A Systematic Approach to the Development of Cilostazol Nanosuspension by Liquid Antisolvent Precipitation (LASP) and Its Combination with Ultrasound.

Nanosizing is an approach to improve the dissolution rate of poorly soluble drugs. The first aim of this work was to develop nanosuspension of cilostazol with liquid antisolvent precipitation (LASP) and its combination with ultrasound. Second, to systematically study the effect of bottom-up processing factors on precipitated particles' size and identify the optimal settings for the best reduction. After solvent and stabilizer screening, in-depth process characterization and optimization was performed using Design of Experiments. The work discusses the influence of critical factors found with statistical analysis: feed concentration, stabilizer amount, stirring speed and ultrasound energy governed by time and amplitude. LASP alone only generated particle size of a few microns, but combination with ultrasound was successful in nanosizing (d10 = 0.06, d50 = 0.33, d90 = 1.45 µm). Micro- and nanosuspension's stability, particle morphology and solid state were studied. Nanosuspension displayed higher apparent solubility than equilibrium and superior dissolution rate over coarse cilostazol and microsuspension. A bottom-up method of precipitation-sonication was demonstrated to be a successful approach to improve the dissolution characteristics of poorly soluble, BCS class II drug cilostazol by reducing its particle size below micron scale, while retaining nanosuspension stability and unchanged crystalline form.

A simple LC-MS/MS method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley rat plasma and its application to drug-drug pharmacokinetic interaction study following oral delivery in rats.

Recently, a combination of cilostazol and ambroxol has been used in the clinical treatment of stroke-associated pneumonia (SAP). However, the pharmacokinetic drug-drug interaction (DDI) of cilostazol and ambroxol has not been reported. In this paper, a rapid, reproducible and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley (SD) rat plasma was established and validated for the first time. Domperidone was used as the internal standard (IS) and one-step liquid-liquid extraction (LLE) method was used to extract analytes and IS from plasma samples with methyl tert-butyl ether as extractant. A rapid chromatographic separation within 4.8 min was carried on an Ultimate ® XB-C18 column with a mobile phase consisting of methanol-acetonitrile-formic acid (0.1%) aqueous solution (90:2:8, v/v/v) at a flow rate of 500 µL/min. The quantitative detection of the analytes and IS were performed on a positive electrospray ionization mode (ESI), and scanned by multi-reaction monitoring (MRM) with the ion transitions m/z 370.3 â†’ m/z 288.2 for cilostazol, m/z 378.8 â†’ m/z 263.8 for ambroxol and m/z 426.2 â†’ m/z 175.1 for domperidone (IS), respectively. It had good linearity in the range of 5.0-1000 ng/mL for cilostazol and 1.0-200 ng/mL for ambroxol in rat plasma. The methodology was fully validated with selectivity, linearity, lower limits of quantification, precision, accuracy, extraction recovery, matrix effect, stability and carry-over effect. The validated data have met the determination requirements of biological samples in FDA guideline. The method was successfully applied to the pharmacokinetics and DDI study of cilostazol and ambroxol in male SD rats. The current study found that the interaction between cilostazol and ambroxol may be caused by CYP3A4 and the pharmacological properties of cilostazol, which may be helpful for therapeutic drug monitoring, clinical dose reference and provide a valuable tool for drug-drug interactions.

A new simple method for quantification of cilostazol and its active metabolite in human plasma by LC-MS/MS: Application to pharmacokinetics of cilostazol associated with CYP genotypes in healthy Chinese population.

A simple, sensitive, and fully automated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous quantification of cilostazol (CIL) and its active metabolite, 3,4-dehydro cilostazol (CIL-M), in human plasma. Plasma samples were processed by protein precipitation in 2 mL 96-deep-well plates, and all liquid transfer steps were performed through robotic liquid handling workstation, enabling the whole procedure fast, compared to the reported methods. Separation of analytes was successfully achieved on a UPLC BEH C18 column (2.1 × 100 mm, 1.7 µm) with mobile phase A (5 mM ammonium formate containing 0.1% formic acid) and mobile phase B (methanol) at a flow rate of 0.30 mL min-1 . The total run time was 3.5 min per sample. Mass spectrometric detection was conducted by electrospray ion source in positive ion multiple reaction monitoring mode. Calibration curves were linear over the concentration range of 1.0-800 ng·mL-1 for CIL and 0.05-400 ng·mL-1 for CIL-M. The coefficient of variation for the assay's precision was 12.3%, and the accuracy was 88.8-99.8%. It was fully validated and successfully applied to assess the influence of CYP genotypes on the pharmacokinetics of CIL after oral administration of 50 mg tablet formulations of CIL to healthy Chinese volunteers. The results suggest that, in Chinese population, the genotype of CYP3A5 affects the plasma exposure of CIL.

Fabrication and evaluation of fast disintegrating pellets of cilostazol.

The present study was designed to formulate and develop fast disintegrating pellets of poorly soluble model drug (cilostazol) by reducing the proportion of micro-crystalline cellulose with pre-gelatinized starch (PGS), lactose and chitosan. The bioavailability enhancement of a model drug was achieved by preparing inclusion complex with Captisol® (Sulfobutyl Ether ß cyclodextrin - SBE-ß-CD). Extrusion-spheronization technique was used to formulate pellets. Placket-Burman design was used for the initial screening of most significant factors such as screen size (mm), ratio of micro crystalline cellulose: PGS + lactose + chitosan and % of HPMC which affects pellet properties. The inclusion complex of drug and Captisol® (SBE-ß-CD) was prepared by Solvent Evaporation method and were incorporated into pellets in a predefined proportion. Formulation was optimized by using 32 full factorial design, the optimized batch was selected on the basis of dependent variables such as % yield, pellet size, disintegration time and % Cumulative drug release (%CDR), the obtained results were 87.15%, 0.75 mm, 13 min and 91.024% respectively. Differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR) study revealed no significant interaction between drug and polymer. Scanning electron microscopy (SEM) confirmed uniform and spherical shaped pellets having pores on the surface which facilitates wicking action and fast disintegrating property of pellets. A design space was constructed to meet the desirable target and optimized batch. The scope of study can further extended to hydrophobic molecules which may useful due to rapid disintegration and enhanced dissolution rate.

Utilization of a fattigation platform gelatin-oleic acid sodium salt conjugate as a novel solubilizing adjuvant for poorly water-soluble drugs via self-assembly and nanonization.

Solubilizing adjuvants are commonly used to dissolve insoluble drugs by simply adding in a formulation. In this study, gelatin and oleic acid sodium salt (OAS), a generally recognized as safe-listed material were chosen and conjugated to develop a natural solubilizing adjuvant using the fattigation platform technology to enhance solubility and dissolution rate of poorly water-soluble drugs according to self-assembly and nanonization principle when simply mixed with poorly water-soluble drugs. We synthesized the gelatin and OAS conjugates (GOC) at three different ratios (1:1, 1:3, 1:5; GOC 1, GOC 2, and GOC 3, respectively) via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide reaction using a spray dryer. This amphiphilic micronized GOC was self-assembled into nanoparticles. The synthesis of new amphiphilic conjugates was identified through Fourier transform-infrared (FT-IR) spectroscopy. The powder properties of the GOCs, such as angle of repose, bulk density, and tapped density were varied with the oleic acid bonding ratio. Then, GOCs were utilized to investigate the enhanced solubility and release rate of various poorly water-soluble drugs such as cilostazol (CSZ), coenzyme Q10, ticagrelor, telmisartan, aprepitant and itraconazole as model drugs. Based on the solubility studies by concentration and type of GOCs, 3% GOC 2 was selected. When this GOC was mixed with these model drugs by the physical mixing, wetting and hot melting methoods, the solubility was highly enhanced compared to the pure control drug, ranging from 20 to 150,000 times. In case of CSZ, all formulations were significantly improved release rate compared to the of CSZ alone and the reference tablet, cilostan® (Korea United Pharm) in simulated intestinal fluid containing 0.2% sodium lauryl sulfate. Differential scanning calorimetry and powder X-ray diffraction were conducted to confirm the crystal polymorphic structure of CSZ, and as a result they changed to diminutive peak intensity compared to CSZ alone. Field-emission scanning electron microscopy indicated that GOC was round with a reduced size of about 100 nm. The reduction of drug particles via nanonization and self-assembly of amphiphilic GOC in an aqueous media could be a key factor to improve poor water solubility by providing a favorable dispersion of drug molecules in an amphiphilic network.

Progress in the Mechanism and Clinical Application of Cilostazol.

Cilostazol is a unique platelet inhibitor that has been used clinically for more than 20 years. As a phosphodiesterase type III inhibitor, cilostazol is capable of reversible inhibition of platelet aggregation and vasodilation, has antiproliferative effects, and is widely used in the treatment of peripheral arterial disease, cerebrovascular disease, percutaneous coronary intervention, etc. This article briefly reviews the pharmacological mechanisms and clinical application of cilostazol.

Double controlled release of highly insoluble cilostazol using surfactant-driven pH dependent and pH-independent polymeric blends and in vivo bioavailability in beagle dogs.

Commercially available cilostazol (CIL) tablet releases drug immediately and is given twice a day as an antiplatelet and vasodilatory agent. However, clinical usefulness of immediate release (IR) preparation is limited due to its extremely poor water solubility and the difficulty in sustaining the blood concentration, resulting in unwanted side effects such as headaches, pyknocardia and heavy-headed symptoms. To achieve once a day dosage form with enhanced solubility and controlled release, double controlled release CIL matrix tablets (DCRT) were designed by modulating a sol-gel process of binary polymeric blends of a pH-independent hydroxylpropylmethylcellulose (HPMC) and a pH-dependent polymer (carbomer) assisted with anionic surfactant (sodium lauryl sulfate, SLS). The release profiles of the DCRT were varied according to the ratio of the two polymers. This DCRT enhanced dissolution rate of CIL in a controlled manner due to the sol-gel and erosion process of HPMC, and SLS-driven modulation of charged carbomer via neutralization and micellar interaction. The near-infrared (NIR) chemical imaging and gravimetric behaviors of DCRT clearly showed dynamic modulation of CIL during the swelling and hydration process. Furthermore, the plasma concentration of CIL in DCRT was highly improved and sustained in beagle dogs in a controlled manner.

Cilostazol-loaded electrospun three-dimensional systems for potential cardiovascular application: Effect of fibers hydrophilization on drug release, and cytocompatibility.

Currently marketed drug-eluting stents are non-selective in their anti-restenotic action. New active substance introduction to polymeric stents and vascular grafts can promote early re-endothelialization, crucial in preventing implant restenosis. Additionally, managing material hydrophobicity by blending synthetic polymers limits adverse effects on bulk properties and controls active substance release. However, the influence of hydrophilic synthetic polymer on human cells in the cardiovascular system remains to be determined. In this report, effects of both poly(ε-caprolactone) (PCL) fibers hydrophilization with Pluronic P123 (P123) and cilostazol (CIL) loading were studied. Physicochemical and mechanical properties of electrospun tubular structures produced from PCL and PCL/P123 fibers with and without CIL were investigated and compared. Release profiles studies and in vitro cell proliferation assays of electrospun materials were conducted. It was found that P123 located near the surface of electrospun fibers increased the rate of CIL release. PCL formulation sustained human umbilical vein endothelial cells (HUVEC) growth for 48 h. Despite improved hydrophilicity, PCL/P123 formulations were found to reduce HUVEC viability. Both PCL and PCL/P123 materials reduced primary aortic smooth muscle cells (PASM) viability after 48 h. In PCL formulations containing CIL, drug release caused a decrease in PASM viability. P123 blending with PCL was found to be as a useful pre-fabrication technique for modulating surface hydrophobicity of electrospun materials and the release profile of incorporated active substance. The cytotoxicity of P123 was evaluated to improve the design of drug-loaded vascular grafts for cardiovascular applications.