Preparation of stable aqueous suspension of a hydrophobic drug with polymers

Nanosuspension coated multiparticulates for controlled delivery of albendazole

OBJECTIVE

Improving solubility and bioavailability of albendazole (ALB).

SIGNIFICANCE

ALB is a broad-spectrum anthelminthic BCS class II drug with aqueous solubility of solubility of 4.1 mg/l at 25 °C and oral bioavailability of <5%.

METHODS

ALB nanosuspensions (NSs) were prepared by evaporative antisolvent precipitation using tocopherol polyethylene glycol succinate (TPGS) and polyvinyl pyrrolidone (PVP) as stabilizers and characterized for particle size, polydispersity index, and zeta potential. 3² factorial design was used to investigate effect of stabilizer concentration and speed of stirring on particle size. Concentration of TPGS was varied from 0.03 to 0.05% w/v and PVP K-30 was constant at 0.04% w/v. Stirring speed range was 1000-3000 rpm. Optimized NS was loaded on Espheres and coated with Eudragit S10& L100 and studied for friability, surface morphology and release kinetics.

RESULTS

Factorial experiments revealed pronounced effect of TPGS on particle size. Optimized batch had particle size of 251 ± 7.2 nm and zeta potential -16.2 ± 2.68 mV. Saturation solubility showed increase of 16-fold in water whereas in phosphate buffer increase was fourfold. ALB-NS secondary coated Espheres released 94.3% drug in 10 h whereas ALB-MS (microsuspension) coated Espheres showed 58% release. A 1.3-fold increase in AUC_0-10h was evident. Permeation from ALB-NS coated Espheres was 32% in 60 min while for ALB-MS coated Espheres it was 20%. Permeation increase occurred due to presence of TPGS which acts as a permeation enhancer.

Preparation of honokiol nanoparticles by liquid antisolvent precipitation technique, characterization, pharmacokinetics, and evaluation of inhibitory effect on HepG2 cells

Background

Honokiol is a bioactive lignanoid and has been utilized in traditional Chinese medicine for a long time. It exhibits several pharmacological properties, such as anticancer effects, anti-inflammatory effects, and antianxiety effects. However, the poor aqueous solubility of honokiol has impeded clinical applications.

Materials and methods

In the present study, we adopted the liquid antisolvent precipitation (LAP) technique to prepare nanoparticles of honokiol for enhancement of solubility and bioavailability. Moreover, the honokiol nanoparticles obtained were investigated and evaluated in terms of morphology, physicochemical properties, saturation solubility, dissolution in vitro, bioavailability in vivo, toxicity, and the inhibitory effect on growth of HepG2 cells.

Results

The obtained honokiol nanoparticles existed nearly in spherical shape and could be turned into amorphous structure by the LAP method. Moreover, the solubility of the honokiol nanoparticles was extremely higher than that of free honokiol, and the nanoparticle dissolution rate was also higher than that of free honokiol, which was about 20.41 times and 26.2 times than that of free honokiol in artificial gastric juice and in artificial intestinal juice. The area under the curve [AUC(0–t)] value of honokiol nanoparticles was about 6.52 times greater than that of free honokiol; therefore, the honokiol nanoparticles had a higher bioavailability than free honokiol but were innoxious to the organs of rats. Additionally, the honokiol nanoparticles exhibited a higher inhibition of HepG2 cells due to their lower IC₅₀ compared to free honokiol.

Conclusion

Honokiol nanoparticles have high solubility and bioavailability, and can become a new oral drug formulation and produce a better response for its clinical applications.

Preparation, characterization and antitumor activity evaluation of silibinin nanoparticles for oral delivery through liquid antisolvent precipitation

In order to improve the solubility and bioavailability of silibinin (SLB), the SLB nanoparticles were prepared by liquid antisolvent precipitation, and the oral bioavailability of SLB nanoparticles obtained was about 6.48 times higher than that of the free SLB.

Influence of Hydroxypropyl Methylcellulose on Metronidazole Crystallinity in Spray-Congealed Polyethylene Glycol Microparticles and Its Impact with Various Additives on Metronidazole Release

The purpose of this study was to investigate the effect of a hydrophilic polymer, hydroxypropyl methylcellulose (HPMC), on the crystallinity and drug release of metronidazole (MNZ) in spray-congealed polyethylene glycol (PEG) microparticles and to further modify the drug release using other additives in the formulation. HPMC has been used in many pharmaceutical formulations and processes but to date, it has not been employed as an additive in spray congealing. Crystallinity of a drug is especially important to the development of pharmaceutical products as active pharmaceutical ingredients (APIs) are mostly crystalline in nature. A combination of X-ray diffractometry, differential scanning calorimetry, Raman spectroscopy and Fourier transform-infrared spectroscopy (FT-IR) spectroscopy was employed to investigate the degree of crystallinity and possible solid-state structure of MNZ in the microparticles. The microparticles with HPMC were generally spherical. Spray congealing decreased MNZ crystallinity, and the presence of HPMC reduced the drug crystallinity further. The reduction in MNZ crystallinity was dependent on the concentration of HPMC. Smaller HPMC particles also resulted in a greater percentage reduction in MNZ crystallinity. Appreciable modification to MNZ release could be obtained with HPMC. However, this was largely attributed to the role of HPMC in forming a diffusion barrier. Further modification of drug release from spray-congealed PEG-HPMC microparticles was achieved with the addition of 5% w/w dicalcium phosphate but not with magnesium stearate, methyl cellulose, polyvinylpyrrolidone, silicon dioxide and sodium oleate/citric acid. Dicalcium phosphate facilitated formation of the diffusion barrier.

The development of carbamazepine-succinic acid cocrystal tablet formulations with improved in vitro and in vivo performance

The use of soluble cocrystal for delivering drugs with low solubility, although a potentially effective approach, often suffers the problem of rapid disproportionation during dissolution, which negates the solubility advantages offered by the cocrystal. This necessitates their robust stabilization in order for successful use in a tablet dosage form. The cocrystal between carbamezepine and succinic acid (CBZ-SUC) exhibits a higher aqueous solubility than its dihydrate, which is the stable form of CBZ in water. Using this model system, we demonstrate an efficient and material-sparing tablet formulation screening approach enabled by intrinsic dissolution rate measurements. Three tablet formulations capable of stabilizing the cocrystal both under accelerated condition of 40 °C and 75% RH and during dissolution were developed using three different polymers, Soluplus® (F1), Kollidon VA/64 (F2) and Hydroxypropyl methyl cellulose acetate succinate (F3). When compared to a marketed product, Epitol® 200 mg tablets (F0), drug release after 60 min from formulations F1 (∼82%), F2 (∼95%) and F3 (∼95%) was all higher than that from Epitol® (79%) in a modified simulated intestinal fluid. Studies in albino rabbits show correspondingly better bioavailability of F1-F3 than Epitol.

Evaluation of Influence of Various Polymers on Dissolution and Phase Behavior of Carbamazepine-Succinic Acid Cocrystal in Matrix Tablets

The aim of current study was to explore the influence of three commonly used polymers, that is, cellulosics and noncellulosics, for example, Methocel K4M, Kollidon VA/64, and Soluplus, on the phase disproportionation and drug release profile of carbamazepine-succinic acid (CBZ-SUC) cocrystal at varying drug to polymer ratios (1 : 1 to 1 : 0.25) in matrix tablets. The polymorphic phase disproportionation during in-depth dissolution studies of CBZ-SUC cocrystals and its crystalline properties were scrutinized by X-ray powder diffractrometry and Raman spectroscopy. The percent drug release from HPMC formulations (CSH) showed inverse relation with the concentration of polymer; that is, drug release increased with decrease in polymer concentration. On contrary, direct relation was observed between percent drug release and polymer concentrations of Kollidon VA 64/Soluplus (CSK, CSS). At similar polymer concentration, drug release from pure carbamazepine was slightly lower with HPMC formulations than that of cocrystal; however, opposite trend in release rate was observed with Kollidon VA/64 and Soluplus. The significant increase in dissolution rate of cocrystal occurred with Kollidon VA/64 and Soluplus at higher polymer concentration. Moreover, no phase change took place in Methocel and Kollidon formulations. No tablet residue was left for Soluplus formulation so the impact of polymer on cocrystal integrity cannot be predicted.

Review: physical chemistry of solid dispersions

Objectives

With poorly soluble drug candidates emerging in the drug discovery pipeline, the importance of the solid dispersion formulation approach is increasing. This strategy includes complete removal of drug crystallinity, and molecular dispersion of the poorly soluble compound in a hydrophilic polymeric carrier. The potential of this technique to increase oral absorption and hence bioavailability is enormous. Nevertheless, some issues have to be considered regarding thermodynamic instability, as well in supersaturated solutions that are formed upon dissolution as in the solid state.

Key findings

After a brief discussion on the historical background of solid dispersions and their current role in formulation, an overview will be given on the physical chemistry and stability of glass solutions as they form supersaturated solutions, and during their shelf life.

Conclusions

Thorough understanding of these aspects will elicit conscious evaluation of carrier properties and eventually facilitate rational excipient selection. Thus, full exploitation of the solid dispersion strategy may provide an appropriate answer to drug attrition due to low aqueous solubility in later stages of development.

Micronization of gemfibrozil by reactive precipitation process

Ultrafine gemfibrozil (GEM) was prepared by reactive precipitation process in which methyl cellulose (MC) was employed to inhibit the growth and the agglomeration of particles. The impact of NaOH concentrations on bulk GEM consumption was explored. The effects of H2SO4 concentrations and the drying methods on the particle size and morphology were also discussed. The produced ultrafine powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, specific surface area analysis and dissolution test. XRD patterns and FT-IR spectra showed that the as-obtained ultrafine GEM was a crystalline powder with the structure and components similar to those of bulk GEM. The ultrafine GEM had a mean particle size of about 1.25 microm with a narrow distribution from 0.6 to 3 microm. The specific surface area reached up to 11.01 m2/g, which was about 6 times as large as that of bulk GEM. In the dissolution tests, about 91.2% of ultrafine GEM was dissolved after 120 min, while there was only 23.6% of bulk GEM dissolved, proving that the dissolution property of ultrafine GEM was significantly enhanced when compared to commercial GEM owing to a decreased particle size and an increased specific surface area.

Cyclodextrins as pharmaceutical solubilizers

Cyclodextrins are useful functional excipients that have enjoyed widespread attention and use. The basis for this popularity from a pharmaceutical standpoint, is the ability of these materials to interact with poorly water-soluble drugs and drug candidates resulting in an increase in their apparent water solubility. The mechanism for this solubilization is rooted in the ability of cyclodextrin to form non-covalent dynamic inclusion complexes in solution. Other solubilizing attribute may include the ability to form non-inclusion based complexes, the formation of aggregates and related domains and the ability of cyclodextrins to form and stabilize supersaturated drug solutions. The increase in solubility also can increase dissolution rate and thus improve the oral bioavailability of BCS Class II and IV materials. A number of cyclodextrin-based products have reached the market based on their ability to camouflage undesirable physicochemical properties. This review is intended to give a general background to the use of cyclodextrin as solubilizers as well as highlight kinetic and thermodynamic tools and parameters useful in the study of drug solubilization by cyclodextrins.