The influence of povidone K17 on the storage stability of solid dispersions of nimodipine and polyethylene glycol

Insoluble Polymers in Solid Dispersions for Improving Bioavailability of Poorly Water-Soluble Drugs

In recent decades, solid dispersions have been demonstrated as an effective approach for improving the bioavailability of poorly water-soluble drugs, as have solid dispersion techniques that include the application of nanotechnology. Many studies have reported on the ability to change drug crystallinity and molecular interactions to enhance the dissolution rate of solid dispersions using hydrophilic carriers. However, numerous studies have indicated that insoluble carriers are also promising excipients in solid dispersions. In this report, an overview of solid dispersion strategies involving insoluble carriers has been provided. In addition to the role of solubility and dissolution enhancement, the perspectives of the use of these polymers in controlled release solid dispersions have been classified and discussed. Moreover, the compatibility between methods and carriers and between drug and carrier is mentioned. In general, this report on solid dispersions using insoluble carriers could provide a specific approach and/or a selection of these polymers for further formulation development and clinical applications.

Torsemide Fast Dissolving Tablets: Development, Optimization Using Box-Bhenken Design and Response Surface Methodology, In Vitro Characterization, and Pharmacokinetic Assessment

The present study planed to develop new fast dissolving tablets (FDTs) of torsemide. Solid dispersions (SDs) of torsemide and sorbitol (3:1) or polyvinylpyrrolidone (PVP) k25 were prepared. The prepared SDs were evaluated for in-vitro dissolution. Fourier transform infrared spectroscopy and differential scanning calorimetry for SDs revealed no drug/excipient interactions and transformation of torsemide to the amorphous form. Torsemide/sorbitol SD was selected for formulation of torsemide FDTs by direct compression method. Box-Bhenken factorial design was employed to design 15 formulations using croscarmellose sodium and crospovidone at different concentrations. The response surface methodology was used to analyze the effect of changing these concentrations (independent variables) on disintegration time (Y₁), percentage friability (Y₂), and amount torsemide released at 10 min. The physical mixtures of torsemide and the used excipients were evaluated for angle of repose, Hausner's ratio, and Carr's index. The prepared FDTs tablets were evaluated for wetting and disintegration time, weight variation, drug content, percentage friability, thickness, hardness, and in vitro release. Based on the in-vitro results and factorial design characterization, F10 and F7 were selected for bioavailability studies following administration to Albino New Zealand rabbits. They showed significantly higher C _max and (AUC_0-12) and shorter T _max than those obtained after administration of the corresponding ordinary commercial Torseretic ® tablets. Stability study was conducted for F10 that showed good stability upon storage at 30°C/75% RH and 40°C/75% RH for 3 months.

Development and characterization of nifedipine-amino methacrylate copolymer solid dispersion powders with various adsorbents

Solid dispersions of nifedipine (NDP), a poorly water-soluble drug, and amino methacrylate copolymer (AMCP) with aid of adsorbent, that is, fumed silica, talcum, calcium carbonate, titanium dioxide, and mesoporous silica from rice husks (SRH), were prepared by solvent method. The physicochemical properties of solid dispersions, compared to their physical mixtures, were determined using powder X-ray diffractometry (PXRD) and differential scanning calorimetry (DSC). The surface morphology of the prepared solid dispersions was examined by scanning electron microscopy (SEM). The dissolution of NDP from solid dispersions was compared to NDP powders. The effect of adsorbent type on NDP dissolution was also examined. The dissolution of NDP increased with the ratio of NDP:AMCP:adsorbent of 1:4:1 when compared to the other formulations. As indicated from PXRD patterns, DSC thermograms and SEM images, NDP was molecularly dispersed within polymer carrier or in an amorphous form, which confirmed the better dissolution of solid dispersions. Solid dispersions containing SRH provided the highest NDP dissolution, due to a porous nature of SRH, allowing dissolved drug to fill in the pores and consequently dissolve in the medium. The results suggested that solid dispersions containing adsorbents (SRH in particular) demonstrated improved dissolution of poorly water-soluble drug when compared to NDP powder.

Development and evaluation of solid dispersion of spironolactone using fusion method

Introduction:

Solubility and dissolution of a poor water-soluble drug are the two major barriers for formulation scientists in development of drug delivery. Many of the potent drugs do not show the therapeutic effects due to solubility issues but may show toxicity issues when used in high doses. Solid dispersion (SD) technology is an excellent tool for enhancing the solubility and dissolution and hence related bioavailability.

Materials and Methods:

SD of spironolactone (SPL) was developed using an inert carrier polyethylene glycol 4000 (PEG 4000) by the conventional fusion method and characterized for various characterization parameters.

Results:

Solubility of pure drug and SD of SPL in water was found to be 23.54 ± 1.75 μg/mL and 61.73 ± 1.26 μg/mL, respectively. The maximum cumulative percentage release from pure drug, SPL marketed product (tablet), physical mixture, and SPL SD at 60 min was 27.25 ± 1.83%, 35.64 ± 3.65%, 47.72 ± 2.45%, and 74.24 ± 3.25%, respectively in 0.1 N HCl.

Conclusions:

SD of SPL was developed successfully. The solubility of SPL SD was found to be significantly increased (P < 0.05) as compared to SPL active pharmaceutical ingredient (API) and physical mixture of PEG 4000 and SPL. The current study indicated that SD of SPL was a better option for enhancing solubility of a poorly soluble therapeutic agent.

Solid dispersions in the development of a nimodipine floating tablet formulation and optimization by artificial neural networks and genetic programming

The present study investigates the use of nimodipine-polyethylene glycol solid dispersions for the development of effervescent controlled release floating tablet formulations. The physical state of the dispersed nimodipine in the polymer matrix was characterized by differential scanning calorimetry, powder X-ray diffraction, FT-IR spectroscopy and polarized light microscopy, and the mixture proportions of polyethylene glycol (PEG), polyvinyl-pyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC), effervescent agents (EFF) and nimodipine were optimized in relation to drug release (% release at 60 min, and time at which the 90% of the drug was dissolved) and floating properties (tablet's floating strength and duration), employing a 25-run D-optimal mixture design combined with artificial neural networks (ANNs) and genetic programming (GP). It was found that nimodipine exists as mod I microcrystals in the solid dispersions and is stable for at least a three-month period. The tablets showed good floating properties and controlled release profiles, with drug release proceeding via the concomitant operation of swelling and erosion of the polymer matrix. ANNs and GP both proved to be efficient tools in the optimization of the tablet formulation, and the global optimum formulation suggested by the GP equations consisted of PEG=9%, PVP=30%, HPMC=36%, EFF=11%, nimodipine=14%.

A formulation comparison between micro- and nanosuspensions: the importance of particle size for absorption of a model compound, following repeated oral administration to rats during early development

AIM

The aim of this study was to maximize the exposure of a model compound (MC) for forthcoming high-dose toxicological studies with the physical form of the original compound unaffected.

METHOD

The two evaluated formulation approaches for the present poorly water-soluble compound were micro- and nanosuspensions.

RESULTS

The particle size was about 280 nm for the nanosuspensions and about 4 μm for the microsuspensions. The crystallinity and the crystalline form of the ground samples were conserved. The physical and the chemical stabilities of the two kinds of suspensions were unaffected during the investigated time period. The in vivo results of the study showed that the pharmacokinetic parameters investigated were comparable at the low-dose level (6 μmol/kg) for both formulations after single administration. However, at the two higher doses (60 and 300 μmol/kg), a significant difference in exposure was observed between the two suspensions with an improved exposure for smaller particles. After Day 7 of repeated administration, a significant difference in exposure was observed at all dose levels. The overall exposures were higher on Day 7, compared to the exposures on Day 1 (most significant for nanoparticles), due to an accumulation of compound in the body.

CONCLUSIONS

The nanoparticles have a larger surface, resulting in faster in vivo dissolution rate, faster absorption, and increased bioavailability, compared to microparticles. The differences in systemic exposure of model compound, following oral administration of nano- or microparticles of the drug substance, are probably caused by differences in the in vivo dissolution rate and possibly further enhanced by saturation of the systemic elimination.