Comparison of solvent⿿wetted and kneaded l -sulpiride⿿loaded solid dispersions: Powder characterization and in vivo evaluation

Accepted Manuscript Title: Comparison of solvent-wetted and kneaded L-sulpiride-loaded solid dispersions: Powder characterization and in vivo evaluation Author: Dong Shik Kim Jong Seo Choi Dong Wuk Kim Kyeong Soo Kim Youn Gee Seo Kwan Hyung Cho Jong Oh Kim Chul Soon Yong Yu Seok Youn Soo-Jeong Lim Sung Giu Jin Han-Gon Choi PII: DOI: Reference:

S0378-5173(16)30636-6 http://dx.doi.org/doi:10.1016/j.ijpharm.2016.07.006 IJP 15903

To appear in:

International Journal of Pharmaceutics

Received date: Revised date: Accepted date:

6-5-2016 20-6-2016 6-7-2016

Please cite this article as: Kim, Dong Shik, Choi, Jong Seo, Kim, Dong Wuk, Kim, Kyeong Soo, Seo, Youn Gee, Cho, Kwan Hyung, Kim, Jong Oh, Yong, Chul Soon, Youn, Yu Seok, Lim, Soo-Jeong, Jin, Sung Giu, Choi, Han-Gon, Comparison of solvent-wetted and kneaded l-sulpiride-loaded solid dispersions: Powder characterization and in vivo evaluation.International Journal of Pharmaceutics http://dx.doi.org/10.1016/j.ijpharm.2016.07.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Comparison of solvent–wetted and kneaded L-sulpiride–loaded solid dispersions: powder characterization and in vivo evaluation

Dong Shik Kim1,*, Jong Seo Choi1,*, Dong Wuk Kim1,*, Kyeong Soo Kim1, Youn Gee Seo2, Kwan Hyung Cho3, Jong Oh Kim2, Chul Soon Yong2, Yu Seok Youn4, Soo-Jeong Lim5, Sung Giu Jin1, ‡, Han-Gon Choi1, ‡

1

College of Pharmacy & Institute of Pharmaceutical Science and Technology, Hanyang

University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan 426-791, South Korea 2

College of Pharmacy, Yeungnam University, 214-1, Dae-Dong, Gyongsan 712-749, South

Korea 3

College of Pharmacy, Inje University, Inje-ro 197 Gimhae, 621-749, South Korea

4

School of Pharmacy, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon

440-746, South Korea 5

Department of Bioscience and biotechnology, Sejong University, Gunja-Dong, Seoul 143-

747, South Korea

* These authors contributed equally to this work.

‡

Corresponding author:

‡

Co-corresponding author:

Han-Gon Choi, Prof. Tel: +82-31-400-5802 Fax: +82-31-400-5958 E-mail: [email protected] Sung Giu Jin, Dr. Tel: +82-31-400-4784 Fax: +82-31-400-5958 E-mail: [email protected]

1

Graphical abstract

Abstract

The purpose of this study was to compare the powder properties, solubility, dissolution and oral absorption of solvent–wetted (SWSD) and kneaded (KNSD) L-sulpiride–loaded solid dispersions. The SWSD and KNSD were prepared with silicon dioxide, sodium laurylsulfate and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) using a spray dryer and high shear mixer, respectively. Their powder properties, solubility, dissolution and oral absorption were assessed compared to L-sulpiride powder. The drug in SWSD was in the amorphous state; however, in KNSD, it existed in the crystalline state. The SWSD with a drug/sodium laurylsulphate/TPGS/silicon dioxide ratio of 5/1/2/12 gave the higher drug solubility and dissolution compared to the KNSD with the same composition. The oral absorption of drug in the SWSD was 1.4 fold higher than the KNSD and 3.0 fold higher than the L-sulpiride powder (p < 0.05) owing to better solubility and reduced crystallinity. Furthermore, the SWSD at the half dose was bioequivalent of commercial L-sulpiride–loaded product in rats. Thus, the SWSD with more improved oral absorption would be recommended as an alternative for the Lsulpiride–loaded oral administration. 2

Key words: L-sulpiride; TPGS–based solid dispersion; solvent–wetted; kneaded; oral absorption

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1. Introduction

L-sulpiride, a benzamide derivative, has antiulcer, antidyspeptic, antidepressive and antiemetic effects owing to its specific D2- and D3- dopamine receptor antagonistic activity in the central and peripheral nervous systems. However, it provides low oral bioavailability (about 20 – 30%) since it is largely insoluble in water and poorly permeable in the gastro-intestinal tract. Moreover, its oral absorption is limited by the intestinal P-glycoprotein (Baluom et al., 2001; Cho and Lee, 2003; Cho et al., 2010). L-sulpiride is classified as a class IV drug according to the biopharmaceutical classification system (BCS) (Helmy, 2013; Hoosain et al., 2014). Thus, various L-sulpiride–loaded oral formulations, such as the gastric retained form (Kohri et al., 1996), matrix system with P-glycoprotein inhibitor (Baluom et al., 2001), sodium oleate mixture (Naasani et al., 1995), solid lipid nanoparticle (Ibrahim et al., 2014) and selfmicroemulsifying drug delivery systems (Chitneni et al., 2011) were developed to improve its oral bioavailability. Solid dispersion is a simple and industrially useful technique to increase the solubility and dissolution of poorly water–soluble drugs. Various methods have been studied for the fabrication of solid dispersion, including solvent evaporation, melting, solvent wetting and kneading (Lee et al., 2013; Rashid et al., 2015). However, the melting method can lead to decomposition of the drug since it requires a high preparation temperature. The solvent evaporation method requires large amounts of organic solvent because the drug and carrier must be dissolved in organic solvent (Vo et al., 2013). In comparison, the solvent wetting method requires minimal amounts of solvent in order to dissolve the poorly water–soluble drug (Kim et al., 2015b; Jang and Kang, 2014). The kneading method is economical and environmentally friendly. Moreover, the solid dispersion prepared using the kneading method 4

is very stable and more easily formulated in tablet dosage form in comparison with the solvent wetting and evaporation methods (Maulvi et al., 2011; Pandit et al., 2012). In the present study, the solvent wetting and kneading methods were chosen to prepare the solid dispersions with the aim of enhancing the dissolution rate and oral absorption of Lsulpiride. The powder properties and oral absorption of L-sulpiride were also investigated by the solvent–wetted (SWSD) and kneaded (KNSD) L-sulpiride–loaded solid dispersion approach. The SWSD and KNSD were prepared using a spray dryer and high shear mixer, respectively. The powder properties were characterized by particle size analysis, SEM (scanning electron microscopy), DSC (differential scanning calorimetry) and PXRD (powder X-ray diffraction). Moreover, the solubility, dissolution rate and pharmacokinetics in rats were compared between the L-sulpiride powder, physical mixture, SWSD and KNSD. In addition, pharmacokinetics were compared with the SWSD at the half dose and the commercial Lsulpiride–loaded product.

2. Materials and methods

2.1. Materials L-sulpiride and D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) were kindly provided by Hanmi Pharm. Co. (Hwasung, South Korea). Labrafac PG, Labrafil M 2125CS and Transcutol P were obtained from Gattefosse (Saint-Priest Cedex, France). Castor oil, corn oil, soybean oil, propylene glycol, sodium laurylsulphate and sorbitan monooleate 80 (Span 80) were obtained from Daejung Chemical Co. (Siheung, South Korea). Poloxamer 407 and Cremophore EL were purchased from BASF (Ludwigshafen, Germany). Silicon dioxide (Aerosil® 200) was obtained from Degussa (Frankfurt, Germany). The commercial Lsulpiride–loaded product (Levopride™; tablet form) was purchased from SK Pharm. Co. 5

(Seoul, South Korea). All other chemicals and solvents were of reagent grade and were used without additional purification.

2.2. Animals Male Sprague-Dawley rats (250 ± 20 g) were given with standard water and food. During the procedures, the experimental organisms were confined in cages under the following environmental conditions: temperature, 20-25 °C; relative humidity, 45-60%. Food was eliminated about 24 h before the onset of the pharmacokinetic evaluation procedures. However, the animals gave free access to drinking water. The procedures for the animal studies were consistent with NIH Policy and the Animal Welfare Act under the approval of the Institutional Animal Care and Use Committee (IACUC) at Hanyang University.

2.3. Solubility The solubility of L-sulpiride was evaluated for the selection of appropriate ingredients in the development of solid dispersion system. An excess of L-sulpiride powder was added to a 2 ml microtube containing 1 ml of lipids or 1% aqueous surfactant solution, and then vortexed. The tubes were kept on a mechanical shaker in a water bath (37 °C) and agitated at 100 rpm for 7 days. Afterwards, each sample was centrifuged at 10,000 g for 10 min (Hanil Science Industrial Co., Smart 15; Gangneung, South Korea). The supernatant was diluted with methanol and passed through a nylon disc filter (0.45 m). The concentration of L-sulpiride in the filtrate (10 l) was quantified by HPLC (Agilent 1220 Infinity, Agilent technologies, Santa Clara, CA, USA). An Inertsil Sil-100 column (GL Sciences Inc., 4.6 mm I.D. x 150 mm, 5 μm; Tokyo, Japan) was used for RP-HPLC analysis, with a column temperature of 30 °C. A mixture

6

of methanol and 20 mM KH2PO4 adjusted to pH 3.5 by phosphoric acid (4:6, v/v) was used as a mobile phase. A flow rate was 0.75 ml/min, and the eluent was monitored at 216 nm.

2.3. Preparation Solvent wetted L-sulpiride–loaded solid dispersion (SWSD) – The KNSD was prepared using mini spray-dryer (Büchi, Flawil, Switzerland). L-sulpiride, sodium laurylsulphate and TPGS, in various weight proportions, were dissolved in 1 L of 50% ethanol (Table 1). Subsequently, silicon dioxide (12 g) was suspended in these ethanol solution by magnetic stirring, and delivered through the pneumatic nozzle (0.7 mm diameter), leading to the SWSD. The air flow was fixed at the aspirator setting of 100%. The spraying air pressure was set at 4 kg/cm2. The inlet and outlet temperatures were 130 °C and 65 °C, respectively. Kneaded L-sulpiride–loaded solid dispersion (KNSD) – The KNSD was prepared using a high shear mixer (Diosna, Osnabrück, Germany). First, silicon dioxide (12 g) was added to the high shear mixer. Sodium laurylsulphate and TPGS (in concentrations determined according to formulation III in Table 1) were dissolved individually in 20 ml of 50% ethanol. Subsequently, L-sulpiride (5 g) was suspended in the above solution by magnetic stirring. The resulting mixture was added into the high shear mixer. After 10 min of kneading, the product was placed in an oven at 40 °C for 6 h. The dried product was sieved through a 250 µm mesh.

2.4. Solid characterization Powder X-ray diffraction (PXRD) – The crystallinities of the L-sulpiride powder, physical mixture, SWSD and KNSD were determined using an X-ray diffractometer (D/MAX2500 PC, Rigaku Co., Tokyo, Japan) equipped with a Miniflex Goniometer. The analysis was carried out at 25 °C using a Cu Kα1 monochromatic radiation source at 100 mA current and 40

7

kV voltage. X-ray diffraction patterns were given in the range of 3-50° with a 2θ scanning mode, a scan speed of 4°/minute and a step size of 2°/second. Differential scanning calorimetry (DSC) – Their thermal features of were assessed using a differential scanning calorimeter (DSC Q20, TA Instruments; New Castle, Delaware, USA). Each sample (about 5 mg) was sealed in an aluminium pan and subjected to heating over the range of 50 – 300 °C at the rate of 10 °C/min under a nitrogen flow of 50 ml/min. Scanning electron microscopy (SEM) – The morphological aspects of the L-sulpiride powder, silicon dioxide, SWSD and KNSD were investigated using a scanning electron microscope (S-4800, Hitachi; Tokyo, Japan). The samples were anchored on a brass sampling disc using double–sided adhesive carbon tape. These were then made electrically conductive with a sputter–coating of platinum using the EMI Teck Ion Sputter (K575K) under a vacuum (8 x 10-3 mbar) for 4 minutes at a current of 15 mA and 100% turbo speed. Particle size – The particle size analysis for the L-sulpiride powder, SWSD and KNSD was assessed using a Mastersizer (Malvern, Worcestershire, UK). The instrument was set with the air pressure of 1.0 bar and feed rate of 100%. Each sample was analyzed three times. The obtained results were expressed as d50 measured in volume, which indicated that 50% of the particles were below this size.

2.5. In vitro drug dissolution The dissolution experiment was performed using a USP dissolution apparatus II (paddle apparatus) (Vision® Classic 6TM, Hanson Research Co., Chatsworth, CA, USA). Each Lsulpiride–loaded solid dipsersion or drug powder equivalent to 25 mg L-sulpiride was put in a hard gelatine capsule. These capsules inserted into the sinker were immersed in the dissolution medium. The distilled water (900 ml) was used a dissolution medium. The dissolution test was performed at 37 ± 0.5 °C using a paddle rotation of 50 rpm. At predetermined time intervals, 5 8

ml of dissolution medium was withdrawn and filtered through a nylon disc filter (0.45 m). The concentration of L-sulpiride in the filtrate (10 l) was assayed by HPLC, as described above for the solubility test.

2.6. In vivo pharmacokinetics Pharmacokinetic studies of the L-sulpiride powder, physical mixture, SWSD, KNSD and commercial tablet at a dose of 10 mg/kg L-sulpiride were performed in rats. Moreover, the pharmacokinetics of SWSD a dose of 5 mg/kg L-sulpiride (half dose) was carried out. The rats in each group were orally administered a small hard capsule (#9, Suheung, Seoul, Korea) filled with the L-sulpiride powder, physical mixture, SWSD, KNSD or half dose of SWSD. In addition, each commercial L-sulpiride–loaded tablet was broken into small caplet form, and orally administered. The right femoral artery was cannulated with polyethylene tubing filled with a heparin solution (50 IU/ml) for blood sampling. After dose administration, 0.7 ml of blood was withdrawn from the cannulated right femoral artery at specified time points. The blood sample was centrifuged at 3000 g for 10 min. The collected plasma was stored at −20 °C until further use. Each 50 µl of tiapride (4 µg/ml in methanol, internal standard) and 100 µl of 1 N NaOH were added in 300 µl of plasma sample. It was extracted with 1.5 ml of methylene chloride, and centrifuged at 3000 g for 5 min. A volume of 150 μl of the mobile phase was added to dissolve the evaporated residue, and a 100 μl aliquot was automatically injected into the HPLC systems. The HPLC was performed on a Waters 2795 HPLC system consisting of a Waters 2795 separation module and a Waters 470 fluorescence detector. The column (4.6 mm I.D × 250 mm, 5 µm) was a HiChrome C18 column (HiChrome, Theale, UK). The mobile phase consisting of acetonitrile: 20 mM KH2PO4, pH 3.0 (3:7, v/v) was filtered (0.45 μm) and eluted at a flow rate of 0.8 ml/min. The eluents were monitored at 300 nm for excitation and 9

350 nm for emission. The inter-day and intra-day precision and accuracy were within the acceptable limits (r2 = 0.999).

3. Results and discussion

In this study, in order to overcome the low oral absorption of poorly water–soluble Lsulpiride, two solid dispersion systems, SWSD and KNSD were compared with the respect to powder characterization and in vivo pharmacokinetics (Baluom et al., 2001; Joe et al., 2010; Yang et al., 2013). First, in order to choose appropriate ingredients for the L-sulpiride–loaded solid dispersions, the drug solubility in various carriers, such as lipids and surfactants, was investigated (Fig. 1). Among the lipids and surfactants tested, TPGS (Fig. 1A) and sodium laurylsulphate (Fig. 1B) exhibited the highest L- sulpiride solubilities, with values of 618.6 ± 105.8 and 1233.0 ± 76.8 µg/ml, respectively. Thus, these ingredients were chosen for the preparation of solid dispersion formulations. In general, when the solid dispersions were prepared with relatively large amounts of TPGS, they gave a poorly flowing, waxy and sticky property due to the low melting point of TPGS (Pandey et al., 2013; Zhang et al., 2014a). Thus, in this study, silicon dioxide was together used as a carrier to avoid these problems. Silicon dioxide provided a good flow-ability and relatively large specific surface area; therefore, it enabled the creation of free-flowing solid dispersions in which the drug was highly dispersed (Kim et al., 2014; Zhang et al., 2014a). In order to select the optimal sodium laurylsulphate/TPGS ratio, various SWSD formulations were prepared with 5 g L-sulpiride, 12 g silicon dioxide, and various ratios of sodium laurylsulphate/TPGS (total weight: 3 g) using the spray drying technique; then, their drug solubility were investigated (Table 1, formulations I-IV). As the ratio of sodium 10

laurylsulphate/TPGS increased, the drug solubility significantly improved (Nkansah et al., 2013; Yousaf et al., 2015b). However, the formulation III with a sodium laurylsulphate/TPGS ratio of 1:2 showed no significant difference in drug solubility compared to the formulation IV with a sodium laurylsulphate/TPGS ratio of 1.5:1.5 (p > 0.05) (3.0 ± 0.5 vs. 3.2 ± 0.2 mg/ml). Sodium laurylsulphate, an anionic surfactant, is toxic in high oral doses (Hagi-Pavli et al., 2014). Thus, in order to maximize the drug solubility and minimize the surfactant concentration, a sodium laurylsulphate/TPGS ratio of 1:2 was selected. Next, in order to select the appropriate amounts of carriers, the SWSDs were prepared with various amounts of carriers (sodium laurylsulphate/TPGS ratio = 1:2), and their drug solubility was assessed (Table 1, formulation III, V and VI). The formulation III and VI with relatively high amount of carriers gave significantly improved drug solubility than did the formulation V (3.0 ± 0.5, 3.4 ± 0.6 vs. 1.6 ± 0.3 mg/ml); however, there was no significant difference in drug solubility between formulation III and VI (p > 0.05). Particularly, formulation III showed almost a 3 fold improvement in drug solubility compared to the drug powder (1.1 ± 0.2 mg/ml). Therefore, formulation III composed of L-sulpiride/sodium laurylsulphate/TPGS/silicon dioxide at a weight ratio of 5:1:2:12 was selected as the composition of the SWSD. Fig. 2 represents the scanning electron micrographs of L-sulpiride powder, KNSD and SWSD. The KNSD was prepared with the same composition of selected SWSD, Lsulpiride/sodium laurylsulphate/TPGS/silicon dioxide at a weight ratio of 5:1:2:12 using a high shear mixer. The L-sulpiride powder (Fig. 2A) and silicon dioxide (Fig. 2B) showed a flat– surfaced plate–shaped crystal and a porous round shape, respectively. The SWSD (Fig. 2C) had a rough–surfaced sphere–like shape, suggesting that soluble ingredients, such as the L-sulpiride, sodium laurylsulphate and TPGS, might exist in the pores of the silicon dioxide and attached onto the surface of the silicon dioxide. Moreover, the KNSD (Fig. 2D) showed an irregular and 11

non-round shape, indicating that ingredients might be attached primarily to the surface of the silicon dioxide (Baek and Cho, 2015; Bernabeu et al., 2014; Zhang et al., 2014b). In addition, the particle size of the L-sulpiride powder, SWSD and KNSD were 56.3 ± 0.8, 5.6 ± 0.2 and 84.7 ± 9.9 µm, respectively (raw data not shown). Our results indicated that the particle size of the drug was greatly decreased by the SWSD; oppositely, it was increased by the KNSD (Bartos et al., 2015; Kim et al., 2015a). Their PXRD and DSC patterns are given in Fig. 3. The physical mixture was prepared by simply mixing the same composition of SWSD using a geometric dilution. In the PXRD pattern, the L-sulpiride (3A-a) showed the sharp intrinsic peaks which are characteristic of a crystalline form. All the main intrinsic peaks of the drug were detected in the physical mixture (3A-b). However, there were no peaks in the SWSD (3A-c). On the other hand, the KNSD (3Ad) showed the intrinsic peaks characteristic of the drug, but with a lower intensity. In the DSC pattern, the L-sulpiride (3B-a) showed the endothermic peak at about 190°C, equivalent to its melting point and indicating its crystalline nature. The physical mixture (3B-b) showed the same endothermic peak as the drug. Like the PXRD pattern, the drug peak disappeared in the SWSD (3B-c). The KNSD (3B-g) showed the same endothermic peak as the drug, however, at a lower intensity compared to the physical mixture. A drug could be converted to the amorphous state in solvent–wetted solid dispersions (Joe et al., 2010; Rashid et al., 2015). Our PXRD and DSC results indicated that the drug in the SWSD was completely converted into the amorphous form (Mahmah et al., 2014; Yousaf et al., 2015c). However, in the KNSD, the drug existed partially in a microcrystalline state and was not entirely changed to the amorphous form. Thus, the KNSD method was insufficient for the complete transformation of L-sulpiride to the amorphous state (Alves et al., 2014; Yousaf et al., 2015a). The effect of two solid dispersions on the drug solubility and dissolution was investigated (Fig. 4). The aqueous solubilities of the L-sulpiride powder, physical mixture, 12

SWSD and KNSD were 0.72 ± 0.04, 1.70 ± 0.40, 2.61 ± 0.19 and 3.01 ± 0.09 mg/ml, respectively (Fig. 4A). The physical mixture significantly improved the drug solubility, indicating that the simple mixing of ingredients (L-sulpiride, sodium laurylsulphate and TPGS) was sufficient to improve solubility over the powdered form. However, the SWSD and KNSD significantly enhanced the drug solubility compared to the physical mixture. Additionally, the SWSD significantly improved the drug solubility than did and KNSD. Particularly, the SWSD enhanced the drug solubility about 4.2 fold over the drug. Similar to the solubility result, the physical mixture significantly increased the dissolution rates of the drug. Moreover, the solid dispersions gave higher dissolution rates than the physical mixture and L-sulpiride powder (Fig. 4B). Up to 30 min, the SWSD showed significantly higher initial dissolution rates compared to the KNSD, followed by similar dissolution rates to 120 min. Particularly, SWSD enhanced the drug dissolution by 5.2 fold compared with the L-sulpiride powder (17.8 ± 7.1 vs. 92.6 ± 2.3 % at 30 min). The SWSD considerably enhanced the solubility and dissolution of poorly water– soluble L-sulpiride due to reducing the particle size and converting the crystalline drug into the amorphous state (Khan et al., 2015; Oh et al., 2013; Sathigari et al., 2012). Moreover, such enhancement was owing to the wetting effect of solvent by the use of 50% ethanol (Kim et al., 2014; Patel et al., 2008). On the other hand, even though KNSD did enhance the solubility and dissolution of L-sulpiride, the improvement was lower for KNSD compared to SWSD. This might reflect the fact that the KNSD method did not lead to a reduction in particle size and only produced a partial conversion to the amorphous form (Yousaf et al., 2015c). Fig. 5 demonstrates the plasma level-time profiles of L-sulpiride after oral administration of the drug powder, physical mixture, KNSD and SWSD at a drug dose equivalent to 10 mg/kg in rats. The physical mixture, KNSD and SWSD were composed of the L-sulpiride/sodium laurylsulphate/TPGS/silicon dioxide at the weight ratio of 5:1:2:12. The 13

physical mixture gave higher plasma concentrations with a significant difference after 2 h compared with the drug powder. Until 4 h, the KNSD and SWSD showed significantly higher plasma concentration compared with drug powder and physical mixture. From 30 min to 2 h, the plasma concentration of the SWSD was significantly higher than that of the KNSD. The corresponding pharmacokinetic parameters are given in Table 2. As compared to each formulation, the AUC and Cmax values were significantly increased as follows; drug powder < physical mixture < KNSD < SWSD. In particular, the SWSD gave about 3 and 1.4 fold higher AUC compared to the L-sulpiride powder and KNSD, respectively. However, there were no significant differences in the other pharmacokinetic parameters, such as Tmax, t1/2 and Kel. The enhanced oral bioavailability of two solid dispersion, such as SWSD and KNSD, were likely a result of the increased solubility and dissolution (Lee et al., 2014; Kim et al., 2013; Kim et al., 2015c). In addition, such improvement might be due to the absorption enhancing effects of carriers and the P-glycoprotein inhibitory activity of TPGS. The carriers TPGS and sodium laurylsulfate played role as the absorption enhancers by reversibly opening tight junctions in the intestinal tracts, leading to increased paracellular permeability (Andey et al., 2015; Ates et al., 2016; Liu et al., 2014; Malathi et al., 2015). TPGS was reported to improve oral absorption through effective inhibition of efflux of several P-glycoprotein substrates containing L-sulpiride (Guo et al., 2013; Sun et al., 2014) as well as to be stabilization of amorphous drug state (Lee et al., 2015). Moreover, more improved oral bioavailability of L-sulpiride by the SWSD method compared to the KNSD may stem from its more increased solubility and dissolution due to the particle size reduction and complete conversion to an amorphous state (Oh et al., 2013; Sathigari et al., 2012; Yousaf et al., 2016). To develop a novel practical L-sulpiride–loaded SWSD, its pharmacokinetics after oral administration at the half dose to rats was carried out, and compared with the commercial Lsulpiride–loaded product. In this study, the administered doses of SWSD and the commercial 14

product were equivalent to 5 and 10 mg/kg L-sulpiride, respectively. The plasma level-time profiles of the L-sulpiride formulations are illustrated in Fig. 6. At all-time points, the plasma concentrations of L-sulpiride in the SWSD and commercial product were not significantly different. Moreover, the SWSD (half–dose) and commercial product provided no significant differences in the pharmacokinetic parameters, such as AUC (713.7 ± 35.1 vs. 757.7 ± 94.9 h·μg/ml), Cmax (293.6 ± 41.9 vs. 249.5 ± 32.0 μg/ml), Tmax (0.36 ± 0.16 vs. 0.36 ± 0.09 h), t1/2 (13.7 ± 0.9 vs. 14.1 ± 0.5 h) and Kel (0.051 ± 0.002 vs. 0.049 ± 0.005 h-1). Thus, the L-sulpiride– loaded SWSD at half–dose was bioequivalent to the commercial L-sulpiride–loaded product in rats.

4. Conclusion The SWSD formulation showed a greater improvement in the solubility, dissolution and oral absorption of poorly water–soluble L-sulpiride compared to the KNSD preparation. This enhancement was due to differences in the particle size reduction and the degree of conversion of crystalline drug into the amorphous state. Furthermore, in rats, the L-sulpiride–loaded SWSD at half–dose was bioequivalent to the commercial L-sulpiride–loaded product. Thus, the SWSD would be recommended as an alternative for L-sulpiride–loaded oral administration.

Acknowledgements This work was supported by the National Research Foundation of South Korea (NRF) grant funded by the South Korea government (MEST) (No. 2015R1A2A2A05027872).

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studies. Int. J. Pharm. 465(1–2), 306–316. FIGURE LEGENDS

Fig. 1. Aqueous solubility of L-sulpiride: (A) lipids; and (B) surfactant. Each value represents the mean + S.D. (n = 3). Fig. 2. Scanning electron micrographs: (A), L-sulpiride (×1000); (B), silicon dioxide (×3000); (C), SWSD (×5000); (D), KNSD (×400). Fig. 3. PXRD patterns (A) and DSC thermograms (B); (a) L-sulpiride; (b) physical mixture; (c) SWSD; (d) KNSD. Fig. 4. Drug solubility (A) and dissolution profiles (B) of KNSD and SWSD. Each value represents the mean + S.D. (n = 3 or 6). The physical mixture, KNSD and SWSD were composed of L-sulpiride/sodium laurylsulphate/TPGS/silicon dioxide at the weight ratio of 5:1:2:12. * p < 0.05 compared with drug powder. # p < 0.05 compared with drug powder and physical mixture. + p < 0.05 compared with drug powder, physical mixture and KNSD. Fig. 5. Mean plasma level-time profiles of L-sulpiride after oral administration of KNSD and SWSD at a drug dose equivalent to 10 mg/kg in rats. Each value represents the mean + S.D. (n = 6). The physical mixture, KNSD and SWSD were composed of Lsulpiride/sodium laurylsulphate/TPGS/silicon dioxide at the weight ratio of 5:1:2:12. * p < 0.05 compared with drug powder.

#

p < 0.05 compared with drug powder and

physical mixture. + p < 0.05 compared with drug powder, physical mixture and KNSD. Fig. 6. Mean plasma level-time profiles of L-sulpiride after oral administration of SWSD and commercial product in rats. The SWSD was composed of L-sulpiride/sodium laurylsulphate/TPGS/silicon dioxide at the weight ratio of 5:1:2:12. The SWSD and

22

commercial product were orally administered at the equivalent dose of 5 and 10 mg/kg L-sulpiride, respectively.

23

24 40

l

7

eG ly co

am er

le n

lo x

P

fa te

ol

ry lsu

cu t

L

80

rE

an

ho

ns

la u

py

Po

iu m

Pr o

So d

em op

Tr a

Cr

Sp

Solubility of levosulpiride (g/ml)

So yb ea n

oi l

oi l

ste ro il

Co rn

Ca

TP G S

La br af ac La PG br af il M 21 25 CS

Solubility of levosulpiride (g/ml)

A 800

600

400

200

0

B 1500

1200

900

600

300

0

Fig. 1

(A)

(B)

(C)

(D)

Fig. 2

25

A

(a) (b) (a) (b) (c)

(c) (d)

(d)

0

10

20

30

40

50

2θ [deg]

B (a) (b) (c) (d)

0

50

100

150

200

250

300

Temperature (oC)

Fig. 3

26

A + Solubility of levosulpiride (mg/ml)

3.0

# 2.5

*

2.0

1.5

1.0

0.5

0.0

os u Lev

ide lpir Ph

tu mix l a ysic

re

SD KN

SW

SD

B Dissolution rate (%)

100

80

60

40 Drug powder Physical mixture KNSD SWSD

20

0 0

20

40

60

80

100

120

Time (min)

Fig. 4

27

1000

Plasma concentration (ng/ml)

+ + 800

+

600

400

Drug powder Physical mixture KNSD SWSD

#

+

#

#

*

#

*

200

#

# #

0 0

2

4

6

8

Time (h)

Fig. 5

28

Plasma concentration (ng/ml)

400

300

Commercial product SWSD (half dose) 200

100

0 0

2

4

6

8

Time (h)

Fig. 6

Table 1. Composition and drug solubility of solvent–wetted solid dispersions.

Formulations (g)

I

II

III

IV

V

VI

levosulpiride

5

5

5

5

5

5

silicon dioxide

12

12

12

12

12

12

sodium laurylsulphate

-

0.6

1.0

1.5

0.5

1.5

TPGS

3.0

2.4

2.0

1.5

1.0

3.0

Drug solubility

1.1

1.8

3.0

3.2

1.6

3.4

(mg/ml)

± 0.2

± 0.4

± 0.5

± 0.2

± 0.3

± 0.6

All the materials were dissolved or dispersed in 1 L of 50% ethanol and spray–dried.

29

30

Table 2. Pharmacokinetic parameters after oral administration of KNSD and SWSD at a dose equivalent to 10 mg/kg levosulpiride in rats.

AUC

Cmax

Tmax

t1/2

Kel

(h·ng/ml)

(ng/ml)

(h)

(h)

(x 10-2, h-1)

768.5 ± 99.8

232.6 ± 47.8

0.31 ± 0.07

14.9 ± 0.8

4.7 ± 0.2

Physical mixture

1119.5 ± 265.5*

310.9 ± 16.0*

0.28 ± 0.09

15.2 ± 0.6

4.5 ± 0. 2

KNSD

1604.2 ± 306.0#

524.8 ± 52.8#

0.31 ± 0.07

14.9 ± 0.3

4.6 ± 0. 9

SWSD

2318.0 ± 225.1+

820.1 ± 12.6+

0.39 ± 0.14

14.1 ± 0.4

4.8 ± 0. 4

Parameter Drug powder

Each value represents the mean ± S.D. (n = 6). The physical mixture, KNSD and SWSD were composed of levosulpiride/sodium laurylsulphate/TPGS/silicon dioxide at the weight ratio of 5:1:2:12. * p < 0.05 compared with drug powder. #

p < 0.05 compared with drug powder and physical mixture.

+

p < 0.05 compared with drug powder, physical mixture and KNSD.

31