Search

The aim of this present study was to investigate the ability of different dissolution methods to predict the in vivo performance of efonidipine hydrochloride (EFH). The solid dispersions of EFH were prepared by solvent evaporation method with HPMC-AS as matrix and urea as a pH adjusting agent. The paddle method, the open-loop, and the closed-loop flow-through cell methods were studied. In the study, Weibull's model was the best fit to explain release profiles. The pharmacokinetics behaviors of two kinds of solid dispersions with different release rate were investigated in comparison to the EFH after oral administration in rats. In vivo absorption was calculated by a numerical deconvolution method. In the study, the level A in vivo and in vitro correlation (IVIVC) was utilized. The correlation coefficient was calculated and interpreted by means of linear regression analysis (Origin.Pro.8.5 software). As a result, excellent IVIVC for solid dispersions and crude drug (r 2  = 0.9352-0.9916) was obtained for the dissolution rate determined with flow-through cell open-loop system in phosphate buffer solution with 0.1% (w/v) polysorbate 80 at pH 6.5, the flow-rate of 4 mL/min. In addition, the self-assembled flow cell system had good repeatability and accuracy. The dissolution rate of the solid dispersion could be slowed down by the flow-through method, and the difference caused by preparation was significantly distinguished. The study demonstrated that flow-through cell method of the open-loop, compared with paddle method, was suitable for predicting in vivo performance of EFH solid dispersions.

The aim of this study was to improve the oral bioavailability of a practically insoluble drug, efonidipine hydrochloride (EFH), by agglomeration in acid solution/gastric fluid. The EFH nanosuspension was prepared by the wet-milling method with F68 as a dispersing agent, SDS as an auxiliary stabilizer and l-arginine as a pH adjusting agent. The EFH nanosuspension have been prepared in industrial scale-up. The dissolution rate of the EFH nanosuspension was greater than that of bulk EFH. An in vitro intestinal permeability study showed a clear increase in the apparent permeability of different intestinal segments compared with bulk EFH. Also, a pharmacokinetic study showed that the C max and AUC 0-24h of the nanosuspensions were approximately 1.76-fold and 2.2-fold greater than that of bulk EFH, respectively, and there was no significant difference compared with commercial tablets. It appears that wet-milling offers an effective approach to improve the dissolution rate and oral absorption of this practically insoluble drug., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, chitosan, a cationic polymer with positive charge, was introduced to modify the nanocrystals of nitrendipine with negative charge. The nanocrystals were prepared via precipitation-high pressure homogenization method. Then the nanocrystals were dispersed into chitosan solution, and the free chitosan was removed by centrifugation to obtain the chitosan modified nanocrystals, which remained the same particle size. However, the zeta-potential changed to positive after modification. The physical stability of the chitosan modified nanocrystals was remarkably improved under ambient conditions. During the in vitro dissolution test, the modified nanocrystals showed a certain degree of slow-release property. In the in vivo study, the C(max) of nitrendipine remained the same, however, the T(max) delayed from 0.75 h to 1.5 h with the chitosan modified nanocrystals. The surface modification by chitosan improved the bioavailability compared with the initial nanocrystals, which had demonstrated significant improvement of bioavailability compared to the traditional coarse powder form. Based on the experimental results, modification of the nanocrystals with certain polymer was supposed to be a good method to control the in vitro and in vivo behaviors of the nanocrystals, which could further increase the bioavailability of the water insoluble drug., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Purpose: To investigate anti-solvent crystallization and growth mechanism of nitrendipine spherical crystals in an aqueous solution containing polymeric additives., Methods: Size and shape of crystals were investigated using laser diffractometry, optical microscopy and scanning electron microscopy (SEM). Crystalline form was determined by X-ray powder diffractometer (XRPD). During crystal growth, morphological changes at different time points were observed using SEM., Results: Morphology of nitrendipine crystals was affected by polymers and temperature. Monodispersed micro-spherical crystals were obtained when polyvinyl alcohol (PVA) and PEG 200 were present in crystallization medium at 2°C. During crystallization, large number of amorphous nanoparticles was first observed, followed by aggregation into a core for spherical crystals. Once crystalline state was achieved, rapid growth on core surface was observed with amorphous particles acting as a reservoir allowing formation of star-like particles with needle-like subunits. Spherical crystals were formed by filling the gap between needle-like distinct crystalline units of star-like templates with molecules from dissolved amorphous particles., Conclusions: Monodispersed nitrendipine spherical crystals were obtained using carefully controlled conditions. A mechanism for the nitrendipine spherical crystal growth is suggested. These findings provide a new insight into spherulitic crystallization of active pharmaceutical ingredients.

The present investigation was undertaken with the objective of developing a solid formulation containing nitrendipine nanocrystals for oral delivery. Nitrendipine nanocrystals were prepared using a tandem precipitation-homogenization process. Then, spray drying, a cost-effective method very popular in industrial situations, was employed to convert the nanocrystals into a solid form. The parameters of the preparation process were investigated and optimized. The optimal process was as follows: firstly, nitrendipine/acetone solution (100 mg/ml) was added to a polyvinyl alcohol solution (1 mg/ml) at 10°C, then the pre-suspension was homogenized for 20 cycles at 1,000 bar. Both differential scanning calorimetry and X-ray diffraction analysis indicated that nitrendipine was present in crystalline form. The in vitro dissolution rate of the nanocrystals was significantly increased compared with the physical mixture and commercial tablet. The in vivo testing demonstrated that the C(max) of the nanocrystals was approximately 15-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively. In addition, the AUC(0→24) of the nanocrystals was approximately 41-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively.

Purpose: To investigate the effect of crystal size on the dissolution and oral absorption of nitrendipine, a poorly soluble drug, in rats., Methods: Five types of nitrendipine crystal suspensions with different particle sizes (200 nm, 620 nm, 2.7 microm, 4.1 microm, 20.2 microm) were prepared either by the precipitation-ultrasonication or the anti-solvent precipitation method. The simulated intestinal fluid in the fasted state (FaSSIF) was selected as the dissolution medium, and the dissolution behaviors of different nitrendipine crystals were simulated based on a Noyes-Whitney type equation. The in vivo absorption and the absolute bioavailability of the different nitrendipine crystals were evaluated in Wistar rats., Results: The dissolution rate of nitrendipine was significantly increased by a reduction in particle size. The dissolution test in FaSSIF could discriminate between the differences in the dissolution rates of the different particle sizes, and the simulated results were in agreement with the observed dissolution curves. From the simulated T(50%) values (50% dissolution time), the dissolution rates of crystals with particle sizes of 200 nm, 620 nm, 2.7 microm, 4.1 microm and 20.2 microm were calculated to be 5.1 x 10(4), 1.0 x 10(4), 237, 64 and 11-fold greater than that of the raw crystals and resulted in absolute bioavailability of 61.4% 51.5%, 29.4%, 26.7%, 24.7%, respectively. The reduction in the drug particle size correlated well with incremental improvements in oral absorption. A good linear relationship was observed between the Log (T(50%)) and the absolute bioavailability of nitrendipine., Conclusions: The dissolution rate and the oral bioavailability of nitrendipine were significantly affected by the crystal size, and the oral bioavailability could be improved significantly by preparing it as nanocrystals. FaSSIF can be used to predict differences in oral absorption of crystals with different particle sizes.

The aim of this study was to prepare and characterize nitrendipine nanosuspensions to enhance the dissolution rate and oral bioavailability of this drug. Nanosuspensions were prepared by the precipitation-ultrasonication method. The effects of five important process parameters, i.e. the concentration of PVA in the anti-solvent, the concentration of nitrendipine in the organic phase, the precipitation temperature, the power input and the time length of ultrasonication on the particle size of nanosuspensions were investigated systematically, and the optimal values were 0.15%, 30 mg/ml, below 3 degrees C, 400 W and 15 min, respectively. The particle size and zeta potential of nanocrystals were 209 nm (+/- 9 nm) and -13.9 mV (+/-1.9 mV), respectively. The morphology of nanocrystals was found to be flaky in shape by scanning electron microscopy (SEM) observation. The X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) analysis indicated that there was no substantial crystalline change in the nanocrystals compared with raw crystals. The in vitro dissolution rate of nitrendipine was significantly increased by reducing the particle size. The in vivo test demonstrated that the C(max) and AUC(0-->12) values of nanosuspension in rats were approximately 6.1-fold and 5.0-fold greater than that of commercial tablets, respectively., (2010 Elsevier B.V. All rights reserved.)