Drug-Induced Dynamics of Bile Colloids.

Bile colloids containing taurocholate and lecithin are essential for the solubilization of hydrophobic molecules including poorly water-soluble drugs such as Perphenazine. We detail the impact of Perphenazine concentrations on taurocholate/lecithin colloids using analytical ultracentrifugation, dynamic light scattering, small-angle neutron scattering, nuclear magnetic resonance spectroscopy, coarse-grained molecular dynamics simulations, and isothermal titration calorimetry. Perphenazine impacted colloidal molecular arrangement, structure, and binding thermodynamics in a concentration-dependent manner. At low concentration, Perphenazine was integrated into stable and large taurocholate/lecithin colloids and close to lecithin. Integration of Perphenazine into these colloids was exothermic. At higher Perphenazine concentration, the taurocholate/lecithin colloids had an approximately 5-fold reduction in apparent hydrodynamic size, heat release was less exothermic upon drug integration into the colloids, and Perphenazine interacted with both lecithin and taurocholate. In addition, Perphenazine induced a morphological transition from vesicles to wormlike micelles as indicated by neutron scattering. Despite these surprising colloidal dynamics, these natural colloids successfully ensured stable relative amounts of free Perphenazine throughout the entire drug concentration range tested here. Future studies are required to further detail these findings both on a molecular structural basis and in terms of in vivo relevance.

Formulation of aripiprazole-loaded pH-modulated solid dispersions via hot-melt extrusion technology: In vitro and in vivo studies.

The objective of this study was to formulate aripiprazole (ARI)-loaded pH-modulated solid dispersions (SD) to enhance solubility, dissolution, and bioavailability via hot-melt extrusion (HME) technology. Kollidon® 12 PF (PVP) and succinic acid (SA) were selected after solubility screenings of various polymers and acidifiers. Several formulations, varying in screw speed and drug/polymer/acidifier ratios, were extruded using an 11 mm twin-screw extruder and were investigated for the effect of these variables. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to perform solid-state characterizations of the pure drug and extrudates. The aqueous solubility and dissolution were evaluated for the pure drug and milled extrudates. Among the prepared formulations, N6 was chosen for in vivo absorption studies. Solid-state characterization demonstrated the transformation of the crystalline ARI to an amorphous state in the formulations. Each formulation showed increased solubility and dissolution compared to the drug powder. The oral bioavailability (Cmax and AUC0-12) of N6 was significantly improved when compared to the pure ARI. This novel study not only discusses the incorporation of acidifiers in SDs but also the preparation of SDs using HME technology as effective techniques to improve drug release and bioavailability.

Micropellets coated with Kollicoat® Smartseal 30D for taste masking in liquid oral dosage forms.

The objective of this study was to develop delivery systems for taste masking based on multiparticulates coated with Kollicoat® Smartseal 30D formulated as liquid oral suspensions. Coating of particles containing bitter drugs with Kollicoat® Smartseal reduced drug leaching into aqueous medium, especially when increasing pH, therefore can be used for the formulation of liquid dosage forms. Application of an intermediate layer of ion exchange resins between drug layer and coating can further decrease drug leaching into aqueous vehicle that is beneficial in terms of taste masking. Using optimized compositions of liquid vehicles such as addition of sugar alcohols and ion exchange resin, reconstitutable or ready-to-use liquid dosage forms with micropellets can be developed with bitter taste protection after redispersion lasting longer than 3 weeks, which exceeds the usual period of application.

Curing mechanism of flexible aqueous polymeric coatings.

The objective of this study was to explain curing phenomena for pellets coated with a flexible polymeric coating based on poly(vinyl acetate) (Kollicoat® SR 30D) with regard to the effect of starter cores, thickness of drug layer, adhesion of coating to drug-layered-cores as well as coating properties. In addition, appropriate approaches to eliminate the curing effect were identified. Sugar or MCC cores were layered with the model drugs carbamazepine, theophylline, propranolol HCl, tramadol HCl and metoprolol HCl using HPMC (5 or 25% w/w, based on drug) as a binder. Drug-layered pellets were coated with Kollicoat® SR 30D in a fluidized bed coater using TEC (10% w/w) as plasticizer and talc (35-100% w/w) as anti-tacking agent. Drug release, pellet properties (morphology, water uptake-weight loss and osmolality) and adhesion of the coating to the drug layer were investigated as a function of curing at 60°C or 60°C/75% RH for 24h. The film formation of the aqueous dispersion of Kollicoat® SR 30D was complete, and therefore, a strong curing effect (decrease in drug release) at elevated temperature and humidity (60°C/75% RH) could not be explained by the well-known hydroplasticization and the further gradual coalescence of the colloidal polymer particles. According to the provided mechanistic explanation, the observed curing effect was associated with (1) high flexibility of coating, (2) adhesion between coating and drug layer, (3) water retaining properties of the drug layer, and (4) osmotically active cores. Unwanted curing effects could be minimized/eliminated by the addition of talc or/and pore-forming water soluble polymers in the coating, increasing binder amount or applying an intermediate coating, by increasing the thickness of drug layer or using non-osmotic cores. A new insight into curing phenomena mainly associated with the adhesion between drug layer and coating was provided. Appropriate approaches to avoid unwanted curing effect were identified.

Hot melt extrusion as an approach to improve solubility, permeability and oral absorption of a psychoactive natural product, piperine.

OBJECTIVE: The aims of the current research project were to investigate the efficiency of various polymers to enhance the solubility and increase the systemic absorption of piperine using hot melt extrusion technology. METHODS: Piperine 10-40% w/w and Eudragit(®) EPO/Kollidon(®) VA 64 or Soluplus(®) were mixed, and the resulting blends were extruded using a twin-screw extruder (Process 11, Thermo Fisher Scientific). Drug release profiles and piperine solubility studies of the extrudates were evaluated. A non-everted intestinal sac was employed for the most promising formulation, 10% w/w piperine/Soluplus(®) , and pure piperine to study the permeability characteristics. KEY FINDINGS: Dissolution studies demonstrated enhancement in piperine per cent release of 10% and 20% w/w piperine/Soluplus(®) extrudates up to 95% and 74%, respectively. The solubility of 10% and 20% piperine/Soluplus(®) increased more than 160- and 45-fold in water, respectively. Furthermore, permeability studies demonstrated the enhancement in piperine absorption of 10% w/w piperine/Soluplus(®) extrudates up to 158.9 µg/5 ml compared with pure piperine at 1.3 µg/5 ml within 20 min. CONCLUSION: These results demonstrated that increasing the bioavailability of piperine may be achieved as demonstrated by findings in this study.

Optimization of hot melt extrusion parameters for sphericity and hardness of polymeric face-cut pellets.

The aim of this study was to formulate face-cut, melt-extruded pellets, and to optimize hot melt process parameters to obtain maximized sphericity and hardness by utilizing Soluplus(®) as a polymeric carrier and carbamazepine (CBZ) as a model drug. Thermal gravimetric analysis (TGA) was used to detect thermal stability of CBZ. The Box-Behnken design for response surface methodology was developed using three factors, processing temperature ( °C), feeding rate (%), and screw speed (rpm), which resulted in 17 experimental runs. The influence of these factors on pellet sphericity and mechanical characteristics was assessed and evaluated for each experimental run. Pellets with optimal sphericity and mechanical properties were chosen for further characterization. This included differential scanning calorimetry, drug release, hardness friability index (HFI), flowability, bulk density, tapped density, Carr's index, and fourier transform infrared radiation (FTIR) spectroscopy. TGA data showed no drug degradation upon heating to 190 °C. Hot melt extrusion processing conditions were found to have a significant effect on the pellet shape and hardness profile. Pellets with maximum sphericity and hardness exhibited no crystalline peak after extrusion. The rate of drug release was affected mainly by pellet size, where smaller pellets released the drug faster. All optimized formulations were found to be of superior hardness and not friable. The flow properties of optimized pellets were excellent with high bulk and tapped density.

Solid-state characterization of Felodipine-Soluplus amorphous solid dispersions.

The aim of the current study is to develop amorphous solid dispersion (SD) via hot melt extrusion technology to improve the solubility of a water-insoluble compound, felodipine (FEL). The solubility was dramatically increased by preparation of amorphous SDs via hot-melt extrusion with an amphiphilic polymer, Soluplus® (SOL). FEL was found to be miscible with SOL by calculating the solubility parameters. The solubility of FEL within SOL was determined to be in the range of 6.2-9.9% (w/w). Various techniques were applied to characterize the solid-state properties of the amorphous SDs. These included Fourier Transform Infrared Spectrometry spectroscopy and Raman spectroscopy to detect the formation of hydrogen bonding between the drug and the polymer. Scanning electron microscopy was performed to study the morphology of the SDs. Among all the hot-melt extrudates, FEL was found to be molecularly dispersed within the polymer matrix for the extrudates containing 10% drug, while few small crystals were detected in the 30 and 50% extrudates. In conclusion, solubility of FEL was enhanced while a homogeneous SD was achieved for 10% drug loading.

Conjugation of Hot-Melt Extrusion with High-Pressure Homogenization: a Novel Method of Continuously Preparing Nanocrystal Solid Dispersions.

Over the past few decades, nanocrystal formulations have evolved as promising drug delivery systems owing to their ability to enhance the bioavailability and maintain the stability of poorly water-soluble drugs. However, conventional methods of preparing nanocrystal formulations, such as spray drying and freeze drying, have some drawbacks including high cost, time and energy inefficiency, traces of residual solvent, and difficulties in continuous operation. Therefore, new techniques for the production of nanocrystal formulations are necessary. The main objective of this study was to introduce a new technique for the production of nanocrystal solid dispersions (NCSDs) by combining high-pressure homogenization (HPH) and hot-melt extrusion (HME). Efavirenz (EFZ), a Biopharmaceutics Classification System class II drug, which is used for the treatment of human immunodeficiency virus (HIV) type I, was selected as the model drug for this study. A nanosuspension (NS) was first prepared by HPH using sodium lauryl sulfate (SLS) and Kollidon® 30 as a stabilizer system. The NS was then mixed with Soluplus® in the extruder barrel, and the water was removed by evaporation. The decreased particle size and crystalline state of EFZ were confirmed by scanning electron microscopy, zeta particle size analysis, and differential scanning calorimetry. The increased dissolution rate was also determined. EFZ NCSD was found to be highly stable after storage for 6 months. In summary, the conjugation of HPH with HME technology was demonstrated to be a promising novel method for the production of NCSDs.

Influence of Molecular Weight of Carriers and Processing Parameters on the Extrudability, Drug Release, and Stability of Fenofibrate Formulations Processed by Hot-Melt Extrusion.

The objective of this study was to investigate the extrudability, drug release, and stability of fenofibrate (FF) formulations utilizing various hot-melt extrusion processing parameters and polyvinylpyrrolidone (PVP) polymers of various molecular weights. The different PVP grades selected for this study were Kollidon® 12 PF (K12), Kollidon® 30 (K30), and Kollidon® 90 F (K90). FF was extruded with these polymers at three drug loadings (15%, 25%, and 35% w/w). Additionally, for FF combined with each of the successfully extruded PVP grades (K12 and K30), the effects of two levels of processing parameters for screw design, screw speed, and barrel temperature were assessed. It was found that the FF with (K90) was not extrudable up to 35% drug loading. With low drug loading, the polymer viscosity significantly influenced the release of FF. The crystallinity remaining was vital in the highest drug-loaded formulation dissolution profile, and the glass transition temperature of the polymer significantly affected its stability. Modifying the screw configuration resulted in more than 95% post-extrusion drug content of the FF-K30 formulations. In contrast to FF-K30 formulations, FF release and stability with K12 were significantly influenced by the extrusion temperature and screw speed.

Stability-enhanced hot-melt extruded amorphous solid dispersions via combinations of Soluplus® and HPMCAS-HF.

The aim of this study was to evaluate a novel combination of Soluplus® and hypromellose acetate succinate (HPMCAS-HF) polymers for solubility enhancement as well as enhanced physicochemical stability of the produced amorphous solid dispersions. This was accomplished by converting the poorly water-soluble crystalline form of carbamazepine into a more soluble amorphous form within the polymeric blends. Carbamazepine (CBZ), a Biopharmaceutics Classification System class II active pharmaceutical ingredient (API) with multiple polymorphs, was utilized as a model drug. Hot-melt extrusion (HME) processing was used to prepare solid dispersions utilizing blends of polymers. Drug loading showed a significant effect on the dissolution rate of CBZ in all of the tested ratios of Soluplus® and HPMCAS-HF. CBZ was completely miscible in the polymeric blends of Soluplus® and HPMCAS-HF up to 40% drug loading. The extrudates were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and dissolution studies. DSC and XRD data confirmed the formation of amorphous solid dispersions of CBZ in the polymeric blends of Soluplus® and HPMCAS-HF. Drug loading and release of CBZ was increased with Soluplus® (when used as the primary matrix polymer) when formulations contained Soluplus® with 7-21% (w/w) HPMCAS-HF. In addition, this blend of polymers was found to be physically and chemically stable at 40°C, 75% RH over 12 months without any dissolution rate changes.

Investigation of phase diagrams and physical stability of drug-polymer solid dispersions.

Solid dispersion technology has been widely explored to improve the solubility and bioavailability of poorly water-soluble compounds. One of the critical drawbacks associated with this technology is the lack of physical stability, i.e. the solid dispersion would undergo recrystallization or phase separation thus limiting a product's shelf life. In the current study, the melting point depression method was utilized to construct a complete phase diagram for felodipine (FEL)-Soluplus® (SOL) and ketoconazole (KTZ)-Soluplus® (SOL) binary systems, respectively, based on the Flory-Huggins theory. The miscibility or solubility of the two compounds in SOL was also determined. The Flory-Huggins interaction parameter χ values of both systems were calculated as positive at room temperature (25 °C), indicating either compound was miscible with SOL. In addition, the glass transition temperatures of both solid dispersion systems were theoretically predicted using three empirical equations and compared with the practical values. Furthermore, the FEL-SOL solid dispersions were subjected to accelerated stability studies for up to 3 months.

The use of inorganic salts to improve the dissolution characteristics of tablets containing Soluplus®-based solid dispersions.

The dissolution enhancement advantages inherent to amorphous solid dispersions systems are often not fully realized once they are formulated into a solid dosage form. The objective of this study was to investigate the ability of inorganic salts to improve the dissolution rate of carbamazepine (CBZ) from tablets containing a high loading of a Soluplus®-based solid dispersion. Cloud point and viscometric studies were conducted on Soluplus® solutions to understand the effect of temperature, salt type and salt concentration on the aqueous solubility and gelling tendencies of Soluplus®, properties that can significantly impact dissolution performance. Studies indicated that Soluplus® exhibited a cloud point that was strongly dependent on the salt type and salt concentration present in the dissolving medium. The presence of kosmotropic salts dehydrated the polymer, effectively lowering the cloud point and facilitating formation of a thermoreversible hydrogel. The ability of ions to impact the cloud point and gel strength generally followed the rank order of the Hofmeister series. Solid dispersions of CBZ and Soluplus® were prepared by KinetiSol® Dispersing, characterized to confirm an amorphous composition was formed and incorporated into tablets at very high levels (70% w/w). Dissolution studies demonstrated the utility of including salts in tablets to improve dissolution properties. Tablets that did not contain a salt or those that included a chaotropic salt hydrated at the tablet surface and did not allow for sufficient moisture ingress into the tablet. Conversely, the inclusion of kosmotropic salts allowed for rapid hydration of the entire tablet and the formation of a gel structure with strength dependent on the type of salt utilized. Studies also showed that, in addition to allowing tablet hydration, potassium bicarbonate and potassium carbonate provided effervescence which effectively destroyed the gel network and allowed for rapid dissolution of CBZ. Subsequent dissolution studies in 0.1 N HCl showed that potassium bicarbonate was an effective tablet disintegrant at levels as low as 1% and provided for tablets that rapidly disintegrated over a wide range of applied compression forces, presumably due to synergy between the ability to form a weak hydrogel structure and carbon dioxide liberation. Similar dissolution performance was measured in pH 4.5 acetate buffer, despite reduced polymer solubility caused by kosmotropic salts in solution, demonstrating robustness. With the use of inorganic salts such as potassium bicarbonate, it may be possible to substantially improve disintegration and dissolution characteristics of tablets containing Soluplus®.

Soluplus® as an effective absorption enhancer of poorly soluble drugs in vitro and in vivo.

As many new active pharmaceutical ingredients are poorly water soluble, solubility enhancers are one possibility to overcome the hurdles of drug dissolution and absorption in oral drug delivery. In the present work a novel solubility enhancing excipient (Soluplus®) was tested for its capability to improve intestinal drug absorption. BCS class II compounds danazol, fenofibrate and itraconazole were tested both in vivo in beagle dogs and in vitro in transport experiments across Caco-2 cell monolayers. Each drug was applied as pure crystalline substance, in a physical mixture with Soluplus®, and as solid solution of the drug in the excipient. In the animal studies a many fold increase in plasma AUC was observed for the solid solutions of drug in Soluplus® compared to the respective pure drug. An effect of Soluplus® in a physical mixture with the drug could be detected for fenofibrate. In vitro transport studies confirm the strong effect of Soluplus® on the absorption behavior of the three tested drugs. Furthermore, the increase of drug flux across Caco-2 monolayer is correlating to the increase in plasma AUC and C(max)in vivo. For these poorly soluble substances Soluplus® has a strong potential to improve oral bioavailability. The applicability of Caco-2 monolayers as tool for predicting the in vivo transport behavior of the model drugs in combination with a solubility enhancing excipient was shown. Also the improvement of a solid dispersion compared to physical mixtures of the drugs and the excipient was correctly reflected by Caco-2 experiments. In the case of fenofibrate the possible improvement by a physical mixture was demonstrated, underscoring the value of the used tool as alternative to animal studies.

Effect of water-soluble polymers on the physical stability of aqueous polymeric dispersions and their implications on the drug release from coated pellets.

PURPOSE: To investigate the physical stability and drug release-related properties of the aqueous polymer dispersions Kollicoat((R)) SR 30 D and Aquacoat((R)) ECD (an ethylcellulose-based dispersion) in the presence water-soluble polymers (pore formers) with special attention to the potential flocculation of the polymer dispersions. METHODS: A precise characterization of the flocculation phenomena in undiluted samples was monitored with turbidimetric measurements using the Turbiscan Lab-Expert. Theophylline or propranolol HCl drug-layered pellets were coated with Kollicoat((R)) SR 30 D and Aquacoat((R)) ECD by the addition of water-soluble polymers polyvinyl pyrrolidone (Kollidon((R)) 30 and 90 F), polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat((R)) IR), and hydroxypropyl methylcellulose (Pharmacoat((R)) 603 or 606) in a fluidized bed coater Glatt GPCG-1 and drug release was performed according to UPS paddle method. RESULTS: Stable dispersions were obtained with both Kollicoat((R)) SR 30 D (a polyvinyl acetate-based dispersion) and Aquacoat((R)) ECD with up to 50% hydrophilic pore formers polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat((R)) IR) and polyvinyl pyrrolidone (Kollidon((R)) 30). In general, Kollicoat((R)) SR 30 D was more stable against flocculation than Aquacoat((R)) ECD. Stable dispersions were also obtained with higher amounts of water-soluble polymer or by reducing the concentration of the polymer dispersion. Flocculated dispersions resulted in porous films and, thus, in a sharp increase in drug release. CONCLUSIONS: Kollicoat((R)) SR 30 D was more resistant to flocculation upon addition of water-soluble polymers than Aquacoat((R)) ECD. The continuous adjustment of drug release from Kollicoat((R)) SR 30-coated pellets was possible with Kollicoat((R)) IR amounts over a broad range.

Dissolution rate improvement of poorly water-soluble drugs obtained by adsorbing solutions of drugs in hydrophilic solvents onto high surface area carriers.

The dissolution rate of the model drugs carbamazepine and nifedipine was improved by adsorbing solutions of the drugs in hydrophilic non-volatile or volatile solvents onto carriers with a large surface area. This was accomplished by dissolving the drug in methanol or the non-toxic hydrophilic liquids PEG 400 or 2-pyrrolidone, and adsorbing these solutions onto the surface of silica (Aerosil) or crosslinked polyvinylpyrrolidone (Kollidon CL-M). The solvent binding capacities decreased in the order of methanol, PEG 400, 2-pyrrolidone for Aerosil 200, 300, 380 and for Kollidon CL-M. Kollidon bound less liquid than Aerosil because of the smaller surface area. Differential scanning calorimetry measurements showed higher interactions between drugs and Kollidon compared to Aerosil, suggesting a low aggregation of precipitated drug particles. The drug release from the adsorbent systems was enhanced when compared to micronized drug and independent of the drug loading in the investigated range. The drugs were also dissolved in various liquid, paste-like or solid solubilisers (polyoxyl-40-hydrogenated castor oil (Cremophor RH 40), macrogol-15-hydroxystearate (Solutol HS), poloxamers (Lutrol F68, Pluronic F87NF and Pluronic L44NF) and adsorbed onto Kollidon. These adsorbent systems also exhibited an increased dissolution rate when compared to pure drug.