Celecoxib-Loaded Self-micellizing Solid Dispersion Suppresses Its Delayed Absorption in Rats with Impaired Gastrointestinal Motility.

The aim of this study was to develop a self-micellizing solid dispersion of celecoxib (SMSD/CEL) with enhanced dissolution to suppress a delay in absorption under impairment of gastrointestinal (GI) secretion and motility induced by severe pain. Soluplus®-based SMSD/CEL was prepared by lyophilization and physiochemically characterized. A pharmacokinetic study of orally-dosed CEL samples was carried out in rats with propantheline (PPT)-induced the impairment of GI secretion and motility. SMSD/CEL was micellized in aqueous media with a mean diameter of 153 nm, and it showed improved dissolution behavior of CEL under acidic conditions with 2.1-fold higher dissolved CEL at 120 min than crystalline CEL. SMSD/CEL was found to be in an amorphous state, and there was no significant crystallization even after storage under accelerated conditions for 8 weeks, indicating relatively high storage stability of the amorphous form. Orally-dosed crystalline CEL in PPT-treated rats showed a delayed mean absorption time (MAT) and area under the curve of plasma concentration versus time from 0 to 4 h (AUC0-4) was reduced to 12% compared with that in normal rats, whereas SMSD/CEL suppressed the delay and decrease of absorption in PPT-treated rats. From these findings, SMSD/CEL might be efficacious to suppress poor and delayed absorption of CEL for better pain medication in the presence of impaired GI secretion and motility associated with severe pain.

Characterization of a novel polymeric prodrug of an antibacterial agent synthesized by mechanochemical solid-state polymerization.

Polycrystalline methacryloyl monomers of the antibacterial drug nalidixic acid with an anhydride bond to the drug carboxyl group were prepared. The physicochemical properties of the synthesized vinyl monomer were characterized using X-ray powder diffraction, thermal analysis, and polarized light microscopy measurements. Mechanochemical solid-state polymerization of the resulting monomers was carried out to yield a novel polymeric prodrug. The in vitro hydrolysis behavior of the polymeric prodrug indicated that the release rate of drug from the polymeric prodrug was clearly dependent on the pH value of the hydrolysis solution. Moreover, sustained release of the drug at an almost constant rate for more than 10 hr was shown in both neutral and alkaline solutions. The results suggest that anhydride-based polymeric prodrugs could be potentially useful in colon targeted drug delivery systems.

Improved Dissolution of Dipyridamole with the Combination of pH-Modifier and Solid Dispersion Technology.

The aim of this study was to develop a pH-independent release formulation of dipyridamole (DP) by the combined use of pH-modifier technology and solid dispersion (SD) technology employing enteric polymer, Eudragit® S100 (Eud). Tartaric acid (TA) was selected as an appropriate pH-modifier in terms of improving the dissolution behavior of DP under neutral conditions. Upon optimization of the ratio of TA to DP, SD of DP with Eud and TA (SD-Eud/DP/TA) was prepared by a freeze-drying method. Scanning electron microscopic images revealed that DP was dispersed in the polymer in SD-Eud/DP/TA, and DP in SD-Eud/DP/TA was in an amorphous state, supported by powder X-ray diffraction and differential scanning calorimetry analyses. The dissolution behavior of SD-Eud/DP/TA was not dependent on the pH of the medium, although SD-Eud/DP exhibited very limited dissolution behavior under neutral conditions. Spectroscopic analysis suggested that there might be inter-molecular interaction among DP, TA and enteric polymer in SD-Eud/DP/TA, possibly leading to the stable pH-independent dissolution behavior of SD-Eud/DP/TA. TA in SD-Eud/DP/TA promoted the degradation of DP, suggesting that improving the stability of DP in SD-Eud/DP/TA might be key for its practical use. From these results, pH-independent dissolution behavior of SD-Eud/DP/TA could be achieved by an enteric polymer-based solid dispersion with a pH-modifier.

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen.

A detailed electron spin resonance (ESR) analysis of mechanically induced free radicals (mechanoradicals) formation of glucose-based polysaccharides, dextran (Dx) and glycogen (Gly) was performed in comparison with amylose mechanoradicals. The ESR spectra of the samples mechanically fractured at room temperature were multicomponent. The radical concentration of Dx and Gly mechanoradicals gradually decreased during vibratory milling after reaching the maximum value. Although the molecular weight of Dx or the particle diameter of Gly steeply diminished until reaching the each maximum value of radical concentration, after that the molecular weight or the particle diameter slowly decreased. These results suggested that Dx and Gly mechanoradicals might be more unstable than amylose radicals possessing an intramolecular helical structure due to the branched structure.

Development of Novel Polymeric Prodrugs Synthesized by Mechanochemical Solid-State Copolymerization of Hydroxyethylcellulose and Vinyl Monomers.

Novel polymeric prodrugs were synthesized by mechanochemical solid-state copolymerization of hydroxyethylcellulose and the methacryloyloxy derivative of 5-fluorouracil (5-FU). Copolymerization was about 94% complete after 4 h, and the polymeric prodrug was quantitatively obtained after 14 h of reaction. The number average molecular weight (Mn) and polydispersity (H) of the polymeric prodrug were 39000 g/mol and 6.20, respectively. Mechanical fracturing of the polymer in a stainless steel twin-shell blender improved these properties (Mn=16000 g/mol and H=1.94). 5-FU was sustainably released from the polymeric prodrugs, and the rate was not affected by the molecular weight or molecular weight distribution of the prodrug under the experimental conditions used. These results suggest that novel polymeric prodrugs composed of a polysaccharide and a synthetic polymer can be fabricated by mechanochemical solid-state copolymerization under anaerobic conditions.

Novel pH-responsive polymeric micelles prepared through self-assembly of amphiphilic block copolymer with poly-4-vinylpyridine block synthesized by mechanochemical solid-state polymerization.

We fabricated polymeric micelles containing 5-fluorouracil (5-FU) or fluorescein using the amphiphilic block copolymer, poly-4-vinylpyridine-b-6-O-methacryloyl galactopyranose. Although the polymeric micelles were stable at pH 7.4, they readily decomposed at pH 5, resulting in near complete release of 5-FU. Uptake of polymeric micelles containing fluorescein by HepG2 and HCT116 cells was also investigated. With both cell types, strong fluorescence was observed after a 12-h incubation, but the fluorescence weakened after 24 h of incubation. The fluorescein incorporated into the polymeric micelles was released into acidic organelles (endosome and/or lysosome), from which it diffused throughout the cell. The cytotoxicity of polymeric micelles containing 5-FU was evaluated against HepG2 cells using a CCK-8 assay. The results suggest that polymeric micelles containing 5-FU are more cytotoxic to HepG2 cells than free 5-FU.

Dextran-based nanoparticles with 5-FU-conjugated polymethacrylate segments for drug delivery: Synthesis of amphiphilic graft copolymers by mechanochemical solid-state polymerization and characterization.

Dextran (Dx) is a biodegradable and biocompatible polysaccharide, thus promising as a drug delivery carrier for tumor therapy. Herein, we applied mechanical energy to a high molecular weight Dx to control its molecular weight and simultaneously generate mechanoradicals. The solid-state polymerization of methacrylate- or methacrylamide derivatives initiated with Dx mechanoradicals showed polymer conversion of >95%, yielding Dx-based graft copolymers with molecular weights of approximately 30,000 g mol-1. The Dx-based graft copolymers with hydrophobic segments formed nanoparticles with a particle size of 25-35 nm in an aqueous solution. The anti-pancreatic tumor drug 5-fluorouracil (5-FU) was covalently conjugated onto the hydrophobic segments of the amphiphilic Dx, and the nanoparticles were also prepared. The drug release profile from 5-FU-conjugated nanoparticles corresponded well to the Korsmeyer-Peppas model applied to drug release from matrix substrates, and was also immensely predicted by the Logistic and Gompertz curves. The 5-FU-conjugated nanoparticles showed cytotoxicity against the pancreatic adenocarcinoma cell lines (BxPC-3) that were not significantly inferior to the 5-FU positive group. Furthermore, the fluorescein-labeled nanoparticles internalized into BxPC-3 within 6 h and actively migrated into the cytosol. These results suggest that Dx-based graft copolymers with hydrophobic segments might be used to enhance therapeutic activity.

Development of meloxicam salts with improved dissolution and pharmacokinetic behaviors in rats with impaired gastric motility.

PURPOSE: Because of its poor solubility in acidic solution, oral absorption and efficacy of meloxicam (MEL) may be reduced in severe pain patients with impaired gastric motility. The present study aimed to develop salt forms to overcome these drawbacks. METHOD: Upon MEL salt screening with eight counterions, five MEL salts were obtained. The physicochemical properties of these MEL salts were characterized with a focus on morphology, crystallinity, thermal behavior, dissolution, and chemical/photo-stability. Pharmacokinetic profiling of an orally administered MEL salt was also carried out in both normal rats and rats treated with propantheline for the suppression of gastric motility. RESULTS: Dissolution behaviors for all obtained MEL salts were markedly better than that of crystalline MEL; in particular, the initial dissolution rate of arginine MEL dihydrate (MEL/Arg) was ca. 14-fold higher than that of crystalline MEL. MEL/Arg was found to be chemically and physically stable. There was ca. 18-fold reduction of AUC(0-4) for orally dosed crystalline MEL (1.0 mg-MEL/kg) in propantheline-treated rats compared with that in normal rats. In contrast, there was only a ca. 3-fold difference in AUC(0-4) between normal and propantheline-treated rats after oral administration of MEL/Arg (1.0 mg-MEL/kg). CONCLUSION: From these findings, MEL/Arg may provide improved oral absorption in severe pain patients.

Characterization of novel pH-sensitive polymeric micelles prepared by the self-assembly of amphiphilic block copolymer with poly-4-vinylpyridine block synthesized by mechanochemical solid-state polymerization.

We fabricated novel pH-sensitive polymeric micelles consisting of amphiphilic block copolymer containing pyridyl groups as side chains in the hydrophobic block. The number average particle diameter of the polymeric micelles at pH 7 was approximately 200 nm. A decrease in pH resulted in deformation of the polymeric micelles over a very narrow pH range (between pH 5.7 and 5.6). Interestingly, micellization and demicellization occurred reversibly in this narrow pH range. Polymeric micelles incorporating 5-fluorouracil (5FU) were also prepared. Decreasing the pH of this polymeric micelle solution from 7 to 5.5 resulted in the rapid release of 5FU at pH 5.6; the drug was completely released within 30 min. These results suggest that deformation of the polymeric micelles caused the rapid release of 5FU.

High-throughput screening system for identifying phototoxic potential of drug candidates based on derivatives of reactive oxygen metabolites.

PURPOSE: The present study aimed to develop a high-throughput screening strategy for predicting the phototoxic potential of pharmaceutical substances, using a derivatives-of-reactive-oxygen-metabolites (D-ROM) assay. METHODS: The assay conditions of the D-ROM assay were optimized with a focus on screening run time, sensitivity, solvent system, and reproducibility. The phototoxic potentials of 25 model compounds were assessed by the D-ROM assay, as well as by other screening systems for comparison, including the reactive oxygen species (ROS) assay, the DNA-photocleavage assay, and the 3T3 neutral red uptake phototoxicity test (3T3 NRU PT). RESULTS: Some phototoxic drugs tended to yield D-ROM when exposed to simulated sunlight (250 W/m(2)), whereas D-ROM generation was negligible for non-phototoxic chemicals. Compared with the ROS assay, the assay procedure for the D-ROM assay was highly simplified with a marked reduction in screening run time. Comparative experiments also demonstrated that D-ROM data were related to the outcomes of the DNA-photocleavage assay and the 3T3 NRU PT, with prediction accuracies of 76 and 72%, respectively. CONCLUSION: The D-ROM assay has potential for identifying the phototoxic potential of a large number of new drugs as a 1st screening system in the early stages of drug discovery.

Novel application of plasma treatment for pharmaceutical and biomedical engineering.

The nature of plasma-induced surface radicals formed on a variety of organic polymers has been studied by electron spin resonance (ESR), making it possible to provide a sound basis for future experimental design of polymer surface processing using plasma treatment. On the basis of the findings from such studies, several novel bio-applications in the field of drug- and biomedical- engineering have been developed. Applications for drug engineering include the preparation of reservoir-type drug delivery system (DDS) of sustained- and delayed-release, and floating drug delivery system (FDDS) possessing gastric retention capabilities, followed by preparation of "Patient-Tailored DDS". Furthermore, the preparation of composite powders applicable to matrix-type DDS was developed by making a mechanical application to the surface radical-containing polymer powders with drug powders. In applications for biomedical engineering, the novel method to introduce the durable surface hydrophilicity and lubricity on hydrophobic biomedical polymers was developed by plasma-assisted immobilization of carboxyl group-containing polymer on the polymer substrate. The surfaces thus prepared were further used for the covalent immobilization of oligo-nucleotides (DNA) onto the polymer surfaces applicable to constructing DNA diagnosis system, and also plasma-assisted preparation of functionalized chemo-embolic agent of vinyl alcohol-sodium acrylate copolymer (PVA- PAANa).

In vitro phototoxicity of dihydropyridine derivatives: a photochemical and photobiological study.

Some photosensitizing drugs can cause phototoxic skin responses even after systemic administration; therefore, avoidance of undesired side-effects is a key consideration in drug discovery and development. As a prediction tool for phototoxic risk, we previously proposed the monitoring of reactive oxygen species (ROS) generated from compounds irradiated with UVA/B, which can be effective for understanding photochemical/photobiological properties. In this investigation, we evaluated the photosensitizing properties of a novel dihydropyridine derivative, with bradykinin B(2) receptor antagonist activity (compound A) using our ROS assay and several analytical/biochemical techniques. Exposure of compound A, and several dihydropyridine-type calcium channel antagonists to simulated sunlight resulted in the significant production of singlet oxygen, superoxide, or both, which indicates their photosensitive/phototoxic potential. This is consistent with the observation that compound A under UVA/B light exposure caused significant photodegradation and even peroxidation of fatty acid, which could lead to phototoxic dermatitis. Interestingly, the addition of radical scavengers, especially GSH, MPG and BHA, could attenuate the lipid peroxidation, suggesting the involvement of ROS generation in the phototoxic pathways of compound A. In the 3T3 neutral red uptake phototoxicity test, compound A also showed a phototoxic effect on 3T3 mouse fibroblast cells. These findings also support the usefulness of the ROS assay for the risk assessment studies on the drug-induced phototoxicity even at the early stages of pharmaceutical development.

Evaluation of hydrate formation of a pharmaceutical solid by using diffuse reflectance infrared Fourier-transform spectroscopy.

Ampicilline and nitrofurantoin, in both anhydrous and hydrate forms, were characterized by powder X-ray diffractometry (PXRD), thermogravimetric and differential thermal analyses (TG/DTA) and diffuse reflectance FT-IR spectroscopy (DRIFTS). Of all the analytical tools applied, only DRIFTS was able to indicate the formation of hydrogen bonds between the molecules of the anhydrous drug substance and crystalline water uptaken from atmospheric moisture as evidenced by the significant absorption at 3500-3700cm(-1) corresponding to crystal water. These results suggested that DRIFTS could provide information on hydration without a standard sample and accurately evaluate the physical stability focusing on the qualification of slight hydration in the early stages of pharmaceutical development. In addition, DRIFTS was applied to the besylate salt of pharmaceutical compound A to identify any possible hydration. This salt had the stable form BSA-I, metastable form BSA-II and hydrate form BSA-III. DRIFTS was able to show the hydration of BSA-II even when stored in a capped bottle, eventually leading to the transformation into BSA-III, which was not detected by PXRD. These findings verify the usefulness of DRIFTS for the solid-state characterization of pharmaceutical substances, especially the monitoring of gradual hydration.

Amorphous Solid Dispersion of Meloxicam Enhanced Oral Absorption in Rats With Impaired Gastric Motility.

Meloxicam (MEL) shows a slow onset of action in severe pain patients on account of delayed gastric motility. This study aimed to develop an amorphous solid dispersion (ASD) of MEL to achieve rapid oral absorption in severe pain patients. ASD formulations of MEL with hydroxypropylmethylcellulose (ASD-MEL/HPMC) and polyacrylates and polymethacrylates (ASD-MEL/EUD) were prepared and physicochemically characterized. Oral absorption behavior of MEL samples was also clarified in both normal and propantheline (PPT)-pretreated rats with impaired gastric motility. MEL in the formulations was amorphous, and ASD formulations of MEL exhibited high dissolution behavior in acidic solution. After oral administration of crystalline MEL (1 mg-MEL/kg), a 69% reduction in AUC0-4 was observed between normal and PPT-pretreated rats. For orally dosed ASD-MEL/HPMC (1 mg-MEL/kg), there were approximately 9- and 12-fold increases of AUC0-4 in normal and PPT-pretreated rats, respectively, in comparison with crystalline MEL (1 mg-MEL/kg). However, the oral absorption behavior of ASD-MEL/EUD (1 mg-MEL/kg) was low and similar to that of crystalline MEL. The infrared spectroscopic study revealed potent interactions between MEL and EUD, possibly leading to marked attenuation of MEL absorption. This ASD approach might provide rapid oral absorption of MEL in severe pain patients, possibly leading to better clinical outcomes.

PAMPA--critical factors for better predictions of absorption.

PAMPA, log P(OCT), and Caco-2 are useful tools in drug discovery for the prediction of oral absorption, brain penetration and for the development of structure-permeability relationships. Each approach has its advantages and limitations. Selection criteria for methods are based on many different factors: predictability, throughput, cost and personal preferences (people factor). The PAMPA concerns raised by Galinis-Luciani et al. (Galinis-Luciani et al., 2007, J Pharm Sci, this issue) are answered by experienced PAMPA practitioners, inventors and developers from diverse research organizations. Guidelines on how to use PAMPA are discussed. PAMPA and PAMPA-BBB have much better predictivity for oral absorption and brain penetration than log P(OCT) for real-world drug discovery compounds. PAMPA and Caco-2 have similar predictivity for passive oral absorption. However, it is not advisable to use PAMPA to predict absorption involving transporter-mediated processes, such as active uptake or efflux. Measurement of PAMPA is much more rapid and cost effective than Caco-2 and log P(OCT). PAMPA assay conditions are critical in order to generate high quality and relevant data, including permeation time, assay pH, stirring, use of cosolvents and selection of detection techniques. The success of using PAMPA in drug discovery depends on careful data interpretation, use of optimal assay conditions, implementation and integration strategies, and education of users.

[Radical formation by grinding of commercial tablets according to hospital and pharmacy prescription].

We examined mechanoradical formation in the grinding process of commercial tablets using electron spin resonance (ESR). Mechanoradicals were detected in all tested samples (23 types of commercial tablets) when the ball-milling of tablets was conducted under anaerobic conditions and some were fairly stable even in air. Thus the grinding may cause changes in the physicochemical properties of ingredients included in commercial tablets. Because high quality is demanded in pharmaceuticals, these results suggest more caution should be taken in the grinding of commercial tablets in hospitals and pharmacies.

Development of novel solid dispersion of tranilast using amphiphilic block copolymer for improved oral bioavailability.

The present study aimed to develop novel solid dispersion (SD) of tranilast (TL) using amphiphilic block copolymer, poly[MPC-co-BMA] (pMB), to improve the dissolution and pharmacokinetic behavior of TL. pMB-based SD of TL (pMB-SD/TL) with drug loading of 50% (w/w) was prepared by wet-mill technology, and the physicochemical properties were characterized in terms of morphology, crystallinity, dissolution, and hygroscopicity. Powder X-ray diffraction and polarized light microscopic experiments demonstrated high crystallinity of TL in pMB-SD/TL. The pMB-SD/TL exhibited immediate micellization when introduced to aqueous media, forming fine droplets with a mean diameter of ca. 122 nm. There was marked improvement in the dissolution behavior for the pMB-SD/TL even under acidic conditions, although the supersaturated TL concentration gradually decreased. NMR analyses demonstrated interaction between TL and pMB, as evidenced by the chemical shift drifting and line broadening. Pharmacokinetic behaviors of orally dosed TL formulations were evaluated in rats using UPLC/ESI-MS. After oral administration of pMB-SD/TL (10mg TL/kg) in rats, enhanced TL exposure was observed with increases of Cmax and AUC by 125- and 52-fold, respectively, compared with those of crystalline TL. From these findings, pMB-based SD formulation approach might be an efficacious approach for enhancing the therapeutic potential of TL.

Physicochemical and pharmacokinetic characterization of amorphous solid dispersion of tranilast with enhanced solubility in gastric fluid and improved oral bioavailability.

In the present study, amorphous solid dispersion (ASD) formulations of tranilast (TL) with 8 hydrophilic polymers were prepared by a solvent evaporation method with the aim of improving dissolution behavior in gastric fluid and thereby enhancing oral bioavailability. The physicochemical properties were characterized with a focus on morphology, crystallinity, thermal behavior, dissolution, drug-polymer interaction, and stability. Of all TL formulations, ASD formulation with Eudragit EPO exhibited the highest improvement in dissolution behavior with a 3,000-fold increase in the first-order dissolution rate under acidic conditions (pH 1.2). Spectroscopic studies using infrared and near-infrared analyses revealed the drug-polymer interaction in the Eudragit EPO-based ASD formulation. On the basis of dissolution, crystallinity, and stability data, the maximum allowable drug load in the Eudragit EPO-based ASD formulation was deduced to be ca. 50%. Pharmacokinetic profiling of orally dosed TL formulations in rats was also carried out using UPLC/ESI-MS. After oral administration of the Eudragit EPO-based ASD formulation in rats, enhanced TL exposure was observed with an increase of oral bioavailability by 19-fold, and the variation of AUC was ca. 4 times lower than that with crystalline TL. With these data, the ASD approach could be a viable formulation strategy for enhancing the wettability and oral bioavailability of TL, resulting in improved therapeutic potential of TL for the treatment of inflammatory diseases.

Improved dissolution and pharmacokinetic behavior of dipyridamole formulation with microenvironmental pH-modifier under hypochlorhydria.

The present study aimed to develop and characterize new formulations of dipyridamole (DP), a pH-dependent poorly soluble drug, employing an acidic pH-modifier for improving dissolution and absorption under hypochlorhydric condition. Granule formulations of DP (DPG) with and without fumaric acid (FA) were prepared with wet granulation, physicochemical properties of which were characterized focusing on morphology, dissolution and stability. Pharmacokinetic profiling of orally dosed DPG or DPG with 60% loading of FA (DPG/FA60) was carried out in omeprazole-treated rats as a hypochlorhydric model. Although pH-dependent dissolution behavior was observed in DPG, DPG/FA exhibited high rate and extent of dissolution in both acidic and neutral media. Complete supersaturation was achieved with a 2 h testing period in pH6.8 medium, and co-existing fumaric acid had no impact on the chemical/photochemical stability of DP in solid-state. After oral administration of DPG or DPG/FA60 (10 mg-DP/kg), there was ca. 40% reduction of AUC(0-3) for DPG in omeprazole-treated rats as compared to that in normal rats; however, AUC(0-3) for DPG/FA60 under hypochlorhydria was almost identical to that of DPG in normal rats. Given the improved systemic exposure early after oral administration in hypochlorhydric rats, the DPG/FA might provide better clinical outcomes in hypochlorhydric patients.

Comparative studies on physicochemical stability of cyclosporine A-loaded amorphous solid dispersions.

The present study aimed to evaluate the physical stability on amorphous solid dispersion (SD) of cyclosporine A (CsA) employing hydroxypropyl cellulose (HPC). SD formulations (5-30% CsA) of CsA such wet-milled SD (WM/SD) and freeze-dried SD (FD/SD) were prepared, and both SD formulations were stored at 40 °C/75% relative humidity for 8 weeks. Transitions in morphology, dissolution behavior, crystallinity and thermal behavior of CsA were evaluated. There was at least 84-fold improvement in initial dissolution rate of SD formulations compared with that of amorphous CsA powder, although their dissolution rate was gradually decreased under accelerated conditions. In particular, aged FD/SD with a drug load of 30% exhibited highly limited dissolution as evidenced by 40% reduction of solubility after 8 weeks of storage. In contrast, aged WM/SD exhibited less reduction in dissolution rate compared with FD/SD. No significant changes were seen in crystallinity and thermal behavior after aging of SD formulations for 8 weeks; however, electron microscopic observations revealed aggregation of drug molecules/particles in the aged FD/SD, possibly leading to the reduced dissolution. From these findings, stability on CsA-loaded SD might be variable depending on the preparation methodology, and the wet-milling approach could be a viable option for preparing efficacious SD formulations with improved stability.