delivery: a review on nanocarriers for antibacterial chemotherapy.

As the WHO stated, lower respiratory infections are the third leading cause of death. In addition, it is remarkable that antimicrobial resistance represents a huge threat. Thus, new therapeutic weapons are required. Among the possible alternatives, antibiotic encapsulation in nanoparticles has gained much attention in terms of improved tolerability, activity and ability to combat the resistance mechanisms of bacteria. In this regard, this review article focuses on the latest nanocarrier approaches for inhalatory therapy of antibiotics. First, the technology related to lung disposition will be reviewed. Then, nanocarrier systems will be introduced and the challenges required to perform adequate pulmonary deposition analysed. In the following part, drug delivery systems (DDSs) on the market or in clinical trials are described and, finally, new approaches of nanoparticles that have reached pre-clinical stage are enumerated. Altogether, this review aims at gathering together the novel nanosystems for anti-infectious therapy, underlining the potential of DDSs to improve and optimize currently available antibiotic therapies in the context of lung infections.

The state-of-the-art of approved and under-development cholera vaccines.

Cholera remains a huge public health problem. Although in 1894, the first cholera vaccination was reported, an ideal vaccine that meets all the requirements of the WHO has not yet been produced. Among the different approaches used for cholera vaccination, attenuated vaccines represent a major category; these vaccines are beneficial in being able to induce a strong protective response after a single administration. However, they have possible negative effects on immunocompromised patient populations. Both the licensed CVD103-HgR and other vaccine approaches under development are detailed in this article, such as the Vibrio cholerae 638 vaccine candidate, Peru-15 or CholeraGarde(®) and the VA1.3, VA1.4, IEM 108 VCUSM2 and CVD 112 vaccine candidates. In another strategy, killed V. cholerae vaccines have been developed, including Dukoral(®), mORCAX(®) and Sanchol™. The killed vaccines are already sold, and they have successfully demonstrated their potential to protect populations in endemic areas or after natural disasters. However, these vaccines do not fulfill all the requirements of the WHO because they fail to confer long-term protection, are not suitable for children under two years, require more than a single dose and require a distribution chain with cold storage. Lastly, other vaccine strategies under development are summarized in this review. Among these strategies, vaccine candidates based on alternative drug delivery systems that have been reported lately in the literature are discussed, such as microparticles, proteoliposomes, LPS subunits, DNA vaccines and rice seeds containing toxin subunits. Preliminary results reported by many groups working on alternative delivery systems for cholera vaccines demonstrate the importance of new technologies in addressing old problems such as cholera. Although a fully ideal vaccine has not yet been designed, promising steps have been reported in the literature resulting in hope for the fight against cholera.

An approach to a cold chain free oral cholera vaccine: in vitro and in vivo characterization of Vibrio cholerae gastro-resistant microparticles.

The present work describes the formulation of Eudragit(®) L30 D-55 microparticles (MP) alone or with mucoadhesive agents, alginate or Carbopol(®), as an approach for the development of an oral cholera vaccine. In the first part, a spray drying technique was optimized for microparticle elaboration, obtaining a microparticle size ranging from 7 to 9 µm with high encapsulation efficiencies. Moreover, gastro resistant properties and Vibrio cholerae (VC) antigenicity were maintained, but for Eudragit(®)-Carbopol(®) microparticles which showed low antigenicity values, ≈25%. Next, a stability study was performed following ICH Q1 A (R2) guidelines, i.e. 25°C-60% relative humidity (RH) for 12 months, and 30°C-65% RH and 40°C-75% RH for 6 months. Upon storage, microparticle size changed slightly, 1 µm for Eudragit(®)-alginate MPs and 0.36 µm for Eudragit(®)MP. However, gastro resistance and antigenicity values were kept in an acceptance range. In the third stage of this work, in vivo experiments were performed. The immune response evoked was measured by means of vibriocidal titer quantification, observing that Eudragit(®)-alginate MPs were able to induce stronger immune responses, comparable to the free VC. Therefore, microencapsulation of VC by spray drying could be proposed as an approach to a cold chain free and effective oral cholera vaccine.

Mechanisms of resistance in clinical isolates of Pseudomonas aeruginosa less susceptible to cefepime than to ceftazidime.

The MIC of cefepime determined with the MicroScan WalkAway system was ≥2 times higher than that of ceftazidime for 105 clinical isolates of Pseudomonas aeruginosa. This phenotype was confirmed by reference microdilution in 68 (64.8%) isolates, corresponding to 48 different rep-PCR patterns. The PSE-1 blactamase was identified in only 13.2% isolates, while oxacillinases were not identified in any of the 68 isolates. The level of expression of mexB, mexD and mexY was determined by real-time RT-PCR in eight clinical isolates representative of the different clones and patterns of susceptibility to cefepime and ceftazidime and in strain PAO1. All clinical strains overexpressed the mexY gene (18.3- to 152.7-fold in comparison with PAO1), although there was not a linear relationship between MIC of cefepime and level of mexY expression. Five of these strains contained mutations in the regulatory gene mexZ. mexD and mexB were also overexpressed in three and two isolates, respectively. Different mutations were observed in the regulatory genes nalD, mexR, nfxB and nalC. In conclusion, we have documented in our institution a polyclonal spread of P. aeruginosa with higher MICs of cefepime than of ceftazidime, related to overexpression of MexXY-OprM, coincident in some isolates with the production of PSE-1, MexCD-OprJ or MexAB-OprM.

Preparation and stability of agarose microcapsules containing BCG.

An emulsification/internal gelation method of preparing small-sized agarose microcapsules containing Bacillus Calmette-Guerin (BCG) is reported. Agarose microcapsules have been prepared by the emulsification of the hydrogel within a vegetable oil followed by its gelation due to the cooling of the system. Four different oils (sesame, sweet almonds, camomile and jojoba) were assayed. The rheological analysis of the oils showed a Newtonian behaviour, with viscosity values of 37.7, 51.2, 59.3 and 67.1 mPa s for jojoba, camomile, sesame and sweet almonds oil, respectively. The particle size of the microcapsules obtained ranged from 23.1 microm for the microcapsules prepared with sweet almonds oil to 42.6 microm for those prepared with jojoba. The microcapsule particle size was found to be dependent on the viscosity of the oil used in the emulsification step. The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Once prepared, microcapsules were freeze-dried using 5% trehalose as cryoprotectant and the stability of the microcapsules was assayed during 12 months storage at room temperature, observing that agarose microcapsules were stable after 12 months storage, since there was no evidence of alteration in the freeze-dried appearance, resuspension rate, observation under microscope, or particle size.

Effect of lecithins on BCG-alginate-PLL microcapsule particle size and stability upon storage.

Alginate-PLL microcapsules containing BCG were prepared by emulsification/internal gelation of an alginate solution dispersed within a vegetable oil containing lecithins as emulsifiers. The lecithins studied were soy bean lecithin at 0.1, 0.5, 1 and 2% concentration; and dried egg yolk lecithin at 0.1, 0.25, 0.5 and 1%. The microcapsule particle size showed a dependence upon the amount and type of lecithin added to the oil. Increasing the emulsifying agent concentration was found to reduce particle size, from 50.9 microm obtained when lecithins were not used in the emulsification step, to 13.9 microm obtained when 1% dried egg yolk lecithin was employed. The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Once prepared, microcapsules were freeze-dried using 5% trehalose as cryoprotectant in order to preserve their stability upon storage. The stability of the microcapsules was assayed over 12 months at room temperature, finding that alginate-PLL microcapsules were stable up to 6 months. Moreover, in the case of microcapsules prepared with lecithins, a significant increase in particle size was observed, from 16.9 microm at the beginning of the study to 25.2 microm at 12 months storage.

Enhanced immune response after subcutaneous and oral immunization with biodegradable PLGA microspheres.

PLGA microspheres containing bovine serum albumin (BSA) as a model antigen, were prepared by a double emulsion/solvent extraction method and their in vitro characterization was performed. The same microspheres were used in a series of in vivo studies to evaluate the immune response induced after subcutaneous or oral inoculation following different immunization protocols. The in vivo data confirm that the immunogenicity of the albumin is not affected by the encapsulation procedure. The subcutaneous administration of microspheres showed an immune response (serum IgG levels by ELISA) statistically above BSA solution, even when the dose administered was 10 times lower. The adjuvanticity of the microspheres was found to be comparable to that of Freund's complete adjuvant (FCA), but in contrast to FCA they are biocompatible and did not induce any adverse reaction at the site of injection. A single oral administration of the microspheres was not a successful strategy for the induction of a reproducible response. Therefore, microspheres of 1 and 5 micrometer were orally administered on 3 consecutive days and the response obtained showed that the use of a boosting dose was not necessary for the 1 micrometer particles. These results suggest the possibility of simplifying the immunization schedule to a primary immunization if 1 micrometer particles are administered.

Determination of salbutamol enantiomers by high-performance capillary electrophoresis and its application to dissolution assays.

Capillary zone electrophoresis was successfully applied to the chiral separation of salbutamol after addition of a suitable cyclodextrin chiral selector to the electrophoresis buffer. Parameters important in achieving enantiomeric separation are cyclodextrin type, mobile phase pH and applied field strength. In our study, salbutamol enantiomeric separation was obtained with the following conditions: heptakis (2,6-di-O-methyl)-beta-cyclodextrin in 40 mM Tris (pH 2.5) and at 15 kV, obtaining a 3.09 resolution with migration times of 13.74 min for (R)-salbutamol and 13.98 min for (S)-salbutamol. Linearity, limit of quantitation, precision and accuracy were established using this method. The calibration curve was linear in a range of 1-40 micrograms ml-1 of racemic salbutamol (0.5-20 micrograms ml-1 of each enantiomer). This method was applied to evaluate the enantioselective release of salbutamol and taking into account the hypothesis that one enantiomer of a chiral drug would be released faster than the other from a pharmaceutical dosage form containing a racemic drug and a chiral excipient. For this purpose, matrix tablets formed by chiral excipients such as hydroxypropylmethylcellulose (HPMC) were considered. The release of the enantiomers of salbutamol from the formulations containing HPMC was found to be equivalent, with constant dissolution values (K) of 1.187 +/- 0.223% min-n for (R)-salbutamol and 1.076 +/- 0.268% min-n for (S)-salbutamol.

Production of BCG alginate-PLL microcapsules by emulsification/internal gelation.

A biocompatible emulsification method for microencapsulation of live cells and enzymes within a calcium alginate matrix applied to Bacillus Calmette-Guérin (BCG) has been developed. Small-diameter alginate beads (microcapsules) were formed via internal gelation of an alginate solution emulsified within vegetable oil. Five different oils (sesame, sweet almond, perhydrosqualene, camomile and jojoba) were used. The rheological analysis of the oils showed a Newtonian behaviour, with viscosities = 30.0, 37.7, 51.2, 59.3 and 67.1 mPa.s for perhydrosqualene, jojoba, camomile, sesame and sweet almond oil respectively. The particle size of the microcapsules obtained ranged from 30.3 microns for the microcapsules prepared with sweet almond oil to 57.0 microns for those made with perhydrosqualene. The mean particle diameter obtained was found to be dependent on the viscosity of the oil employed, according to the equation: phi (micron) = 76.6-0.628 eta (mPa.s) (r2 = 0.943). The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Freeze-drying of the microcapsules was carried out to ensure their stability during storage. Two batches of microcapsules (those prepared with sesame and jojoba oil) and four types of cryoprotectors (glucose, trehalose, mannitol and sorbitol), at three concentration levels (5, 10 and 20% w/v) were studied. The parameters evaluated were particle size, physical appearance, reconstitution of lyophilizates and microscopical evaluation. For both batches of microcapsules the best results were obtained with trehalose 5%, showing particle sizes of 42.1 microns in the case of the microcapsules prepared with sesame oil, and of 45.3 microns for those prepared with jojoba.

Influence of formulation variables on the in-vitro release of albumin from biodegradable microparticulate systems.

Poly(D,L-lactide-co-glycolide) microspheres containing BSA were prepared by a modified solvent evaporation method using a double emulsion. These microspheres were characterized for size, morphology, surface absorbed protein, encapsulation efficiency and release kinetics. The influence of two formulation variables (the procedure to obtain the first emulsions and the lyophilization of the microspheres once obtained) on the physical characteristics and release behaviour of the microspheres was also investigated. Sonicated microspheres were smooth and spherical, with a mean particle size of 20 microns and an encapsulation efficiency of 81%. When the first emulsion was prepared by vortex mixing the particles were irregular and porous, with a mean size of 31 microns and a lower encapsulation efficiency (56%). The sonication allows a more homogeneous emulsion as well as a lower percentage of albumin adsorbed on the surface. The in vitro release profile was described as a biexponential process with an initial burst effect due to the release of the protein adsorbed on the microsphere surface and a second sustained release phase due to protein diffusion through the channels or pores formed in the polymer coat. The release of BSA was dependent on the preparation method. The greatest burst release was found for microspheres formulated using the vortex mixer, 58% of the encapsulated protein was released during the first 24 h, whereas sonicated microspheres released 32.2%. This burst effect could be reduced by lyophilizing the microspheres following their preparation. The amount of protein released decreased to 28.3% and 51.6% in sonicated and non-sonicated microspheres respectively, when they were lyophilized.