The effects of organic salts on the cyclodextrin solubilization of drugs

Improved Topical Ophthalmic Natamycin Suspension for the Treatment of Fungal Keratitis

Purpose: Natamycin (NT) is used as a first-line antifungal prescription in the treatment of fungal keratitis (FK) and is commercially available as a 5% w/v ophthalmic suspension. NT shows poor water solubility and light sensitivity. Thus, the present investigation is aimed to enhance the fraction of NT in solution in the commercial formulation by adding cyclodextrins (CDs), thereby improving the delivery of the drug into deeper ocular tissues. Methods: The solubility of NT in different CDs, the impact of ultraviolet (UV) light exposure, stability at 4°C and 25°C, in vitro release, and ex vivo transcorneal permeation studies were performed. Results: NT exhibited the highest solubility (66-fold) in randomly methylated-β-cyclodextrin (RM-βCD) with hydroxypropyl-βCD (HP-βCD) showing the next highest solubility (54-fold) increase in comparison to market formulation Natacyn® as control. The stability of NT-CD solutions was monitored for 2 months (last-time point) at both storage conditions. The degradation profile of NT in NT-RM-βCD and NT-HP-βCD solutions under UV-light exposure followed first-order kinetics exhibiting half-lives of 1.2 h and 1.4 h, respectively, an almost 3-fold increase over the control solutions. In vitro release/diffusion studies revealed that suspensions containing RM-βCD and HP-βCD increased transmembrane flux significantly (3.1-fold) compared to the control group. The transcorneal permeability of NT from NT-RM-βCD suspension exhibited an 8.5-fold (P < 0.05) improvement compared to Natacyn eyedrops. Furthermore, the addition of RM-βCD to NT suspension increases the solubilized fraction of NT and enhances transcorneal permeability. Conclusion: Therefore, NT-RM-βCD formulations could potentially lead to a decreased frequency of administration and significantly improved therapeutic outcomes in FK treatment.

Preparation and Characterisation of Zinc Diethyldithiocarbamate-Cyclodextrin Inclusion Complexes for Potential Lung Cancer Treatment

Zinc diethyldithiocarbamate (Zn (DDC)2), a disulfiram metabolite (anti-alcoholism drug), has shown a strong anti-cancer activity in vitro. However, its application was limited by its low aqueous solubility and rapid metabolism. In this study, the solubility enhancement of Zn (DDC)2 is investigated by forming inclusion complexes with cyclodextrins. The inclusion complexes were prepared using two different types of beta-cyclodextrins, SBE-CD and HP-CD. Phase solubility diagrams for the resulting solutions were assessed; subsequently, the solutions were freeze-dried for further characterisation studies using DSC, TGA, XRD, and FTIR. The cytotoxic activity of the produced inclusion complexes was evaluated on human lung carcinoma cells using the MTT assay. The solubility of Zn (DDC)2 increased significantly upon adding beta-cyclodextrins, reaching approximately 4 mg/mL for 20% w/w CD solutions. The phase solubility diagram of Zn (DDC)2 was of the Ap-type according to the Higuchi and Connors model. Characterisation studies confirmed the inclusion of the amorphous drug in the CD-Zn (DDC)2 complexes. The cytotoxicity of Zn (DDC)2 was enhanced 10-fold by the inclusion complexes compared to the free drug. Overall, the resulting CD-Zn (DDC)2 inclusion complexes have a potential for treatment against lung cancer.

Solubility and Pharmacokinetic Profile Improvement of Griseofulvin through Supercritical Carbon Dioxide-Assisted Complexation with HP-γ-Cyclodextrin

Since griseofulvin was marketed as a non-polyene antifungal antibiotic drug in 1958, its poor water solubility has been an issue for its wide applications, and over the last sixty years, many attempts have been made to increase its water solubility; however, a significant result has yet to be achieved. Through supercritical carbon dioxide-assisted cyclodextrin complexation with the addition of a trace amount of water-soluble polymer surfactant, the griseofulvin inclusion complex with HP-γ-cyclodextrin was prepared and confirmed. The 1:2 ratio of griseofulvin and HP-γ-cyclodextrin in the complex was determined based on its NMR study. After complexation with HP-γ-cyclodextrin, griseofulvin's water solubility was increased 477 times compared with that of griseofulvin alone, which is the best result thus far. The complex showed 90% of griseofulvin release in vitro in 10 min, in an in vivo dog pharmacokinetic study; the Cmax was increased from 0.52 µg/mL to 0.72 µg/mL, AUC0-12 was increased from 1.55 μg·h/mL to 2.75 μg·h/mL, the clearance was changed from 51.78 L/kg/h to 24.16 L/kg/h, and the half-life time was changed from 0.81 h to 1.56 h, indicating the obtained griseofulvin complex can be a more effective drug than griseofulvin alone.

Anomalous Properties of Cyclodextrins and Their Complexes in Aqueous Solutions

Cyclodextrins (CDs) are cyclic oligosaccharides that emerged as industrial excipients in the early 1970s and are currently found in at least 130 marketed pharmaceutical products, in addition to numerous other consumer products. Although CDs have been the subject of close to 100,000 publications since their discovery, and although their structure and properties appear to be trivial, CDs are constantly surprising investigators by their unique physicochemical properties. In aqueous solutions, CDs are solubilizing complexing agents of poorly soluble drugs while they can also act as organic cosolvents like ethanol. CDs and their complexes self-assemble in aqueous solutions to form both nano- and microparticles. The nanoparticles have diameters that are well below the wavelength of visible light; thus, the solutions appear to be clear. However, the nanoparticles can result in erroneous conclusions and misinterpretations of experimental results. CDs can act as penetration enhancers, increasing drug permeation through lipophilic membranes, but they do so without affecting the membrane barrier. This review is an account of some of the unexpected results the authors have encountered during their studies of CDs as pharmaceutical excipients.

Encapsulation Efficiency and Functional Stability of Cinnamon Essential Oil in Modified β-cyclodextrins: In Vitro and In Silico Evidence

Essential oils (EOs) have good natural antioxidant and antimicrobial properties; however, their volatility, intense aroma, poor aqueous solubility, and chemical instability limit their applications in the food industry. The encapsulation of EOs in β-cyclodextrins (β-CDs) is a widely accepted strategy for enhancing EO applications. The complexation of cinnamon essential oil (CEO) with five types of β-CDs, containing different substituent groups (β-CD with primary hydroxyl, Mal-β-CD with maltosyl, CM-β-CD with carboxymethyl, HP-β-CD with hydroxypropyl, and DM-β-CD with methyl), inclusion process behaviors, volatile components, and antioxidant and antibacterial activities of the solid complexes were studied. The CEOs complexed with Mal-β-CD, CM-β-CD, and β-CD were less soluble than those complexed with DM-β-CD and HP-β-CD. Molecular docking confirmed the insertion of the cinnamaldehyde benzene ring into various β-CD cavities via hydrophobic interactions and hydrogen bonds. GC-MS analysis revealed that HP-β-CD had the greatest adaptability to cinnamaldehyde. The CEO encapsulated in β-, Mal-β-, and CM-β-CD showed lower solubility but better control-release characteristics than those encapsulated in DM- and HP-β-CD, thereby increasing their antioxidant and antibacterial activities. This study demonstrated that β-, Mal-β-, and CM-β-CD were suitable alternatives for the encapsulation of CEO to preserve its antioxidant and antibacterial activities for long-time use.

Solvent Free Twin Screw Processed Silybin Nanophytophospholipid: In Silico, In Vitro and In Vivo Insights

Silybin (SIL) is a polyphenolic phytoconstituent that is commonly used to treat liver disorders. It is difficult to fabricate an orally delivered SIL product due to its low oral bioavailability (0.95%). Therefore, the current research focusses on the development of a novel composition of a phospholipid complex, termed as nanophytophospholipid, of SIL by employing a unique, solvent-free Twin Screw Process (TSP), with the goal of augmenting the solubility and bioavailability of SIL. The optimised SIL-nanophytophospholipid (H6-SNP) was subjected to physicochemical interactions by spectrometry, thermal, X-ray and electron microscopy. The mechanism of drug and phospholipid interaction was confirmed by molecular docking and dynamics studies. Saturation solubility, in vitro dissolution, ex vivo permeation and preclinical pharmacokinetic studies were also conducted. H6-SNP showed good complexation efficiency, with a high practical yield (80%). The low particle size (334.7 ± 3.0 nm) and positively charged zeta potential (30.21 ± 0.3 mV) indicated the immediate dispersive nature of H6-SNP into nanometric dimensions, with good physical stability. Further high solubility and high drug release from the H6-SNP was also observed. The superiority of the H6-SNP was demonstrated in the ex vivo and preclinical pharmacokinetic studies, displaying enhanced apparent permeability (2.45-fold) and enhanced bioavailability (1.28-fold). Overall, these findings indicate that not only can phospholipid complexes be formed using solvent-free TSP, but also that nanophytophospholipids can be formed by using a specific quantity of lipid, drug, surfactant, superdisintegrant and diluent. This amalgamation of technology and unique composition can improve the oral bioavailability of poorly soluble and permeable phytoconstituents or drugs.

Bioavailability Enhancement Techniques for Poorly Aqueous Soluble Drugs and Therapeutics

The low water solubility of pharmacoactive molecules limits their pharmacological potential, but the solubility parameter cannot compromise, and so different approaches are employed to enhance their bioavailability. Pharmaceutically active molecules with low solubility convey a higher risk of failure for drug innovation and development. Pharmacokinetics, pharmacodynamics, and several other parameters, such as drug distribution, protein binding and absorption, are majorly affected by their solubility. Among all pharmaceutical dosage forms, oral dosage forms cover more than 50%, and the drug molecule should be water-soluble. For good therapeutic activity by the drug molecule on the target site, solubility and bioavailability are crucial factors. The pharmaceutical industry’s screening programs identified that around 40% of new chemical entities (NCEs) face various difficulties at the formulation and development stages. These pharmaceuticals demonstrate less solubility and bioavailability. Enhancement of the bioavailability and solubility of drugs is a significant challenge in the area of pharmaceutical formulations. According to the Classification of Biopharmaceutics, Class II and IV drugs (APIs) exhibit poor solubility, lower bioavailability, and less dissolution. Various technologies are discussed in this article to improve the solubility of poorly water-soluble drugs, for example, the complexation of active molecules, the utilization of emulsion formation, micelles, microemulsions, cosolvents, polymeric micelle preparation, particle size reduction technologies, pharmaceutical salts, prodrugs, the solid-state alternation technique, soft gel technology, drug nanocrystals, solid dispersion methods, crystal engineering techniques and nanomorph technology. This review mainly describes several other advanced methodologies for solubility and bioavailability enhancement, such as crystal engineering, micronization, solid dispersions, nano sizing, the use of cyclodextrins, solid lipid nanoparticles, colloidal drug delivery systems and drug conjugates, referring to a number of appropriate research reports.

In silico formulation prediction of drug/cyclodextrin/polymer ternary complexes by machine learning and molecular modeling techniques

Ternary cyclodextrin (CD) complexes (drug/CD/polymer) can effectively improve the solubility of water-insoluble drugs with large size than binary CD formulations. However, ternary formulations are screened by a trial-and-error approach, which is laborious and material-wasting. Current research aims to develop a prediction model for ternary CD formulations by combined machine learning and molecular modeling. 596 ternary formulations data were collected to build a prediction model by machine learning. The random forest model achieved good performance with R² = 0.887 in S_T prediction and R² = 0.815 in S_T/S_B prediction. Two ternary formulations (Hydrocortisone/β-CD/HPMC and dovitinib/γ-CD/CMC) were used to validate the prediction model. Molecular modeling results showed that HPMC not only warped around hydrocortisone but also prevented CD molecules from self-aggregation to increase solubility. In conclusion, a prediction model for the ternary CD formulations was successfully developed, which will significantly accelerate the formulation screening process to benefit the formulation development of water-insoluble drugs.

A Cyclodextrin-Stabilized Spermine-Tagged Drug Triplex that Targets Theophylline to the Lungs Selectively in Respiratory Emergency

Ion‐pairing a lifesaving drug such as theophylline with a targeting moiety could have a significant impact on medical emergencies such as status asthmaticus or COVID‐19 induced pneumomediastinum. However, to achieve rapid drug targeting in vivo the ion‐pair must be protected against breakdown before the entry into the target tissue. This study aims to investigate if inserting theophylline, when ion‐paired to the polyamine transporter substrate spermine, into a cyclodextrin (CD), to form a triplex, could direct the bronchodilator to the lungs selectively after intravenous administration. NMR demonstrates that upon the formation of the triplex spermine protruded from the CD cavity and this results in energy‐dependent uptake in A549 cells (1.8‐fold enhancement), which persists for more than 20 min. In vivo, the triplex produces a 2.4‐fold and 2.2‐fold increase in theophylline in the lungs 20 min after injection in rats and mice, respectively (p < 0.05). The lung targeting is selective with no increase in uptake into the brain or the heart where the side‐effects of theophylline are treatment‐limiting. Selectively doubling the concentration of theophylline in the lungs could improve the benefit‐risk ratio of this narrow therapeutic index medicine, which continues to be important in critical care.

Supramolecular cyclodextrin complex: Diversity, safety, and applications in ocular therapeutics

Approximately 30-70% of the existing and new chemical entities exhibit poor aqueous solubility. For topical ocular delivery, drug molecules need to possess both hydrophilic and lipophilic nature to enable absorption through the aqueous tear layer and permeation through the corneal lipophilic barrier. To overcome the aqueous solubility related issues, various techniques such as solid dispersion, particle size reduction, cyclodextrin complexation, co-solvency, prodrug, derivatization, and salt formation are being explored in the healthcare sector. Cyclodextrin inclusion complexation techniques have been established by several pharmaceutical industries for systemic administration allowing a transition from the lab to the clinics. Though cyclodextrins are exploited in ocular drug delivery, there are prevailing concerns regarding its absorption enhancing capacity and mechanism, retention at the ocular surfaces and, irritation and toxicity profiles. In the present review, the efforts taken by various research groups to address the concerns of using cyclodextrin and its derivatives in ocular therapeutics are summarized. Also, considerations and utility of cyclodextrin systems in fabricating newer formulations such as contact lens, inserts, and implants have been discussed in the review.

Evaluation of the bioavailability of hydrocortisone when prepared as solid dispersion

This study was conducted to formulate, characterize, and investigate the bioavailability of hydrocortisone (HCT) when prepared as solid dispersions. HCT was mixed in an organic solvent with polyethylene glycol 4000 (PEG 4000) and Kolliphor® P 407. Spray drying technique was employed to form a solid dispersion formulation at a specific ratio. Physical and chemical characterization of the formed particles were achieved using differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffractometry. Furthermore, comparative in vitro and in vivo studies were conducted between the formulated particles against neat HCT. The formulated solid dispersion showed elongated particles with leaf-like structure. Formation of new chemical bonds in the formed particle was suggested due to the change in the vibrational wave numbers and the significant improvement in the bioavailability of the dispersed particles proved the importance of this technique.

Self-association of cyclodextrins and cyclodextrin complexes in aqueous solutions

Cyclodextrins (CDs) are oligosaccharides that self-assemble in aqueous solutions to form transient clusters, nanoparticles and small microparticles. The critical aggregation concentration (cac) of the natural αCD, βCD and γCD in pure aqueous solutions was estimated to be 25, 8 and 9 mg/ml, respectively. The cac of 2-hydroxypropyl-β-cyclodextrin (HPβCD), that consists of mixture of isomers, was estimated to be significantly higher or 118 mg/ml. Addition of chaotropic agents (i.e. that disrupts non-covalent bonds such as hydrogen bonds) to the aqueous media increases the cac. Formation of drug/CD complexes can increase or decrease the cac. Due to the transient nature of the CD clusters and nanoparticles they can be difficult to detect and their presence is frequently ignored. However, they have profound effect on the physiochemical properties of CDs and their pharmaceutical applications. For example, the values of stability constants of drug/CD complexes can be both concentration dependent and method dependent. Like in the case of micelles water-soluble polymers can enhance the solubilizing effect of CDs. Also, formation of drug/CD complex nanoparticles appears to increase the ability of CDs to enhance drug delivery through some mucosal membranes.

Formulation of a film-coated dutasteride tablet bioequivalent to a soft gelatin capsule (Avodart®): Effect of γ-cyclodextrin and solubilizers

The aim of this study was to optimize a tablet formulation of dutasteride that is bioequivalent to a commercially available soft gelatin capsule (Avodart^®). The effect of cyclodextrin on enhancing the aqueous solubility of dutasteride was investigated, after which the formulation was further optimized with solubilizing polymer and surfactant. Among the cyclodextrins tested, the highest solubility was observed when dutasteride was complexed with γ-cyclodextrin. Moreover, the addition of polyvinylpyrrolidone and Gelucire/TPGS further enhanced the solubility of dutasteride. Differential scanning calorimetry (DSC) and powder X-ray diffraction (pXRD) studies demonstrated that dutasteride existed in the amorphous form in the complex. Optimized dutasteride complexes were selected after a pharmacokinetic study in rats, and film-coated tablets were prepared by the direct compression method. In vitro dissolution profiles for the tablets of dutasteride complexes were similar to those of the reference. Moreover, pharmacokinetic parameters including the C_max and AUC values after oral administration in beagle dogs were not significantly different from those of the reference with a relative bioavailability of 92.4%. These results suggest the feasibility of developing a tablet formulation of dutasteride using cyclodextrin complex in addition to a solubilizing polymer and surfactant.

Solubility of Cyclodextrins and Drug/Cyclodextrin Complexes

Cyclodextrins (CDs), a group of oligosaccharides formed by glucose units bound together in a ring, show a promising ability to form complexes with drug molecules and improve their physicochemical properties without molecular modifications. The stoichiometry of drug/CD complexes is most frequently 1:1. However, natural CDs have a tendency to self-assemble and form aggregates in aqueous media. CD aggregation can limit their solubility. Through derivative formation, it is possible to enhance their solubility and complexation capacity, but this depends on the type of substituent and degree of substitution. Formation of water-soluble drug/CD complexes can increase drug permeation through biological membranes. To maximize drug permeation the amount of added CD into pharmaceutical preparation has to be optimized. However, solubility of CDs, especially that of natural CDs, is affected by the complex formation. The presence of pharmaceutical excipients, such as water-soluble polymers, preservatives, and surfactants, can influence the solubilizing abilities of CDs, but this depends on the excipients' physicochemical properties. The competitive CD complexation of drugs and excipients has to be considered during formulation studies.

Effect of Switching to Travoprost Preserved With SofZia in Glaucoma Patients With Chronic Superficial Punctate Keratitis While Receiving BAK-preserved Latanoprost

PURPOSE

To assess the effect of switching 1 eye to topical travoprost 0.004% preserved with SofZia (TRAVATAN Z solution) in patients who had chronic superficial punctate keratitis (SPK) in both eyes treated with benzalkonium chloride-preserved latanoprost 0.005% (XALATAN).

METHODS

This was a prospective, randomized, controlled, multicenter, open-label, comparative 3-month follow-up study. Patients with open-angle glaucoma or ocular hypertension who received XALATAN monotherapy for at least 3 months and had SPK in both eyes were enrolled at 9 facilities. For each patient, 1 eye was randomly selected and switched to TRAVATAN Z solution (T-group); the contralateral control eye was treated with XALATAN (X-group). SPK in 5 corneal regions, conjunctival hyperemia, tear breakup time (TBUT), and intraocular pressure (IOP) were examined in a masked manner at baseline, 1 month, and 3 months. Changes in SPK, hyperemia, TBUT, and IOP were compared within treatment groups and between treatment groups.

RESULTS

Fifty-six patients completed the study. The frequency of SPK significantly decreased from baseline in the T-group and the X-group at 1 and 3 months (T-group, P<0.001; X-group, P<0.05). In the T-group, SPK scores were significantly improved in 4 corneal regions, excluding the superior region, at 1 and 3 months (all P<0.05), whereas in the X-group, SPK scores were significantly improved only in the temporal region at 1 month and in the inferior region at 3 months (P<0.05 for both). The total SPK score at 1 and 3 months in the T-group was significantly lower compared with the score in the X-group (P=0.0023 and 0.0102, respectively). The SPK score for the superior and central corneal region at 3 months in the T-group was significantly lower compared with the score in the X-group (P=0.0212 and 0.022, respectively). There were no substantial intergroup or intragroup differences in changes from baseline for hyperemia scores, TBUT, or IOP reduction.

CONCLUSIONS

Switching therapy from benzalkonium chloride-preserved latanoprost to travoprost preserved with SofZia ameliorated chronic SPK. There were no clinically relevant changes in hyperemia, TBUT, or IOP.

The Effects of Latanoprost With Benzalkonium Chloride Versus Travoprost With SofZia on the Ocular Surface

PURPOSE

To assess ocular surface changes in participants using latanoprost with benzalkonium chloride (Xalatan) and travoprost with SofZia (Travatan Z).

METHODS

In this prospective, open-label, nonrandomized cohort study, participants were classified into two groups: group 1 (n=28) naive to glaucoma therapy, group 2 (n=27) on previous Xalatan monotherapy in both eyes. Both groups started (or continued) Xalatan in the right eye and Travatan Z in the left eye. Baseline, 1-, and 2-month measurements of tear breakup time (TBUT), corneal staining score, conjunctival staining score, conjunctival hyperemia score, tear production, and intraocular pressure were obtained. The Ocular Surface Disease Index questionnaire measured participants' comfort and dryness symptoms. Medication preference was recorded.

RESULTS

Data were collected from 55 participants. Tear breakup time at baseline and 1-month follow-up in group 1 was significantly longer than that of group 2 (P=0.005). At 2 months, there was no significant difference in TBUT between the two groups (P=0.779). Tear production in group 1 at all three time points was significantly higher than group 2 (P<0.05). Conjunctival staining score at 2 months in group 1 was significantly higher than group 2 (P=0.031). There was no significant difference in other parameters between the groups at any other time point. No significant difference in any parameter was found between Xalatan and Travatan Z (intragroup comparison).

CONCLUSIONS

Significant differences in ocular surface characteristics were detected between groups, but no significant difference was detected between participants treated with Xalatan and Travatan Z.

Inclusion Complexation of Etodolac with Hydroxypropyl-beta-cyclodextrin and Auxiliary Agents: Formulation Characterization and Molecular Modeling Studies

The present investigation was aimed to prepare inclusion complexes of a therapeutically important nonsteroidal anti-inflammatory drug, etodolac (ETD) with hydroxypropyl-beta-cyclodextrin (HP-β-CD) and to study the effect of l-arginine (l-Arg) as an auxiliary agent on the complexation efficiency of HP-β-CD to improve aqueous solubility and the dissolution property of ETD. The binary and ternary complexes were prepared by physical mixing, coevaporation, and spray drying methods. The complexes were characterized using differential scanning colorimetry (DSC), Fourier transform-infrared spectroscopy (FT-IR), and powder X-ray diffraction (PXRD) studies. The mechanism of inclusion interaction of guest and host was established through ¹H NMR, molecular docking, and molecular dynamics studies. On the basis of preliminary screening studies, l-Arg was found to be the most efficient auxiliary agent for the present research problem. The change in crystallinity of ETD was evident from DSC and PXRD studies which indicated the formation of new solid forms. A remarkable increase in apparent stability constant (K_c) and complexation efficiency (CE) of HP-β-CD was observed in the presence of l-Arg in ternary complexes with improvement in solubility and dissolution of ETD than binary complexes. However, inclusion complexes of ETD obtained by computational studies is in good correlation with the results obtained through experimental methods. More stable complex formation with l-Arg was confirmed by molecular simulation studies too. Thus, the present study led to the conclusion that the ternary complex of ETD-HP-β-CD-l-Arg could be an innovative approach to augment the solubility and dissolution behavior of ETD.

Electrospun polyacrylonitrile/β-cyclodextrin based porous carbon nanofiber self-supporting electrode for capacitive deionization

With β-CD as both pore-forming reagent and carbon precursor, conductive porous carbon nanofibers are fabricated with excellent capacitive deionization performance.

Factors to consider in developing individual pharmaceutical product quality risk profiles useful to government procurement agencies

Governments that procure pharmaceutical products from an Essential Medicine List (EML) bear special responsibility for the quality of these products. In this article we examine the possibility of developing a pharmaceutical product quality risk assessment scheme for use by government procurement officials. We use the Chinese EML as a basis, and US recall data is examined as it is publically available.This is justified as the article is only concerned with inherent product quality risks. After establishing a link between Chinese essential medicines and those available in the US, we examine US recall data to separate product specific recalls. We conclude that, in addition to existing manufacturing based risks, there are two other product specific risks that stand out from all others, degradation and dissolution failure. Methodology for relative product risk for degradation is needed to be developed and further work is required to better understand dissolution failures which largely occur with modified-release solid oral products. We conclude that a product specific quality risk profile would be enhanced by including a risk assessment for degradation for all products, and in the case of solid oral products, dissolution.

Intestinal uptake and toxicity evaluation of acetazolamide and its multicomponent complexes with hidroxypropyl-β-cyclodextrin in rats

Large oral doses of ACZ lower the intraocular pressure (IOP), but usually lead to a multitude of systemic side effects, including gastrointestinal upset. The present study was undertaken to evaluate the effect of ACZ on the histological structure of rat duodenal mucosa and to assess a possible protective role of the complex formation of ACZ with HP-β-CD, either separately or in combination with a third compound, on the gut epithelial layer by histological and ultrastructural examinations of sections of rat duodenum exposed to ACZ or its formulations. In addition, the transport process of ACZ and its binary or ternary complexes across the duodenal mucosa by means of the single-pass intestinal perfusion (SPIP) method in rats was evaluated. Evidence was found that ACZ alters intestinal permeability and induces damage to the rat small intestine. In contrast, ACZ-induced intestinal injury may be abrogated by ACZ complexation. In addition, the complexation of ACZ with HP-β-CD, alone or in combination with a third compound, facilitated significant levels of ACZ uptake across the rat duodenal segment. Ternary complexes of ACZ with HP-β-CD in combination with TEA (triethanolamine) or calcium ions were found to provide an excellent approach that enabled an increased apparent permeability of ACZ across the duodenal epithelium, with a concomitant ability to preserve the integrity of the gut epithelium from ACZ-induced injury. These results could be useful for the design and development of novel ACZ formulations that can reduce GI toxicity, while still maintaining their essential therapeutic efficacies.

Pattern recognition methods as supplementary techniques for identification of salicylamide — cyclodextrins inclusion complexes

The objective of this study was to learn whether or not the pattern recognition methods, such as agglomerative cluster analysis (CA) and principal component analysis (PCA), can be used as supplementary techniques for identification of salicylamide (SAA) inclusion complexes with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). To do this, phase-solubility of SAA in the presence of the cyclodextrins was studied by the Higuchi-Connors method, which showed that the cyclodextrins enhanced the solubility of SAA in water as compared to that of the drug. Next, the solid phase complexes of the drug with β-CD and HP-β-CD were prepared by using the coprecipitation, precipitation-evaporation, and kneading methods. Identification of the inclusion complexes was performed by using thermal analysis, infrared spectroscopy, and wide angle X-ray scattering. Two multivariate statistical methods, CA and PCA, were used as the supplementary techniques for identification of the inclusion complexes. The results of the statistical analysis have shown that CA and PCA are helpful for interpretation of the thermoanalytical and spectral data. Moreover, these methods enabled proper classification of the products in all doubtful cases. They can be used as supplementary techniques to verify the conclusions of the above-mentioned standard methods.

Cyclodextrins

Although cyclodextrins (CDs) have been studied for over 100 years and can be found in at least 35 pharmaceutical products, they are still regarded as novel pharmaceutical excipients. CDs are oligosaccharides that possess biological properties that are similar to their linear counterparts, but some of their physicochemical properties differ. CDs are able to form water-soluble inclusion complexes with many poorly soluble lipophilic drugs. Thus, CDs are used to enhance the aqueous solubility of drugs and to improve drug bioavailability after, for example, oral administration. Through CD complexation, poorly soluble drugs can be formulated as aqueous parenteral solutions, nasal sprays and eye drop solutions. These oligosaccharides are being recognized as non-toxic and pharmacologically inactive excipients for both drug and food products. Recently, it has been observed that CDs and CD complexes in particular self-assemble to form nanoparticles and that, under certain conditions, these nanoparticles can self-assemble to form microparticles. These properties have changed the way we perform CD research and have given rise to new CD formulation opportunities. Here, the pharmaceutical applications of CDs are reviewed with an emphasis on their solubilizing properties, their tendency to self-assemble to form aggregates, CD ternary complexes, and their metabolism and pharmacokinetics.

Cyclodextrins as functional excipients: methods to enhance complexation efficiency

Cyclodextrins have gained currency as useful solubilizing excipients with an ever increasing list of beneficial properties and functionalities. Although their use in liquid dosage forms including oral and parenteral solutions is straightforward, their application to solids can be confounded by the added bulk that is contributed to the formulation. This factor has limited the use of cyclodextrin in tablets and relates systems mainly to potent drug substances. Increasing the ability of cyclodextrins to complex with drug through a manipulation of their complexation efficiency (CE) may expand the use of these materials to the increasing list of drug candidates and marketed drugs who may benefit from this technology. This brief review assesses tools and materials that have been suggested for increasing the CE for pharmaceutically useful cyclodextrins and drugs. The relative importance of impacting the drug solubility (S(0) ) and phase-solubility isotherm slope is discussed in the context of drug ionization and salt use; the impact of polymers, charge interactions, and charge shielding; and the coincidental formation of other complex types in the media. The influence of drug form as well as supersaturation is also discussed in the context of the responsible mechanisms along with aggregation, inclusion, and noninclusion complex formation.

Preparation and characterization of mosapride citrate inclusion complexes with natural and synthetic cyclodextrins

The aim of this work was to investigate the inclusion complexes between mosapride citrate and SBE7β-CD in comparison with the natural β-CD to enhance its bioavailability by improving the solubility and dissolution rate. The complexation efficiency value of SBE7β-CD was higher than that for β-CD. Solid binary systems of mosapride citrate with CDs were prepared by physical mixing, kneading and freeze-drying techniques at molar ratio of 1:1(drug:CD). Physicochemical characterization of the prepared systems was studied using X-ray diffractometry, differential scanning calorimetry, Fourier-transform infrared spectroscopy and scanning electron microscopy (SEM). Amorphous drug was detectable to large extent in inclusion complexes prepared using the freeze-drying technique. From the dissolution study of different inclusion complexes in simulated saliva solution (pH 6.8), we could concluded that irrespective of the preparation technique, the systems prepared using SBE7β-CD showed better performance than the corresponding ones prepared using β-CD. In addition, the freeze-drying technique showed superior dissolution enhancement than other methods especially when combined with the SBE7β-CD.

Carotenoids and β-cyclodextrin inclusion complexes: Raman spectroscopy and theoretical investigation

In the present study, the inclusion processes of β-carotene, astaxanthin, lycopene, and norbixin (NOR) into the β-cyclodextrin (β-CD) cavity were investigated by means of Raman spectroscopy and quantum mechanics calculations. The Raman ν(1) band assigned to C═C stretching was sensitive to the host-guest interaction and in general undergoes a blue shift (3-13 cm(-1)) after inclusion takes place, which is the consequence of the localization of single and double bonds. This is supported by the molecular modeling prediction, which inclusion complexes show the ν(1) band blue shifted by 1-8 cm(-1). The calculated complexation energies was small for most of derivatives and was found to be -11.1 kcal mol(-1) for inclusion of AST and +0.27 kcal mol(-1) for NOR. The stability order was qualitatively correlated to topological parameters accounting for the opening angle of the chain. This means that after inclusion the guest molecules assume a slightly more extended conformation, which enhances the host-guest contact, improving the interaction energy. The results discussed here clearly demonstrate the matrix effect on the carotenes' spectroscopic profile and should contribute to fully characterize the raw samples.

Complexation of microcystins and nodularin by cyclodextrins in aqueous solution, a potential removal strategy

Cyanotoxins are potent toxic compounds produced by cyanobacteria during algal blooms, which threaten drinking water supplies. These compounds can poison and kill animals and humans. The host-guest interactions of α-, β-, and γ-cyclodextrins (CD) with problematic cyanotoxins, including microcystins (MCs) and nodularin (NOD), were investigated to demonstrate the potential application of CDs for the removal of these toxins from drinking water or applications related to their separation or purification. MCs and NOD have a hydrophobic Adda chain, which contains diene and benzene functional groups. The complexation of these cyanotoxins with CDs was monitored by nuclear magnetic resonance (NMR). The (1)H NMR spectra for MCs are unchanged upon addition of α-CD (smallest host). However, addition of larger hosts, β-CD and γ-CD, leads to significant changes in chemical shifts of the benzene and diene resonances on the 3-amino-9-methoxy-2,6,8-trimethal-10-phenyldeca-4,6-dienoic acid (Adda) chain of MCs and NOD. Solution pH, natural organic matter, and salinity do not appreciably influence the host-guest complexation under our experimental conditions. The experimental binding constants for MCs and NOD with γ-CD are relatively strong, ranging from 1155 to 507 M(-1). The observed changes in chemical shifts for specific protons and competitive binding experiments demonstrate a 1:1 inclusion complex between γ-CD and MCs or NOD, with the Adda chains threading through the CD ring, resulting in an inclusion complex. Our results suggest that CD-type substrates are useful hosts for the complexation of MCs and NOD. CDs can be readily attached to a number of polymeric or solid supports and their functionality tailored to strengthen specific host-guest interactions. With further development of such materials, CD host-guest chemistry may find direct application in the removal and/or separation science of these compounds.

Enhancement of plant essential oils' aqueous solubility and stability using alpha and beta cyclodextrin

Sodium benzoate has been shown to produce benzene in combination with ascorbic acid. This has led to research for safe alternatives from plant essential oils and parabens that have shown some antimicrobial activity, but many of these compounds exhibit poor solubility in aqueous solutions. Cyclodextrins can increase the solubility of many compounds. This work aimed to investigate the solubility of 23 plant essential oils and 4 parabens in water and an apple juice medium. Four of these compounds were chosen for their low aqueous solubility to determine if complexing the compound with α- and β-cyclodextrin would increase solubility. Three of the complexes were dissolved in an acidified aqueous solution and then studied in glass and polyethylene terephthalate (PET) to determine if storage material would affect the stability. Solubility of the 27 compounds in distilled water ranged from 1.6 mg/L to 2460.6 mg/L and the solubility of 18 of the compounds decreased from 2.5 to 84.7% in apple juice medium (pH = 3.4, 12-13 °Brix). Complexation with cyclodextrin dramatically increased the solubility of the compounds, up to 10-fold. Packaging material had no effect on concentration of compounds present over 7 days. Cyclodextrins were able to increase solubility of these compounds to more suitable concentrations, and may lead to viable natural alternatives to sodium benzoate.

Self-assembled cyclodextrin aggregates and nanoparticles

Cyclodextrins (CDs) are widely used as enabling pharmaceutical excipients, mainly as solubilizing complexing agents. CDs are cyclic oligosaccharides with hydrophilic outer surface and a somewhat lipophilic central cavity. In aqueous solutions CDs are able to solubilize lipophilic drugs by taking up some lipophilic moiety of the drug molecule into the central cavity, i.e. through formation of hydrophilic inclusion complexes. Recently it has been observed that that other types of CD complexes, such as non-inclusion complexes, are also participating in the CD solubilization of poorly soluble drugs. However, in aqueous solutions CDs are also able self-assemble to form nanosized aggregates that can contribute to their solubilizing properties. At low CD concentrations (at about 1%, w/v) the fraction of CD molecules forming aggregates is insignificant but the aggregation increases rapidly with increasing CD concentration. Also, formation of CD complexes can increase the tendency of CDs to form aggregates and can lead to formation of micellar-type CD aggregates capable to solubilize poorly soluble compounds that do not readily form inclusion complexes. In this article formation of CD aggregates and CD nanoparticles is reviewed with emphasis on the physicochemical properties of self-assembled CDs and CD complexes.