Multimodal mechanisms and enhanced efficiency of atrial fibrillation cardioversion by pulmonary delivery of a novel flecainide formulation.

INTRODUCTION: Inhaled flecainide significantly alters atrial electrical properties with the potential to terminate atrial fibrillation (AF) efficiently by optimizing dose and drug formulation. METHODS: Seventeen Yorkshire pigs were studied. Intrapericardial acetylcholine and burst pacing were used to induce AF. Effects of a novel cyclodextrin formulation (hydroxypropyl-ß-cyclodextrin [HPßCD]) of flecainide (75 mg/mL, 0.5 or 1.0 mg/kg, bolus) instilled intratracheally at 2 minutes after AF initiation were studied. Concentration time-area analyses of flecainide HPßCD were compared to the traditional acetate formulation. RESULTS: Intratracheal instillation of flecainide HPßCD accelerated the conversion of AF to sinus rhythm in a dose-proportional manner, shortening AF duration by 47% (P = .014) and 79% (P = .002) at the lower and higher doses, respectively, compared to intratracheal sterile water placebo. AF dominant frequency was reduced by 11% (P = .04) and 29% (P = .004) respective to dose. At 2 minutes after intratracheal flecainide HPßCD, atrial depolarization (Pa ) duration increased by 12% (P = .02) and 17% (P = .009) at the lower and higher doses, respectively. At this time, the PR interval was prolonged by 9% (P = .04 for the higher dose) and AV node conduction was slowed, decreasing the ventricular rate during AF by 16% (P = .002) and 28% (P = .007) for the lower and higher doses. Flecainide HPßCD achieved the more efficient conversion of AF than the acetate formulation, reflected in a markedly reduced area under the curve (P = .04). CONCLUSION: Intratracheal instillation of the new flecainide HPßCD formulation effectively terminates AF through efficient multimodal actions including slowing of atrial conduction velocity and decreasing AF dominant frequency, allowing reduced net drug delivery and inhalation time.

Cocrystalline Solids of Telaprevir with Enhanced Oral Absorption.

A combination of coformer screening and modeling, followed by characterization using calorimetry, structure elucidation, and solubility led to the identification of novel crystalline forms of the hepatitis C protease inhibitor, telaprevir. The lead crystalline form, a cocrystalline solid of telaprevir with 4-aminosalycilic acid, was identified among the list of possible cocrystals via modeling and confirmed by initial screening. It displayed the most significant aqueous solubility improvement over the neat crystalline form. Enhancement of in vivo performance was further demonstrated: a 10-fold increase in bioavailability was achieved for the cocrystal in comparison to the neat nanocrystalline telaprevir and it was found to be not statistically different from the lead amorphous spray-dried formulation.

Sugar acetates as CO2-philes: molecular interactions and structure aspects from absorption measurement using quartz crystal microbalance.

Sugar acetates, recognized as attractive CO(2)-philic compounds, have potential uses as pharmaceutical excipients, controlled release agents, and surfactants for microemulsion systems in CO(2)-based processes. This study focuses on the quantitative examination of absorption of high pressure CO(2) into these sugar derivatives using quartz crystal microbalance (QCM) as a detector. In addition to the absorption measurement, the QCM is initially found to be able to detect the CO(2)-induced deliquescence of sugar acetates, and the CO(2) pressure at which the deliquescence happens depends on several influencing factors such as the temperature and thickness of the film. The CO(2) absorption in alpha-D-glucose pentaacetate (Ac-alpha-GLU) is revealed to be of an order of magnitude larger in comparison with its anomer Ac-beta-GLU, whereas alpha-D-galactose pentaacetate (Ac-alpha-GAL) absorbs CO(2) less than Ac-alpha-GLU due to the steric-hindrance between the acetyl groups on the anomeric and C4 carbons, implying the significant importance of the molecular structure and configuration of sugar acetates on the absorption. The effects of molecular size and acetyl number of sugar acetates on the CO(2) absorption are evaluated and the results indicate that the conformation and packing of crystalline sugar acetate as well as the accessibility of the acetyls are also vital for the absorption of CO(2). It is additionally found that a CO(2)-induced change in the structure from a crystalline system to an amorphous system results in an order of magnitude increase in CO(2) absorption. Further investigation illustrates the interaction strength between sugar acetates and CO(2) by calculating the thermodynamic parameters such as Henry's law constant, enthalpy and entropy of dissolution from the determined CO(2) absorption. Experiments and calculations demonstrate that sugar acetates exhibit high CO(2) absorption, as at least comparable to ionic liquids. Since the ionic liquids have potential uses in the separation of acidic gases, it is evident from this study that sugar acetates could be used as possible materials for CO(2) separation.

Examination of glass transitions in CO(2)-processed, peracetylated sugars using sum frequency generation spectroscopy.

The present study utilizes vibrational sum frequency generation (SFG) spectroscopy to study changes in the surface crystallinity of various peracetylated sugars, a class of materials that have a high affinity for carbon dioxide (CO(2)). Studies of the solid-air interface of acetylated beta-cyclodextrin (Ac-beta-CD) and sucrose octaacetate (SOA) show that diffuse reflectance SFG spectroscopy is sensitive to changes in crystallinity from processing with either heat or solvation in CO(2), due to the loss of signal after glassification occurs. beta-d-Glucose pentaacetate (Ac-beta-GLC) was used as a control for this experiment due to the fact that it does not undergo a crystalline phase transition, regardless of processing conditions. The crystalline to amorpohous transitions of these bulk materials were verified using differential scanning calorimetry (DSC) as a function of thermal and CO(2) processing. In addition, preliminary results suggest that the SFG technique is sensitive in detecting the degree of crystallinity at the interface as a result of incomplete processing and presents new opportunities for the examination and detection of surface crystallinity changes.

Quartz crystal microbalance (QCM) in high-pressure carbon dioxide (CO2): experimental aspects of QCM theory and CO2 adsorption.

The quartz crystal microbalance (QCM) technique has been developed into a powerful tool for the study of solid-fluid interfaces. This study focuses on the applications of QCM in high-pressure carbon dioxide (CO2) systems. Frequency responses of six QCM crystals with different electrode materials (silver or gold) and roughness values were determined in helium, nitrogen, and carbon dioxide at 35-40 degrees C and at elevated pressures up to 3200 psi. The goal is to experimentally examine the applicability of the traditional QCM theory in high-pressure systems and determine the adsorption of CO2 on the metal surfaces. A new QCM calculation approach was formulated to consider the surface roughness contribution to the frequency shift. It was found that the frequency-roughness correlation factor, Cr, in the new model was critical to the accurate calculation of mass changes on the crystal surface. Experiments and calculations demonstrated that the adsorption (or condensation) of gaseous and supercritical CO2 onto the silver and gold surfaces was as high as 3.6 microg cm(-2) at 40 degrees C when the CO2 densities are lower than 0.85 g cm(-3). The utilization of QCM crystals with different roughness in determining the adsorption of CO2 is also discussed.