Controlled Sublimation Rate of Guest Drug from Polymorphic Forms of a Cyclodextrin-Based Polypseudorotaxane Complex and Its Correlation with Molecular Dynamics as Probed by Solid-State NMR.

Encapsulation of active pharmaceutical ingredients (APIs) in confined spaces has been extensively explored as it dramatically alters the molecular dynamics and physical properties of the API. Herein, we explored the effect of encapsulation on the molecular dynamics and physical stability of a guest drug, salicylic acid (SA), confined in the intermolecular spaces of γ-cyclodextrin (γ-CD) and poly(ethylene glycol) (PEG)-based polypseudorotaxane (PPRX) structure. The sublimation tendency of SA encapsulated in three polymorphic forms of the γ-CD/PEG-based PPRX complex, monoclinic columnar (MC), hexagonal columnar (HC), and tetragonal columnar (TC), was investigated. The SA sublimation rate was decreased by 3.0-6.6-fold and varied in the order of MC form > HC form > TC form complex. The 13C and 1H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectra and 13C spin-lattice relaxation time (T1) indicated that the encapsulated SA molecules existed as the monomeric form, and its molecular mobility increased in the order of MC form > HC form > TC form complex. In the complexes, a rapid chemical exchange between two dynamic states of SA (free and bound) was suggested, with varying adsorption/desorption rates accounting for its distinct molecular mobility. This adsorption/desorption process was influenced by proton exchange at the interaction site and interaction strength of SA in the complexes, as evidenced by 1H MAS spectra and temperature dependency of the 13C carbonyl chemical shift. A positive correlation between the molecular mobility of SA and its sublimation rate was established. Moreover, the molecular mobility of γ-CD and PEG in the complexes coincided with that of SA, which can be explained by fast guest-driven dynamics. This is the first report on the stability improvement of an API through complexation in polymorphic supramolecular host structures. The relationship between the molecular dynamics and physical properties of encapsulated API will aid in the rational design of drug delivery systems.

Improved Liver Function After Sustained Virologic Response Enhanced Prognosis in Hepatitis C with Compensated Advanced Liver Fibrosis.

BACKGROUND AND AIM: Liver function can be improved in patients with chronic hepatitis C virus (HCV) infection who achieved sustained virologic response (SVR) with direct-acting antiviral (DAA) treatment. However, to our knowledge, the impact of liver function improvement after SVR on prognosis has not been investigated. METHODS: A total of 716 patients with chronic HCV infection and compensated advanced liver fibrosis who began receiving DAA treatment between September 2014 and August 2018 in 25 Japanese hospitals and achieved SVR were enrolled. RESULTS: The median age was 73 years, and 336 (47%) and 380 (53%) patients had albumin-bilirubin (ALBI) grade 1 and grade 2, respectively. Improvement to ALBI grade 1 at 1 year after the end of treatment (EOT) was observed in 76% of the patients with baseline ALBI grade 2. Among 380 patients with baseline ALBI grade 2, alanine aminotransferase (ALT) levels ≥ 40 U/L (p < 0.001) and modified ALBI (mALBI) grade 2a (p < 0.001) were significantly associated with improvement to ALBI grade 1 at 1 year after EOT in multivariate analysis. During the median observation period of 51.8 months, 4 and 10 patients with baseline ALBI grade 1 and 2, respectively, died. In patients with baseline ALBI grade 2, only the absence of improvement to ALBI grade 1 at 1 year after EOT was significantly associated with all-cause mortality in univariate analysis. CONCLUSIONS: Baseline ALT levels and mALBI grade were significantly associated with improvement in liver function after SVR. Patients whose liver function improved after SVR could have better prognosis.

The efficacy and safety of adaptive servo-ventilation therapy for heart failure with preserved ejection fraction.

It is unclear whether adaptive servo-ventilation (ASV) therapy for heart failure with preserved ejection fraction (HFpEF) is effective. The aim of this study was to investigate the details of ASV use, and to evaluate the effectiveness and safety of ASV in real-world HFpEF patients. We retrospectively enrolled 36 HFpEF patients at nine cardiovascular centers who initiated ASV therapy during hospitalization or on outpatient basis and were able to continue using it at home from 2012 to 2017 and survived for at least one year thereafter. The number of hospitalizations for heart failure (HF) during the 12 months before and 12 months after introduction of ASV at home was compared. The median number of HF hospitalizations for each patient was significantly reduced from 1 [interquartile range: 1-2] in the 12 months before introduction of ASV to 0 [0-0] in the 12 months after introduction of ASV (p < 0.001). In subgroup analysis, reduction in heart failure hospitalization was significantly greater in female patients, patients with a body mass index < 25, and those with moderate or severe tricuspid valve regurgitation. In patients with HFpEF, the number of HF hospitalizations was significantly decreased after the introduction of ASV. HFpEF patients with female sex, BMI < 25, or moderate to severe tricuspid valve regurgitation are potential candidates who might benefit from ASV therapy.

Chest computer tomography is safe without additional interrogation or monitoring for modern cardiac implantable electrical devices.

INTRODUCTION: Whether diagnostic computed tomography (CT) scans to cardiac implantable electronic devices (CIED) is safe in recent models remains unknown. METHODS: A two-centers observational study. Over 14 years, consecutive 2362 chest CT scans (1666 pacemakers [PMs], 145 cardiac resynchronization therapy PM, 316 implantable cardioverter-defibrillator, and 233 cardiac resynchronization therapy defibrillator) were interrogated and monitored upon imaging. RESULTS: Electromagnetic interference occurred only in a few old models: InSync 8040 (n = 14), InSync III Marquis (n = 1), and Kappa (n = 4), which resulted no adverse events. CONCLUSION: CIEDs, especially recent ones, are confirmed safe on chest CT.

Risk of hepatocellular carcinoma after sustained virologic response in hepatitis C virus patients without advanced liver fibrosis.

AIM: Hepatocellular carcinoma (HCC) after sustained virologic response (SVR) has been observed even in hepatitis C virus (HCV) patients without advanced liver fibrosis. Identifying predictors for HCC incidence in patients without advanced liver fibrosis will enable efficient post-SVR HCC surveillance. This study aimed to develop a scoring system to predict the incidence of HCC after SVR in HCV patients without advanced liver fibrosis. METHODS: A total of 1682 HCV patients without advanced liver fibrosis (defined as Fibrosis-4 index <3.25) with no history of HCC who initiated direct-acting antiviral treatment between September 2014 and October 2020 at 26 institutions, and achieved SVR24, were included. We divided 1682 patients into training (1122) and validation (560) cohorts. RESULTS: In the multivariate analysis, baseline age ≥ 65 years (p = 0.030), alanine aminotransferase (ALT) levels at SVR24 ≥ 30 U/l (p = 0.001), and α-fetoprotein (AFP) levels at SVR24 ≥ 5.0 ng/ml (p = 0.001) were independent predictors for HCC incidence in the training cohort. We developed a scoring system to predict HCC incidence after SVR24 using these three factors (1 point was added for each factor). The cumulative HCC incidence rates at 5 years were 7.1% in patients who scored 2 or 3, and no patients developed HCC in those who scored 0 in the validation cohort. CONCLUSIONS: Our scoring system using the three factors of baseline age, ALT levels at SVR, and AFP levels at SVR is useful for post-SVR HCC surveillance of patients without advanced liver fibrosis.

Size Reduction Efficiency of Alpha-Mangostin Suspension Using High-Pressure Homogenization.

In this study, we aimed to investigate the effects of stabilizers and processing parameters on the size reduction of alpha-mangostin (AMG) using high-pressure homogenization (HPH). The solubility of AMG in various stabilizers was studied. Selected stabilizers were used to prepare AMG suspensions by HPH under different conditions. After HPH, the particle size of AMG suspensions with stabilizers significantly decreased to microns. Percent size reduction efficiency of all AMG suspensions with each stabilizer increased with the increase in the number of homogenization cycles. Sodium lauryl sulfate and poloxamer188 provided a greater extent of particle size reduction than polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. AMG suspensions with binary stabilizers at higher pressure were also prepared. The use of high pressure increased percent size reduction efficiency.

Crystallization of Probucol in Nanoparticles Revealed by AFM Analysis in Aqueous Solution.

The crystallization behavior of a pharmaceutical drug in nanoparticles was directly evaluated by atomic force microscopy (AFM) force curve measurements in aqueous solution. A ternary spray-dried sample (SPD) was prepared by spray drying the organic solvent containing probucol (PBC), hypromellose (HPMC), and sodium dodecyl sulfate (SDS). The amorphization of PBC in the ternary SPD was confirmed by powder X-ray diffraction (PXRD) and solid-state 13C NMR measurements. A nanosuspension containing quite small particles of 25 nm in size was successfully prepared immediately after dispersion of the ternary SPD into water. Furthermore, solution-state 1H NMR measurements revealed that a portion of HPMC coexisted with PBC as a mixed state in the freshly prepared nanosuspension particles. After storing the nanosuspension at 25 °C, a gradual increase in the size of the nanoparticles was observed, and the particle size changed to 93.9 nm after 7 days. AFM enabled the direct observation of the morphology and agglomeration behavior of the nanoparticles in water. Moreover, AFM force-distance curves were changed from (I) to (IV), depending on the storage period, as follows: (I) complete indentation within an applied force of 1 nN, (II) complete indentation with an applied force of 1-5 nN, (III) partial indentation with an applied force of 5 nN, and (IV) nearly no indentation with an applied force of 5 nN. This stiffness increase of the nanoparticles was attributed to gradual changes in the molecular state of PBC from the amorphous to the crystal state. Solid-state 13C NMR measurements of the freeze-dried samples demonstrated the presence of metastable PBC Form II crystals in the stored nanosuspension, strongly supporting the AFM results.

Direct evaluation of molecular States of piroxicam/poloxamer nanosuspension by suspended-state NMR and Raman spectroscopies.

A nanosuspension of piroxicam (PXC) and poloxamer 407 (poloxamer) prepared by the wet milling method was directly evaluated at the molecular level from the viewpoint of both solution and solid phases. (13)C solution-state NMR measurements revealed a reduction in the concentration of dissolved poloxamer in the nanosuspension. Furthermore, the fraction of dissolved poly(ethylene oxide) (PEO) chain, which is the hydrophilic part of poloxamer, was higher than that of dissolved poly(propylene oxide) (PPO) chain, the hydrophobic part. (13)C suspended-state NMR and Raman spectroscopies detected both solid-state PXC and poloxamer involved in the nanoparticles. Interestingly, the coexistence of crystalline and amorphous PXC in the nanoparticle was demonstrated. The yellow color of the nanosuspension strongly supported the existence of amorphous PXC. Changes in the peak intensity depending on the contact time in the suspended-state NMR spectrum revealed that the PEO chain of poloxamer in the nanoparticle had higher mobility compared with the PPO chain. The PEO chain should project into the water phase and form the outer layer of the nanoparticles, whereas the PPO chain should face the inner side of the nanoparticles. Amorphous PXC could be stabilized by intermolecular interaction with the PPO chain near the surface of the nanoparticles, whereas crystalline PXC could form the inner core.

Equilibrium state at supersaturated drug concentration achieved by hydroxypropyl methylcellulose acetate succinate: molecular characterization using (1)H NMR technique.

The maintenance mechanism of the supersaturated state of poorly water-soluble drugs, glibenclamide (GLB) and chlorthalidone (CLT), in hydroxypropyl methylcellulose acetate succinate (HPMC-AS) solution was investigated at a molecular level. HPMC-AS suppressed drug crystallization from supersaturated drug solution and maintained high supersaturated level of drugs with small amount of HPMC-AS for 24 h. However, the dissolution of crystalline GLB into HPMC-AS solution failed to produce supersaturated concentrations, although supersaturated concentrations were achieved by adding amorphous GLB to HPMC-AS solution. HPMC-AS did not improve drug dissolution and/or solubility but efficiently inhibited drug crystallization from supersaturated drug solutions. Such an inhibiting effect led to the long-term maintenance of the amorphous state of GLB in HPMC-AS solution. NMR measurements showed that HPMC-AS suppressed the molecular mobility of CLT depending on their supersaturation level. Highly supersaturated CLT in HPMC-AS solution formed a gel-like structure with HPMC-AS in which the molecular mobility of the CLT was strongly suppressed. The gel-like structure of HPMC-AS could inhibit the reorganization from drug prenuclear aggregates to the crystal nuclei and delay the formation of drug crystals. The prolongation subsequently led to the redissolution of the aggregated drugs in aqueous solution and formed the equilibrium state at the supersaturated drug concentration in HPMC-AS solution. The equilibrium state formation of supersaturated drugs by HPMC-AS should be an essential mechanism underlying the marked drug concentration improvement.

Characterization of a riboflavin non-aqueous nanosuspension prepared by bead milling for cutaneous application.

The purpose of this study was to characterize the non-aqueous nanosuspension of a hydrophilic drug prepared by bead milling for cutaneous application. Riboflavin was used as the model hydrophilic drug. The non-aqueous nanosuspensions were prepared by grinding riboflavin with zirconia beads using eight non-aqueous bases. The mean particle size of riboflavin in the suspensions ranged from 206 to 469 nm, as determined by the dynamic light scattering method. Among the well-dispersed samples, riboflavin nanosuspension prepared in oleic acid was selected for evaluation of the drug permeability through rat skin. The cumulative amount and permeation rate of riboflavin from the nanosuspension were approximately three times higher than those for unprocessed riboflavin in oleic acid. Fluorescence imaging of the riboflavin nanosuspension suggested improved penetration of riboflavin into the stratum corneum. Furthermore, the addition of polysorbate 65 or polyglyceryl-6 polyricinoleate to the nanosuspension prepared in oleic acid markedly improved the riboflavin dispersibility. These results show that the preparation of a nanosuspension in a non-aqueous base by bead milling is one of the simple methods to improve the skin permeability of hydrophilic drugs.

Insights into atomic-level interaction between mefenamic acid and eudragit EPO in a supersaturated solution by high-resolution magic-angle spinning NMR spectroscopy.

The intermolecular interaction between mefenamic acid (MFA), a poorly water-soluble nonsteroidal anti-inflammatory drug, and Eudragit EPO (EPO), a water-soluble polymer, is investigated in their supersaturated solution using high-resolution magic-angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy. The stable supersaturated solution with a high MFA concentration of 3.0 mg/mL is prepared by dispersing the amorphous solid dispersion into a d-acetate buffer at pH 5.5 and 37 °C. By virtue of MAS at 2.7 kHz, the extremely broad and unresolved (1)H resonances of MFA in one-dimensional (1)H NMR spectrum of the supersaturated solution are well-resolved, thus enabling the complete assignment of MFA (1)H resonances in the aqueous solution. Two-dimensional (2D) (1)H/(1)H nuclear Overhauser effect spectroscopy (NOESY) and radio frequency-driven recoupling (RFDR) under MAS conditions reveal the interaction of MFA with EPO in the supersaturated solution at an atomic level. The strong cross-correlations observed in the 2D (1)H/(1)H NMR spectra indicate a hydrophobic interaction between the aromatic group of MFA and the backbone of EPO. Furthermore, the aminoalkyl group in the side chain of EPO forms a hydrophilic interaction, which can be either electrostatic or hydrogen bonding, with the carboxyl group of MFA. We believe these hydrophobic and hydrophilic interactions between MFA and EPO molecules play a key role in the formation of this extremely stable supersaturated solution. In addition, 2D (1)H/(1)H RFDR demonstrates that the molecular MFA-EPO interaction is quite flexible and dynamic.

High-speed classification of coherent X-ray diffraction patterns on the K computer for high-resolution single biomolecule imaging.

Single-particle coherent X-ray diffraction imaging using an X-ray free-electron laser has the potential to reveal the three-dimensional structure of a biological supra-molecule at sub-nanometer resolution. In order to realise this method, it is necessary to analyze as many as 1 × 10(6) noisy X-ray diffraction patterns, each for an unknown random target orientation. To cope with the severe quantum noise, patterns need to be classified according to their similarities and average similar patterns to improve the signal-to-noise ratio. A high-speed scalable scheme has been developed to carry out classification on the K computer, a 10PFLOPS supercomputer at RIKEN Advanced Institute for Computational Science. It is designed to work on the real-time basis with the experimental diffraction pattern collection at the X-ray free-electron laser facility SACLA so that the result of classification can be feedback for optimizing experimental parameters during the experiment. The present status of our effort developing the system and also a result of application to a set of simulated diffraction patterns is reported. About 1 × 10(6) diffraction patterns were successfully classificatied by running 255 separate 1 h jobs in 385-node mode.

Novel image analysis method using ultrasound elastography for noninvasive evaluation of hepatic fibrosis in patients with chronic hepatitis C.

It has been established that the long-term infection of chronic hepatitis C leads to the increased risk of hepatic fibrosis and hepatocellular carcinoma. Currently, histological diagnosis by invasive and painful liver biopsy is the gold standard for evaluating the hepatic fibrosis stage. Because of a side effect or patient inability to cope with the pain, it is difficult to assess the fibrosis stage frequently using liver biopsy. Recently, instead of liver biopsy, many articles have been published showing the usefulness of ultrasound elastography to evaluate the stage of hepatic fibrosis. We also reported the usefulness of real-time tissue elastography (RTE) for liver fibrosis staging in 2007. However, in our previous report, fibrosis classification was performed manually and the number of patients involved was also small. In the current study, the fibrosis staging is performed automatically using software by characterizing the elastography images. We have also increased the number of patients from 64 to 310. Thus, the aim of this study is to increase objectivity by using a newly developed automatic analysis method. We obtain the Liver Fibrosis Index (LFI), which is calculated from image features of RTE images, using multiple regression analysis performed on clinical data of 310 cases as the training data set. The correlation coefficient obtained between the LFI and the stage of hepatic fibrosis was r = 0.68, and significant differences exist between all stages of fibrosis (p < 0.001). Our new method seems promising since it has the ability to diagnose fibrosis even in the presence of inflammation.

Inhibitory effect of hydroxypropyl methylcellulose acetate succinate on drug recrystallization from a supersaturated solution assessed using nuclear magnetic resonance measurements.

We examined the inhibitory effect of hydroxypropyl methylcellulose acetate succinate (HPMC-AS) on drug recrystallization from a supersaturated solution using carbamazepine (CBZ) and phenytoin (PHT) as model drugs. HPMC-AS HF grade (HF) inhibited the recrystallization of CBZ more strongly than that by HPMC-AS LF grade (LF). 1D-1H NMR measurements showed that the molecular mobility of CBZ was clearly suppressed in the HF solution compared to that in the LF solution. Interaction between CBZ and HF in a supersaturated solution was directly detected using nuclear Overhauser effect spectroscopy (NOESY). The cross-peak intensity obtained using NOESY of HF protons with CBZ aromatic protons was greater than that with the amide proton, which indicated that CBZ had hydrophobic interactions with HF in a supersaturated solution. In contrast, no interaction was observed between CBZ and LF in the LF solution. Saturation transfer difference NMR measurement was used to determine the interaction sites between CBZ and HF. Strong interaction with CBZ was observed with the acetyl substituent of HPMC-AS although the interaction with the succinoyl substituent was quite small. The acetyl groups played an important role in the hydrophobic interaction between HF and CBZ. In addition, HF appeared to be more hydrophobic than LF because of the smaller ratio of the succinoyl substituent. This might be responsible for the strong hydrophobic interaction between HF and CBZ. The intermolecular interactions between CBZ and HPMC-AS shown by using NMR spectroscopy clearly explained the strength of inhibition of HPMC-AS on drug recrystallization.

Ghrelin counteracts salt-induced hypertension via promoting diuresis and renal nitric oxide production in Dahl rats.

Ghrelin is the endogenous ligand for the growth hormone-secretagogue receptor expressed in various tissues including the heart, blood vessels and kidney. This study sought to determine the effects of long-term treatment with ghrelin (10 nmol/kg, twice a day, intraperitoneally) on the hypertension induced by high salt (8.0% NaCl) diet in Dahl salt-sensitive hypertensive (DS) rats. Systolic blood pressure (SBP) was measured by a tail cuff method. During the treatment period for 3 weeks, high salt diet increased blood pressure compared to normal salt (0.3% NaCl) diet, and this hypertension was partly but significantly (P<0.01) attenuated by simultaneous treatment with ghrelin. Ghrelin significantly increased urine volume and tended to increase urine Na⁺ excretion. Furthermore, ghrelin increased urine nitric oxide (NO) excretion and tended to increase renal neuronal nitric oxide synthase (nNOS) mRNA expression. Ghrelin did not alter the plasma angiotensin II level and renin activity, nor urine catecholamine levels. Furthermore, ghrelin prevented the high salt-induced increases in heart thickness and plasma ANP mRNA expression. These results demonstrate that long-term ghrelin treatment counteracts salt-induced hypertension in DS rats primarily through diuretic action associated with increased renal NO production, thereby exerting cardio-protective effects.

Understanding the rod-to-tube transformation of self-assembled ascorbyl dipalmitate lipid nanoparticles stabilized with PEGylated lipids.

We previously established a nanoparticle-based drug delivery system (DDS) for high-dose ascorbic acid therapy by self-assembly of a lipid-modified ascorbic acid derivative, L-ascorbyl 2,6-dipalmitate (ASC-DP). The particles' morphology should be modified for effective DDSs. Here, we modulated the morphology of self-assembled ASC-DP nanoparticles using two different PEGylated lipids, distearoylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG) and cholesterol-polyethylene glycol (Chol-PEG), with various PEG molecular weights. At the preparation molar ratio of 10 : 1 (ASC-DP/PEGylated lipid), rod-like nanoparticles emerged in the ASC-DP/DSPE-PEG system, whereas the ASC-DP/Chol-PEG system yielded tube-like nanoparticles. The internal structures of both rod-like ASC-DP/DSPE-PEG and tube-like ASC-DP/Chol-PEG nanoparticles were similar to that of repeated ASC-DP bilayers. The particles' surfaces featured PEGylated lipids, which stabilized the structure and dispersion of the nanoparticles. For both systems, the particle size increased slightly with increasing the PEGylated lipid's PEG molecular weight. Increasing the PEG molecular weight decreased the inner tunnel size of tube-like ASC-DP/Chol-PEG nanoparticles. A mechanism has been proposed for the rod-to-tube transformation. Surface-layer free-energy changes owing to the mixing of multiple lipids and PEG chain repulsion are thought to underlie the inner tunnels' formation. The rod-to-tube morphology of self-assembled ASC-DP nanoparticles can be modulated by controlling the PEGylated lipids' structure, including the lipid species and the PEG chain length.

Successful treatment with bortezomib for POEMS syndrome, overcoming complicated severe heart block.

Cardiac bradyarrhythmia and conduction disorder may be rare, but recurrent adverse events caused by bortezomib. Here we report a case with POEMS syndrome presenting severe heart block after bortezomib plus dexamethasone therapy. After permanent pacemaker implantation, bortezomib was restarted and maintained, resulting in sustained complete response for POEMS syndrome.

Functional molecular imaging of ILK-mediated Akt/PKB signaling cascades and the associated role of beta-parvin.

Visualization and quantification of the dynamics of protein-protein interactions in living cells can be used to explore the macromolecular events involved in signal transduction processes. In this study, functional molecular imaging using a luciferase-based complementation method demonstrated how the integrin-linked kinase (ILK)-mediated protein complex controls downstream signals. The luciferase complementation assay showed that Akt1 preferentially binds to beta-parvin rather than to ILK within the complex. Moreover, photon flux from the interaction between beta-parvin and Akt1 increased following serum stimulation, and the beta-parvin-Akt1 interaction was dependent on phosphoinositide 3-kinase. Intriguingly, small interfering (si)RNA-mediated beta-parvin knockdown increased photon flux from the interaction between ILK and Akt1, leading to stabilization of hypoxia-inducible factor-1alpha and increased expression of vascular endothelial growth factor-A. These data from functional molecular imaging demonstrated that beta-parvin plays a regulatory role in the ILK-mediated Akt (also called protein kinase B) signaling cascades, suggesting that beta-parvin might be a crucial modulator of cell survival.

Mechanistic differences in permeation behavior of supersaturated and solubilized solutions of carbamazepine revealed by nuclear magnetic resonance measurements.

A solid dispersion (SPD) of carbamazepine (CBZ) with hydroxypropyl methylcellulose acetate succinate (HPMC-AS) was prepared by the spray drying method. The apparent solubility (37 °C, pH 7.4) of CBZ observed with the SPD was over 3 times higher than the solubility of unprocessed CBZ. The supersaturated solution was stable for 7 days. A higher concentration of CBZ in aqueous medium was also achieved by mixing with Poloxamer 407 (P407), a solubilizing agent. From permeation studies of CBZ using Caco-2 monolayers and dialysis membranes, we observed improved CBZ permeation across the membrane in the supersaturated solution of CBZ/HPMC-AS SPD. On the contrary, the CBZ-solubilized P407 solution exhibited poor permeation by CBZ. The chemical shifts of CBZ on the (1)H NMR spectrum from CBZ/HPMC-AS SPD solution were not altered significantly by coexistence with HPMC-AS. In contrast, an upfield shift of CBZ was observed in the CBZ/P407 solution. The spin-lattice relaxation time (T(1)) over spin-spin relaxation time (T(2)) indicated that the mobility of CBZ in the HPMC-AS solution was much lower than that in water. Meanwhile, the mobility of CBZ in P407 solution was significantly higher than that in water. NMR data indicate that CBZ does not strongly interact with HPMC-AS. CBZ mobility was suppressed due to self-association and microviscosity around CBZ, which do not affect permeation behavior. Most of the CBZ molecules in the CBZ/P407 solution were solubilized in the hydrophobic core of P407, and a few were free to permeate the membrane. The molecular state of CBZ, as evaluated by NMR measurements, directly correlated with permeation behavior.

Stabilization of a supersaturated solution of mefenamic acid from a solid dispersion with EUDRAGIT(®) EPO.

PURPOSE: The stabilization mechanism of a supersaturated solution of mefenamic acid (MFA) from a solid dispersion with EUDRAGIT(®) EPO (EPO) was investigated. METHODS: The solid dispersions were prepared by cryogenic grinding method. Powder X-ray diffractometry, in vitro dissolution test, in vivo oral absorption study, infrared spectroscopy, and solid- and solution-state NMR spectroscopies were used to characterize the solid dispersions. RESULTS: Dissolution tests in acetate buffer (pH 5.5) revealed that solid dispersion showed > 200-fold higher concentration of MFA. Supersaturated solution was stable over 1 month and exhibited improved oral bioavailability of MFA in rats, with a 7.8-fold higher area under the plasma concentration-versus-time curve. Solid-state (1)H spin-lattice relaxation time (T(1)) measurement showed that MFA was almost monomolecularly dispersed in the EPO polymer matrix. Intermolecular interaction between MFA and EPO was indicated by solid-state infrared and (13)C-T(1) measurements. Solution-state (1)H-NMR measurement demonstrated that MFA existed in monomolecular state in supersaturated solution. (1)H-T(1) and difference nuclear Overhauser effect measurements indicated that cross relaxation occurred between MFA and EPO due to the small distance between them. CONCLUSIONS: The formation and high stability of the supersaturated solution were attributable to the specifically formed intermolecular interactions between MFA and EPO.