Effect of Soluplus on the supersaturation and absorption of tacrolimus formulated as inclusion complex with dimethyl-β-cyclodextrin

The application of tacrolimus (FK506) is hampered by its poor solubility and dissolution, which can be promoted by the use of inclusion complex. However, in supersaturated environment, crystallization of the drug inclusion complex may occur, leading to reduced absorption in vivo. In this study, Soluplus, an amphiphilic copolymer of polyvinyl caprolactam, polyvinyl acetate and polyethylene glycol, was used to improve the supersaturated stability and absorption of FK506. Using dimethyl-β-cyclodextrin (DM-β-CD), the inclusion complex (FK506-CD) was prepared, which showed favorable dissolution profiles. But in supersaturated condition, the drug concentration was rapidly decreased, with 10.64?±?0.69?μg/ml of FK506 at 12?h. Ternary complex (FK506-SCD) containing Soluplus contributed steadier drug concentration. The FK506-SCD with 1.2% Soluplus best promoted the supersaturated stability of the inclusion complex, with 62.90?±?3.34?μg/ml of FK506 at 12?h. Soluplus also reduced the crystallization and degradation of FK506 in the stress test. In the single-pass intestinal perfusion test, the absorption of FK506 in the ileum and colon was significantly increased. Pharmacokinetic results showed that the bioavailability of FK506-SCD was 2.34-fold that of FK506-CD. Our data suggested that Soluplus had an excellent capability in improving the supersaturated stability and in vivo absorption of FK506 inclusion complex.     

The intestinal absorption properties of flavonoids in Hippophaë rhamnoides extracts by an in situ single-pass intestinal perfusion model

The purpose of this study was to investigate the absorption properties of isorhamnetin (IS), quercetin (QU), and kaempferol (KA) in total flavones of Hippophaë rhamnoides L. (TFH) by an in situ single-pass intestinal perfusion model. The results indicated that IS, QU, and KA in TFH were absorbed site-dependently, and both enterohepatic circulation and intestinal flora could participate in their absorption processes. The absorption mechanisms of IS, QU, and KA in TFH were involved in both passive diffusion and active transport, and the mediation of efflux transporter multidrug resistance-associated proteins (MRPs) should not be neglected.     

Transdermal delivery of the in situ hydrogels of curcumin and its inclusion complexes of hydroxypropyl-β-cyclodextrin for melanoma treatment

Curcumin (Cur) is a hydrophobic polyphenol with diverse pharmacological effects, especially for cancer treatment. However, its weak water solubility and stability was the major obstacle for the formulation research of Cur. The complexation of Cur and hydroxypropyl-β-cyclodextrin (HP-β-CD) was done by grinding. The increasing solubility of Cur was achieved due to complexation and the photochemical stability of Cur was improved. The inclusion of Cur could happen when two ends of Cur were embedded into the cavity of the HP-β-CD rings. The in situ hydrogels (ISGs) of Cur and its inclusion complexes were prepared using poloxamers 407 and 188 as the matrix. The extent of drug’s in vitro release from the ISGs depended on the dissolution of drugs. Both of the ISGs had transdermal effect and cytotoxicity on B16-F10 cells. However, the effects of the ISGs containing Cur inclusion complexes were much higher than those of Cur ISGs because of the improved Cur solubility in the former. The cytotoxicity of Cur on melanoma cells was related to blocking of cellular proliferation in the G₂/M stage followed by cellular apoptosis. The ISGs of Cur inclusion complexes are a promising formulation for melanoma treatment.     

Improvement of water solubility and in vitro dissolution rate of aceclofenac by complexation with β-cyclodextrin and hydroxypropyl-β-cyclodextrin

The present study deals with the inclusion complexation of aceclofenac with β-cyclodextrin by grinding, microwave and spray-drying techniques. A derivative of β-cyclodextrin, hydroxypropyl-β-cyclodextrin, was also subjected to the complexation process with aceclofenac by spray-drying technique. The samples were subjected to in-vitro dissolution studies, fourier transform infra-red spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy and x-ray diffraction studies. The in-vitro dissolution of aceclofenac-hydroxypropyl-β-cyclodextrin complex was faster as compared to the aceclofenac- β-cyclodextrin complex and aceclofenac alone. Spray-dried aceclofenac-β-cyclodextrin complex were subjected to anti-inflammatory and analgesic activity and showed significant anti-inflammatory and analgesic activity.     

Effects of β-cyclodextrin and di-O-methyl-β-cyclodextrin on the percutaneous absorption of butylparaben,indomethacin and sulfanilic acid

The effects of β-cyclodextrin (β-CD) and di-O-methyl-β-cyclodextrin (DM-β-CD) on the percutaneous absorption of butylparaben (BP), indomethacin (IM), and sulfanilic acid (SA) were investigated. The flow-through type diffusion cell was used for in vitro penetration experiments. All of the recorded data were fitted to the diffusion equation describing the drug penetration through a homogeneous plane membrane by the non-linear least-squares computer program, and two parameters corresponding to diffusion constant of drug and partition coefficient of that between skin and vehicle were obtained. Both cyclodextrins (CDs) decreased the penetration of BP depending on their concentrations. The decrease in BP penetration was explained by that in calculated apparent partition coefficient of BP and good correlation was observed between the partition coefficient and free BP fraction estimated based on the complex formation stoichiometry. IM penetration was also decreased by complex formation but some additional effects, somewhat different between β-CD and DM-β-CD, were observed. On the contrary, the penetration of SA which scarcely formed complex with either CD was significantly enhanced by DM-β-CD. This was attributed to the effect of DM-β-CD on the skin to reduce its barrier function.     

Inclusion complex of colchicine in hydroxypropyl-β-cyclodextrin tenders better solubility and improved pharmacokinetics

Context: Colchicine (CLC) causes cell death by destabilizing the tubulin unit. However, it ionizes at physiological pH resultant low bioavailability and therapeutic efficacy.

Objectives: We have attempted to augment the bioavailability of CLC by fabricating the inclusion complex with hydroxypropyl-β-cyclodextrin (HP-β-CD).

Materials and methods: CLC-HP-β-CD inclusion complex was prepared and evaluated with Fourier-transform infrared spectroscopy, differential scanning calorimetry, powder X-ray diffractometry, scanning electron microscopy, ¹H nuclear magnetic resonance (¹H NMR) spectroscopy and rotating frame overhauser enhancement spectroscopy (ROESY). Oral bioavailability of CLC-HP-β-CD inclusion complex was analyzed using high performance liquid chromatography method.

Results and discussion: Our phase-solubility data indicated the formation of a stable complex with K_c ~0.31?mM^?1 at pH 7.4. ¹H NMR ascertains that NHCOCH₃ moiety of CLC enters in the HP-β-CD cavity and deshielded the H-3 and H-5 protons. ROESY also correlates the H_f and H_g of CLC with H-3 and H-5 protons of HP-β-CD and indicates that H_f and H_g protons of CLC are present either as cis and/or trans form in CLC-HP-β-CD inclusion complex. Pharmacokinetic studies showed a 1.82-fold increase in absolute bioavailability of CLC upon complexation.

Conclusion: CLC-HP-β-CD inclusion complex may potentially be used as a viable formulation of CLC.     

Physico-chemical characterization and in vitro/in vivo evaluation of loratadine:dimethyl-β-cyclodextrin inclusion complexes

A tricyclic, piperidine derivative of antihistamines, loratadine, which belongs in class II of the Biopharmaceutical Classification System, was investigated. It is an ionizable drug, whose solubility depends on the gastrointestinal pH, and the bioavailability is therefore very variable. Inclusion complexes were prepared by kneading method, containing loratadine (LOR) and dimethyl-β-cyclodextrin (DIMEB) in two different molar ratios in an attempt to achieve better dissolution and therefore the better bioavailability of loratadine. The formation and physicochemical properties of the inclusion complexes were investigated by means of dissolution tests, pH-dependent solubility studies, electrospray ionization mass spectrometry and diffusion-ordered 1H NMR spectroscopy. The in vivo efficiency of the complexes was examined in rat animal experiments to confirm the better in vitro dissolution. The instrumental examinations proved the presence of total complexes in 1:1 ratio in both compositions. However, the in vitro pH-dependent solubility results, the in vivo blood levels and the greater pharmacological effect prove that excess DIMEB is needed to achieve the pH-independent and complete solubility of LOR, and therefore better and more consistent bioavailability.     

Comparison of the intestinal absorption and bioavailability of γ-tocotrienol and α-tocopherol: in vitro, in situ and in vivo studies

The aim of this work was to compare the intestinal absorption kinetics and the bioavailability of γ-tocotrienol (γ-T3) and α-tocopherol (α-Tph) administered separately as oil solutions to rats in vivo. Also, to explain the significant difference in the oral bioavailability of the compounds: (1) the release profiles using the dynamic in vitro lipolysis model, (2) the intestinal permeability and (3) carrier-mediated uptake by Niemann-Pick C1-like 1 (NPC1L1) transporter were examined. Absolute bioavailability studies were conducted after oral administration of γ-T3 or α-Tph prepared in corn oil to rats. In situ rat intestinal perfusion with ezetimibe (a NPC1L1 inhibitor) was performed to compare intestinal permeability. The in vitro interaction kinetics with NPC1L1 was examined in NPC1L1 transfected cells. While the in vitro release studies demonstrated a significantly higher release rate of γ-T3 in the aqueous phase, the oral bioavailability of α-Tph (36%) was significantly higher than γ-T3 (9%). Consequent in situ studies revealed significantly higher intestinal permeability for α-Tph compared with γ-T3 in rats. Moreover, the NPC1L1 kinetic studies demonstrated higher Vmax and Km values for α-Tph compared with γ-T3. Collectively, these results indicate that intestinal permeability is the main contributing factor for the higher bioavailability of α-Tph. Also, these results emphasize the potentially important role of intestinal permeability in the bioavailability of γ-T3, suggesting that enhancing its permeability would increase its oral bioavailability.     

Solubilization of naphthoquinones by complexation with hydroxypropyl-β-cyclodextrin

The effects of the hydroxypropyl-β-cyclodextrin (HPCD) on the solubility of 2-hydroxy-N-(5-methyl-3-isoxazolyl)-1,4-naphthoquinone-4-imine (I) were investigated. I is an experimental drug for the treatment of cancer which exhibits low water solubility and it is therefore difficult to prepare the solutions for biological tests. The presence of an ionizable hydroxyl moiety (pK_a=5.80) increases the solubility via pH adjustment, but only a solubility of 0.124 mg/ml was obtained at pH 8.00. I was found to form inclusion complexes in either its neutral or its anionic form with HPCD. Although the stability constant of the I complex is larger in the neutral form, a greater overall solubility is obtained when I is in its ionized form. A 270-fold solubility enhancement is possible by using a combined approach of pH adjustment and complexation with HPCD.     

In vitro and in vivo evaluation of oral tablet formulations prepared with ketoconazole and hydroxypropyl-β-cyclodextrin

The objective of this study was to enhance the solubility, dissolution rate, and oral bioavailability of a very poorly water-soluble anti-fungal agent, ketoconazole (KET), by inclusion complexation with a highly-soluble cyclodextrin derivative, hydroxypropyl-β cyclodextrin (HP-β-CD). Two groups of tablets containing KET alone and KET:HP-β-CD (1:2) kneaded product (KP) including magnesium stearate and lactopress (anhydrous and spray-dried) as excipients were prepared by direct compression method. After the characterization studies, the in vitro dissolution studies of these tablets in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were carried out. To evaluate the in vivo bioavailability, the tablets were administered orally to rabbits and drug levels in serum were determined by HPLC. Tablets containing the cyclodextrin complex showed a higher in vitro dissolution rate and bioavailability compared to the tablets containing KET alone.     

Beneficial effect of 17β-estradiol on hyperglycemia and islet β-cell functions in a streptozotocin-induced diabetic rat model

The modulating effect of estrogen on glucose homeostasis remains a controversial issue at present. In this study, we sought to determine the beneficial effect of 17β-estradiol (E₂) on hyperglycemia and islet β-cell functions in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were injected i.p. with STZ to induce a relatively mild diabetic condition. The rats were then treated with E₂ orally at 500 μg/kg body weight/day for 15 days to evaluate the modulating effect on hyperglycemia, insulin secretion, and islet β-cell proliferation. E₂ administration for 10 days significantly lowered plasma glucose levels, increased plasma insulin levels, and improved glucose tolerance by attenuating insulin response to oral glucose loading. These beneficial effects of E₂ were accompanied by increases in islet number and volume, rate of islet cell proliferation, and the amount of insulin secreted. The growth-stimulatory effect of E₂ on islet cells was linked to the functions of the estrogen receptor α. Notably, these protective effects of E₂ on diabetic conditions were basically not observed when the STZ-treated rats had a more severe degree of islet damage and hyperglycemia. Taken together, we conclude that E₂ can promote the regeneration of damaged pancreatic islets by stimulating β-cell proliferation in diabetic rats, and this effect is accompanied by improvements in glucose tolerance and a decrease in plasma glucose levels. These findings suggest that oral administration of E₂ may be beneficial in diabetic patients with an accelerated loss of islet β-cells.     

Enhancement of norfloxacin solubility via inclusion complexation with β-cyclodextrin and its derivative hydroxypropyl-β-cyclodextrin

The objectives of the study were to investigate the effects of β-cyclodextrin (βCD) and hydroxypropyl-β-cyclodextrin (HPβCD) on the solubility and dissolution rate of norfloxacin prepared using three different methods, at drug to cyclodextrin weight ratios of 1:1, 1:2, 1:4 and 1:8. All the methods increased the solubility and dissolution rate of norfloxacin via inclusion complexation with βCD and HPβCD. Norfloxacin was converted from crystalline to amorphous form through inclusion complexation. Solvent evaporation method was the most effective method in terms of norfloxacin solubilisation, while inclusion complex of HPβCD has higher solubility than βCD complex when prepared using the same procedure.     

Effects of Kollicoat IR® and hydroxypropyl-β-cyclodextrin on the dissolution rate of omeprazole from its microparticles and enteric-coated capsules

Omeprazole microparticles were prepared by different drying techniques using Kollicoat IR^® and hydroxypropyl-β-cyclodextrin hydrophilic polymers. Physico-chemical properties were investigated using differential scanning calorimetry and powder X-ray diffractometry. Dissolution rate was determined and compared to the physical mixtures and the morphology was studied using a scanning electron microscope. Omeprazole transformed from the crystalline state to the amorphous state as confirmed by the disappearance of its melting peak and the characteristic of the crystalline peaks. Omeprazole dissolution rate was enhanced significantly from its spray- and freeze-dried microparticles as compared to the corresponding physical mixtures and drug alone (P?<?0.05). F3 and F5 formula possessed superior release rate over other formulations. In acidic medium, the release of drug from enteric-coated capsules was not detectable, while it is completely released within 40?min after changing dissolution medium to phosphate buffer (pH 7.4). The transformation of OME from crystalline to amorphous state by using either Kollicoat IR^® or hydroxylpropyl-β-cyclodextrin is considered a promising way to improvement of drug dissolution.     

Doxycycline and hydroxypropyl-β-cyclodextrin complex in poloxamer thermal sensitive hydrogel for ophthalmic delivery

The present study aimed to prepare a chemically and physically stable formulation of doxycycline (Doxy) in an in situ thermally sensitive hydrogel for ophthalmic delivery. An inclusion complex of Doxy and hydroxypropyl-β-cyclodextrin (HP-β-CD) was first developed to increase the stability of Doxy in aqueous solution. The physical characteristics (phase solubility profiles, thermal analysis, X-ray powder diffractograms and infrared spectra) of the Doxy-HP-β-CD inclusion complex indicated the formation of a stable 1:1 complex. Poloxamers P407 (16–22%) and P188 (0–5%) were mixed to obtain a hydrogel with an appropriate gelation temperature for opthalmic use. Formulation of the inclusion complex in the poloxamer hydrogel exhibited a suitable gelation temperature (33.3 °C) after dilution with simulated tear fluid (Gel:STF=40:7, v/v). The release of Doxy from the poloxamer hydrogel followed a zero order equation suggesting it occurs through corrosion of the poloxamer hydrogel. Stability studies demonstrated that the inclusion of Doxy by HP-β-CD markedly improved its stability in aqueous solution both at 8 and 40 °C. This formulation of a doxycycline-HP-β-CD inclusion complex in an in situ thermally sensitive poloxamer hydrogel represents a potentially effective ophthalmic Doxy delivery system.     

Effect of a single oral dose of pp′DDT on the absorption of nutrients in vitro and on brush border enzymes in rat intestine

The effect of a single oral dose of ppDDT (100 mg/kg body wt.) has been studied on the intestinal uptake of certain nutrients and on brush border enzymes in rats. Intestinal uptake of leucine, and phenylalanine was considerably increased but there was no change in the absorption of glucose and alanine in DDT fed rats, compared to controls. The activities of brush border sucrase, alkaline phosphatase and Na⁺, K⁺-ATPase were significantly depressed in pesticide treated animals, but leucine aminopeptidase levels remained unaffected under these conditions. Analysis of the chemical composition of the microvillus membranes revealed a considerable enhancement in total lipids, phospholipids and triglyceride contents of the membranes in DDT exposed rats, but membrane protein, sialic acid and cholesterol fractions did not record any change. 1-¹⁴C-acetate incorporation into various lipid classes was studied to explain the observed increase in membrane lipids in DDT exposed animals.     

Enhanced anti-tumor effect of 9-nitro-camptothecin complexed by hydroxypropyl-β-cyclodextrin and safety evaluation

The aim of this study was to evaluate the safety and anti-tumor effect of 9-nitro-camptothecin/hydroxypropyl-β-cyclodextrin (9-NC/HP-β-CD) complex on tumor-bearing mice. The in vitro anti-tumor activity was tested by MTT assay. Our study revealed that the 9-NC/HP-β-CD complex showed significant anti-tumor activity towards Skov-3, MCF-7, HeLa and S180 cell lines with IC(50) values of 0.24 ± 0.09, 0.59 ± 0.20, 0.83 ± 0.11, and 6.30 ± 2.42 μg/ml, respectively, significantly superior to the free 9-NC. The in vivo therapeutic efficacy was investigated in ICR mice bearing mouse sarcoma S180. Both the high (3mg/kg) and low (1mg/kg) doses of 9-NC/HP-β-CD complex demonstrated high inhibition ratio of tumor growth (>75%). The subacute toxicity test was performed by measuring the body weight, histopathology, blood cell counts and clinical chemistry parameters (total bilirubin, alanine transferase, aspartate transferase, blood urea nitrogen and creatinine), and the results indicated the good safety profile of the complex. Taken together, the results suggested that the 9-NC complexed in HP-β-CD, instead of dissolved in the organic solvent, presented significant anti-tumor activity and low toxicity for the treatment of cancer.     

Determination of terbutaline enantiomers in human urine by capillary electrophoresis using hydroxypropyl-β-cyclodextrin as a chiral selector

A method for the determination of terbutaline enantiomers in human urine by capillary electrophoresis has been developed. Optimum resolution was achieved using 50 mM phosphate buffer, pH 2.5, containing 15 mM of hydroxypropyl-beta-cyclodextrin as a chiral selector. Urine samples were prepared by solid-phase extraction with Sep-pak silica, followed by CE. The assay was linear between 2-250 ng/mL (R = 0.9998 for (S)-(+)-terbutaline and R = 0.9999 for (R)-(-)terbutaline) and detection limit was 0.8 ng/mL. The intra-day variation ranged between 6.3 and 14.5% in relation to the measured concentration and the inter-day variation was 8.2-20.1%. It has been applied to the determination of (S)-(+)terbutaline and (R)-(-)-terbutaline in urine from healthy volunteer dosed with racemic terbutaline sulfate.     

Alpha-Mangostin protects rat articular chondrocytes against IL-1β-induced inflammation and slows the progression of osteoarthritis in a rat model

Osteoarthritis (OA) is a joint disease characterized by inflammation and cartilage degradation. α-Mangostin (α-MG), which can be isolated from the fruit of the tropical evergreen tree Garcinia mangostana-L, is known to have anti-inflammatory properties. The aim of the study was to investigate the use of α-MG in the treatment of OA, using both rat chondrocytes and an OA rat model induced by destabilization of the medial meniscus (DMM). Rat chondrocytes were pretreated with α-MG (0, 1.25, 2.5, and 5.0 μg/ml for 24 h) prior to stimulation with interleukin-1β (IL-1β) (10 ng/ml for 24 h). Nitric oxide (NO) production was determined using the Griess method and prostaglandin E₂ (PGE₂) was assessed using an enzyme-linked immunosorbent assay (ELISA). The expression of inducible nitric oxide synthase (INOS), cyclooxygenase-2 (COX-2), matrix metalloproteinase-3, -9, and -13 (MMP-3, MMP-9, and MMP-13), Collagen II, and Aggrecan were detected by both quantitative real-time PCR (qRT-PCR) and a western blot analysis. Nuclear factor-κB (NF-κB) signaling molecules were detected by western blot analysis. Detection of p65 nuclear translocation of NF-κB was examined using immunofluorescence staining. The OA rats received intraperitoneal injections of α-MG (10 mg/kg) or saline every other day. Hematoxylin and eosin and Safranin-O-Fast green staining were used to evaluate the severity of cartilage lesions up to 8 weeks following surgery. α-MG inhibited the production of NO and PGE₂. The elevated expression of INOS, COX-2, MMP-3, MMP-9, and MMP-13, and the degradation of Collagen II and Aggrecan, were reversed by α-MG in IL-1β-stimulated chondrocytes. In addition, IL-1β induced considerable phosphorylation of the NF-kB signaling pathway, which was inhibited by α-MG. Furthermore, the immunofluorescence staining demonstrated that α-MG could suppress IL-1β-induced p65 nuclear translocation. In vivo, cartilage treated with α-MG showed attenuated degeneration and had low Osteoarthritis Research Society International (OARSI) scores compared with the control group. Taken together, these results show that α-MG has potential therapeutic value in the treatment of OA.