Development and pharmacological evaluation of cyclodextrin complexes of etoricoxib

Etoricoxib is an anti-inflammatory drug largely used in a variety of acute and chronic inflammatory diseases, but is associated with low aqueous solubility and poor dissolution leading to a delayed rate of absorption and onset of action. This study focuses on the development and pharmacological evaluation of a series of binary systems of etoricoxib with cyclodextrins. The binary systems of etoricoxib with beta-cyclodextrin (beta-CD) and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) were prepared by the kneading method. Drug-cyclodextrin interactions in solution were investigated by the phase solubility analysis. X-ray diffractometry studies were carried out for the characterization of all binary systems. In vivo studies were performed using the tail flick and Eddy's hot plate apparatus. The results of the phase solubility studies indicated an increase in etoricoxib solubility upon complexation with beta-cyclodextrin (stability constant, Kc value of 198.6 and 209.9 L/mol for 1:1 and 1:2 beta-CD complexes of the drug, respectively) and a further increase on complexation with HP-beta-CD (stability constant, Kc value of 265.3 and 355.8 L/mol for 1:1 and 1:2 HP-beta-CD complexes of the drug, respectively). Results of the in vivo drug activity studies also pointed towards an enhanced antinociceptive effect of etoricoxib upon cyclodextrin complexation with 1:2 drug HP-beta-CD complex showing maximum effect.     

Correlation and in vitro studies on radioactive and nonradioactive albendazole-beta-cyclodextrin complex tablets

The work aims to confirm the complexation of albendazole (ABZ) by beta-cyclodextrin (beta-CD), and to compare them with pure ABZ tablets using radioactive and nonradioactive dissolution studies. The complex tablets were prepared by kneading a binary mixture of ABZ and beta-CD and a direct compression method. Nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were examined to prove the formation of complexes in the final products. The radiolabelled tablets were labelled with 99mTc-DTPA. Dissolution studies were performed with radiolabelled and nonradiolabelled tablets in two dissolution media (pH 1.2 and pH 7.4). The tablets were added to an acidic solution (pH = 1.2) to quantify the concentration of the drug inside the beta-CD cavity. The other medium (pH = 7.4) was used to prove the existence of non-complexed drug in each powder, as the drug's solubility increases with pH. It was observed that complexation occurred in all tablets, and beta-cyclodextrin (beta-CD) could increase the aqueous solubility. Further, a correlation was shown between dissolution results for radiolabelled and nonradiolabelled tablets. This study shows that the characterization studies were a good indicator for the ABZ: beta-CD complex. According to the phase solubility studies, the solubility of ABZ increased when the amount of beta-CD increased, and drug release from tablets in pH 7.4 and pH 1.2 media was dramatically improved by the addition of beta-CD compared with the pure ABZ tablet.     

Availability of phenindione-beta-cyclodextrin inclusion complex.

The inclusion complexation was occurred between beta-cyclodextrin (beta-CD) and phenindione (1) in aqueous solution. The complex formation was proved by solubility, dissolution and permeation study. The inclusion complex was prepared and its physicochemical properties was studied. 1 was combined with beta-CD in 1:1 molar ratio. Using the solubility data, the value of apparent stability constant obtained of 1/beta-CD complex was 492.7. The dissolution rate of 1 was increased in presence of beta-CD. The permeability coefficients of 1 were 7.86 x 10(-3), 4.76 x 10(-3) and 5.0 x 10(-3), corresponding to pure drug, its physical mixture with beta-CD and the inclusion complex, respectively. The presence of human albumin generally decreased the permeability coefficient of the drug. The reduction (79.5%) was found to be nearly equal in case of either pure 1 or its complex with beta-CD. Administration of 1 or its inclusion complex with beta-CD to rabbits increase prothrombin times, the effect was more pronounced in the complex form of drug than free one.     

Enhancement in dissolution pattern of piribedil by molecular encapsulation with beta-cyclodextrin

The aim of this study was to improve the dissolution behavior of piribedil by molecular encapsulation with beta-cyclodextrin (beta-CD). Toward this aim, physical mixing, co-grinding, and spray-drying methods were used to prepare solid binary systems. Differential scanning calorimetry, X-ray diffractometry, and particle size analysis were used to characterize the binary systems obtained. Complexes of piribedil and beta-CD could be prepared using the spray-drying method. Dissolution of piribedil was improved to a great extent by the complex prepared.     

Preparation, characterization and dissolution enhancement of mefloquine hydrochloride-betaCD inclusion complex

The solid state properties and dissolution behaviour of binary systems of mefloquine hydrochloride (MH) with betaCD were investigated. MH-betaCD interaction in the solution state was studied by phase solubility analysis and demonstrates the ability of 3CD to complex with MH giving AL type profile with 120.34 M-1 stability constant. The kneading method was adopted to prepare binary sytems of MH with betaCD in 1:1 molar ratio. The solid inclusion was characterized by differential scanning calorimetry, fourier transformation infrared spectroscopy and X-ray powder diffractometry. Experimental results confirmed the existence of 1:1 inclusion complex of MH with ICD. Aqueous solubility of MH was found to be enhanced by 118% for inclusion complex. The dissolution properties of binary systems were studied in simulated gastric fluid without enzyme and compared with MH alone. The inclusion complex of MH prepared with 3CD showed a dissolution rate several times faster than that of physical mixture and pure drug.     

Inclusion complex of trimethoprim with beta-cyclodextrin

The complexation of trimethoprim (TMP) with beta-cyclodextrin (beta-CD) was studied. UV-spectrophotometry and phase-solubility techniques were employed to investigate the complexation behaviour in liquid medium, and to demonstrate that the aqueous solubility of TMP increased 2.2-fold due to complexation with beta-CD. Solid samples prepared by co-evaporation (in 2 wt% acetic acid solution) have also been studied, using differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD), to assess the formation of the inclusion complex. The water content of the complex and beta-CD was determined using thermo gravimetric analysis (TGA). In vitro dissolution analysis indicated that dissolution properties of TMP/beta-CD complex were superior compared to both pure TMP and the corresponding physical mixture of TMP and beta-CD.     

Physicochemical investigation of the solid dispersion systems of etoricoxib with poloxamer 188

Solid dispersion systems of a poorly water-soluble drug, etoricoxib were prepared with poloxamer 188 in 1:0.5, 1:1.5 and 1:2.5 ratios and evaluated by FTIR, powder XRD and dissolution studies. Physical studies demonstrated a strong hydrogen bonding with significant decrease in the crystallinity and formation of amorphous etoricoxib in its binary systems. All binary systems of etoricoxib showed faster dissolution than pure drug alone (P?<?0.001). However, 1:2.5 proportion of etoricoxib: poloxamer 188 showed superior performance (DE₄₅: 71.27%?±?3.85) in enhancing solubility and dissolution rate of etoricoxib suggesting optimum ratio of the carrier.     

Influence of cyclodextrin complexation on piroxicam gel formulations

The aim of this work was to evaluate the role of cyclodextrins in topical drug formulations. Solid piroxicam (PX) complexes with beta-cyclodextrin (beta-CD) and randomly methylated beta-cyclodextrin (RAMEB) were prepared by freeze-drying and characterized using differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), Fourier transform infrared spectroscopy (FTIR) and near infrared spectroscopy (NIR). A physical mixture of PX and cyclodextrins was characterized by enhanced dissolution properties compared to the dissolution profile of the pure drug due to in situ complex formation. Formation of the PX-cyclodextrin inclusion complex additionally improved the drug dissolution properties. Influence of CDs on drug permeation from the water dispersion and the prepared hydroxypropyl methylcellulose (HPMC) gels was investigated. Permeation of the drug involved three consecutive processes: dissolution of the solid phase, diffusion across the swollen polymer matrix and drug permeation through the membrane. Complexation increased PX diffusion by increasing the amount of diffusible species in the donor phase. Slower drug diffusion through the HPMC matrix was the rate limiting step in the overall diffusion process. Possible interaction between the hydrophilic polymer and cyclodextrin may result in physicochemical changes, especially in a change of rheological parameters.     

Solid-state characterization and dissolution properties of naproxen-arginine-hydroxypropyl-beta-cyclodextrin ternary system.

The effect of ternary complexation of naproxen, a poorly water soluble anti-inflammatory drug, with hydroxypropyl-beta-cyclodextrin and the basic aminoacid L-arginine on the drug dissolution properties has been investigated. Equimolar binary (drug-cyclodextrin or drug-arginine) and ternary (drug-cyclodextrin-arginine) systems were prepared by blending, cogrinding, coevaporation, and characterized by differential scanning calorimetry, thermogravimetric analysis, FT-IR spectroscopy, X-ray diffractometry. The dissolution behavior of naproxen from the different products was evaluated by means of a continuous flow through method. The results of solid state studies indicated the presence of strong interactions between the components in ternary coevaporated and coground systems, which were both of totally amorphous nature. In contrast, the presence of either free drug or free arginine was detected when the third component (cyclodextrin or aminoacid) was physically mixed, respectively, to the drug-arginine binary system (as physical mixture, coevaporate, or coground product) or to the drug-cyclodextrin binary system (as physical mixture, coevaporate, or coground product). All ternary combinations were significantly (P<0.001) more effective than the corresponding binary drug-cyclodextrin and drug-arginine systems in improving the naproxen dissolution rate. The best performance in this respect was given by the ternary coevaporate, with about 15 times increase in terms of both drug relative dissolution rate and dissolution efficiency. The synergistic effect of the simultaneous use of arginine and cyclodextrin on the dissolution rate of naproxen was attributed to the combined effects of inclusion in cyclodextrin and salt formation, as well as to a specific role played by arginine in this interaction.     

Complexation of celecoxib with beta-cyclodextrin: characterization of the interaction in solution and in solid state

Inclusion complexation between celecoxib, a specific cyclooxygenase II inhibitor, and beta-cyclodextrin (beta-CD) was studied in solution and solid state. Drug cyclodextrin complexes were prepared by spray drying while physical mixtures were obtained by simple blending. Inclusion complexes were characterized by nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), and polarimetry. Phase solubility analysis was carried out to determine the stability constant. Solubility studies revealed the existence of a 1:1 complex between celecoxib and beta-CD. NMR studies suggested a strong interaction between celecoxib and beta-CD prepared by spray drying. XRD and SEM analysis illustrated that celecoxib existed as an amorphous complexed form in spray-dried complexes. Dissolution studies showed that the celecoxib entrapped in spray-dried complexes dissolved much faster than the uncomplexed drug and physical mixtures. The data obtained suggest that celecoxib forms an inclusion complex with beta-CD in solution and solid state, which was confirmed by various analytical techniques. A shorter t50% of dissolution is found for the formulation prepared by spray drying when compared on a weight basis in a USP II apparatus.     

羟丙基-β-环糊精包合对穿心莲内酯的增溶作用

目的研究羟丙基-β-环糊精(HP-β-CD)包合对穿心莲内酯(AND)溶解度和溶出度的增强作用。方法以HP-β-CD为载体,分别采用研磨法、超声波法和共沉淀法制备AND的HP-β-CD包合物,测定其溶出度和溶解度,并与AND原药、AND和HP-β-CD的物理混合物的溶出性能进行比较。结果 AND与HP-β-CD形成了包合物,HP-β-CD可使AND溶解度增加55.4倍。结论HP-β-CD极大地增加了AND的溶解度和溶出度。     

A Study on Improvement of Solubility of Rofecoxib and its effect on Permeation of Drug from Topical Formulations

Rofecoxib, a practically insoluble cox-2 selective nonsteroidal antiinflammatory agent was subjected to improvement in solubility by preparing its binary mixtures with β cyclodextrin using various methods such as physical mixing, co-grinding, kneading with aqueous methanol and co-evaporation from methanol-water mixture. Characterization of the resulting binary mixtures by differential scanning calorimetry and X-ray diffraction studies indicated partial amorphization of the drug in its binary mixtures. In vitro dissolution studies exhibited remarkable increase in rate and extent of dissolution of the drug from its complexes with β -cyclodextrin. Pure rofecoxib as well as its co-ground binary mixture were formulated as aqueous gels for topical application. In vitro skin permeation of rofecoxib from formulation containing rofecoxib-cyclodextrin complex was significantly higher (p<0.05) at 1, 2, 12, 18 and 24 hr as compared to formulation containing pure rofecoxib. This could be attributed to better solubility of binary mixture in the aqueous gel vehicle leading to greater concentration gradient between the vehicle and skin and hence higher flux of the drug.     

Studies on benexate.CD: effect of inclusion compound formation on the antiulcer activity of benexate, the effective ingredient of benexate.CD

Benexate.CD, a new orally active antiulcer agent, is an inclusion compound of benexate and beta-cyclodextrin (beta-CD). The present report investigated the significance of complex formation on the antiulcer activity of benexate, the effective ingredient of benexate.CD. To evaluate the improvement of solubility, the dissolution properties of benexate from various pharmaceutical forms into the 1st fluid of the Pharmacopoeia of Japan, a model of gastric juice, were compared. Benexate itself was hardly soluble, but the physical mixture of benexate and beta-CD showed a solubility increase of benexate. On the other hand, benexate.CD showed a supersaturated dissolution curve and its peak concentration was 8 times higher than the solubility of the physical mixture. When benexate.CD was administered orally to pylorus ligated rats in the powder formulation, the similar supersaturated dissolution behavior was observed in the stomach, and the benexate level in gastric tissue was higher than that in benexate or the physical mixture administration. Benexate.CD extremely inhibited the ulcer formation caused by HCl-ethanol ingestion, but there was no significant inhibition after treatment with benexate or the physical mixture. These results indicated that it is necessary for benexate to form an inclusion compound in order to exert a strong antiulcer activity.     

In vitro and in vivo evaluation of an amylobarbitone/hydroxypropyl-beta-cyclodextrin complex prepared by a freeze-drying method

The complex formation of amylobarbitone (AMB) with 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was investigated in aqueous solution and in the solid state. The apparent stability constant for complex formation (Kc) calculated by phase solubility and spectral shift methods was 524 M-1 and 568 M-1, respectively. The stoichiometric molar ratio of the complex was estimated to be 1:1 and the solubility of AMB in water was increased about 3 fold. The solid dispersion system of AMB/HP-beta-CD in 1:1 molar ratio was prepared by a freeze-drying method. Differential scanning calorimetry (DSC), x-ray diffractometry, (IR) and 1H NMR spectroscopy were used to confirm that inclusion between the drug and HP-beta-CD occurred. The dissolution behavior of the drug as a physical mixture as well as the prepared complex, showed enhanced drug dissolution properties of the prepared complex compared to the physical mixture or the drug alone. The dissolution rate appeared in the first 2 min, 25 times greater for the complex than for the drug alone. Furthermore, in-vivo study revealed that the duration and hypnotic activity of AMB after its oral administration to mice were improved by inclusion.     

Study on solubility improvement of lidocaine by ternary solid dispersion

In the present study, we aimed to probe the possibility of using mixed poloxamers as carriers to prepare ternary solid dispersion (SD) that facilitated solubility and dissolution rate of the poorly water soluble drug and compare with binary SD with single poloxamer. Lidocaine (LIC) was selected as a model drug, and poloxamer 188 (P188) and poloxamer 407 (P407) were utilized as single and mixed carriers. Depending on DSC and the dissolution testing, the appropriate ratio of SD prepared by melting method was optimized. Ternary and binary SD was characterized by DSC, XRD, SEM and FTIR. In vitro dissolution study, phase solubility study and saturated solubility study were performed to clarify solubilization from apparent phenomena and inherent reason. Moreover, stability study under different relative humidity (RH) was investigated. Physical characterizations of binary and ternary SD exhibited the formation of eutectic mixture and the presence of molecular interaction. Compared with the pure LIC, the dissolution rate and solubility of LIC in binary and ternary SDs were enhanced. The phase solubility study revealed an AL-type curve. Furthermore, the stability test indicated that ternary and binary SD was stable. The results of this study demonstrated that SD with mixed poloxamers could improve dissolution rate and solubility of poorly water-soluble drug.     

Solid-state characterization and dissolution properties of bicalutamide-beta-cyclodextrin inclusion complex

The solid-state properties and dissolution profile of bicalutamide beta-cyclodextrin (betaCD) inclusion complex were investigated. The phase solubility profile of bicalutamide with beta-cyclodextrin was classified as A(L)-type. Stability constant with 1:1 molar ratio was calculated from the phase solubility diagram and the aqueous solubility of bicalutamide was found to be enhanced by 86% for beta-cyclodextrin. Binary systems of bicalutamide with betaCD were prepared by the kneading method. The solid-state properties of the complex were characterized by differential scanning calorimetry, Fourier transformation-infrared spectroscopy and X-ray powder diffractometry. It could be concluded that bicalutamide could form an inclusion complex with beta-cyclodextrin. The dissolution profile of the inclusion complex was determined and compared with those of bicalutamide alone and its physical mixture. The dissolution rate of bicalutamide was significantly increased bycomplexation with betaCD, as compared with pure drug and physical mixture.     

Physical solid-state properties and dissolution of sustained-release matrices of polyvinylacetate.

Solid-state compatibility and in vitro dissolution of direct-compressed sustained-release matrices of polyvinylacetate (PVAc) and polyvinylpyrrolidone (PVP) containing ibuprofen as a model drug were studied. Polyvinylalcohol (PVA) was used as an alternative water-soluble polymer to PVP. Differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) were used for characterizing solid-state polymer-polymer and drug-polymer interactions. The mechanical treatment for preparing physical mixtures of polyvinyl polymers and the drug (i.e. simple blending or stressed cogrinding) was shown not to affect the physical state of the drug and the polymers. With the drug-polymer mixtures the endothermic effect due to drug melting was always evident, but a considerable modification of the melting point of the drug in physical binary mixtures (drug:PVP) was observed, suggesting some interaction between the two. On the other hand, the lack of a significant shift of the melting endothermic peak of the drug in physical tertiary drug-polymer mixtures revealed no evidence of solid-state interaction between the drug and the present polymers. Sustained-release dissolution profiles were achieved from the direct-compressed matrices made from powder mixtures of the drug and PVAc combined with PVP, and the proportion of PVAc in the mixture clearly altered the drug release profiles in vitro. The drug release from the present matrix systems is controlled by both diffusion of the drug through the hydrate matrix and the erosion of the matrix itself.     

Meloxicam-Paracetamol Binary Solid Dispersion Systems with Enhanced Solubility and Dissolution Rate:Preparation,Characterization, and In Vivo Evaluation

The aim of this work included the improvement of meloxicam solubility and maximizing its pharmacological activity by forming binary solid dispersions with paracetamol. Different binary solid dispersions were prepared using paracetamol as a pharmacologically related coformer with favorable structural, dissolution, and solubility properties. The prepared binary solid dispersions were characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Saturation solubility and dissolution rate were determined for meloxicam-paracetamol binary solid dispersions and compared to each drug individually. The pharmacological effects of meloxicam were enhanced in binary solid dispersions compared to the physical mixture using mice as animal models. This finding could be attributed to the improvement of meloxicam saturation solubility in the binary solid dispersion systems. Solid state characterization demonstrated the formation of amorphous phase with low crystallinity as obtained by XRD data. The solid dispersion prepared by freeze drying at 1:10 molar ratio showed more than sevenfold increase in solubility of meloxicam and more than 65% increase in dissolution rate compared to both generic preparation and physical mixture tablets. Significant differences (P < 0.05) in the analgesic effect represented by the increase in time of licking of forepaws to 7.92 s for the solid dispersion (SD) (F4) system compared to 6.15 and 4.82 s, for physical mixture and control groups were observed, respectively. A significant difference (P < 0.05) in the anti-inflammatory effect was demonstrated for the binary solid dispersion showing more than 50% decrease in the volume of carrageenan-induced tail edema compared to that of the physical mixture. Therefore, the freeze dried binary solid dispersion of meloxicam and paracetamol has shown to increase the analgesic and anti-inflammatory activities as compared to the physical mixture.     

Preformulation study of the inclusion complex warfarin-beta-cyclodextrin

Inclusion complex between warfarin and beta-cyclodextrin was obtained to improve the in vitro bioavailability of the drug in acidic media. Inclusion complexation in solution was studied by phase solubility technique. The apparent stability constant was influenced by the pH of the medium ranging from 633.26 M(-1) (at pH 1.2, where the drug was in unionised form) to 99.81 M(-1) (at pH 7.4, where the drug was in ionised form). Phase solubility study showed an AL-type diagram indicating the formation of an inclusion complex in 1:1 molar ratio. Solid binary mixtures of the drug with beta-cyclodextrin were prepared by several methods (physical mixing, kneading, co-evaporation, freeze-drying). Physicochemical characterizations were performed using differential scanning calorimetry, powder X-ray diffractometry and dissolution studies. Preparation method influenced the physicochemical properties of the binary mixtures. An inclusion complex was obtained by freeze-drying, and it showed a high solubility and drug dissolution rate. The physical stability of the complex was also studied. After one year storage in glass container at room temperature no significant changes were detected in the diffractogram, thermogram and dissolution profile of the freeze-dried product.     

Fosinopril-cyclodextrin inclusion complexes: phase solubility and physicochemical analysis

Fosinopril is one of the most hydrophobic substances among the angiotensin-converting enzyme inhibitors, exhibiting low water solubility and poor bioavailability following oral administration. Inclusion complexes between the drug substance and cyclodextrins (CDs) were obtained in order to improve its solubility. The purpose of this study was to investigate the guest-host interaction of fosinopril sodium (FOS) with beta-cyclodextrin (beta-CD) and its derivative, randomly methylated beta-cyclodextrin (RAMEB) in solution by phase solubility diagrams (PSD) and in solid state by using thermal analysis, powder X-ray diffractometry (PXRD) and Fourier transform infrared spectroscopy (FTIR). The phase solubility analysis indicated that the solubility of FOS in simulated gastric fluid was increased in the presence of CDs and revealed for RAMEB an A(L)-type diagram, suggesting the formation of a 1:1 inclusion complex, and for beta-CD a B(s)-type phase diagram. The estimated apparent stability constant (K1:1), according to the Higuchi and Connors method, is 3209.99 M(-1) and 1770.34 M(-1) for RAMEB and beta-CD complexes respectively. The binary systems FOS/CDs were prepared using the kneading method in the molar ratio 1:1. The PXRD patterns and the thermograms indicated a drug amorphization process, higher for FOS/RAMEB binary system and the FTIR analysis suggested that the ester group of FOS is probably enclosed in the CD's cavity. The results of this study confirm the formation of inclusion complexes both in solution and in solid state and suggest that the complexes formation between FOS and CDs could improve the bioavailability of the drug due to the enhancing absorption expected from increased drug solubility.