Enhancement of cyclosporine aqueous solubility using α- and hydroxypropyl β-cyclodextrin mixtures

The Optimization and Evaluation of Flibanserin Fast-Dissolving Oral Films

Flibanserin (FLB) is a drug used for female hypotensive sexual desire disorder approved by the FDA in August 2015. FLB exhibits extensive hepatic first-pass metabolism and low aqueous solubility, hence poor oral bioavailability. In this study, beta hydroxypropyl cyclodextrin-FLB inclusion complexes were incorporated into orally fast dissolving films. This dosage form was expected to improve FLB aqueous solubility, which would give fast onset of action and decrease presystemic metabolism, hence improving oral bioavailability. The inclusion complex at a ratio of 1:1 was prepared by the kneading method. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffractometry (XRD) were used to confirm complex formation. The Box–Behnken design (15 different formulae of FLB fast-dissolving oral films (FLBFDOFs) were utilized for the optimization of the prepared films. The Expert Design 11 program was utilized to examine the effects of three selected factors, polymer concentration (X₁), plasticizer concentration (X₂), and disintegrant concentration (X₃) on four responses: disintegration time (DT), initial dissolution rate (IDR), dissolution efficiency (DE), and film quality (QF). Numerical optimization was performed by minimizing disintegration time (Y1), while maximizing the initial drug dissolution rate (Y₂), dissolution efficiency (Y₃), and the quality factor (Y₄). The statistical analysis showed that X₁ has a significant positive effect on the disintegration time and a significant negative effect on IDR. While X₂ and X₃ produced a nonsignificant negative effect on IDR. Dissolution efficiency was maximized at the middle concentration of both X₂ and X₃. The best film quality was observed at the middle concentration of both X₁ and X₂. In addition, increasing X₃ leads to an improvement in film quality. The optimized film cast from an aqueous solution contains hydroxypropyl cellulose (2%) as a hydrophilic film-forming agent and propylene glycol (0.8%) as a plasticizer and cross povidone (0.2%) as a disintegrant. The prepared film released 98% of FLB after 10 min and showed good physical and mechanical properties. The optimized formula showed a disintegration time of 30 s, IDR of 16.6% per minute, DE₁₅ of 77.7%, and QF of 90%. This dosage form is expected to partially avoid the pre-systemic metabolism with a fast onset of action, hence improving its bioavailability that favors an advantage over conventional dosage forms.

Development of cyclosporine A nanosuspension: cytotoxicity and permeability on Caco-2 cell lines

Cyclosporine A is a calcineurin inhibitor and is usually used as an immunosuppressant medication. The main purpose of this study is to develop nanosuspension of polypeptide cyclosporine A by using the wet milling method for oral administration. Cell culture studies were also performed with human intestinal Caco-2 cell lines. Hydroxypropyl methylcellulose and sodium dodecyl sulfate were used as stabilizers in nanosuspension. In vitro characterization studies such as Fourier-transform infrared analysis and morphological imaging with scanning electron microscopy have been carried out with obtained cyclosporine A nanosuspension. The particle size, particle size distribution, and zeta potential values of the nanosuspension were measured approximately 400 nm, 0.4, and -25 mV, respectively. The solubility of cyclosporine A was increased 4.5 times in nanosuspension compared to the coarse cyclosporine A powder. As a result of cytotoxicity studies conducted with different concentrations, it was decided to conduct permeability studies at a dose equivalent to 150 µg/mL cyclosporine A. Permeation studies have shown that the nanosuspension increases cyclosporine A transport by 5 and 1.5 times, respectively, compared to coarse powder and commercial product.

Preparation, characterization, dissolution, and permeation of flibanserin - 2-HP-β-cyclodextrin inclusion complexes

Flibanserin (FLB), an antiserotonin drug, is used to treat women with hypoactive sexual appetite disorder. FLB shows low bioavailability (~33%) probably due to its low water solubility. The current study investigated the impact of hydroxypropyl-β-cyclodextrin (HP-β-CD) and sodium lauryl sulfate (SLS) on the dissolution and permeation of FLB. HP-β-CD-FLB inclusion complexes were prepared using physical mixing and kneading at 1:1 and 1:2 M ratios and characterized using differential scanning calorimetry, Fourier transform infrared spectroscopy, and powder X-ray diffractometry. The dissolution and permeation of the complexes through a cellophane membrane were performed in, 0.1, 0.3 and 0.5% SLS in phosphate buffer (pH 6.8). Derived from the slope of the linear phase solubility diagram, the apparent stability constant (K 1:1) was 372.54 M-1. Kneading changed the crystalline form of FLB to an amorphous appearance characterized by minimal crystalline peaks, indicating successful inclusion complex formation. In addition, the HP-β-CD-FLB inclusion complexes showed twofold increased dissolution efficiency at 6 h. The cumulative FLB amount permeated at 6 h increased from 14.1% to 21.88% and 34.56% in the presence of 0.1% and 0.3% of SLS, respectively. However, increasing SLS to 0.5% did not show an increase in FLB permeation. Therefore, the HP-β-CD-FLB inclusion complex has an improved dissolution rate compared to FLB alone. The presence of SLS in the dissolution medium increases the dissolution rate of pure FLB and its complex with HP-β-CD. kneaded 1:1 complex was formulated bioadhesive buccal tablets and showed enhanced drug release.

Solubility enhancement of poorly water soluble domperidone by complexation with the large ring cyclodextrin

The water solubility of domperidone (DMP) could be improved by complexation with large ring cyclodextrins (LR-CDs). LR-CDs contain a relatively hydrophobic cavity that is capable of entrapping the molecules to form inclusion complexes. The complex formation capability of mixture LR-CDs having a degree of polymerization (DP) of 22-48, with DMP was investigated. The phase solubility profile of mixture LR-CD/DMP was classified as A_N-type, resulting in increased DMP solubility in water by 3-fold. Various physicochemical techniques confirmed the mixture LR-CD/DMP complex formation. Single LR-CD with DP of 26, 27, 28, 29, 30, 33 and 34 (CD26 ~ CD34) were isolated from LR-CD mixtures using ODS column for HPLC separation. The CD33/DMP complex has demonstrated the most significant improvement compared to other single LR-CD complexes with a 2.7-fold increase in DMP solubility. The molecular dynamic result revealed that DMP formed stable complexes with CD33 by positioned fully encapsulated inside the cavity and covered by 13-14 subunits of CD33.

Solubilization of Cyclosporine in Topical Ophthalmic Formulations: Preformulation Risk Assessment on a New Solid Form

Owing to the discovery of a less soluble crystalline form (form 2) of cyclosporine (CsA), risks in solubility and physical stability of these formulations need to be revisited. This work focused on understanding the solubility behavior of various CsA forms in different media, including water, castor oil, and selected cosolvent micellar systems. In water, form 2 was approximately 8-9 times less soluble than form 1 (aka. tetragonal dihydrate). In neat nonaqueous solvent, for example, castor oil, form 3 (aka. orthorhombic hydrate) was found to have the lowest solubility and therefore the most stable form. In addition, the solubility-temperature relationship of CsA is complex and solvent-dependent. In aqueous vehicles, retrograde temperature dependence of solubility was observed in aqueous vehicles, that is, the solubility of CsA decreased with temperature, which was attributed to the effect of temperature on the strength of hydrogen bonding interactions; conversely, the solubility of CsA increased with temperature in nonaqueous solvents. In addition, the solubility of these CsA forms was very sensitive to temperature. Temperature-dependent form transformation was also observed in the media studied, with faster form conversion occurring at elevated temperatures. These studies provided key information to support the risk assessment for topical ophthalmic formulation development of CsA.

Origin of non-linearity in phase solubility: solubilisation by cyclodextrin beyond stoichiometric complexation

The low solubility of drugs, which poses a serious problem in drug development, can in part be overcome by the use of cyclodextrins (CDs) and their derivatives. Here, the key to solubilisation is identified as the formation of inclusion complexes with the drug molecule. If inclusion complexation were the only contribution to drug solubility, it would increase linearly with CD concentration (as per the Higuchi-Connors model); this is because inclusion complexation is a 1 : 1 stoichiometric process. However, solubility curves often deviate from this linearity, whose mechanism is yet to be understood. Here we aim to clarify the origin of such non-linearity, based on the Kirkwood-Buff and the McMillan-Mayer theories of solutions. The rigorous statistical thermodynamic theory shows that non-linearity of solubilisation can be rationalised by two contributions: CD-drug interaction and the drug-induced change of CD-CD interaction.

Cyclosporin A--a review on fermentative production, downstream processing and pharmacological applications

In present times, the immunosuppressants have gained considerable importance in the world market. Cyclosporin A (CyA) is a cyclic undecapeptide with a variety of biological activities including immunosuppressive, anti-inflammatory, antifungal and antiparasitic properties. CyA is produced by various types of fermentation techniques using Tolypocladium inflatum. In the present review, we discuss the biosynthetic pathway, fermentative production, downstream processing and pharmacological activities of CyA.