Juan J. Torrado

Preparation, dissolution and characterization of albendazole solid dispersions

In this study, solid dispersion systems of the sparingly water soluble drug, albendazole (ABZ), were mixed with varying concentrations of polyvinylpyrrolidone (PVP K 12) in an attempt to improve the solubility and dissolution rate of ABZ. Physical characteristics were investigated by Powder X-ray diffraction. As expected, the albendazole dissolution rate, expressed as the dissolution efficiency, and also the solubility coefficient were increased when albendazole was mixed with PVP. An increase in the concentration of the polymer in the solid dispersion produced an increase in both parameters. The powder X-ray diffraction patterns showed that the solid dispersion presented an amorphous form of albendazole in this coprecipitate system.

Bioavailability and efficacy characteristics of two different oral liquid formulations of albendazole

The oral bioavailability and anthelmintic efficacy in mice of a new formulation of albendazole (ABZ) dissolved in a solution of hydroxypropyl-beta-cyclodextrin (HPCD) are compared with a conventional ABZ suspension of carboxymethylcellulose. Plasma concentrations of ABZ and albendazole sulphoxide (ABZ-SO), its active and main metabolite, were assayed by HPLC. The AUC(0- infinity ) and C(max) values obtained for both ABZ and ABZ-SO, after administration of the ABZ-HPCD solution were significantly higher (P<0.01) than those obtained from the ABZ suspension. Although, the differences between the ABZ and ABZ-SO-T(max) values were found not to be significant, regardless of the formulation. The anthelmintic activities against enteral (pre-adult) and parenteral (migrating and encysted larvae) stages of Trichinella spiralis were studied in mice. The ABZ solution was more efficient against pre-adult and encysted larvae than the ABZ suspension. The efficacy differences between both formulations against the migrating larvae, were found to be not significant (P<0.05). For the migrating parasite stage, there was a linear correlation between the anthelmintic activity and pharmacokinetical parameters with respect to the ABZ-AUC(0- infinity ) value. Meanwhile, for the muscular encysted parasite stage, better relationships were obtained for AUC(0- infinity ) and C(max) values from ABZ-SO, which had correlation coefficients of 0.996 and 0.987, respectively.

Effect of aggregation state on the toxicity of different amphotericin B preparations.

The aim of this work was to study the effect of aggregation of amphotericin B (AMB) in their toxicity. The aggregation of AMB depends on different formulation factors such as pH and excipients, therefore three formulations with different AMB aggregation states were prepared: a monomeric form (M-AMB), a dimeric form (D-AMB) and a poly-aggregated form (P-AMB). The predominant aggregation state of each AMB formulation was characterized by spectrophotometry and their size by dynamic laser light scattering. Toxicity was evaluated by lethality in mice and hemolysis test from human erythrocytes and the experimental AMB formulations were compared with reference formulations of AmBisome, Fungizone and heated Fungizone. The less toxic aggregation form of AMB was the poly-aggregated one which was similar to AmBisome. Moreover, the P-AMB and heated Fungizone were centrifuged to isolate different size fractions. The toxicity of these two heterogeneous formulations was related to their size, so the smaller the aggregation size fraction the higher the toxicity determined by hemolysis. It can be concluded that the aggregation state of AMB and their size affects critically the toxicity of AMB. The low toxic P-AMB formulations contain a different poly-aggregated state to that of AmBisome, heated Fungizone and the other studied AMB aggregation states.

Quantitative determination of albendazole and its main metabolites in plasma

Three different and complementary chromatographic methods are described for quantitative determination of albendazole (ABZ) and its two main metabolites: albendazole sulphoxide (SOABZ) and albendazole sulphone (SO2ABZ). ABZ, SOABZ and SO2ABZ can be quantified by two RP-HPLC methods with an ODS2 column and two different mobile phases. One of methanol-water (60:40) for ABZ and a second one of phosphoric acid in water-acetonitrile (80:20) for SOABZ and SO2ABZ. SOABZ bears an asymmetric sulphur centre. Quantitative assay of (+) SOABZ and (-) SOABZ can be performed by HPLC. A chiral AGP column and a mobile phase of sodium phosphate buffer (8 mM, pH 7.0) containing different amounts of 2-propanol between 0 to 2% were used. Pharmacokinetic characteristics of ABZ following oral administration of a liquid formulation of ABZ (12 mg/kg) in mice has been studied with these three complementary HPLC methods and the results are reported.

Influence of CYP2C8 and CYP2C9 polymorphisms on pharmacokinetic and pharmacodynamic parameters of racemic and enantiomeric forms of ibuprofen in healthy volunteers.

OBJECTIVES (i) To define the incidence of alleles CYP2C8*1 to *5 in a Spanish population; (ii) to test the impact of such alleles, and those of CYP2C9, on the metabolism of racemic ibuprofen, R-ibuprofen and S-ibuprofen; and (iii) to discern whether those metabolic alterations have safety implications. METHODS Data from three phase I clinical trials with 69 healthy volunteers taken ibuprofen were analyzed. Genotyping were performed by PCR. Pharmacokinetic parameters were determined in studies 1 and 2 by non-compartmental analysis. Levels of COX-1, COX-2, eNOS and iNOS were determined by Western Blots in gastric biopsies of study 3. RESULTS Allelic frequencies were 0.80, 0.02, 0.11, 0.07 and 0 for CYP2C8*1, *2, *3, *4 and *5. CYP2C9*3 allele had a decreased racemic ibuprofen metabolism, leading to a 30% augmentation of AUC(0-infinity) and a 30% reduction of clearance compared to CYP2C9*1 (p < 0.05). CYP2C8*3 had a 20% augmentation of clearance compared to CYP2C8*1 (p < 0.05) of R-ibuprofen. CYP2C9*3 had a 45% reduction of clearance, as well as a 87% and 47% augmentation of AUC(0-infinity) and t(1/2) with respect to CYP2C9*1 of S-ibuprofen and a 30% reduction of clearance of R-ibuprofen. A decreased iNOS expression was found in CYP2C8*3 compared to wild type (p < 0.05). Adverse events in CYP2C8*3 (20%) and *4 (20%) were fewer than in CYP2C8*1 (77%). CONCLUSIONS This study suggest an impaired metabolism of racemic, S-ibuprofen and R-ibuprofen in CYP2C9*3; an increased R-ibuprofen metabolism in CYP2C8*3; and fewer adverse events in CYP2C8*3 volunteers; that correlates with a decreased expression of iNOS.

Formulation parameters of albendazole solution

Abstract The solubility of albendazole, a poorly water-soluble drug was evaluated. The effect of cosolvents and pH on the aqueous solubility of albendazole are described here. Albendazole aqueous solubility was tested over the pH range of 1.2–7.5. Albendazole solubility was lower for the highest pH values. The solubility coefficient obtained was 0.376 mg/ml in a 1.2 pH buffer solution. Transcutol was the cosolvent with which the increase of the solubility was highest. Albendazole solubility at different percentages of transcutol presented a sigmoid kinetic with an initial acceleration phase. This kinetic shows an exponential correlation for transcutol values smaller than 80%). The exponent value (n) was higher as the pH of the solution was increased. This high value of the exponent (n) is due to a stronger influence of the transcutol on the solubility of albendazole at elevated pH values. The albendazole solution containing 40% w/w of transcutol in a pH 1.2 buffer solution was selected because of its high solubility (2.226 mg/ml). Analysis of the stability data of this albendazole solution showed good correlation ( r = 0.9831) when the data were fitted to a first order equation. This albendazole solution showed good stability, with less than 10%, degradation occurring after 30 days of storage at 4°C.

Oral particle uptake and organ targeting drives the activity of amphotericin B nanoparticles

There are very few drug delivery systems that target key organs via the oral route, as oral delivery advances normally address gastrointestinal drug dissolution, permeation, and stability. Here we introduce a nanomedicine in which nanoparticles, while also protecting the drug from gastric degradation, are taken up by the gastrointestinal epithelia and transported to the lung, liver, and spleen, thus selectively enhancing drug bioavailability in these target organs and diminishing kidney exposure (relevant to nephrotoxic drugs). Our work demonstrates, for the first time, that oral particle uptake and translocation to specific organs may be used to achieve a beneficial therapeutic response. We have illustrated this using amphotericin B, a nephrotoxic drug encapsulated within N-palmitoyl-N-methyl-N,N-dimethyl-N,N,N-trimethyl-6-O-glycol chitosan (GCPQ) nanoparticles, and have evidenced our approach in three separate disease states (visceral leishmaniasis, candidiasis, and aspergillosis) using industry standard models of the disease in small animals. The oral bioavailability of AmB-GCPQ nanoparticles is 24%. In all disease models, AmB-GCPQ nanoparticles show comparable efficacy to parenteral liposomal AmB (AmBisome). Our work thus paves the way for others to use nanoparticles to achieve a specific targeted delivery of drug to key organs via the oral route. This is especially important for drugs with a narrow therapeutic index.

Hemolytic and pharmacokinetic studies of liposomal and particulate amphotericin B formulations.

Amphotericin B (AmB) is a very effective antifungal and antiparasitic drug with a narrow therapeutic window. To improve its efficacy/toxicity balance, new controlled release formulations have been developed based on different encapsulation systems, aggregation states and particle sizes modifications. The kinetics of the hemolytic process was studied not only to characterize the toxicity of different formulations but also as an indicator of drug release. Pharmacokinetic studies in beagle dogs were carried out with those formulations that exhibited the least hemolytic toxicity: liposomal formulation (AmBisome), poly-aggregated AmB and encapsulated particulate AmB formulation. A novel poly-aggregated AmB formulation proved to be comparable in terms of low hemolytic activity with the marketed gold standard formulation: AmBisome. Its pharmacokinetic profile, characterized by a smaller area under the curve and larger volume of distribution, was markedly different from AmBisome, resulting in a cost-effective alternative for the treatment of leishmaniasis which can enhance the AmB passive target by the uptake by the cells of the reticulo-endothelial system. Effects of different variables such as type of formulation, dose, microencapsulation, anesthesia and dogs healthy state on AmB pharmacokinetics were studied.

New amphotericin B-gamma cyclodextrin formulation for topical use with synergistic activity against diverse fungal species and Leishmania spp

Amphotericin B (AmB) has a broad antifungal and leishmanicidal activity with low incidence of clinical resistance. Its parenteral administration has high risk of nephrotoxicity that limits its use. In order to treat cutaneous infections, AmB topical administration is a safer therapy because of the low systemic absorption of the drug across mucous membranes. Moreover, in some developing countries both fungal topical infections and cutaneous leishmaniasis are an important health problem. The aim of this work is to formulate a topical amphotericin preparation and test its in vitro antifungal (against 11 different fungal species) and antileishmanial activity. γ-Cyclodextrin (γ-CD) was chosen to solubilise AmB. Furthermore, γ-CD has shown a synergistic effect on membrane destabilization with AmB. Topical novel formulations based on AmB-CD complex have exhibited greater antifungal activity (48%, 28% and 60% higher) when compared to AmB Neo-Sensitabs(®) disks, AmB dissolved in dimethyl sulfoxide (DMSO) and Clotrimazole(®) cream, respectively. Furthermore, AmB-CD methyl cellulose gel has shown significantly higher inhibition activity on biofilm formation, larger penetration through yeast biofilms and higher fungicidal activity on biofilm cells compared to AmB dissolved in DMSO. In addition, AmB-CD gel exhibited both high in vitro leishmanicidal efficacy with wider therapeutic index (between 2 and 8-fold higher than AmB deoxycholate depending on Leishmania spp.) and also in vivo activity in an experimental model of cutaneous leishmaniasis. These results illustrate the feasibility of a topical AmB formulation easy to prepare, physicochemically stable over 6 months, safe and effective against diverse fungal and parasitic cutaneous infections.

In vivo distribution and therapeutic efficacy of a novel amphotericin B poly-aggregated formulation

OBJECTIVES The purpose of this investigation is the study of toxicity, in vivo distribution and therapeutic activity against candidiasis of poly-aggregated amphotericin B, in two different formulations: not microencapsulated (P-AMB) or incorporated in albumin microspheres (MP-AMB). METHODS The therapeutic efficacy and toxicity of amphotericin B formulations was studied in an immunocompetent murine model of systemic candidiasis. A pharmacokinetic study was also performed to measure the plasma, kidney, liver and spleen amphotericin B concentrations after administration of the three formulations to mice. RESULTS The acute toxicity of P-AMB in mice is lower than that of the conventional amphotericin B reference formulation (D-AMB). The 50% lethal doses were increased at least eight times. Intravenous bolus administration of doses up to 40 mg/kg of body weight of poly-aggregated amphotericin B, either P-AMB or MP-AMB, did not produce acute symptoms of toxicity. Interestingly, in the pharmacokinetic study, significant (P < 0.05) lower plasma and kidney amphotericin B concentrations and higher liver and spleen amphotericin B concentrations were achieved after poly-aggregated amphotericin B formulation (P-AMB and MP-AMB) administration in relation to the reference formulation (D-AMB). At high amphotericin B doses, no significant differences in efficacy (P > 0.05) were observed among the formulations (D-AMB, P-AMB and MP-AMB). CONCLUSIONS Although the efficacy in the candidiasis treatment was decreased as a consequence of amphotericin B aggregation, it can be compensated by the possibility of increasing the doses with lower nephrotoxicity. Moreover, due to its lower toxicity while maintaining its effectiveness, the poly-aggregated formulations (P-AMB and MP-AMB) have a better therapeutic index than the conventional formulation (D-AMB).