Host-Guest Interaction Study of Olmesartan Medoxomil with ß-Cyclodextrin Derivatives.

Olmesartan medoxomil (OLM) is a selective angiotensin II receptor antagonist used in the treatment of hypertension. Its therapeutic potential is limited by its poor water solubility, leading to poor bioavailability. Encapsulation of the drug substance by two methylated cyclodextrins, namely randomly methylated ß-cyclodextrin (RM-ß-CD) and heptakis(2,3,6-tri-O-methyl)-ß-cyclodextrin (TM-ß-CD), was carried out to overcome the limitation related to OLM solubility, which, in turn, is expected to result in an improved biopharmaceutical profile. Supramolecular entities were evaluated by means of thermoanalytical techniques (TG-thermogravimetry; DTG-derivative thermogravimetry), spectroscopic methods including powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier-transform infrared (UATR-FTIR) and UV spectroscopy, saturation solubility studies, and by a theoretical approach using molecular modeling. The phase solubility method reveals an AL-type diagram for both inclusion complexes, indicating a stoichiometry ratio of 1:1. The values of the apparent stability constant indicate the higher stability of the host-guest system OLM/RM-ß-CD. The physicochemical properties of the binary systems are different from those of the parent compounds, emphasizing the formation of inclusion complexes between the drug and CDs when the kneading method was used. The molecular encapsulation of OLM in RM-ß-CD led to an increase in drug solubility, thus the supramolecular adduct can be the subject of further research to design a new pharmaceutical formulation containing OLM, with improved bioavailability.

Risperidone/Randomly Methylated ß-Cyclodextrin Inclusion Complex-Compatibility Study with Pharmaceutical Excipients.

Risperidone (RSP) is an atypical antipsychotic drug used in treating schizophrenia, behavioral, and psychological symptoms of dementia and irritability associated with autism. The drug substance is practically insoluble in water and exhibits high lipophilicity. It also presents incompatibilities with pharmaceutical excipients such as magnesium stearate, lactose, and cellulose microcrystalline. RSP encapsulation by randomly methylated ß-cyclodextrin (RM-ß-CD) was performed in order to enhance drug solubility and stability and improve its biopharmaceutical profile. The inclusion complex formation was evaluated using thermal methods, powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy, and saturation solubility studies. The 1:1 stoichiometry ratio and the apparent stability constant of the inclusion complex were determined by means of the phase solubility method. The compatibility between the supramolecular adduct and pharmaceutical excipients starch, anhydrous lactose, magnesium stearate, and cellulose microcrystalline was studied employing thermoanalytical tools (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow) and spectroscopic techniques (UATR-FTIR, PXRD). The compatibility study reveals that there are no interactions between the supramolecular adduct with starch, magnesium stearate, and cellulose microcrystalline, while incompatibility with anhydrous lactose is observed even under ambient conditions. The supramolecular adduct of RSP with RM-ß-CD represents a valuable candidate for further research in developing new formulations with enhanced bioavailability and stability, and the results of this study allow a pertinent selection of three excipients that can be incorporated in solid dosage forms.

Encapsulation of Risperidone by Methylated ß-Cyclodextrins: Physicochemical and Molecular Modeling Studies.

Risperidone (RSP) is an atypical antipsychotic drug which acts as a potent antagonist of serotonin-2 (5TH2) and dopamine-2 (D2) receptors in the brain; it is used to treat schizophrenia, behavioral and psychological symptoms of dementia and irritability associated with autism. It is a poorly water soluble benzoxazole derivative with high lipophilicity. Supramolecular adducts between drug substance and two methylated ß-cyclodextrins, namely heptakis(2,6-di-O-methyl)-ß-cyclodextrin (DM-ß-CD) and heptakis(2,3,6-tri-O-methyl)-ß-cyclodextrin (TM-ß-CD) were obtained in order to enhance RSP solubility and improve its biopharmaceutical profile. The inclusion complexes were evaluated by means of thermoanalytical methods (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow), powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy and saturation solubility studies. Job's method was employed for the determination of the stoichiometry of the inclusion complexes, which was found to be 2:1 for both guest-host systems. Molecular modeling studies were carried out for an in-depth characterization of the interaction between drug substance and cyclodextrins (CDs). The physicochemical properties of the supramolecular systems differ from those of RSP, demonstrating the inclusion complex formation between drug and CDs. The RSP solubility was enhanced as a result of drug encapsulation in the CDs cavity, the higher increase being obtained with DM-ß-CD as host; the guest-host system RSP/DM-ß-CD can thus be a starting point for further research in developing new formulations containing RSP, with enhanced bioavailability.

The Effect of Temperature and Fe3+ Concentration on the Formation of γ-Fe2O3 Nanoparticles Embedded in Silica Matrix.

The paper presents a study on the formation and thermal stability of γ-Fe2O3 nanoparticles within the silica matrix depending on the Fe(III) carboxylate-type precursors, their annealing temperature and the concentration of Fe3+. Obtaining of the precursors, within the pores of the gel, bases on the redox reaction between Fe(NO3)3 and diols: ethylene glycol (EG) and 1,4 buthane diol (1,4 BG), respectively. Thus, we have prepared gels with different Fe2O3/SiO2 ratios (20, 30, 50, 70 wt% Fe2O3) which were annealed in the temperature range 573-1273 K. The formation and stability of the single γ-Fe2O3 phase within the pores is strongly influenced by the reducing atmosphere generated upon thermal decomposition of the Fe(III) carboxylates. The XRD analysis evidenced a much stronger crystallization of γ-Fe2O3 in case of the nanocomposites synthesized with 1,4 BG than with EG. The magnetic measurements confirm the crystallinity of γ-Fe2O3 within the silica matrix.