Modification of physical characteristics of microcrystalline cellulose by codrying with beta-cyclodextrins

Potential Use of Polyvinyl Acetate-Polyvinylpyrrolidone Mixture for the Development of Atenolol Sustained Release Matrix Tablets: Optimization of Formulation through in Vitro-in Vivo Assessment Study

The objective of this study was to develop sustained release matrix tablets of atenolol (AT) using different concentrations of polyvinyl acetate-polyvinylpyrrolidone mixture (KSR) (20, 30, or 40%) with various types of fillers such as spray dried lactose (SP.D.L), avicel pH 101 (AV), and emcompress (EMS). The physical characteristics of the prepared tablets were evaluated. Characterization of the optimized formulation was performed using Fourier transform (FT)-IR spectroscopy and differential scanning calorimetry (DSC). Moreover, the in vitro release profiles of AT formulations were investigated in different pH dissolution media. Drug release kinetics and mechanisms were also determined. The results revealed that there was no potential incompatibility of the drug with the polymer. The release profiles of AT were affected by the concentration of KSR, fillers used, and pH of the dissolution media. The drug release kinetic from most of the formulations obeyed Higuchi diffusion model. The selected formulae were investigated for their stability by storage at 30 and 40°C with atmospheric humidity and 75% relative humidity (RH), respectively. The results demonstrated that no change in the physicochemical properties of the tablets stored at 30°C/atmospheric RH in comparison with some changes at 40°C/75% RH. Finally, the in vivo study provided an evidence that the optimized AT tablet containing 40% KSR and SP.D.L exhibited prominent higher oral bioavailability and more efficient sustained-release effect than the drug alone or the commercial tablet product. It is noteworthy that KSR could be considered as a promising useful release retardant for the production of AT sustained release matrix tablets.

Practical considerations in development of solid dosage forms that contain cyclodextrin

The following is a review of the literature that addresses the use of cyclodextrin in solid dosage forms. Care was taken to exclude physical and chemical characteristics of cyclodextrin, which have been discussed in the literature. A flow diagram is provided to outline the decision-making steps that are involved in the development process. Both preparation of physical mixtures and inclusion complexes are considered. Analytical techniques to determine the presence of inclusion complexes, the effect of other excipients on complex formation, the effect of size limitation of solid dosages forms, powder processing, and storage of solid dosage forms are discussed.

Cyclodextrins in drug delivery: an updated review

The purpose of this review is to discuss and summarize some of the interesting findings and applications of cyclodextrins (CDs) and their derivatives in different areas of drug delivery, particularly in protein and peptide drug delivery and gene delivery. The article highlights important CD applications in the design of various novel delivery systems like liposomes, microspheres, microcapsules, and nanoparticles. In addition to their well-known effects on drug solubility and dissolution, bioavailability, safety, and stability, their use as excipients in drug formulation are also discussed in this article. The article also focuses on various factors influencing inclusion complex formation because an understanding of the same is necessary for proper handling of these versatile materials. Some important considerations in selecting CDs in drug formulation such as their commercial availability, regulatory status, and patent status are also summarized. CDs, because of their continuing ability to find several novel applications in drug delivery, are expected to solve many problems associated with the delivery of different novel drugs through different delivery routes.

Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes

A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes.

Physical properties and compact analysis of commonly used direct compression binders

This study investigated the basic physico-chemical property and binding functionality of commonly used commercial direct compression binders/fillers. The compressibility of these materials was also analyzed using compression parameters derived from the Heckel, Kawakita, and Cooper-Eaton equations. Five classes of excipients were evaluated, including microcrystalline cellulose (MCC), starch, lactose, dicalcium phosphate (DCP), and sugar. In general, the starch category exhibited the highest moisture content followed by MCC, DCP, lactose, and finally sugar; DCP displayed the highest density, followed by sugar, lactose, starch, and MCC; the material particle size is highly processing dependent. The data also demonstrated that MCC had moderate flowability, excellent compressibility, and extremely good compact hardness; with some exceptions, starch, lactose, and sugar generally exhibited moderate flowability, compressibility, and hardness; DCP had excellent flowability, but poor compressibility and hardness. This research additionally confirmed the binding mechanism that had been well documented: MCC performs as binder because of its plastic deformation under pressure; fragmentation is the predominant mechanism in the case of lactose and DCP; starch and sugar perform by both mechanisms.

Complexation with tolbutamide modifies the physicochemical and tableting properties of hydroxypropyl-beta-cyclodextrin

The physicochemical and tableting properties of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and its tolbutamide (TBM) complex were studied. The kinetics of TBM/HP-beta-CD inclusion complex formation in solution were determined by the phase solubility method. Solid complexes were prepared by freeze-drying and spray-drying. Water sorption-desorption behaviour of the materials were studied and compacts were made using a compaction simulator. TBM and HP-beta-CD formed 1:1 inclusion complexes in aqueous solution with an apparent stability constant of 63 M(-1). HP-beta-CDs and TBM/HP-beta-CD complexes were amorphous whereas the freeze-dried and spray-dried TBMs were polymorphic forms II and I, respectively. Sorption-desorption studies showed that HP-beta-CDs were deliquescent at high relative humidities. TBM/HP-beta-CD complexes had slightly lower water contents at low relative humidities than the physical mixtures. However, at high humidities their water sorption and desorption behaviours were similar to those of corresponding physical mixtures, indicating a glass transition of the complexed materials. TBM/HP-beta-CD complexes demonstrated a worse compactability than similarly prepared HP-beta-CDs or physical mixtures. Also particle properties that resulted from these preparation methods affected the compactability of the materials. In conclusion, the physicochemical and tableting properties of HP-beta-CD were modified by complexation it with TBM.

Influence of wet granulation and lubrication on the powder and tableting properties of codried product of microcrystalline cellulose with beta-cyclodextrin

The individual influence of wet granulation and lubrication on the powder and tableting properties of codried product of microcrystalline cellulose (MCC) with beta-cyclodextrin (beta-CD) was examined in this study. Avicel PH 101 and 301 were included for comparison. The codried product, Avicel PH 101 and 301 were granulated with water, and the granules were milled to retain three different size fractions: 37-60 microm, 60-150 microm, and 150-420 microm. The original Avicels and codried product were lubricated with magnesium stearate in three different percentages (0.2, 0.5, and 1.0%). The results showed that the powder flowability and disintegration of codried product and Avicels were significantly improved after wet granulation. However, the compactibility of codried product and Avicels decreased with increasing particle size. Nevertheless, the compactibility of the codried excipient after granulation was still better than the non-granulated Avicel PH 101 and 301. On the other hand, codried product and Avicels were sensitive to lubrication and resulted in decreasing compactibility and increasing disintegration. Because of the rounder shape of particles, the codried excipient was more sensitive to magnesium stearate and produced weaker tablets than did Avicels.

Deformation behaviors of tolbutamide, hydroxypropyl-beta-cyclodextrin, and their dispersions

PURPOSE

The deformation behaviors of compressed freeze-dried and spray-dried tolbutamide/hydroxypropyl-beta-cyclodextrin molecular dispersions were evaluated and compared with similarly prepared tolbutamides (TBM), hydroxypropyl-beta-cyclodextrins (HP-beta-CD) and as their physical dispersions.

METHODS

TBM, HP-beta-CD, and their 1:1 molecular dispersions were prepared by freeze-drying and spray-drying, and physical dispersions of TBM and HP-beta-CD were blended. Deformation properties of the prepared materials were evaluated by using a compaction simulator and constants derived from Heckel plots. Molecular dynamics (MD) simulations were performed in order to gain a molecular-level view on the deformation behavior of TBM-HP-beta-CD inclusion complex.

RESULTS

The freeze-dried TBM polymorphic form II was less prone to overall particle deformation than the spray-dried stable form I. Formation of molecular dispersions decreased the plastic and elastic behaviors of these materials. Also, the MD simulations showed a reduced molecular flexibility of the TBM-HP-beta-CD inclusion complex, as compared to HP-beta-CD.

CONCLUSIONS

The formation of TBM and HP-beta-CD molecular dispersion resulted in more rigid molecular arrangements, which were less prone to deformation than either HP-beta-CDs or physical dispersions. The results showed how differing molecular, solid, particle, and powder state properties affect the deformation properties of the materials studied.