Development of novel formulations for Chagas' disease: Optimization of benznidazole chitosan microparticles based on artificial neural networks

Benznidazole (BZL) is one of the two therapeutic agents used for the treatment of Chagas' disease. However, the use of BZL in most pharmaceutical preparations and research experiments is still limited due to its low water solubility (0.4mg/mL). To overcome the dissolution rate-limiting step in oral absorption, chitosan microparticles prepared by the coacervation method were chosen, owing to non-toxicity of the polymer and mild conditions of the method. The influence of process parameters such as encapsulation efficiency, size, yield, and dissolution rate was optimized by using artificial neural networks (ANNs). The optimal conditions were found to be 1.5% (w/v) for the polymer concentration, 6.0% (w/v) for the coacervation agent concentration, 1400.0rpm for the stirring rate, and 5.0mL/min for the spraying rate. Confirmation experiments showed good agreement between predicted and experimental values of the optimized properties. These results indicate that ANNs is a valuable tool for the development of optimized BZL chitosan microparticles. To our knowledge it is the first report based on the development of optimized BZL microparticles.     

Preparation of microcapsules from complex coacervation of Gantrez-gelatin. I. Development of the technique

Trials to induce complex coacervation between two grades Gantrez-AN polymer (G-AN), and Type A gelatin were made. Physical parameters influencing the coacervation process were studied. Maximum coacervation was attained when the pH of the gelatin solution was at 6.8. Increasing the molecular weight of Gantrez decreased the ratio of combination of both polymers. The ratio for optimum coacervation was 1:4 for Gantrez-AN 119-gelatin system and 2:3 for Gantrez-AN 149-gelatin system with total colloid concentration of 2.5 g per cent w/v in both cases. High stirring speed gave almost spherical uniform coacervates. Recovery of the product as water-insoluble discrete units required the use of formaldehyde and isopropanol for coacervate denaturation and flocculation, respectively.     

Characterization of albumin-acacia complex coacervation.

Complex coacervation between oppositely charged albumin and acacia mixtures has been studied, and the applicability of the various theoretical treatments of complex coacervation (the Voorn-Overbeek, Veis-Aranyi, Nakajima-Sato, and Tainaka theories) to this system has been assessed. Under optimum conditions where maximum coacervate yield occurred, the Voorn-Overbeek theory appeared to apply. However, away from the optimum coacervation conditions, coacervate sol formation was observed, which is in accordance with the Veis-Aranyi and Tainaka theories. Microelectrophoretic measurements were used to determine optimum pH and ionic strength conditions for maximum coacervation, based on the method of Burgess & Carless (1984). The effects of pH and ionic strength on coacervate yield are reported. Around the optimum conditions for maximum coacervation a viscous coacervate phase and a relatively clear equilibrium phase are formed.     

Biopharmaceutics: Cytotoxicity of Absorption Enhancers in Caco-2 Cell Monolayers

This study was performed to evaluate the utility of absorption enhancers with reference to mucosal cell cytotoxicity. Overall assessment of the damage to plasma, lysosomal and nuclear membranes by three absorption enhancers, sodium deoxycholate, sodium caprate and dipotassium glycyrrhizinate, was performed on Caco-2 cell monolayers. The cytotoxicities of sodium deoxycholate (0.02–0.1% w/v), sodium caprate (0.1–0.5% w/v) and dipotassium glycyrrhizinate (0.5–2% w/v) were evaluated by the trypan blue-exclusion test, the protein-release test, the neutral-red assay, the DNA-propidium iodide staining test and the test for recovery of transepithelial electrical resistance (TEER) up to 24 h after treatment with each enhancer. Sodium dodecyl sulphate (SDS; 0.1% w/v), a potent surfactant, was used as positive control. SDS at this level was significantly cytotoxic whereas dipotassium glycyrrhizinate was not cytotoxic in any tests. Results from the trypan blue-exclusion and protein-release tests showed that high concentrations of sodium caprate (0.5% w/v) and sodium deoxycholate (0.1% w/v) were significantly cytotoxic to the plasma membrane. The neutral-red assay, an indicator of damage to lysosomal membranes, revealed that 0.5% (w/v) sodium caprate had no effect whereas the uptake of neutral red was slightly increased by treatment with 0.1% (w/v) sodium deoxycholate, implying that the compound had cell-growth-enhancing activity. Nuclear-membrane damage, as evaluated by the DNA-propidium iodide staining test, was severe in cell monolayers treated with 0.5% (w/v) sodium caprate compared with that induced by 0.1% (w/v) sodium deoxycholate. In the TEER recovery test, TEER failed to recover 24 h after treatment with 0.5% (w/v) sodium caprate and 0.1% (w/v) SDS, but recovered after treatment with 0.1% (w/v) sodium deoxycholate. The recovery of TEER might be related to nuclear membrane damage and cell-growth-enhancing activity. These results indicate that of the three classes of enhancer, dipotassium glycyrrhizinate was not cytotoxic and that high concentrations of sodium caprate and sodium deoxycholate could damage plasma and nuclear membranes.     

Investigation into the influence of polymeric stabilizing excipients on inter-particulate forces in pressurised metered dose inhalers

Colloid probe atomic force microscopy (AFM) was utilised to quantify the cohesive forces of salbutamol sulphate in a model non-pressurised fluorinated liquid (mHFA), in the presence of increasing concentrations of poly(ethylene glycol) (PEG; molecular weight (MW) 200, 400 and 600). In addition, samples of PEG 400 (0.05–0.5%, v/w), were analysed in the presence of 0.001% (w/w) of poly(vinyl pyrrolidone) (PVP). In the absence of any stabilizing agents, strong attractive forces were present between particles. Increasing the concentration of the different MW PEG solutions in the mHFA system (up to 0.5%, v/w), significantly decreased the force of interaction (ANOVA, p < 0.05). The decrease in cohesion was particularly evident at very low concentrations of PEG (0.05–0.1%, v/w). Further data analysis (p < 0.05) suggested that the reduction in the force of cohesion was dependent on the concentration and molecular weight of PEG. The addition of low concentration of PVP to the PEG 400-mHFA system had the most significant influence on drug particle cohesion. In the presence of PVP, increasing addition of PEG 400 (0.05–0.5%, v/w) to the mHFA, resulted in no significant reduction in the force of cohesion (p > 0.05). Clearly, an understanding of the conformation of polymer molecules at interfaces is of vital importance when controlling the stability/flocculation behaviour of sterically stabilized pMDI suspensions. In this context, the use of the colloid probe AFM technique has provided a quantitative insight into the interactions of these complex systems and may be an invaluable asset during the early phase of formulation product development.     

Storage of specimens at 4 degrees C or addition of sodium fluoride (1%) prevents formation of ethanol in urine inoculated with Candida albicans.

The microbial synthesis of ethanol was investigated in urine specimens containing 0.5% or 1.0% (w/v) glucose and inoculated with the yeast Candida albicans (100 cfu/mL). Aliquots (10 mL) of urine were dispensed into plastic tubes containing enough sodium fluoride to give final concentrations of 0.1%, 0.25%, 0.5%, 0.75%, 1%, and 2% (w/v), and C. albicans was added. The tubes were tightly stoppered and allowed to stand either at room temperature (22 degrees C) or in a refrigerator (4 degrees C) for up to 34 days before concentrations of ethanol were determined by headspace gas chromatography. Urine samples stored at 22 degrees C without sodium fluoride produced 0.25 g/L ethanol after two days, and the concentration increased to 2.10 g/L and 4.50 g/L after eight days for specimens containing 0.5% (w/v) and 1% (w/v) glucose, respectively. The ratio of the serotonin metabolites 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5HTOL/5HIAA) in urine remained within the reference range (< 15 pmol/nmol) despite high concentrations of ethanol being produced. Urine samples kept at 4 degrees C did not produce any ethanol (< 0.01 g/L) even without sodium fluoride present as a preservative. The production of ethanol by C. albicans was stopped completely by adding 1% or 2% (w/v) sodium fluoride but not by concentrations of 0.75% (w/v) or less. The microbial synthesis of ethanol in urine samples initially stored at room temperature without sodium fluoride was slowed down considerably by moving them into a refrigerator at 4 degrees C. In conclusion, the production of ethanol in urine by C. albicans can be prevented by storage of samples in a refrigerator at 4 degrees C or by adding sodium fluoride > or = 1% (w/v). Measuring the ratio of 5HTOL/5HIAA can help to distinguish postsampling production of ethanol from metabolism and excretion processes.     

Preparation and in vitro evaluation of mucoadhesive properties of alginate/chitosan microparticles containing prednisolone

This study describes the preparation of mucoadhesive alginate/chitosan microparticles containing prednisolone intended for colon-specific delivery. Two methods have been used for the preparation of the particles: the one-step method is the method in which prednisolone was dispersed within sodium alginate solution and this dispersion was then dropped in a solution containing both calcium chloride and chitosan. The two-step method consisted also of the dispersion of prednisolone in alginate solution and then dropping this dispersion into a solution containing calcium chloride, the particles were then transferred to a chitosan solution. The concentration of sodium alginate solution at 2% (w/v), various concentrations of calcium chloride solution (0.5-1.0%, w/v), chitosan solutions (0.5, 1.0 and 1.5%, w/v) and prednisolone drug load (2, 5, 10 and 15%, w/v) have been used. The results for both preparation methods show that the particle size and drug content were mainly depending on the amount of the drug concentration and not the amount of chitosan and calcium chloride. The in vitro mucoadhesive tests for particles prepared from both methods were carried out using the freshly excised gut of pigs. The particles prepared by the one-step method exhibited excellent mucoadhesive properties after 1h test. Increased chitosan concentrations from 0, 0.5, 1.0 to 1.5% (w/v) resulted in 43, 55, 82 and 88% of the particle remaining attached on the gut surface after 1 h, respectively. However, the particles prepared by the two-step method showed significant less mucoadhesion under the same experimental conditions. At chitosan concentrations of 0, 0.5, 1.0 and 1.5% (w/v) the amount of particles remaining attached to the mucosal surface of the pig gut after 1 h was 43, 3, 11 and 11%, respectively. The prednisolone release at a pH of 6.8 after 4 h was between 63 and 79% for the particles prepared by the one-step method and between 57 and 88% for the particles prepared by the two-step method with a prednisolone drug load of 5 and 10% (w/v), respectively. The results show that depending on the preparation method these chitosan coated alginate particles show different mucoadhesiveness whereas their other properties are not statistically significant different.     

Evidence of carrier mediated transport of ascorbic acid through mammalian cornea

The purpose of the present study was to evaluate the transport of ascorbic acid, a water soluble molecule, through a predominantly lipophilic cornea. Thus in-vitro permeation of ascorbic acid from aqueous drops through freshly excised mammalian cornea was studied. Aqueous isotonic ophthalmic solutions of ascorbic acid of different concentrations (0.125% w/v to 2% w/v) (pH 5.4) were made. Further 1.0% w/v or 0.5% w/v ascorbic acid solution containing NaCl or dextrose as tonicity modifiers or Na⁺K⁺-ATPase inhibitors were also made. Permeation characteristics of drug were evaluated by putting 1 ml formulation on freshly excised cornea fixed between donor and receptor compartments of an all-glass modified Franz diffusion cell and measuring the drug permeated in the receptor by spectrophotometry at 265 nm, after 120 min. Statistical analysis was done by one-way analysis of variance (ANOVA) followed by Dunnett’s test or paired t-test. Increase in drug concentration in the formulation resulted in an increase in the quantity permeated but after a certain level increase in permeation with increase in concentration was minimal. Aqueous drops made isotonic with dextrose showed decreased permeation through paired cornea compared with aqueous drops made isotonic with NaCl from 1% w/v ascorbic acid solution suggesting likely involvement of Na⁺ co-transporter but there was decreased permeation through 0.5% w/v ascorbic acid solution made isotonic with NaCl as compared to solution made isotonic with dextrose. Further aqueous drops containing Na⁺K⁺-ATPase inhibitor {MAG-Mono Ammonium Glycyrrhizinate (25 μmol)} showed decreased corneal permeation from 0.5% w/v ascorbic acid solution but there was not significant decrease from 1% ascorbic acid solution since MAG is a competitive inhibitor of ascorbic acid. Aqueous drops containing Na⁺K⁺-ATPase inhibitor {MAG (50 μmol) or Ouabain (1 mmol)} showed decreased corneal permeation of ascorbic acid compared with control from 1% ascorbic acid solution confirming the involvement of Na⁺ co-transporter.     

Evaluation of In-vivo Transdermal Absorption of Cyclosporin with Absorption Enhancer Using Intradermal Microdialysis in Rats

The purpose of this study was to evaluate the effect of absorption enhancer on in-vivo transdermal absorption of cyclosporin using intradermal microdialysis in rats. Cyclosporin oily solutions (0.5, 2, 8% w/v) were prepared from Sandimmun (10% w/v oily oral preparation of cyclosporin) by diluting with olive oil. 1-[2-(Decylthio)ethyl]azacyclopentan-2-one (HPE-101) and glycerin were added to the cyclosporin formulation as an absorption enhancer at various concentrations between 1 and 20%. These formulations were applied to the shaved abdomen of rats treated with intradermal microdialysis at a flow rate of 2.5 μL min^?1 for 6 h. Cyclosporin was immediately detected and attained a plateau in the dermal dialysate after topical application of cyclosporin oily solution alone. Cyclosporin levels in the dialysate increased with increasing cyclosporin concentrations in the formulation from 0.5 to 8% (w/v). HPE-101 did not influence cyclosporin absorption at concentrations less than 6% (w/v). Addition of 10% (w/v) HPE-101 significantly enhanced an apparent absorption rate of cyclosporin by 4.9 times. However, 20% (w/v) HPE-101 did not show the enhancing activity. On the other hand, addition of glycerin at concentrations of 6, 10, and 20% (v/v) significantly enhanced an apparent absorption rate of cyclosporin by 3.0, 64, and 6.9 times, respectively. The time lag for cyclosporin absorption was less than 0.21 h in all tested cases. This microdialysis study shows that glycerin is a suitable enhancer for improving the in-vivo cyclosporin absorption from the skin.     

Influence of chitosan coating on the liposomal surface on physicochemical properties and the release profile of nanocarrier systems

Chitosan-coated nanoliposomes containing etofenprox or alpha-cypermethrin prepared by ultrasonic homogenization maintained a size distribution in the nanometre range. Nanoliposomes were constructed using different types and concentrations of chitosan to regulate the mean size and surface charge. As the chitosan concentration (0.1–0.5%, w/v) and the degree of deacetylation increased, surface charge also increased. The encapsulation efficiency and release profile were measured by gas chromatography. Encapsulation efficiency decreased slightly as chitosan concentration increased (0.1–0.5%, w/v). As the intrinsic surface charge or concentration of the coating material increased, the release period of the entrapped core material was extended (chitosans A and B; 0.1 and 0.3%, w/v). The results indicate that diverse preparation conditions could affect the physicochemical properties and release profile of the resulting nanocarrier systems.     

Influence of chitosan coating on the liposomal surface on physicochemical properties and the release profile of nanocarrier systems

Chitosan-coated nanoliposomes containing etofenprox or alpha-cypermethrin prepared by ultrasonic homogenization maintained a size distribution in the nanometre range. Nanoliposomes were constructed using different types and concentrations of chitosan to regulate the mean size and surface charge. As the chitosan concentration (0.1-0.5%, w/v) and the degree of deacetylation increased, surface charge also increased. The encapsulation efficiency and release profile were measured by gas chromatography. Encapsulation efficiency decreased slightly as chitosan concentration increased (0.1-0.5%, w/v). As the intrinsic surface charge or concentration of the coating material increased, the release period of the entrapped core material was extended (chitosans A and B; 0.1 and 0.3%, w/v). The results indicate that diverse preparation conditions could affect the physicochemical properties and release profile of the resulting nanocarrier systems.     

Calorimetric study of bovine serum albumin dilution and adsorption onto polystyrene particles

Titration calorimetry was used to investigate the interaction between a model antigen, bovine serum albumin (BSA), and a model particulate carrier, polystyrene (PS). The binding enthalpy was much higher than reported in the literature for a similar system and did not display a sigmoidal binding curve. These experiments may have accessed low coverage surface sites due to the irreversible nature of protein binding and stepwise titration. An important correction is the heat of dilution of the protein solution. Two regimes were observed: at low concentrations of BSA (below ca. 0.3% (w/v)) an exothermic dilution enthalpy of ca. -100 mJ mg-1 was determined, whereas at higher concentrations of BSA values of ca. -20 mJ mg-1 were obtained. Solution rheological data also showed a change at 0.3% (w/v) BSA, so we hypothesise that the fraction of the BSA as monomers, dimers and polymers in solution changes at approximately 0.3% (w/v).     

Enhancement of paracellular drug transport with highly quaternized N‐trimethyl chitosan chloride in neutral environments: In vitro evaluation in intestinal epithelial cells (Caco‐2)

Previous studies have established that a partially quaternized derivative of chitosan, N‐trimethyl chitosan chloride (TMC), can be used as an absorption enhancer for large hydrophilic compounds across mucosal surfaces. This study evaluates and compares the effects of the degree of quaternization of TMC, in a neutral environment, on the permeability of intestinal epithelial cells in vitro, where normal chitosan salts are ineffective as absorption enhancers. The effects of TMC‐H [61.2% quaternized, (0.05–1.5% w/v)], TMC‐L [12.3% quaternized, (0.5–1.5% w/v)], and chitosan hydrochloride [0.5–1.5% w/v] on the transepithelial electrical resistance (TEER) and permeability, for the hydrophilic model compound [¹⁴C]‐mannitol, of intestinal epithelial Caco‐2 cell monolayers, were investigated at pH values of 6.20 and 7.40. The viability of the monolayers was checked with the trypan blue exclusion technique. At a pH of 6.20, all the polymers caused a pronounced reduction (37–67% at 0.5% w/v concentrations) in the TEER of Caco‐2 cells. On the contrary, at a pH of 7.40, only TMC‐H was able to decrease the TEER values, even in a concentration as low as 0.05% w/v (35% reduction). Comparable results were obtained with the permeation of [¹⁴C]mannitol. Large increases in the transport rate (18–23‐fold at 0.5% w/v concentrations) were found at pH 6.20, whereas only TMC‐H was able to increase the permeation of [¹⁴C]mannitol at pH 7.40 (31–48‐fold at 0.05–1.5% w/v concentrations of TMC‐H). For all the polymers studied, no deleterious effects to the cells could be demonstrated with the trypan blue exclusion technique. It is concluded that highly quaternized TMC is a potent absorption enhancer and the potential use of this polymer, especially in neutral and basic environments where normal chitosan salts are not effective, is expected to be an important contribution to the development of effective delivery systems for hydrophilic compounds such as peptide drugs.     

Nasal Absorption in the Rat. III. Effect of Lysophospholipids on Insulin Absorption and Nasal Histology

The intranasal absorption enhancing and histological effects of a range of lysophospholipids has been investigated in the rat. Blood glucose levels fell rapidly following the administration of insulin (8 IU/kg) in combination with lysophosphatidylcholines (LPC; 0.625% w/v) which had ten or more carbon groups in their fatty acid chain. The effect of the LPC-caproyl (C6) was comparable to that of an unenhanced insulin formulation; the enhancing effect of LPC-decanoyl (C10) was similar to that of an LPC-palmitoyl/stearoyl (C16/C18) for similar concentrations. The effect of LPC-decanoyl was reduced with concentration but was still significant at 0.2% w/v (5mM). Lysophosphatidylglycerol (LPG) had a marked insulin absorption enhancing effect even at 0.0625% w/v. The histological effects of LPC-caproyl were similar to those of an unenhanced insulin formulation, while co-administration of LPC-decanoyl resulted in evidence of epithelial interaction. LPG (0.5% w/v) resulted in similar histological changes as LPC (0.625% w/v) (1), but at 0.0625% w/v no significant changes in epithelial integrity were observed. The length of the fatty acid residue of lysophospholipids was identified as an important factor for intranasal absorption enhancing activity. The nature of the polar head group may also have an influence. Increased insulin absorption was not necessarily accompanied by severe disruption of the nasal epithelium. Careful selection of lysophospholipid type and concentration may enable therapeutic drug levels to be achieved via the nasal route without prohibitive toxic effects.     

Suitable albumin concentrations for enhanced drug oxidation activities mediated by human liver microsomal cytochrome P450 2C9 and other forms predicted with unbound fractions and partition/distribution coefficients of model substrates

1. Albumin has reportedly enhanced cytochrome P450 (P450)-mediated drug oxidation rates in human liver microsomes. Consequently, measurements of clearances and fractions metabolized could vary depending on the experimental albumin concentrations used.

2. In this study, the oxidation rates of diclofenac and warfarin by human liver microsomes were significantly enhanced in the presence of 0.10% (w/v) bovine serum albumin, whereas those of tolbutamide and phenytoin required 1.0% and 2.0% of albumin for significant enhancement. Values of the fractions metabolized by P450 2C9 for four substrates did not markedly change in the presence of albumin at the above-mentioned concentrations.

3. The oxidation rates of bupropion, omeprazole, chlorzoxazone and phenacetin in human liver microsomes were reportedly enhanced by 0.5%, 1%, 2% and 2% of albumin, respectively. Analysis of reported intrinsic clearance values and suitable albumin concentrations for the currently analyzed substrates and the reported substrates revealed an inverse correlation, with warfarin as an outlier.

4. Suitable albumin concentrations were multivariately correlated with physicochemical properties, that is, the plasma unbound fractions, octanol–water partition coefficient and acid dissociation constant (r?=?0.98, p<.0001, n?=?10). Therefore, multiple physicochemical properties may be determinants of suitable albumin concentrations for substrate oxidations in human liver microsomes.

     

Evaluation of mechanical-green solvent pretreatment of oil palm wastes for reducing sugars production in North-Colombia

The aim of this work was to define optimum conditions to perform the mechanical and chemical pretreatment of empty fruit bunches (EFBs) and kernel shell (KS). Mechanical pretreatment was based on particle size reduction to 0.5, 1, and 2 mm. For chemical pretreatment, a solution of urea (2, 4, and 6 %w/v) was added to the residues under stirring for 18 h and 80 °C. Then, samples were hydrolyzed with sulfuric acid and the resulting reducing sugars were quantified using the 3,5- dinitrosalicyclic acid method. In addition, Van Soest and FTIR analyzes were performed to characterize the biomass suggesting acceptable cellulose contents (EFBs: 36.47%; KS: 20.06 %) and high lignin values (EFBs: 31.27%; KS: 66.49%). Results showed that the highest amount of TRS for EFBs was 105.3 g/L with urea concentration of 4% w/v and a particle size of 0.5 mm. For the KS, the highest amount of TRS was 98.62 g/L using a urea concentration of 6% w/v and a particle size of 0.5 mm. According to these results, it was concluded that pretreatments of oil palm biomass significantly enhance the performance of lignocellulosic material conversion into reducing sugars.     

Preliminary assessment of alginic acid as a factor buffering triethanolamine interacting with artificial skin sebum.

Triethanolamine is an ethanolamine used as counter-ion for fatty acid soaps. Interaction between triethanolamine and free fatty acids is suggested to be useful for cleansing sebaceous follicles in acne prevention. This study describes the preliminary assessment of alginic acid as a factor buffering triethanolamine interacting with stearic acid--a compound of artificial skin sebum. Penetration of triethanolamine into artificial sebum, induced by the above mentioned interaction, was measured using a specific optical method. The values of the penetration depth amounted to 0.07-5.74 mm. pH values were measured. The value of pH is reduced from 10.06 for pure 1.49% (w/w) aqueous triethanolamine solution to 6.61 with the increase of the alginic acid to triethanolamine ratio in the preparations. The data of this in vitro research will support further study on other anionic polymers as factors buffering ethanolamines penetrating artificial skin sebum.     

Characterization of sodium carboxymethylcellulose-gelatin complex coacervation by viscosity, turbidity and coacervate wet weight and volume measurements

A sodium carboxymethylcellulose (SCMC) and gelatin coacervation system has been evaluated and characterized and the effects of pH and colloid mixing ratio on the coacervation process investigated. The colloid mixing ratio at which optimum coacervation occurred varied with the coacervation pH. A viscometric investigation of various isohydric SCMC-gelatin mixtures was used to predict optimum conditions for complex coacervation. Optimum coacervation occurred at pH 3.5 at a SCMC-gelatin weight ratio of 3:7 for the SCMC complex coacervation system. Turbidity data confirmed these viscometric results. Coacervate wet weight and volume measurements could not be used to predict optimal coacervation conditions due to changes in the coacervate morphology with mixing ratio. At pH values where coacervation did not occur, the viscosity showed unexpected positive deviations from additive behaviour.     

Safety data on 19 vehicles for use in 1 month oral rodent pre‐clinical studies: administration of hydroxypropyl‐ß‐cyclodextrin causes renal toxicity

Potential new drugs are assessed in pre‐clinical in vivo studies to determine their safety profiles. The drugs are formulated in vehicles suitable for the route of administration and the physicochemical properties of the drug, aiming to achieve optimal exposure in the test species. The availability of safety data on vehicles is often limited (incomplete data, access restricted/private databases). Nineteen potentially useful vehicles that contained new and/or increased concentrations of excipients and for which little safety data have been published were tested. Vehicles were dosed orally once daily to HanWistar rats for a minimum of 28 days and a wide range of toxicological parameters were assessed. Only 30% (w/v) hydroxypropyl‐ß‐cyclodextrin was found unsuitable owing to effects on liver enzymes (AST, ALT and GLDH), urinary volume and the kidneys (tubular vacuolation and tubular pigment). 20% (v/v) oleic acid caused increased salivation and hence this vehicle should be used with caution. As 40% (v/v) tetraethylene glycol affected urinary parameters, its use should be carefully considered, particularly for compounds suspected to impact the renal system and studies longer than 1 month. There were no toxicologically significant findings with 10% (v/v) dimethyl sulphoxide, 20% (v/v) propylene glycol, 33% (v/v) Miglyol®812, 20% (w/v) Kolliphor®RH40, 10% (w/v) Poloxamer 407, 5% (w/v) polyvinylpyrrolidone K30 or 10% (v/v) Labrafil®M1944. All other vehicles tested caused isolated or low magnitude effects which would not prevent their use. The aim of sharing these data, including adverse findings, is to provide meaningful information for vehicle selection, thereby avoiding repetition of animal experimentation. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of cyclodextrins on the complexation and transdermal delivery of bupranolol through rat skin

Bupranolol (BPL) is a potent beta-blocking agent, the extensive first-pass metabolism (>90%) and rapid elimination half-life (1.5-2.0 h) of this drug make it well suited to be developed as a transdermal delivery system (TDS). Hydroxypropyl betaCD (HPbetaCD) and partially methylated betaCD (PMbetaCD) were used as penetration enhancers for BPL. The formation of inclusion complex of BPL with these cyclodextrins (CDs) was characterized in solution and solid states by phase solubility, X-ray diffractometry and differential scanning calorimetry (DSC) analyses. The effect of CDs on the permeation enhancement of BPL through rat skin was studied using side-by-side diffusion cells and pH 7.4 phosphate-buffered saline (PBS). CDs were employed at different concentrations with 0.4% (w/v) BPL as well as with excess quantity of BPL (1.0%, w/v) that CDs could not complex all the BPL and the drug was in the form of an aqueous suspension. The permeation of BPL from its aqueous suspension (0.4%, w/v) significantly increased when CDs were used at low concentrations (up to 2 and 5%, w/v concentration for HPbetaCD and PMbetaCD, respectively) (P < 0.01). At higher CD concentrations, the permeation of BPL decreased; and both CDs at 10% (w/w), showed similar flux values to that of control (no enhancer, P > 0.05). The permeation of BPL from its 1.0% (w/v) aqueous suspension increased with increase in concentration of CD up to 10% (w/v) for HPbetaCD and PMbetaCD. At 10% (w/v) concentration of HPbetaCD and PMbetaCD, the flux of BPL from its 1.0% aqueous suspension increased 3.8- and 4.6-fold (P < 0.01 and P < 0.001, respectively). The permeation data of skin pretreatment with CDs indicate that HPbetaCD had no effect on the skin, whereas PMbetaCD significantly reduced the skin barrier for BPL, as shown by 1.7-fold increase in the flux by PMbetaCD pretreatment (P < 0.001). Overall, both HPbetaCD and PMbetaCD were found to be suitable for improving the solubility and penetration enhancement of BPL.