Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing

European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

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Research paper

Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing Meimei Zhang a,b, Houli Li b, Bo Lang b, Kevin O’Donnell b, Haohao Zhang a, Zhouhua Wang a, Yixuan Dong a, Chuanbin Wu a,⇑, Robert O. Williams III b,⇑ a b

School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, PR China Division of Pharmaceutics, The University of Texas at Austin, Austin, USA

a r t i c l e

i n f o

Article history: Received 12 February 2012 Accepted in revised form 29 June 2012 Available online xxxx Keywords: Thin film freezing Fenofibrate Amorphous solid dispersion Supersaturation dissolution Dosage form development

a b s t r a c t The objective of this study was to prepare amorphous fenofibrate (FB) solid dispersions using thin film freezing (TFF) and to incorporate the solid dispersions into pharmaceutically acceptable dosage forms. FB solid dispersions prepared with optimized drug/polymer ratios were characterized by modulated differential scanning calorimetry (MDSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific surface area measurements, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and supersaturation dissolution testing. Furthermore, a dry granulation technique was used to encapsulate the TFF compositions for in vitro dissolution and in vivo animal pharmacokinetic studies. The results showed that the TFF process produced amorphous, porous, microstructured, and stable solid dispersions with high surface areas. Development of solid oral dosage forms revealed that the performance of the FB containing solid dispersions was not affected by the formulation process, which was confirmed by DSC and XRD. Moreover, an in vivo pharmacokinetic study in rats revealed a significant increase in FB absorption compared to bulk FB. We confirmed that amorphous solid dispersions with large surface areas produced by the TFF process displayed superior dissolution rates and corresponding enhanced bioavailability of the poorly watersoluble drug, FB. Ó 2012 Elsevier B.V. All rights reserved.

1. Introduction The development of numerous active pharmaceutical ingredients (APIs) has been discontinued because of their low aqueous solubility corresponding poor bioavailability [1]. Some of these drugs belong to Biopharmaceutics Classification System (BCS) Class II compounds, which are characterized by having low aqueous solubility and high permeability. BCS Class II APIs are of particular interest to pharmaceutical scientists who are challenged to develop solubility enhancement strategies to increase oral bioavailability [2]. Techniques have been developed to address the low aqueous solubility challenges, including chemical modification, such as pro-drugs [3] and salt formation [4], or formulation methods, such as particle size reduction [5], co-crystal formation [6], inclusion

⇑ Corresponding authors. School of Pharmaceutical Sciences, Sun Yat-sen University, Zhongshan II Road 74, Guangzhou 510006, PR China. Tel.: +86 02039943120; fax: +86 02039943117 (C. Wu), Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712-1074, USA. Tel.: +1 512 471 4681; fax: +1 512 471 7474 (R.O. Williams). E-mail addresses: [email protected] (C. Wu), [email protected]. edu (R.O. Williams III).

complexes using cyclodextrins [7] and lipid formulations [8], and solid form changes, such as nanocrystals [9] and amorphous dispersions of API and polymers [10]. Of these techniques, amorphous solid dispersion is a useful approach to increase the dissolution rate of poorly soluble drugs and thereby improve their bioavailability [11], although this must be proven for each drug. Some recently used methods to prepare amorphous solid dispersions include mechanical milling [12], fusion [13], hot melt extrusion [14], spray drying [15], freeze drying [16], and supercritical fluid precipitation [17]. Thin film freezing (TFF) is a rapid freezing technology, which has been successfully applied to enhance the solubility of several poorly water-soluble drugs, such as itraconazole [1], danazol [18], and tacrolimus [19]. During the TFF process, droplets of API/ excipient(s) solution are rapidly frozen onto a cryogenically-cooled substrate to form an amorphous solid dispersion [20]. As the supercooling is extremely fast, the nucleation of API crystals is minimized or completely prevented, resulting in amorphous morphology when the formation of a vitrified solution occurs on the surface of the cryogenically-cooled substrate [21]. The resulting product is a solid dispersion in which drug is molecularly dispersed within a polymer matrix, which is acting as a stabilizer to keep the drug in an amorphous morphology [22]. As a result of the fast

0939-6411/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ejpb.2012.06.016

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

cooling rates, the TFF process has produced powders of poorly water-soluble APIs with high surface area, leading to improved dissolution rate and enhanced bioavailability in vivo [18]. Fenofibrate (FB), a pro-drug of fenofibric acid, is used for the treatment of hypertriglyceridemia, mixed dyslipidemia and hypercholesterolemia, since it can reduce the blood triglyceride levels, total cholesterol, and low density lipoprotein cholesterol levels. However, FB is a neutral, lipophilic drug (log P = 5.2), which is practically insoluble in water [22]. It is classified as a BCS class II drug, and its oral bioavailability of about 30% in humans has been reported [23]. Many approaches have been investigated to improve the solubility of FB in order to enhance its therapeutic efficacy, such as liposomes [23], microemulsions [24], nanosuspension [25], silica based formulations [26], micronized drug formulations [27], and nanocrystal formulation [28]. However, most of these formulations used either a special matrix of mesoporous silica [26], superdisintegrants [29] or surfactants [24], which are excipients lacking long-term biocompatibility [30], or involved technically challenging processes [31]. Some reports confirmed that silica might act as an immunogenic sensitizer and induce contact hypersensitivity. Also, the formulation should be carefully designed because the pore architecture of silica may greatly influence its biocompatibility, and high dose and long-term usage should be avoided [32]. In this study, thin film freezing was employed to enhance the performance of FB formulations, without adding surfactants or excipients with a large specific surface area. After lyophilization, the dried powder retained the shape of thin film, but was highly porous due to the channels created as the solvent(s) was sublimated. We hypothesize that the bioavailability of FB will be increased when formulated as a high surface area, amorphous solid dispersion by the TFF process and subsequently incorporated into a solid dosage form. In vitro dissolution tests and an in vivo pharmacokinetic study in rats were used to characterize the FB formulations. 2. Materials The following materials were purchased: FB (Advanced Technology & Industrial Co., Ltd., Hongkong, China); Fenofibric acid (Biofine International Inc., Vancouver, BC), Ketoprofen (Hawkins Pharmaceutical Crop., Minneapolis, MN), PROSOLVÒ SMCC 90 (JRS Pharma LP., Patterson, NY), Ac-Di-SolÒ (FMC BioPolymer, Philadelphia, PA), Pancreatin (MP Biomedical, ILC., Solon, OH), Magnesium stearate, Sodium carboxymethyl cellulose (CMC-Na), Sodium lauryl sulfate (SLS), Polysorbate 80 and NaOH (Spectrum Chemical Mfg. Corp. Garden, CA), KH2PO4, Hydrochloric acid, Phosphoric acid, Na3PO4
12H2O, 1,4-dioxane, acetonitrile and methanol (Fisher Scientific, Fair Lawn, NJ). The following materials were generously donated by suppliers: MethocelÒ E5 (Dow Chemical Comp., Midland, MI, USA); SoluplusÒ (BASF, Ludwigshafen, Germany), Hydroxypropyl methyl-cellulose phthalate NF (HP55, Shin Etsu Chemical, Tokyo, Japan), and Hydroxypropyl methylcellulose acetate succinate LF (HPMCAS-LF, Shin Etsu Chemical, Tokyo, Japan). All organic solvents used were HPLC grade. Other reagents used were at least ACS grade.

6.8 PBS, respectively. The test solutions were placed in a shaker incubator (Orbit Environ Shaker, Lab-Line Instrument) at 37 °C, 100 rpm for 24 h. Then, 5 mL of solution was withdrawn and filtered through a 0.2-lm PTFE filter (TargetÒ, National Scientific, USA). The first 4 mL of the filtrate was discarded to avoid concentration underestimation caused by filter adsorption. The filtrate sample was immediately diluted with methanol in a ratio of 1:1 (v/v) for determining the concentration of FB by high-HPLC method mentioned in 3.12. All solubility measurements were performed in triplicate.

3.2. Stabilizing effect of different polymers HPMC-E5 and Soluplus were pre-dissolved in 20 mL 0.1 N HCl (pH 1.2) solution at the ratio of 4-fold, 6-fold, and 8-fold of FB, respectively. HPMCP-55 and HPMCAS-LF were pre-dissolved in 20 mL PBS (pH 6.8) at the ratio of 4-fold, 6-fold, and 8-fold of FB, respectively. An excess amount of FB (3.2 mg) was added to the polymer solution. The test solutions were placed in the shaker incubator at 37 °C, 100 rpm for 24 h, and the concentrations of FB were measured as item 3.1.

3.3. Preparation of FB solid dispersions using TFF technology The TFF compositions investigated in this study are described in Table 1. The compositions were prepared by dissolving FB and excipients (two immediate release polymers and two enteric polymers) at a designed API-excipient ratio in 1,4-dioxane or a mixture of 1,4-dioxane and water (80:20, v/v) under magnetic stirring. Through the TFF apparatus [18], the FB–excipient feed solution was applied onto the cryogenic substrate, which was previously cooled to a temperature of 45 °C. The resultant frozen solids were collected and lyophilized using a VirTis Advantage bench top tray lyophilizer (The VirTis Company, Inc. Gardiner, NY, USA) as the temperature was increased from 40 to 25 °C over a period of 48 h. The obtained dry powders were stored in a desiccator at room temperature under vacuum.

3.4. Thermal analysis Thermal analysis of the FB solid dispersions and each component was conducted using modulated temperature DSC (Model 2920, TA Instruments, New Castle, DE) equipped with a cooling system. Dry nitrogen gas was used as the purge gas through the DSC cell at a flow rate of 40 mL/min. The mass of the empty sample pan (PerkinElmer Instruments, Norwalk, CT) was matched with that of the empty reference pan within ±0.2 mg, and then, 10– 15 mg of samples was weighed into the aluminum pans and subsequently crimped. Samples were heated at a ramp rate of 3 °C/min from 20 to 200 °C with modulation temperature amplitude of 0.21 °C/40 s for all studies. Data were analyzed using the TA Universal Analysis 2000 software (TA Instruments, New Castle, DE).

3. Methods

3.5. Powder X-ray diffraction (XRD)

3.1. Solubility of FB

All powder samples were examined by wide angle XRD using a Philips 1710 X-ray diffract meter equipped with a copper target and nickel filter (Philips Electronic Instruments Inc., Mahwah, NJ, USA). With the voltage of 40 kV and the current of 40 mA, samples were analyzed ranging from 5° to 50° at a step size of 0.05 2-theta degree and a dwell time of 2 s.

The equilibrium solubility (Ceq) of FB in 0.1 N HCl, deionized water, and pH 6.8 phosphate buffer solution (PBS) was determined using a shake-flask method. Excess amount of FB was added to glass vials containing 20 mL of 0.1 N HCl, deionized water or pH

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx Table 1 Fenofibrate solid dispersion compositions produced using the TFF process. Formulation FB–Soluplus FB–HPMC E5 FB–HPMCAS FB–HP55 a

Active (A) FB FB FB FB

Excipient (E) Ò

Soluplus HPMC E5 HPMCAS-LF HP55

Ratio (w/w) (A:E)

Solvent

Solids contenta (%)

1:4, 1:4, 1:4, 1:4,

1,4-Dioxane 1,4-Dioxane/water (8:2, v/v) 1,4-Dioxane 1,4-Dioxane

1.0 1.0 1.0 1.0

1:6, 1:6, 1:6, 1:6,

1:8 1:8 1:8 1:8

Solid content: it means the solid content in stock solution for TFF (w/v).

3.6. Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) Infrared spectra were acquired using a Bruker Equinox55 FTIR spectrophotometer (Karlsruhe, Germany) equipped with a deuterated triglycine sulfate detector and an attached attenuated total reflectance unit (ATR, Thermo Scientific, Hudson, NH). The scanning range was from 600 to 4000 cm 1 with a resolution of 4 cm 1. The TFF solid dispersions or corresponding physical mixtures were pressed against the diamond crystal of the ATR device. A pressure applicator with a torque knob was used to ensure that the same pressure was applied for all measurements. Background scanning and correction were carried out before each measurement, and all measurements were performed at room temperature. 3.7. Scanning electron microscope (SEM) Prior to imaging, samples were mounted onto aluminum stages using double-sided carbon tape and sputter coated using Electron Microscopy Sputter Coater (Electron Microscopy Sciences, USA) equipped with an Au source. Samples were exposed to the Au for 2.5 min and then examined using a Hitachi S-5500 field emission scanning electron microscope (Hitachi High-Technologies Corp., Tokyo, Japan) operating at an accelerating voltage of 10 kV. SEM images were captured with Quartz PCI software (Quartz Imaging Corporation, Vancouver, BC, Canada).

For FB–HP55 and FB–HPMCAS solid dispersions, supersaturated dissolution testing was performed under varying pH conditions. Aliquots equivalent to 3.5 mg of FB were weighed into the dissolution vessel containing 750 mL of 0.1 N HCl. After 2 h, 250 mL of 0.2 M Na3PO4 solution pre-heated to 37 ± 0.5 °C was added to the dissolution vessel adjusting the medium pH to approximately 6.8 [33,34]. The samples were withdrawn at 5, 30, 120, 125, 130, 140, 150, 180, 210, 240, 360, and 480 min and processed as described above. 3.10. Dosage form containing the solid dispersion powder In the present study, solid dispersions were encapsulated by preparing a dry granulation, which were made by combining the solid dispersions together with SMCC 90, magnesium stearate, and Ac-Di-SolÒ (Proctor Silex, Hamilton Beach, USA) according to the composition in Table 2. Then, the mixtures were compressed into slug tablets using a tablet press (Carver Press, Fred.S.Carver Inc., Menomonee Falls, WI, USA) equipped with a pressure sensor (ISI Industrial Sensors & Instruments, Inc., Austin, TX, USA) to control the force between 800 and 1000 kg. The slug tablets were ground and sieved to obtain granules sized between 20 and 70 mesh for capsule filling. Based on the desired FB content, the granules were filled into size 0 HPMC E5 capsules with the equivalent of 40 mg FB per capsule for further investigation. 3.11. Dissolution testing under sink conditions

3.8. Brunauer–Emmett–Teller (BET) specific surface area Specific surface areas were measured using a MonosorbÒ unit (Quantachrome Instruments, Boynton Beach, FL) with nitrogen as adsorbate gas. Powder samples were placed into the sample bulb, degassed for a minimum of 24 h at 30 °C prior to analysis using Thermoflow Degasser (Quantachrome Instruments, Boynton Beach, FL). 3.9. Dissolution testing under supersaturation conditions for the solid dispersions For the FB–HPMC E5 and FB–Soluplus solid dispersions, supersaturated dissolution testing was carried out under acidic conditions. The medium was composed of 900 mL 0.1 N HCl and maintained at 37 ± 0.5 °C in each vessel, and the paddle speed was 50 rpm [33,34]. An amount of drug composition equivalent to 50-times the aqueous solubility of FB (3.5 mg FB per vessel) was weighed into the vessel. During testing, 5 mL samples were withdrawn from the dissolution vessels with volume replacement after 5, 10, 30, 45, 60, 90, 120, 240, 360, and 480 min. The samples were immediately filtered using 0.2 lm PTFE syringe filter (TargetÒ, National Scientific, USA), and the first 4 mL of filtrate was discarded. To prevent precipitation, 0.5 mL filtrate was immediately diluted in 0.5 mL of methanol under vortex mixing and transferred into a 2 mL vial (VWR International, West Chester, PA) for HPLC analysis.

Dissolution testing under sink conditions was utilized according to USP 32 type II apparatus (paddle method) operating at 75 ± 0.02 rpm. Dissolution medium was deaerated by vacuum before use and maintained at 37 ± 0.5 °C. Capsules containing the equivalent of 40 mg of FB were placed into the dissolution vessels. For the immediate release formulation, the in vitro dissolution study was performed in 1000 mL of deionized water with 0.05 M sodium lauryl sulfate. For the enteric formulations, the dissolution medium was 900 mL of phosphate buffer (pH 6.8 ± 0.1) containing 0.1% pancreatin and 2% polysorbate 80. Aliquots of 1 mL were withdrawn at fixed time points of 5, 10, 20, 30, 45, 60, 90, and 120 min and then immediately filtered using 0.2 lm PTFE syringe filter (TargetÒ, National Scientific, USA). Then, 0.5 mL of filtrate was diluted in 0.5 mL of methanol under vortex mixing and transferred into a 2 mL vial (VWR International, West Chester, PA) for HPLC analysis. Each experiment was carried out in triplicate. 3.12. High performance liquid chromatography (HPLC) FB assay was determined using a Shimadzu LC-10A high performance liquid chromatography (HPLC) system (Shimadzu Corporation, Columbia, MD) equipped with a KinetexÒ, 2.6 lm, C18 4.6 mm  100 mm column (Phenomenex, Inc., Torrance, CA). The mobile phase was composed of acetonitrile/water (63:37, v/v), and the FB peak eluted at approximately 7 min at 25 °C with a flow rate of 1 mL/min. FB absorbance was measured at a wavelength of 288 nm.

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

Table 2 Composition of FB capsules prepared by compressing slug tablets, milling, and encapsulating the dry granulation mixture. Ingredients

Percentage (%)

Function

FB solid dispersion prepared by TFF process SMCC 90 Magnesium stearate Ac-Di-SolÒ

80

Active and carrier

13 1 6

Wetting agent Lubricant Disintegrant

3.13. In vivo pharmacokinetic studies An animal study was designed and approved by the University of Texas at Austin Institute of Animal Care and Use Committee (IACUC). Pre-catheterized male Wistar rats (body weight about 300– 350 g, Charles River Laboratories International, Inc., Wilmington, MA) were housed individually in cages and allowed to acclimatize for at least 3 days prior to the beginning of the study. The rats were deprived of food but provided with free access to water for 12 h prior to dosing and then allowed access to food post-dosing. Each group of rats (n = 6) was administered by gavage with one of the formulations at the dose of 27 mg/kg body weight. Each formulation and bulk FB was suspended in 2 mL of 0.3% sodium carboxymethyl cellulose (CMC-Na) solution and gavaged to rats within 2 min following preparation. Blood samples were taken at time points of 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, and 48 h after administration. At each time point, 300 lL of blood was taken from the jugular catheter followed by injecting the equal volume of warm normal saline back into the rats. Blood samples were collected into heparin-wetted tubes (LH, 500 I.U., Sagent Pharmaceuticals, Schaumburg, ILC), and plasma samples were obtained by centrifugation (4000  g, 25 °C, 5 min) and frozen at 20 °C until analysis.

(Pharsight Corporation, Mountain View, CA). Statistical comparisons were performed by two-tailed Student’s t-test assuming equal variances (a = 0.05). 4. Results and discussion 4.1. Physicochemical properties of FB solid dispersions Solid dispersions with FB/polymer blends at ratios of 1:4, 1:6, and 1:8 (by weight) were successfully prepared using the TFF process. FB is a highly crystalline hydrophobic molecule with characteristic crystalline peaks found at 12, 14.5, 16.2, 16.8, and 22.4 2-theta degrees [35]. The crystallinity of bulk FB and FB/polymer solid dispersions was examined by XRD and the patterns (Fig. 1) illustrated that the crystalline peaks of FB were absent in the solid dispersions composed of FB–HPMC E5, FB–HP55, and FB–HPMCAS, confirming amorphous FB in the solid dispersions. The ability of these excipients, HPMC E5, HP-55 and HPMCAS, to provide superior stability of formulation may be because of the cellulosic polymer backbone which can obstruct FB from interactions that could result in recrystallization [33,34]. However, it was noted that partial crystallinity existed in the FB–Soluplus composition at a ratio of 1:4 and disappeared when the ratio reached 1:6. This may be explained from the low Tg of Soluplus, which in turn led to a lower Tg for the solid dispersion composition when the FB content was high [36]. Further analysis was carried out using modulated DSC to study the thermal properties of the FB solid dispersions. The Tm of FB

3.14. Analysis of plasma samples FB is metabolized to the main active metabolite fenofibric acid by plasma and tissue esterases [22]. In this study, all plasma samples were quantified for fenofibric acid using HPLC–UV. Plasma samples (100 lL) were spiked with internal standard, 40 lL of 100 lg/mL Ketoprofen (PharmIn nova, Waregem, Belgium) in acetonitrile. Subsequently, 160 lL of acetonitrile was added in order to precipitate plasma proteins. The mixture was vortexed for 1 min, followed by centrifugation at 13,000g for 10 min. Finally, about 250 lL of clear supernatant was pipetted into a microvial (National Scientific Target, Atlanta, GA) and transferred to the autosampler for analysis using HPLC–UV method as described below [25]. A Dionex UltiMateÒ 3000 high performance liquid chromatography (HPLC) system (Dionex Corporation, Columbia, MD) equipped with an AcclaimÒ 120 column (2.5 lm, 150 mm  4.6 mm, C18) was used for chromatographic separation. The mobile phase consisted of acetonitrile/0.2% phosphoric acid solution (50:50, v/v), the flow rate was 1.0 mL/min at 40 °C, and the internal standard Ketoprofen and fenofibric acid had retention times of 9.2 and 18.5 min, respectively. The chromatograms were analyzed with Chromeleon Software, and the detection wavelength was 286 nm. A linear calibration curve over the concentration range of 0.02– 100 lg/mL was constructed with the recovery of the standard within an acceptable range of 97.0–102.9%. For 0.02, 2.5 and 80 lg/mL standard solutions, the intra-day variability was 5.67%, 1.14% and 1.06%, respectively (n = 5), and the inter-day variability was 6.87%, 2.53% and 2.16%, respectively. Standard non-compartmental pharmacokinetic parameters were calculated using the pharmacokinetic software WinNonlin

Fig. 1. X-ray powder diffraction patterns of bulk FB, polymers, and FB/polymer solid dispersions prepared using the TFF process.

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

disappeared in the thermograms of the solid dispersions of FB– HPMC E5, FB–HPMCAS, and FB–HP55 due to amorphization of FB when the ratio of FB/polymer was 1:6 and 1:8 (Fig. 2). Soluplus is a polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer. The polyethylene glycol graft segment reportedly melts into solution at about 40 °C, in which FB could dissolve and form an eutectic mixture [37]. In the thermograms of FB–Soluplus solid dispersions, the absence of a Tm of FB confirmed the formation of eutectic mixture of FB and Soluplus, as FB–Soluplus’s phase diagram pointed to eutectic behavior. These results are in agreement with the XRD results. SEM was employed to investigate the surface morphology of the samples. The image of bulk FB exhibited large, compact crystals at the micron-scale. In contrast, a highly porous structure of the FB solid dispersions was observed (Fig. 3). The porous microparticulate aggregates were loosely connected to form a spongelike structure with adjacent aggregates. No crystals of FB were observed because of the homogeneous blending of FB and polymers as a result of the rapid freezing process used to prepare the solid dispersions and the ability of the polymers to inhibit crystal growth. The XRD and MDSC results confirmed that FB was molecularly dispersed within polymers. Therefore, using the TFF process, there is no need to add excipient with huge specific surface area to facilitate the drug release [26]. To further investigate the effect of the TFF process on the morphology of the FB compositions and the mechanism of forming

5

amorphous solid dispersions, FTIR-ATR was used to investigate potential interactions between FB and the polymeric excipients. FB solid dispersions with the FB/polymer ratio of 1:6 and the corresponding physical mixture were chosen for further analysis. Interactions between drug and polymer may be relevant to stabilization of the solid dispersion in the high-energy amorphous state [38]. FB has four functional groups that can act as proton acceptors (i.e., two oxygen atoms of the carbonyl (C@O) and two hydroxyl (OAH) groups), but it lacks proton donors. There are few reports about FB forming hydrogen bonds with polymers typically used in pharmaceutical compositions [39]. The observed broader band shapes and less well resolved peaks in the FTIR-ATR spectra of the FB solid dispersion suggest the presence of amorphous FB (Fig. 4) [35]. Also, the shifts in the spectra of solid dispersions indicate that the strength of the FB–polymer hydrogen bonding was in the order of Soluplus Ò > HPMCAS > HP55 > HPMC E5. However, even the largest spectral shift found in the FB–Soluplus solid dispersion, between 1648 and 1635 cm 1, represented very weak drug–polymer interactions. This explains why the FTIR-ATR spectra of solid dispersions showed no obvious differences compared to those of the corresponding physical mixtures across the entire absorption bands of FB. Several studies have demonstrated that drug–polymer interactions are of importance, as it was found that the crystallization tendency of a series of benzodiazepines with different functional groups was only prevented when the compound was capable of forming hydrogen bonds with the carrier (i.e., a phospholipid) [40]. In contrast, it has also been argued that drug–polymer interactions are not necessary for stabilization of amorphous drug, but the anti-plasticizing effect of the polymer may play an important role. As the viscosity of the drug/polymer binary system increased, the diffusion of drug molecules necessary for recrystallization was inhibited [41]. In the present study, the type of polymer and the drug/polymer ratio, rather than hydrogen bonding, affected the amorphous character of FB, since amorphous FB in the FB–Soluplus solid dispersion was the least physically stable. Besides, the low Tg of Soluplus can facilitate FB recrystallizion since the FB molecules can diffuse through the polymer network more readily. 4.2. Supersaturation dissolution behavior of FB solid dispersions

Fig. 2. Modulated DSC profiles of FB solid dispersions prepared by TFF process with different drug/polymer ratios.

Equilibrium solubility (Ceq) of FB is an important parameter for investigating the dissolution of FB compositions under supersaturated conditions. Ceq was experimentally determined as follows: 0.07, 0.10, and 0.12 lg/mL in 0.1 N HCl, deionized water, and pH 6.8 PBS, respectively. Ceq increased slightly with increasing pH, since FB is a weak acid. But, the Ceq of less than 10 lg/mL indicated FB is poorly soluble in these media. Therefore, its dissolution may represent a rate-limiting step in the oral absorption of the drug. The degree of supersaturation is defined as the concentration (C) of drug dissolved in the dissolution media divided by the equilibrium solubility (Ceq) of crystalline FB in the dissolution media, that is, C/Ceq [42]. Addition of polymers can increase FB concentration in solution as Table 3 revealed. Polymers with supersaturation stabilizing effect provide increased levels of FB in solution excessing the equilibrium solubility through either physical and/or chemical interactions with FB molecules that inhibit precipitation [43]. In our study, polymers may inhibit nucleation or crystal growth by adsorption on the drug crystalline interface thereby preventing the crystal growth [34]. HPMCAS-LF and HPMC E5 showed the good concentration enhancing effect, which was in good agreement with other report [26], and our previous observation involving drug release and further confirmed our formulation optimization. Solid dispersions with the FB/polymer ratio of 1:6 were chosen for the supersaturated dissolution testing, and the drug release profiles are presented in Fig. 5 and summarized in Table 4. In

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

µ

µ

µ

µ

µ

µ

µ

µ

µ

µ

µ

µ

µ

Fig. 3. SEM micrographs of bulk FB and FB solid dispersions prepared by TFF process. (1) Bulk FB; (2) FB-Soluplus (1:4); (3) FB-Soluplus (1:6); (4) FB-Soluplus (1:8); (5) FBHPMC E5 (1:4); (6) FB-HPMC E5 = 1:6; (7) FB-HPMC E5 = 1:8; (8) FB-HPMCAS (1:4); (9) FB-HPMCAS (1:6); (10) FB-HPMCAS (1:8); (11) FB-HP55 (1:4); (12) FB-HP55 (1:6); and (13) FB- HP55 (1:8).

0.1 N HCl media, FB contained in the FB–HPMC E5 and FB–Soluplus solid dispersions dissolved rapidly reaching its maximum supersaturation within 30 min (Fig. 5A), and this immediate release is likely due to the highly porous microstructure of the TFF powder

and its ability to rapidly wet in the dissolution media. Also, the degree of supersaturation of FB–HPMC E5 was much greater than that of FB–Soluplus. It was attributed to the high-energy amorphous FB in FB–HPMC E5, which was superior to the eutectic

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Table 4 Parameters derived from supersaturated dissolution testing of FB solid dispersion compositions and their specific surface area (FB–HPMC E5 (1:6) and FB–Soluplus (1:6) solid dispersion performed in 900 mL of 0.1 N HCl solution for 8 h(n = 3); FB–HPMCAS (1:6) and FB–HP55 (1:6) solid dispersion performed in 750 mL of 0.1 N HCl for 2 h followed by pH adjustment 6.8 ± 0.5 of 0.2 M of tribasic sodium phosphate solution for 6 h (n = 3)). Formulations

AUCss0–8h (lg/mL min)

Bulk FB

34.22 ± 4.8(pH 1.2) 58.51 ± 2.44 (pH 6.8) 260.16 ± 13.42 369.16 ± 21.75 211.60 ± 12.01 373.08 ± 4.21

FB–Soluplus (1:6) FB–HPMC E5 (1:6) FB–HP55 (1:6) FB–HPMCAS (1:6)

Fig. 4. FTIR-ATR spectra of solid dispersions prepared by TFF (black line) process and the corresponding physical mixtures (red line). A: FB-Soluplus (1:6); B: FBHPMC E5 (1:6); C: FB-HPMCAS (1:6); D: FB-HP55 (1:6). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Table 3 The supersaturation degree of fenofibrate in different concentration of polymers solutions (FB–HPMC E5 and FB–Soluplus performed in 20 mL of 0.1 N HCl solution for 24 h (n = 3); FB–HPMCAS and FB–HP55 performed in 20 mL pH 6.8 ± 0.5 of phosphate buffer for 24 h (n = 3)). Supersaturation (C/ Ceq)

Drug–polymer (1:4)

Drug–polymer (1:6)

Drug–polymer (1:8)

FB–Soluplus FB–HPMC E5 FB–HP55 FB–HPMCAS

2.58 ± 0.38 5.49 ± 0.59 2.05 ± 0.57 3.19 ± 0.54

2.63 ± 0.19 5.45 ± 0.68 2.51 ± 0.75 3.43 ± 0.64

3.22 ± 0.95 5.92 ± 0.32 3.08 ± 0.74 3.74 ± 0.53

Fig. 5. Supersaturation dissolution profiles of FB released from different solid dispersion compositions. (A) Testing was performed in 900 mL of 0.1 N HCL solution for 8 h (n = 3) and (B) testing was performed in 750 mL of 0.1 N HCl for 2 h followed by pH adjustment 6.8 ± 0.5 of 0.2 M of tribasic sodium phosphate solution for 6 h (n = 3).

mixture of FB in FB–Soluplus. As opposed to an amorphous dispersion, which contains the drug and carrier in an amorphous state, an eutectic mixture comprises an intimate mixture of amorphous and crystalline drug, hence a two-phase system [44]. In this respect, FB

Specific surface area (m2/g) 0.66 ± 0.43 25.07 ± 1.51 36.67 ± 0.58 41.67 ± 1.15 36.72 ± 0.78

may exist as crystalline or a mixture of crystalline and amorphous drug. SoluplusÒ was not able to prevent crystallization of FB in the solid dispersion formulation, which resulted in reducing the degree of supersaturation of FB. At the first 2 h in 0.1 N HCl, no FB dissolved from FB–HP55 and FB–HPMCAS compositions (Fig. 5B), indicating that FB was sufficiently entrapped by the hydrophobic enteric polymers to prevent dissolution in the acidic media. However, after the media was switched to pH 6.8 PBS buffer solutions, both the FB–HP55 and FB–HPMCAS compositions showed an immediate release, leading to the rapid onset of supersaturation, followed by a rapid decline in concentration toward the equilibrium solubility. As shown in Fig. 5B, at the 30 min time point, the FB–HP55 solid dispersion has FB dissolved at 9.35-times C/Ceq, while FB dissolved from the FB–HPMCAS solid dispersion reached 8.83-times C/Ceq. The maximum concentration reached in the supersaturation (Cmax(ss)) dissolution test for both solid dispersions was 1.12 ± 0.15 and 1.06 ± 0.18 lg/mL for the FB–HP55 and FB–HPMCAS solid dispersions, respectively. No significant differences were observed in degree of supersaturation (P > 0.05) between both compositions, but the ability to sustain the supersaturation was different between the compositions. Due to supersaturation, a drug concentration exceeds its thermodynamically solubility when the drug dissolves in a high-energy form. Then, crystal nucleation is initiated after a certain period of supersaturation, and the concentration of the drug falls to thermodynamically solubility of the stable form [45]. It is estimated that the absorbability of a drug in a high-energy form increases by increasing the effective concentration and period for intestinal absorption [46]. Therefore, the supersaturation sustainability is a critical value to evaluate the concentration and explore period of the amorphous form. After 8 h, the supersaturation was only 2-times C/Ceq for FB–HP55 compared to 6.4-times for FB– HPMCAS. The ability of HPMCAS to increase the degree and extent of dissolution of FB may be due to two properties. Firstly, HPMCAS is partially ionized above pH 5, which supports stable drug/polymer aggregates by steric stabilization, preventing merging into larger aggregates, and leading to easier release of free drug from the composition into solution [47]. Secondly, HPMCAS is an amphiphilic polymer. Its hydrophobic regions may provide sites to enhance the drug’s solubility, while its hydrophilic regions may promote the formation of stable hydrated colloidal structures in aqueous media [1]. In contrast, HP-55, an enteric polymer derived from HPMC, contains a higher degree of substitution (i.e., phthalic acid) than HPMCAS. As the polymers containing the phthalate moieties are very susceptible to hydrolysis, they may have an undesirable effect on the stability of formulations. The formulation may have acid-stability at first, but its stability is gradually decreased over time [48]. This report was in agreement with our supersaturation dissolution results. FB reached a high degree of supersaturation in the first minutes followed by a rapid decline, which was due to the dissolving of HP-55 and more phthalic acid dissociating.

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

With 27–35% phthalyl substitution for HP-55 versus 14–18% succinoyl substitution, the HP-55 polymer contained substantially more hydroxyl groups to reduce the FB in solution than HPMCAS due to the local acidic environment [44,49]. Since FB is a weakly acidic drug, the greater dissolved phthalic acid in solution decreased the solubility of FB. The area-under-the-concentration–time profile of the supersaturation dissolution curve (AUCss) represents an overall measure of the extent of supersaturation, taking into account both the degree and the duration of supersaturation (Table 4). The results shown in Fig. 5 and Table 4 clearly demonstrated that FB solid dispersions prepared by the TFF process were successful in enhancing and maintaining FB in solution, which may certainly increase the exposure of dissolved FB in the gastro-intestinal tract and thus may lead to an increase in the absorption and bioavailability of FB [42]. The results of BET surface area measurements (Table 4) were in good agreement with those observed by SEM and the supersaturated dissolution studies. The TFF process dramatically increased the surface area of the aggregates of FB/polymer compositions by at least 40-times that compared to the bulk FB powder. It is generally recognized that the surface area and morphology of drug containing particles can significantly influence the drug release characteristics through both kinetic and thermodynamic effects [34]. The significant increase in surface area facilitated the increase in dissolution rates of FB in the in vitro and in vivo studies [26]. FB– HP55 showed the largest surface area compared to the other formulations, but somewhat unexpectedly, it also showed the poorest dissolution performance under supersaturated conditions, exhibiting the fastest recrystallization rate in the dissolution media (Fig. 5B). As discussed previously, the solubility of FB in solution is decreased in acidic aqueous solution, and the presence of a greater number of acidic functional groups on the polymer chain for HP-55 compared to HPMCAS probably also contributed to the decreased extent of FB supersaturation in neutral pH media. The larger surface area of the FB–HP55 composition correlated with faster dissolution of HP-55, which contained more phthalyl acid substitution resulting in rapid decrease in FB solubility leading to precipitation in the media. Apart from the advantage of large surface area for the FB–HPMCAS composition, less degree of succinoyl acid in the dissolution medium was thought to be important to maintaining long-term supersaturation of FB. Thus, a high surface area will be essential to offer a sufficiently rapid dissolution rate, producing a higher sustained supersaturation and a greater AUCss. Based on the above studies, it can be concluded that FB–HPMC E5 and FB–HPMCAS compositions at the drug/polymer ratio of 1:6 offered a greater ability to obtain sufficiently sustained extent of supersaturation of FB, so these two FB compositions were chosen for the stability and dosage form development studies.

4.3. Stability study A stability study was conducted on FB–HPMC E5 and FB–HPMCAS solid dispersions at 25 °C/30% RH for 3 months to examine any changes in crystallinity. MDSC results confirmed that the crystallinity of FB did not change (Fig. 6), and the XRD patterns exhibited no change in peak intensity of FB over the 3-month period for either composition. Besides, the supersaturated dissolution results illustrated that the maximum degree of supersaturation was somewhat different between the stability time points (Fig. 7). The AUCss(0–8h) values of FB–HPMC E5 were 369.16 ± 21.75, 389.95 ± 27.10 and 360.42 ± 31.21 lg/mL h for initial, 1-month and 3-month time points, respectively (RSD = 5.12%). While the AUCss(0–8h) values of FB–HPMCAS were 373.08 ± 4.21, 386.06 ± 6.03 and 381.11 ± 3.23 lg/mL h for initial, 1-month and 3-month time points (RSD = 1.72%) for initial, 1-month and 3-month time points,

Fig. 6. MDSC and XPD profiles of FB–HPMC E5 and FB–HPMCAS solid dispersions prepared by TFF process after 3 months storing at 25 °C/30% RH.

Fig. 7. Supersaturation dissolution profiles of solid dispersions prepared by TFF process after 3 months storage at 25 °C/30% RH. (A) FB-HPMC E5 (1:6) solid dispersion performed in 900 mL of 0.1 N HCl solution for 8 h (n = 3); (B) FB-HPMCAS (1:6) solid dispersion performed in 750 mL of 0.1 N HCl for 2 h followed by pH adjustment 6.8 ± 0.5 of 0.2 M of tribasic sodium phosphate solution for 6 h (n = 3).

respectively. These data indicate good stability of the compositions over the 3-month time period at 25 °C/30% RH.

4.4. Studies on granules prepared from solid dispersions Compared to the bulk FB, the solid dispersions prepared by the TFF process had about a 40-times greater surface area. After compressing the powder blend into the slug tablets, the surface areas of FB–HPMCAS and FB–HPMC E5 dry granulation from the milled slug tablets was reduced to 12.49 ± 0.17 and 14.86 ± 0.06 m2/g, respectively, representing only about one-third of the initial surface area of the solid dispersions prepared by the TFF process. Based on the Noyes–Whitney equation, the mass transfer rate of solute

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

particles into a solvent is related to the diffusion coefficient, the surface area of the FB particles, the concentration of the FB particles at the boundary layer, and the thickness of the boundary layer. However, after compaction of the TFF powder into slug tablets, the system was much more complex than just considering the change in surface area. It was possible that the amorphous FB would have an immediately release after the granules came into contact with the dissolution medium. At the same time, FB might recrystallize rapidly due of supersaturation and subsequent precipitation into the dissolution media [50]. Polymer dissolved in the dissolution medium acting as a stabilizer may surround the dissolved drug molecules to prevent the recrystallization. However, compression of the granulation resulted in slower wetting and dissolution of the polymer; therefore, the propensity of FB recrystallization was increased [51]. The dissolution profiles (at sink conditions) of FB contained in FB–HPMC E5 and FB–HPMCAS granules released from the capsules and physical mixtures are compared in Fig. 9. After 3 months storage at 25 °C/30% RH, XRD showed a small characteristic crystalline (Fig. 8A). Further study was carried out by MDSC. As Fig. 8B presented, the melting point of FB was absent in these two formulations even after 3 month storage, indicating an essentially amorphous nature. The dissolution release profiles of FB–HPMC E5 and FB– HPMCAS capsules remained unchanged, confirming the physical and chemical stability of the formulations. Both FB–HPMC E5 and FB–HPMCAS capsules dissolved such that more than 80% of FB was dissolved within 30 min, representing the successful development of a FB formulation exhibiting rapid dissolution. The rapid dissolution rate of FB from the capsules is mainly attributed to the stable, high surface area, and amorphous state of FB. Fig. 9 also shows that there is almost no drug released in the first 10 min because the HPMC capsule shell takes this long to dis-

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Fig. 9. Dissolution profiles of FB–HPMC E5 (A) and FB–HPMCAS (B) capsules at sink conditions after 3 months storage at 25 °C/30% RH. (A) The test was performed in 1000 mL of deionized water with 0.05 M sodium lauryl sulfate (n = 3) and (B) the test performed in 900 mL of phosphate buffer (pH 6.8 ± 0.1) containing 0.1% pancreatin and 2% polysorbate 80 (n = 3).

Fig. 10. Average plasma-drug concentration of Fenofibric acid following singledose oral administration of different formulations to Wistar rats (data presented are mean ± SD, n = 6, dose is 27 mg/kg).

solve. It was reported that VcapsÒ exhibited slower and more variable dissolution [52] than hard gelatin capsule. However, the low moisture content of VcapsÒ is necessary for high-moisture absorbing compositions, such as the amorphous FB solid dispersions. Molecules in an amorphous phase are capable of adsorbing a large amount of water. As the Tg of water is 136 K, water will act as a significant plasticizer, which may be lower the amorphous system’s Tg, and potentially make it unstable [53]. The specification for moisture content are 2–7% for the VcapsÒ HPMC shell corresponding to storage at RH of 10–60% and 13–16% for gelatin capsules corresponding to storage at RH 35–65% [52], which will benefit the long-term stability of the capsule contents. 4.5. In vivo pharmacokinetic study

Fig. 8. MDSC (A) and XPD (B) profiles of FB–HPMC E5 and FB–HPMCAS granules prepared by compassing TFF solid dispersions after 3 months storage at 25 °C/30% RH.

The plasma-drug concentration profiles of FB after single-dose oral administration of each formulation is presented in Fig. 10 and the corresponding pharmacokinetic parameters are summarized in Table 5. As seen in Fig. 10, both FB–HPMC E5 and FB–HPMCAS granules suspended in 0.3% CMC-Na solution showed much higher drug concentration in plasma than bulk FB similarly administered. There are evidenced by FB–HPMCAS and FB–HPMC E5 solid dispersions, which showed high supersaturation degree in vitro and also had higher Cmax in vivo. In this case, FB–HPMCAS and FB–HPMC E5

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

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M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx

Table 5 Pharmacokinetic parameters of fenofibrate formulations dosed in Wistar rats (dose: 27 mg/kg; n = 6; mean ± SD). Formulation

Tmax (h)

Cmax (lg/mL)

AUC0–48 (h lg/mL)

MRT (h)a

Bulk FB in 3.00 ± 0.63 2.57 ± 0.92 22.00 ± 5.38 9.72 ± 2.05 suspension FB:HPMC 1.42 ± 0.86 58.17 ± 14.43 462.78 ± 179.60 7.62 ± 0.78 E5 = 1:6 FB:HPMCAS = 1:6 2.25 ± 0.61 106.28 ± 13.41 866.60 ± 203.63 7.61 ± 1.24 a

Acknowledgment This study was supported by National Natural Science Foundation of China (No. 81173002), National Science & Technology Pillar Program (No. 2012BAI35B02) and International Science & Technology Cooperation and Communication Program of China (No.2008DFA31080). And the authors gratefully acknowledge financial support from the China Scholarship Council and Enavail LLC (Austin, TX).

MRT: mean residence time (MRT).

References granules were dissolved and formed supersaturated solutions resulting in excellent absorption in vivo. The FB–HPMC E5 granule suspension showed the shortest Tmax (1.42 h), which was in agreement with the results of the in vitro dissolution study and was due to the rapid onset of supersaturation. Since HPMCAS is a pH sensitive polymer, which dissolves at pH > 5, the Tmax of FB–HPMCAS granule suspension was 2.25 h. As FB is well absorbed from the stomach to distal small bowel [54], the significant enhancement in oral absorption of FB for both FB–HPMC E5 and FB–HPMCAS granule suspensions was mainly due to the amorphous solid dispersion, which provided a rapid increase in free-drug concentration, and the ability to maintain enhanced drug supersaturation levels for a relatively long period of time in the upper gastrointestinal tract. Fig. 10 also shows that the FB–HPMCAS granule suspension exhibited higher plasma-drug concentration than the FB–HPMC E5 granule suspension. With a similar mean residence time (MRT) in rats, the relative bioavailability of FB from the FB–HPMCAS granule suspension was 187.57%, compared to that of the FB–HPMC E5 formulation. Despite the fact that the maximum degree of supersaturation of FB–HPMC E5 was higher than that of the FB–HPMCAS (approximately 18:10), the Cmax(ss) for FB–HPMC E5 and FB–HPMCAS were 0.13 lg/mL and 0.12 lg/mL, respectively. This indicates that complete dissolution in the proximal small intestine contributed to greater exposure of FB in the gastrointestinal tract and subsequently increases the mean plasma concentration. Additionally, HPMCAS showed a much stronger effect in enhancing FB concentration, which was concluded from the supersaturation dissolution study (Fig. 5), by remaining at least 6-times supersaturation for up to 8 h. Previously, most of the studies used high levels of surfactants or nano-porous silica, such as SylysiaÒ 350, to enhance the absorption of insoluble drugs like FB [55]. In the present study, significant enhancement of oral bioavailability was achieved with non-surfactant, non-porous excipients through TFF processing.

5. Conclusions Amorphous solid dispersions of FB were prepared with polymers by TFF processing. The predominant characteristics of the compositions were high surface area, microstructure, and good wettability, which resulted in an enhancement of drug dissolution. The rapid in vitro dissolution and the high degree of supersaturation, as well as the enhanced in vivo absorption demonstrated the success of these amorphous solid dispersion system prepared by TFF process. We also demonstrated that the dissolution and in vivo pharmacokinetic parameters were not compromised by the dry granulation process used to incorporate the TFF FB powders.

[1] D.T. Friesen, R. Shanker, M. Crew, D.T. Smithey, W.J. Curatolo, J.A.S. Nightingale, Hydroxypropyl methylcellulose acetate succinate-based spray-dried dispersions: an overview, Mol. Pharm. 5 (2008) 1003–1019. [2] D.B. Warren, H. Benameur, C.J.H. Porter, C.W. Pouton, Using polymeric precipitation inhibitors to improve the absorption of poorly water-soluble drugs: a mechanistic basis for utility, J. Drug Target. 18 (2010) 704–731. [3] V.J. Stella, K.W. Nti-Addae, Prodrug strategies to overcome poor water solubility, Adv. Drug Deliv. Rev. 59 (2007) 677–694. [4] A.T.M. Serajuddin, Salt formation to improve drug solubility, Adv. Drug Deliv. Rev. 59 (2007) 603–616. [5] H.G. Brittain, Effects of mechanical processing on phase composition, J. Pharm. Sci. 91 (2002) 1573–1580. [6] N. Qiao, M.Z. Li, W. Schlindwein, N. Malek, A. Davies, G. Trappitt, Pharmaceutical cocrystals: an overview, Int. J. Pharm. 419 (2011) 1–11. [7] M.D. Moya-Ortega, M. Messner, P. Jansook, T.T. Nielsen, V. Wintgens, K.L. Larsen, C. Amiel, H.H. Sigurdsson, T. Loftsson, Drug loading in cyclodextrin polymers: dexamethasone model drug, J. Inclus. Phenom. Macro. Chem. 69 (2010) 377–382. [8] M.A. Rahman, R. Harwansh, M.A. Mirza, S. Hussain, A. Hussain, Oral lipid based drug delivery system (LBDDS): formulation, characterization and application: a review, Curr. Drug Deliv. 8 (2011) 330–345. [9] R.H. Muller, S. Gohla, C.M. Keck, State of the art of nanocrystals – special features, production, nanotoxicology aspects and intracellular delivery, Eur. J. Pharm. Biopharm. 78 (2011) 1–9. [10] J.K. Lee, M.H. Lee, K.B. Kim, Synthesis of bulk amorphous composites with three amorphous phases by consolidation of milled amorphous powders, Intermetallics 18 (2010) 2019–2023. [11] A. Singh, Z.A. Worku, G. Van den Mooter, Oral formulation strategies to improve solubility of poorly water-soluble drugs, Exp. Opin. Drug Deliv. 8 (2011) 1361–1378. [12] L. Peltonen, J. Hirvonen, Pharmaceutical nanocrystals by nanomilling: critical process parameters, particle fracturing and stabilization methods, J. Pharm. Pharmacol. 62 (2010) 1569–1579. [13] J.C. DiNunzio, C. Brough, J.R. Hughey, D.A. Miller, R.O. Williams Iii, J.W. McGinity, Fusion production of solid dispersions containing a heat-sensitive active ingredient by hot melt extrusion and KinetisolÒ dispersing, Eur. J. Pharm. Biopharm. 74 (2010) 340–351. [14] J.P. Lalkshman, Y. Cao, J. Kowalski, A.T.M. Serajuddin, Application of melt extrusion in the development of a physically and chemically stable highenergy amorphous solid dispersion of a poorly water-soluble drug, Mol. Pharm. 5 (2008) 994–1002. [15] A. Alhalaweh, S. Andersson, S.P. Velaga, Preparation of zolmitriptan–chitosan microparticles by spray drying for nasal delivery, Eur. J. Pharm. Sci. 38 (2009) 206–214. [16] W. Yang, J. Tam, D.A. Miller, J. Zhou, J.T. McConville, K.P. Johnston, R.O. Williams, High bioavailability from nebulized itraconazole nanoparticle dispersions with biocompatible stabilizers, Int. J. Pharm. 361 (2008) 177–188. [17] A. Bouchard, Supercritical fluid drying of carbohydrates: selection of suitable excipients and process conditions, Eur. J. Pharm. Biopharm. 68 (2008) 781– 794. [18] K.A. Overhoff, J.D. Engstrom, B. Chen, B.D. Scherzer, T.E. Milner, K.P. Johnston, R.O. Williams, Novel ultra-rapid freezing particle engineering process for enhancement of dissolution rates of poorly water-soluble drugs, Eur. J. Pharm. Biopharm. 65 (2007) 57–67. [19] K.A. Overhoff, J.T. McConville, W. Yang, K.P. Johnston, J.I. Peters, R.O. Williams, Effect of stabilizer on the maximum degree and extent of supersaturation and oral absorption of tacrolimus made by ultra-rapid freezing, Pharm. Res. 25 (2008) 167–175. [20] K.A. Overhoff, K.P. Johnston, J. Tam, J. Engstrom, R.O. Williams, Use of thin film freezing to enable drug delivery: a review, J. Drug Deliv. Sci. Technol. 19 (2009) 89–98. [21] L. Yu, Amorphous pharmaceutical solids: preparation, characterization and stabilization, Adv. Drug Deliv. Rev. 48 (2001) 27–42. [22] M. Vogt, K. Kunath, J.B. Dressman, Dissolution improvement of four poorly water soluble drugs by cogrinding with commonly used excipients, Eur. J. Pharm. Biopharm. 68 (2008) 330–337. [23] Y.P. Chen, Y. Lu, J.M. Chen, J. Lai, J. Sun, F.Q. Hu, W. Wu, Enhanced bioavailability of the poorly water-soluble drug fenofibrate by using liposomes containing a bile salt, Int. J. Pharm. 376 (2009) 153–160.

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016

M. Zhang et al. / European Journal of Pharmaceutics and Biopharmaceutics xxx (2012) xxx–xxx [24] J.D. Wei, H.O. Ho, C.H. Chen, W.T. Ke, E.T.H. Chen, M.T. Sheu, Characterisation of fenofibrate dissolution delivered by a self-microemulsifying drug-delivery system, J. Pharm. Pharmacol. 62 (2010) 1685–1696. [25] X. Li, L. Gu, Y. Xu, Y. Wang, Preparation of fenofibrate nanosuspension and study of its pharmacokinetic behavior in rats, Drug Dev. Ind. Pharm. 35 (2009) 827–833. [26] Z. Jia, P. Lin, Y. Xiang, X. Wang, J. Wang, X. Zhang, Q. Zhang, A novel nanomatrix system consisted of colloidal silica and pH-sensitive polymethylacrylate improves the oral bioavailability of fenofibrate, Eur. J. Pharm. Biopharm. 79 (2011) 126–134. [27] K. Tziomalos, V.G. Athyros, Fenofibrate: a novel formulation (Triglide (TM)) in the treatment of lipid disorders: a review, Int. J. Nanomed. 1 (2006) 129–147. [28] F. Kesisoglou, S. Panmai, Y. Wu, Nanosizing—Oral formulation development and biopharmaceutical evaluation, Adv. Drug Deliv. Rev. 59 (2007) 631–644. [29] P. Srinarong, J.H. Faber, M.R. Visser, W.L.J. Hinrichs, H.W. Frijlink, Strongly enhanced dissolution rate of fenofibrate solid dispersion tablets by incorporation of superdisintegrants, Eur. J. Pharm. Biopharm. 73 (2009) 154– 161. [30] S. Wang, Ordered mesoporous materials for drug delivery, Micropor. Mesopor. Mater. 117 (2009) 1–9. [31] G.P. Sanganwar, R.B. Gupta, Dissolution-rate enhancement of fenofibrate by adsorption onto silica using supercritical carbon dioxide, Int. J. Pharm. 360 (2008) 213–218. [32] S. Lee, H.-S. Yun, S.-H. Kim, The comparative effects of mesoporous silica nanoparticles and colloidal silica on inflammation and apoptosis, Biomaterials 32 (2011) 9434–9443. [33] J.H. Hu, T.L. Rogers, J. Brown, T. Young, K.P. Johnston, R.O. Williams, Improvement of dissolution rates of poorly water soluble APIs using novel spray freezing into liquid technology, Pharm. Res. 19 (2002) 1278–1284. [34] J.C. DiNunzio, D.A. Miller, W. Yang, J.W. McGinity, R.O. Williams, Amorphous compositions using concentration enhancing polymers for improved bioavailability of itraconazole, Mol. Pharm. 5 (2008) 968–980. [35] A. Heinz, K. Gordon, C. McGoverin, T. Rades, C. Strachan, Understanding the solid-state forms of fenofibrate – a spectroscopic and computational study, Eur. J. Pharm. Biopharm. 71 (2009) 100–108. [36] H. de Waard, W.L.J. Hinrichs, H.W. Frijlink, A novel bottom-up process to produce drug nanocrystals: controlled crystallization during freeze-drying, J. Control. Release 128 (2008) 179–183. [37] H. Hardung, D. Djuric, Soluplus (R) a novel excipient for hot melt extrusion, Chim. Oggi – Chem. Today 28 (2010) XIV–XV. [38] R. Wang, C. Pellerin, O. Lebel, Role of hydrogen bonding in the formation of glasses by small molecules: a triazine case study, J. Mater. Chem. 19 (2009) 2747–2753. [39] Q.-P. Huang, J.-X. Wang, Z.-B. Zhang, Z.-G. Shen, J.-F. Chen, J. Yun, Preparation of ultrafine fenofibrate powder by solidification process from emulsion, Int. J. Pharm. 368 (2009) 160–164. [40] H. Konno, L.S. Taylor, Influence of different polymers on the crystallization tendency of molecularly dispersed amorphous felodipine, J. Pharm. Sci. 95 (2006) 2692–2705.

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[41] G. Van den Mooter, M. Wuyts, N. Blaton, R. Busson, P. Grobet, P. Augustijns, R. Kinget, Physical stabilisation of amorphous ketoconazole in solid dispersions with polyvinylpyrrolidone K25, Eur. J. Pharm. Sci. 12 (2001) 261–269. [42] W. Curatolo, J.A. Nightingale, S.M. Herbig, Utility of hydroxypropylmethylcellulose acetate succinate (HPMCAS) for initiation and maintenance of drug supersaturation in the GI Milieu, Pharm. Res. 26 (2009) 1419–1431. [43] M.E. Brewster, R. Vandecruys, G. Verreck, J. Peeters, Supersaturating drug delivery systems: effect of hydrophilic cyclodextrins and other excipients on the formation and stabilization of supersaturated drug solutions, Pharmazie 63 (2008) 217–220. [44] C. Goddeeris, T. Willems, G. Van den Mooter, Formulation of fast disintegrating tablets of ternary solid dispersions consisting of TPGS 1000 and HPMC 2910 or PVPVA 64 to improve the dissolution of the anti-HIV drug UC 781, Eur. J. Pharm. Sci. 34 (2008) 293–302. [45] S. Ozaki, T. Minamisono, T. Yamashita, T. Kato, I. Kushida, Supersaturationnucleation behavior of poorly soluble drugs and its impact on the oral absorption of drugs in thermodynamically high-energy forms, J. Pharm. Sci. 101 (2012) 214–222. [46] A. Newman, G. Knipp, G. Zografi, Assessing the performance of amorphous solid dispersions, J. Pharm. Sci. 101 (2012) 1355–1377. [47] D.A. Miller, J.C. DiNunzio, W. Yang, J.W. McGinity, R.O. Williams, Enhanced in vivo absorption of itraconazole via stabilization of supersaturation following acidic-to-neutral pH transition, Drug Dev. Ind. Pharm. 34 (2008) 890–902. [48] A. Riedel, C.S. Leopold, Degradation of omeprazole induced by enteric polymer solutions and aqueous dispersions: HPLC investigations, Drug Dev. Ind. Pharm. 31 (2005) 151–160. [49] H. Al-Obaidi, G. Buckton, Evaluation of griseofulvin binary and ternary solid dispersions with HPMCAS, AAPS PharmSciTech 10 (2009) 1172–1177. [50] D.E. Alonzo, Y. Gao, D. Zhou, H. Mo, G.G.Z. Zhang, L.S. Taylor, Dissolution and precipitation behavior of amorphous solid dispersions, J. Pharm. Sci. 100 (2011) 3316–3331. [51] D.J. van Drooge, W.L.J. Hinrichs, H.W. Frijlink, Anomalous dissolution behaviour of tablets prepared from sugar glass-based solid dispersions, J. Control. Release 97 (2004) 441–452. [52] M.M. Al-Tabakha, HPMC capsules: current status and future prospects, J. Pharm. Pharm. Sci. 13 (2010) 428–442. [53] P.J. Marsac, A.C.F. Rumondor, D.E. Nivens, U.S. Kestur, L. Stanciu, L.S. Taylor, Effect of temperature and moisture on the miscibility of amorphous dispersions of felodipine and poly(vinyl pyrrolidone), J. Pharm. Sci. 99 (2010) 169–185. [54] T. Zhu, J.C. Ansquer, M.T. Kelly, D.J. Sleep, R.S. Pradhan, Comparison of the gastrointestinal absorption and bioavailability of fenofibrate and fenofibric acid in humans, J. Clin. Pharmacol. 50 (2010) 914–921. [55] M. Van Speybroeck, R. Mellaerts, R. Mols, T. Do Thi, J.A. Martens, J. Van Humbeeck, P. Annaert, G. Van den Mooter, P. Augustijns, Enhanced absorption of the poorly soluble drug fenofibrate by tuning its release rate from ordered mesoporous silica, Eur. J. Pharm. Sci. 41 (2010) 623–630.

Please cite this article in press as: M. Zhang et al., Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing, Eur. J. Pharm. Biopharm. (2012), http://dx.doi.org/10.1016/j.ejpb.2012.06.016