Nimesulide/cyclodextrin/PEG 6000 ternary complexes: physico-chemical characterization, dissolution studies and bioavailability in rats

Enhanced Dissolution and Oral Bioavailability of Cyclosporine A: Microspheres Based on αβ-Cyclodextrins Polymers

Cyclosporine (CsA) has a selective property of suppressing various T-lymphocyte functions. This is of utmost importance in preventing allograft rejection by several organ transplantations, as well as in the treatment of systemic and local autoimmune disorders. However, the poor water solubility of CsA can be a major hurdle for its absorption into the blood stream, which leads to low bioavailability and thus less efficacy. The aim of this study was to prepare, characterize, and evaluate in vitro as well as in vivo, the potential of the innovative CsA drug delivery system. The latter contains CsA in spherical amorphous solid dispersion (SASD) which is embedded in an original α-cyclodextrin and β-cyclodextrin polymer mixture (Poly-αβ-CD) as a multifunctional amorphous carrier. The new developed SASD formulation showed that CsA was molecularly dispersed in αβ-cyclodextrins in an amorphous form, as was confirmed by physicochemical characterization studies. Interestingly, the peptide secondary structure, and thus, the drug activity was not impacted by the preparation of SASD as was shown by circular dichroism. Furthermore, the in vitro CsA release profile kinetics was almost identical to the commercially available product Neoral^®. This study presents the first in vivo proof-of-concept for a novel drug delivery system based on Poly-αβ-CD containing CsA, with SASD allowing for increased bioavailibility. The pharmacokinetic parameters of cyclosporine A from the spherical spray-dried dispersion formulation was demonstrated in a “rat” animal model. For comparison, the commercially available Neoral® was studied. Importantly, the pharmacokinetic parameters were improved by extending T_max from 2 to 3 h after the oral administration in rats, and eventually preventing the enterohepatic circulation. All these results clearly demonstrate the improved pharmacokinetic parameters and enhanced bioavailability of CsA in the new developed drug delivery system. These data demonstrated the superiority of the newly developed Poly-αβ-CD formulation for oral administration of the poorly soluble CsA in vivo without altering its secondary structure. Poly-αβ-CD can be a very useful tool for the oral administration of poorly water-soluble drugs.

Spectral and theoretical study on complexation of sulfamethoxazole with β- and HPβ-cyclodextrins in binary and ternary systems

The inclusion complexes of sulfamethoxazole (SMX) with β-cyclodextrin (βCD) and (2-hydroxypropyl) β-cyclodextrin (HPβCD) were prepared. Fluorescence spectroscopy and electrospray mass spectrometry, ESI-MS, were used to investigate and characterize the inclusion complexation of SMX with cyclodextrins in solutions. Whereas in the solid state the complexes were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD) and Raman techniques. Enhanced twisted intramolecular charge transfer (TICT), emission as well as local excited (LE) bands were observed upon addition of HPβCD indicate that SMX enters deeper into the cyclodextrins cavity. The stoichiometries and association constants of these complexes have been determined by monitoring the fluorescence data. The effect of presence of ternary components like arginine and cysteine on the complexation efficiency of SMX with cyclodextrins was investigated. Molecular Dynamic simulations were also performed to shed an atomistic insight into the complexation mechanism. The results obtained showed that complexes of SMX with both cyclodextrins are stabilized in aqueous media by strong hydrogen bonding interactions.

Nimesulide/methyl β-cyclodextrin inclusion complexes: physicochemical characterization, solubility, dissolution, and biological studies

Nimesulide (NIM) is an insoluble nonsteroidal anti-inflammatory drug (NSAID). Complexation of drug with methyl β-cyclodextrin was evaluated to improve solubility and dissolution rate of NIM. Complexation was achieved via a coevaporation technique to obtain different drug to polymer molar ratios (1:1, 1:2, and 1:3). The physicochemical characterization of the systems using powder X-ray diffraction and infrared spectroscopy was carried out to understand the influence of this technological process on the physical status of single components and complex systems and to detect possible interactions between drug and carrier. Moreover, quantitative solubility and in vitro dissolution studies of NIM alone and NIM inclusion complexes were studied in the dissolution media of phosphate buffer pH 5.5 and 7.4. The analysis provided existence of a molecular interaction between drug and carrier together in the complex state. The study showed that the inclusion systems enhanced of drug solubility, dissolution rate, and anti-inflammatory activity.

2D solid-state NMR analysis of inclusion in drug-cyclodextrin complexes

The solubility of drug molecules can often be improved through preparation and delivery of cyclodextrin (CD) inclusion complexes. These drug-oligosaccharide complexes can be prepared in solution and converted to the solid state via methods such as lyophilization and spray-drying, or they can be prepared directly from solids by a variety of methods. The development of drug-CD complexes as solids allows for potential advantages in dosage form design, such as the preparation of layered formulations, and it also can yield improvements in chemical and physical stability. 2D solid-state NMR (SSNMR) methods provide a direct way to probe drug-CD interactions in solid complexes through dipolar interactions between nuclei within the drug and CD molecules. In this study, 2D heteronuclear and homonuclear correlation SSNMR experiments involving (1)H, (13)C, (19)F, and (31)P nuclei are used to demonstrate the inclusion of drug within the CD cavity in a variety of powder samples. To illustrate the general applicability of the SSNMR approach presented, examples are shown for the drugs diflunisal, adefovir dipivoxil, voriconazole, dexamethasone, and prednisolone in complexes with α-CD, β-CD, and sulfobutylether-substituted β-CD. The quantitative analysis of included and free drug fractions in a solid drug-CD complex using SSNMR is also demonstrated. On the basis of these results, general approaches to the characterization of these materials using SSNMR are proposed.

Preparation of meloxicam-β-cyclodextrin-polyethylene glycol 6000 ternary system: characterization, in vitro and in vivo bioavailability

Ternary complexes of meloxicam (ML), a poorly water-soluble anti-inflammatory drug, with β-cyclodextrin (βCD) and polyethylene glycol (PEG) 6000 were prepared from an equimolar (ML-βCD) and 10% of PEG. Characterization of the ternary complex was carried out by differential scanning calorimetry and X-ray diffractometry. The solubility of ML increased as a function of increasing the concentration of βCD and PEG 6000. Ternary system increased significantly ML solubility in water. Ternary complexes improved drug release compared with ML and ML-βCD. The oral bioavailability of ML-βCD-PEG was investigated by administration to rat and compared with ML and ML-βCD. The results confirmed that the oral bioavailability of ML was significantly improved by complexation with βCD in the presence of PEG.

Effect of pH and water-soluble polymers on the aqueous solubility of nimesulide in the absence and presence of β-cyclodextrin derivatives

The aqueous solubility of nimesulide in the absence and presence of β-cyclodextrin (β-CD) and its alkyl derivatives hydroxypropyl-β-CD and methyl-β-CD was studied. We also investigated the effect of water-soluble polymers, hydroxypropylmethyl-cellulose, sodium-carboxymethyl-cellulose, polyvinyl- pyrrolidone and polyethyleneglycol on the solubilization efficacy and complexation ability of cyclodextrins with nimesulide. The solubility of nimesulide in the absence and presence of cyclodextrins and polymers was studied using a phase solubility technique combined with a spectrophotometric method. The study was carried out at 25°C and pH values of 6.0 and 7.0. Conditions in terms of polymer concentration and polymer heating with and without sonication were optimized. Values of the solubility enhancement factor of nimesulide in the presence of each cyclodextrin and in the absence and presence of each polymer were determined and the formation constants, K, of the inclusion complexes formed calculated. β-CDs increased the aqueous solubility of nimesulide in the following order: methyl-β-CD > β-CD > hydroxypropyl-β-CD. Addition of hydroxypropylmethyl-cellulose at a concentration of 0.1% (w/v) had the greatest influence on complexation of all three β-CDs with nimesulide, while preheating of the polymer at 70°C under sonication resulted in an additional two-fold increase in the aqueous solubility of the drug. Sodium- carboxymethyl-cellulose, polyvinylpyrrolidone and polyethyleneglycol had minor effects on the aqueous solubility of nimesulide. Thus β-CD, hydroxypropyl-β-CD and methyl-β-CD are proposed as good solubilizing agents for nimesulide in the presence and absence of hydroxypropylmethyl- cellulose in order to enhance its oral bioavailability.