Caprolactam-polyvinyl Acetate-polyethylene Glycol Graft Copolymer Research Articles

Direct Measurement of Lateral Molecular Diffusivity on the Surface of Supersaturated Amorphous Solid Dispersions by Atomic Force Microscopy.

Quantifying molecular surface diffusivity is of broad interest in many different fields of science and technology. In this study, the method of surface grating decay is utilized to investigate the surface diffusion of practical relevant amorphous solid dispersions of indomethacin and the polymeric excipient Soluplus (a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) at various polymer concentrations (1-20% w/w). The study confirms that measuring surface diffusivity below the system's glass transition temperature is possible with a simplified atomic force microscopy setup. Results highlight a striking polymer influence on the surface diffusivity of drug molecules at low polymer concentrations and a turnover point to a polymer dominated diffusion at around three percent (w/w) polymer concentration. The surface diffusion measurements further correlate well with the observed increase in physical stability of the system as measured by X-ray powder diffraction. These findings are of vital interest in both the applied use and fundamental understanding of amorphous solid dispersions.

Improving solubility and oral bioavailability of a novel antimalarial prodrug: comparing spray-dried dispersions with self-emulsifying drug delivery systems

To improve the solubility and oral bioavailability of a novel antimalarial agent ELQ-331(a prodrug of ELQ-300), spray-dried dispersions (SDD) and a self-emulsifying drug delivery system (SEDDS) were developed. SDD were prepared with polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®) polymer carrier and Aeroperl® 300 Pharma and characterized by differential scanning calorimetry, powder X-ray diffraction. For SEDDS, solubility in oils, surfactants, and co-surfactants was determined and ternary phase diagram was constructed to show self-emulsifying area. SEDDS were characterized for spontaneous emulsification and droplet size distribution. The amorphous ELQ-331 SDD improved the solubility to 10× in fast-state simulated intestinal fluid and addition of sodium lauryl sulphate externally to SDDs further improved the solubility to ∼28.5× versus non-formulated drug. SEDDS had good self-emulsifying characteristics with small emulsion droplet sizes and narrow particle distribution. Oral pharmacokinetic studies for SDD and SEDDS formulations were performed in rats. The ELQ-331 rapidly converted to ELQ-300 soon after oral administration in rats. Exposure levels of ELQ-300 were about 1.4-fold higher (based on AUC) in SEDDS than SDD formulations. Poorly soluble drugs like ELQ-331 can be formulated using SDD or SEDDS to improve solubility and oral bioavailability.

Dissolution enhancement of carbamazepine using twin-screw melt granulation

The current study explored the twin-screw melt granulation (TSMG) as a potential technology for the water solubility enhancement of biopharmaceutical classification system (BCS) class II drugs. As a model drug, carbamazepine (CBZ) was formulated with three different polymers as melt granules produced in a co-rotating twin-screw granulator. Polyethylene glycol 6000 (PEG 6000) and Kolliphor® (poloxamer) P407 were used as binding materials at two different granulation temperatures (Tmax: 70 °C; 100 °C). Additionally, Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) was chosen as binder of higher melting/ granulation temperature (Tmax: 140 °C). Temperature dependent polymorphic transition of CBZ during melt granulation was observed and identified using XRPD- (X-ray powder diffraction) and FTIR- (Fourier transform infrared spectroscopy) analysis. The effects of polymer type, polymer content (10, 15, 20% (w/w)) and granulation temperature on polymorphic transition, their impact on wettability (contact angle via drop shape-analysis), and the resulting dissolution performance at non-sink conditions in phosphate buffer (pH 6.8), were studied. This study showed that TSMG led to a crystalline system facilitating supersaturation when brought in solution, even when high drug loads (up to 90% (w/w)) were used.In general, for all granules produced, the supersaturation level and its duration varied with the extent of polymorphic transition and binder concentration. The results of this study indicated the importance of temperature control and polymer selection for tailoring desired dissolution profiles.

Understanding the interaction between Soluplus® and biorelevant media components

Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) is a solubilizing copolymer commonly applied as carrier in solid dispersions of poorly soluble drugs. This polymer is used to increase the apparent solubility of drugs with low aqueous solubility and consequently enhance drug absorption by the human gastrointestinal tract. To select the appropriate carrier to compose solid dispersions, in vitro supersaturation studies were applied as a pre-formulation tool, using different dissolution media. During in vitro supersaturation studies performed for the poorly soluble drug candesartan cilexetil, it was found that Soluplus® may interact with components of the biorelevant medium Fasted State Simulated Intestinal Fluid, lowering the drug apparent solubility. Dynamic Light Scattering and Transmission Electron Microscopy analyses were performed, as well as fluorescence measurements, aiming to characterize the interaction behavior and determine the polarity of the microenvironment. It was evidenced that Soluplus® interacted preferentially with lecithin, forming mixed micelles with a more polar microenvironment, which lowered the candesartan cilexetil solubilization capacity and consequently reduced its apparent solubility in the biorelevant medium. These findings are important to emphasize the key role of the media selection for in vitro solubility-supersaturation studies, where media that could mimic the human gastrointestinal environment are recommended.

Molecular modelling and simulation of fusion-based amorphous drug dispersions in polymer/plasticizer blends

A realistic molecular description of amorphous drug-polymer-plasticizer matrices, suitable for the preparation of amorphous solid dispersions (ASDs) with the aid of fusion-based techniques, was evaluated. Specifically, the incorporation of two model drugs (i.e. ibuprofen, IBU, and carbamazepine, CBZ) having substantially different thermal properties and glass forming ability, on the molecular representation of polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (SOL)/polyethylene glycol (PEG, working as a plasticizer) molecular and thermal properties were evaluated with the aid of classical molecular dynamics (MD) and docking simulations. Results showed good agreement between molecular modelling estimations and experimentally determined properties. Specifically, the computed Tg values that resulted from MD simulations for IBU-SOL/PEG and CBZ-SOL/PEG (53.8 and 54.2 °C, respectively) were in reasonable agreement with the corresponding values resulting from differential scanning calorimetry (DSC) measurements (49.8 and 50.1 °C), while both molecular modelling and experimental obtained results suggested miscibility among system components. Additionally, interactions between CBZ and SOL observed during MD simulations were verified by FTIR analysis, while MD simulations of the hydration process suggested strong molecular interactions between IBU-SOL and CBZ-SOL.

Size Reduction Efficiency of Alpha-Mangostin Suspension Using High-Pressure Homogenization.

In this study, we aimed to investigate the effects of stabilizers and processing parameters on the size reduction of alpha-mangostin (AMG) using high-pressure homogenization (HPH). The solubility of AMG in various stabilizers was studied. Selected stabilizers were used to prepare AMG suspensions by HPH under different conditions. After HPH, the particle size of AMG suspensions with stabilizers significantly decreased to microns. Percent size reduction efficiency of all AMG suspensions with each stabilizer increased with the increase in the number of homogenization cycles. Sodium lauryl sulfate and poloxamer188 provided a greater extent of particle size reduction than polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. AMG suspensions with binary stabilizers at higher pressure were also prepared. The use of high pressure increased percent size reduction efficiency.

The role of sodium alginate on the supersaturation state of the poorly soluble drug chlorthalidone

Solid dispersions (SDs) of chlorthalidone (CTD) are promising systems to enhance drug dissolution rate, generate and maintain drug supersaturation levels in gastrointestinal fluids. In this work, SDs of CTD were prepared by spray drying using sodium alginate (SA) as carrier. Six formulations were prepared, varying the drug loading and composition, through the combination of SA with surfactants (sodium lauryl sulfate (SLS) or polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (SOL)). In all SDs, except when SA was used alone at low drug loading, CTD was in the amorphous form. At sink conditions, all SDs showed a faster dissolution rate than the crystalline drug. At non-sink conditions, the SDs prepared with SA and SLS at low drug loading exhibited the best performance to maintain supersaturating drug levels. All SDs, except those prepared with SA alone or SA-SLS at high drug loading, presented no drug recrystallization after 34 months of storage.

New micelle myricetin formulation for ocular delivery: improved stability, solubility, and ocular anti-inflammatory treatment

Myricetin (Myr) is a naturally occurring flavonoid exhibiting diverse biological and pharmacological properties, but its characteristics such as water insolubility, poor aqueous stability, and poor bioavailability limit its clinical application, including in ophthalmology. To increase its clinical application in ophthalmology, Myr was designed to be encapsulated in a polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (PVCL-PVA-PEG) polymeric micelles to increases its aqueous solubility, stability, and corneal permeability to promote its efficacy in eye disease treatments. Thus, the Myr micelle ophthalmic solution was prepared and characterized encapsulation efficiency (EE), micelle size, and zeta potential. The chemical stability of Myr and the short-term storage stability of the Myr micelle ophthalmic solution were evaluated, followed by in vitro cytotoxicity and in vivo ocular irritation; in vitro cellular uptake and in vivo corneal permeation; and in vitro antioxidant activity and in vivo anti-inflammatory efficacy were also further evaluated. Myr could be incorporated into micelles with high EE. PVCL-PVA-PEG micelles significantly enhanced Myr’s aqueous solubility and chemical stability. The Myr micelle ophthalmic solution also showed high storage stability. In rabbits, the Myr micelle ophthalmic solution displayed good in vitro cellular tolerance. Remarkable improvements in in vitro cellular uptake and in vivo corneal permeation were also observed in the Myr micelle ophthalmic solution, and significant improvements in the in vitro antioxidant activity and in vivo anti-inflammatory efficacy were also obtained. Overall, these results supported that the Myr micelle ophthalmic solution could be a promising nanomedicine for ocular tissues.

Novel Orally Disintegrating Tablets Produced Using a High-Pressure Carbon Dioxides Process.

It is well known that high-pressure carbon dioxide (CO2) lowers the glass transition temperature (Tg) of polymers. We therefore investigated whether Tg depression of high-pressure CO2 results in interparticle bridging of a polymer and the tablet characteristics that makes the manufacture of an orally disintegrating tablet (ODT) possible. Copolyvidone (Kollidon®) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®) were examined and found to exhibit a large Tg depression. Placebo ODTs were prepared and hardness, disintegration rate, porosity, and change in thickness and appearance were evaluated before and after the high-pressure CO2 treatment. This enabled the establishment of the optimal conditions for pressure, temperature, and treatment time under pressure. Experimental results showed that it was possible to manufacture ODTs comprising Kollidon® as a water-soluble polymer with CO2 treatment under the suitable conditions such as temperature at 45°C, pressure lower than 8 MPa, and a treatment time shorter than 30 min, which is a new ODT manufacturing process called "Carbon Dioxide Assisted Tablet Formation Scheme" (CATS). In comparison to the conventional processes, which require high temperatures or humidity, CATS is expected to be applicable to drugs that are unstable at high temperature and humidity, and to functional drug particles used for bitter taste masking, sustained release, and other uses.

Molecular simulations for amorphous drug formulation: Polymeric matrix properties relevant to hot-melt extrusion

In the present study molecular modelling was used to evaluate polymeric drug carrier matrix properties suitable for hot-melt extrusion (HME). Specifically, the effect of three commonly used plasticizers, namely, citric acid (CA), triethyl citrate (TEC) and polyethylene glycol (PEG), on Soluplus® (polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer, SOL) properties were evaluated with the aid of classical molecular dynamics (MD) and docking simulations. Differential scanning calorimetry (DSC) and ATR-FTIR spectroscopy of polymer-plasticizer mixtures were used to experimentally verify the in silico predictions. Computed Tg value by MD simulations for SOL was in reasonable agreement with the experimentally determined Tg value (72.0 vs. 69.4 °C, for MD and DSC measurement, respectively). Solubility parameter calculations with the aid of MD simulations along with calculated molecular lipophilicity potential interaction (MLPI) scores based on molecular docking, suggested component miscibility only in the case of SOL and PEG. This was verified by a positive deviation of the Tg values determined by DSC, compared to the Gordon-Taylor theoretical predictions. Additionally, the calculated MLPI scores suggested strong interactions between SOL and PEG, verified also by ATR-FTIR. Finally, MD simulations of the hydration process suggested strong hydrogen bonding between SOL - CA, and CA - water molecules.

HPMCAS as an effective precipitation inhibitor in amorphous solid dispersions of the poorly soluble drug candesartan cilexetil

Among the strategies to improve the biopharmaceutic properties of poorly soluble drugs, Supersaturating Drug Delivery Systems like polymer-based amorphous solid dispersions (SD) have been successfully applied. The screening of appropriate polymeric carriers to compose SD is a crucial point on their development. In this study, hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose acetate succinate (HPMCAS) types L, M and H and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (SOL) were evaluated by in vitro supersaturation studies regarding their anti-precipitant ability on the poorly soluble drug candesartan cilexetil (CC) under two different media, including biorelevant conditions. According to the results, HPMCAS M was considered the best carrier to develop SD containing CC among all the polymers tested, due to its good anti-precipitant performance in both media. In addition, the medium used in the in vitro supersaturation studies played an important role on the results, and its selection should be carefully done.

Evaluation of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer nanomicelle for trigeminal ganglion neurons delivering with intranasal administration

ABSTRACTPurpose How to deliver enough medical agents to the trigeminal ganglion (TG) neurons conveniently still remains a challenge in pharmaceutics and clinics. The purpose of this study was to reveal that intranasal administration of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (PVCL-PVA-PEG) nanomicelle formulation could efficiently deliver agent to TG neurons in mice.Methods Ocular topical or intranasal administration of nanomicelle coumarin-6 was performed in mice, and tissue distribution after administration (0.25, 1, 2, 4, 6, 8, and 10 h) was analyzed. Fluoro-Gold was used as a retrograde tracer to identify corneal and nasal neurons in the TG. Pharmacokinetic profiles after ocular topical or intranasal administration were explored in detail.Results Coumarin-6 levels in the TG neurons were significantly higher in intranasal administration groups than in topical administration groups, and the difference was statistically significant (P < 0.05) at all time points except for 10 h. Interestingly, in cornea, coumarin-6 was detected after intranasal administration. For intranasal administration groups, it was also interestingly found that coumarin-6 levels in the TG neurons were much higher than that in the brain, suggesting that the TG neurons was a target tissue after the intranasal administration of nanomicelle coumarin-6. These levels also indicated the safety of brain tissue after intranasal administration. Using Fluoro-Gold tract tracing techniques, coumarin-6 was detected in TG neurons after either ocular topical or intranasal administration of nanomicelle coumarin-6, indicating the high colocalization of corneal and nasal neurons in the TG.Conclusions Intranasal administration of PVCL-PVA-PEG nanomicelle formulation could efficiently deliver to TG neurons, and it might be a promising therapy for pathological TG neurons.

Rheological analysis of itraconazole-polymer mixtures to determine optimal melt extrusion temperature for development of amorphous solid dispersion

The objective of this investigation was to develop a systematic method for the determination of optimal processing temperatures of drug-polymer mixtures for the development of amorphous solid dispersion (ASD) by melt extrusion. Since melt extrusion is performed at high temperature, it is essential that the processing temperature should be as low as possible to minimize degradation of drug and polymer, and yet the temperature should be high enough that the drug-polymer mixture attains certain viscosity that is extrudable and the drug dissolves in the molten polymer. By using itraconazole (ITZ) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft co-polymer (Soluplus®, BASF) as, respectively, the model drug and the polymeric carrier, melt viscosities of drug-polymer mixtures with 5, 10, 20 and 30% ITZ were studied as functions of temperature and angular frequency. All these concentrations were below the miscibility limit as it was shown separately by film casting that ITZ was miscible with the polymer up to 40%. Since the angular frequency of a rheometer may not be high enough to simulate the shear rate within an extruder, torque analysis as a function of temperature during melt extrusion of selected drug-polymer mixtures was also conducted. The presence of dissolved ITZ had a plasticizing effect on the polymer used, and an intersection point around 150–155°C was observed, above which viscosities of drug-polymer mixtures were lower than that of polymer itself. Drug-polymer mixtures with 5 to 30% ITZ were extrudable at 150°C, and torque analysis showed that the mixture with 20% ITZ can be extruded even at 145°C. These temperatures were 17 to 22°C below the melting point of ITZ (167°C). ITZ dissolved due to the drug-polymer miscibility, the viscosity attained, and the shear rate generated. It was confirmed by PXRD and DSC that the extrudates were amorphous. Viscosity and miscibility of drug-polymer mixtures during melt extrusion were identified as critical factors in determining optimal processing temperature.

Investigation of novel supersaturating drug delivery systems of chlorthalidone: The use of polymer-surfactant complex as an effective carrier in solid dispersions

Supersaturating drug delivery systems (SDDS), as solid dispersions (SDs), stand out among strategies to enhance bioavailability of poorly soluble drugs. After oral administration, their dissolution in gastrointestinal fluids often leads to supersaturation, which drives to a rapid and sustained absorption. Polymers and surfactants play important roles in SDs through inhibiting precipitation caused by transitions from amorphous into crystalline form, in supersaturated solutions, and also through improving SDs physical stability. Novel chlorthalidone SDs, a BCS IV drug, were developed using polymeric and non-polymeric carriers, specially a polymer-surfactant complex. SDs drug releases were evaluated using sink and non-sink conditions in water and biorelevant medium. Their physical stability was also monitored under different storage conditions. Polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (SOL), sodium lauryl sulfate (SLS) and a combination of both showed promising results in apparent solubility studies, and therefore they were selected to compose the spray dried SDs. Dissolution studies demonstrated the SOL-SLS complex potential for providing chlorthalidone fast release (>80% in 15min), producing and maintaining in vitro supersaturation. This formulation comprising high drug loading (75%) reached a high supersaturation degree under non-sink condition (up to 6-fold the equilibrium solubility) once maintained for 6h in biorelevant medium. In addition, this SD presented better physical stability when compared to the chlorthalidone neat amorphous. The SOL-SLS complex impacts positively on chlorthalidone release and physical stability, highlighting its potential as carrier in SDDS of a poorly soluble drug.

Improvement in the water solubility of drugs with a solid dispersion system by spray drying and hot-melt extrusion with using the amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and d-mannitol

The aim of this study was to prepare and characterize solid dispersion particles with a novel amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer, as a water-soluble carrier. Solid dispersion particles were prepared by hot-melt extrusion and spray drying. Indomethacin (IMC) was used as a model comprising drugs with low solubility in water and d-mannitol (MAN) was used as an excipient. The physicochemical properties of prepared particles were characterized by scanning electron microscopy, thermal analysis, powder X-ray diffraction (PXRD) analysis, FTIR spectra analysis, and drug release studies. Stability studies were also conducted under stress conditions at 40°C, 75% relative humidity. We found that dissolution behavior of the original drug crystal could be improved by solid dispersion with the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. The PXRD pattern and thermal analysis indicated that the solid dispersion prepared with the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and IMC was in an amorphous state. FTIR spectra analysis indicated that the interaction manner between the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and IMC may differ with the preparation method and formulation of solid dispersions. Stability studies proved that the amorphous state of IMC in solid dispersion particles was preserved under stress conditions for more than two weeks.

Effect of storage on the physical stability of thin polymethacrylate-perphenazine films

We evaluated the physical stability of thin polymethacrylate-drug films under three different storage conditions by X-ray powder diffraction, differential scanning calorimetry, scanning electron microscopy, polarized light microscopy, and Fourier transform infrared spectroscopy. Mechanical properties i.e. elongation, mechanical strength, and in vitro drug release from the thin films were also determined during storage. The films consisted of ammonium methacrylate copolymer (RLPO)/dimethylaminoethyl methacrylate copolymer (EPO), polyvinylpyrroline (PVP)/polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus) and perphenazine (PPZ). PPZ remained fully amorphous in all RLPO- and EPO -films for up to 12months' storage at 4°C in dry conditions. Instead, in EPO+PVP+PPZ 15% -films, higher temperature induced recrystallization of PPZ within three months and higher humidity also at six months. Crystallization was also observed in EPO+Soluplus+PPZ 10% -films at high temperature at 12months. The amount of PPZ released was significantly lower from recrystallized PPZ films than from stable amorphous films. The better stability of RLPO -films was attributed to PPZ being molecularly dispersed and also because of strong drug–polymer interactions in the films, while increasing storage temperatures weakened the hydrogen bonding interactions in the EPO -films. In addition, the presence of hygroscopic PVP facilitated PPZ recrystallization in the EPO -films if they were stored in a highly humid environment.

On the inherent properties of Soluplus and its application in ibuprofen solid dispersions generated by microwave-quench cooling technology

Polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer, or Soluplus®, is a relatively new copolymer and a promising carrier of amorphous solid dispersions. Knowledge on the inherent properties of Soluplus® (e.g. cloud points, critical micelle concentrations, and viscosity) in different conditions is relatively inadequate, and the application characteristics of Soluplus®-based solid dispersions made by microwave methods still need to be clarified. In the present investigation, the inherent properties of a Soluplus® carrier, including cloud points, critical micelle concentrations, and viscosity, were explored in different media and in altered conditions. Ibuprofen, a BCS class II non-steroidal anti-inflammatory drug, was selected to develop Soluplus®-based amorphous solid dispersions using the microwave-quench cooling (MQC) method. Scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Raman spectroscopy (RS), and Fourier transform infrared spectroscopy (FT-IR) were adopted to analyze amorphous properties and molecular interactions in ibuprofen/Soluplus® amorphous solid dispersions generated by MQC. Dissolution, dissolution extension, phase solubility, equilibrium solubility, and supersaturated crystallization inhibiting experiments were performed to elucidate the effects of Soluplus® on ibuprofen in solid dispersions. This research provides valuable information on the inherent properties of Soluplus® and presents a basic understanding of Soluplus® as a carrier of amorphous solid dispersions.

Effect of polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer on bioadhesion and release rate property of eplerenone pellets

The present study involved the design and development of oral bioadhesive pellets of eplerenone. A solid dispersion of eplerenone was developed with a hydrophilic carrier, polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (Soluplus®). Bioadhesive pellets were prepared from this solid dispersion using a combination of HPMC K4M and Carbopol 934P. Both the solid dispersion and the pellets were evaluated for various physicochemical properties such as solubility, entrapment efficiency, drug content, surface morphology, mucoadhesion and swelling behavior. Analysis carried out using FT-IR, DSC and XRD found no interaction between the eplerenone and excipients. The solid dispersion had irregular-shaped smooth-surfaced particles of diameter 265 ± 105.5 μm. In TEM analysis, eplerenone particles of size 79–120 nm were found. The solubility and dissolution of eplerenone in the Soluplus®-based solid dispersion were 5.26 and 2.50 times greater, respectively. Investigation of the swelling behavior of the pellets showed that the thickness of the gel layer increased continuously over the duration of the study. Moreover, a correlation was observed between the thickness and strength of the gel layer and the percentage release. The mechanism of drug release was found to be non-Fickian (anomalous), with the release kinetics approaching first-order kinetics. The bioavailability of the eplerenone bioadhesive pellet formulation was studied using Wistar rats and was found to be improved. An in vivo mucoadhesion study showed that the pellets are retained for 24 h in rabbits. It was concluded that Soluplus® had a positive effect on the solubility and dissolution of pellets without affecting the bioadhesion.

Solubility and dissolution performances of spray-dried solid dispersion of Efavirenz in Soluplus

Efavirenz (EFV), a first-line anti-HIV drug largely used as part of antiretroviral therapies, is practically insoluble in water and belongs to BCS class II (low solubility/high permeability). The aim of this study was to improve the solubility and dissolution performances of EFV by formulating an amorphous solid dispersion of the drug in polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (Soluplus®) using spray-drying technique. To this purpose, spray-dried dispersions of EFV in Soluplus® at different mass ratios (1:1.25, 1:7, 1:10) were prepared and characterized using particle size measurements, SEM, XRD, DSC, FTIR and Raman microscopy mapping. Solubility and dissolution were determined in different media. Stability was studied at accelerated conditions (40 °C/75% RH) and ambient conditions for 12 months. DSC and XRD analyses confirmed the EFV amorphous state. FTIR spectroscopy analyses revealed possible drug–polymer molecular interaction. Solubility and dissolution rate of EFV was enhanced remarkably in the developed spray-dried solid dispersions, as a function of the polymer concentration. Spray-drying was concluded to be a proper technique to formulate a physically stable dispersion of amorphous EFV in Soluplus®, when protected from moisture.

Electrospun fibers as potential carrier systems for enhanced drug release of perphenazine

Solubility represents an important challenge for formulation of drugs, because the therapeutic efficacy of a drug depends on the bioavailability and ultimately on its solubility. Low aqueous solubility is one of the main issues related with formulation design and development of new molecules. Many drug molecules present bioavailability problems due to their poor solubility. For this reason there is a great interest in the development of new carrier systems able to enhance the dissolution of poorly water-soluble drugs.In this work, fibers containing an insoluble model drug and prepared by an electrospinning method, are proposed and evaluated to solve this problem. Two hydrophilic polymers, polyvinylpyrrolidone (Plasdone® K29/32) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®) were used to increase the water solubility of perphenazine.The physico-chemical characterization suggests that the drug loaded in the fibers is in the amorphous state. Both polymeric carriers are effective to promote the drug dissolution rate in water, where this active pharmaceutical ingredient is insoluble, due to the fine dispersion of the drug into the polymeric matrices, obtained with this production technique. In fact, the dissolution profiles of the fibers, compared to the simple physical mixture of the two components, and to the reference commercial product Trilafon® 8mg tablets, show that a strong enhancement of the drug dissolution rate can be achieved with the electrospinning technique.