Cyclodextrin formulation of dorzolamide and its distribution in the eye after topical administration.

Due to limited aqueous solubility of dorzolamide at physiologic pH, the pH of Trusopt eye drops (cont. 2% dorzolamide) has to be kept at about 5.65, and to increase the topical bioavailability of the drug from Trusopt the contact time of the drug with the eye surface is increased by increasing the viscosity of the eye drops to 100 cps. This low pH and high viscosity can lead to local irritation. In this study, dorzolamide hydrochloride was formulated as 2% and 4% low viscosity solutions (viscosity 3 to 5 cps) containing randomly methylated beta-cyclodextrin at pH 7.45. These formulations were evaluated in rabbits. The animals were sacrificed at various time points after topical administration of the drug and the dorzolamide concentration determined in the different parts of the eye. Trusopt was used as a reference standard. The topical availability of dorzolamide from the cyclodextrin-containing eye drops appeared to be comparable to that from Trusopt and the drug reached retina and optic nerve to give measurable concentrations for at least 8 h after administration of the eye drops.     

Diacyl glyceryl ester prodrugs for slow release in the skin: synthesis and in vitro degradation and absorption studies for naproxen derivatives

Diacyl glyceryl ester derivatives of naproxen were synthesized and tested for transdermal and dermal administration. Diacyl derivatives of aliphatic acids of various chain length were compared. The pharmaceutical properties of these compounds, such as lipophilicity, hydrolysis in a buffer solution at various pH values and degradation in human serum and hairless mouse skin homogenate, were investigated. All the diacyl derivatives were relatively stable in a neutral buffer solution, but were rapidly degraded to release naproxen in human serum and hairless mouse skin homogenate. The diacyl compounds could not penetrate hairless mouse skin in vitro. However, significant absorption into the skin could be measured, and this increased with increasing lipophilicity. A more than 100-fold difference in absorption was observed. The prodrugs were slowly hydrolyzed to naproxen inside the skin. The release of naproxen to the receptor compartment of diffusion cells showed that this type of prodrug could be used for controlled drug delivery.     

Solubilization and Stabilization of a Benzylpenicillin Chemical Delivery System by 2-Hydroxypropyl-β-cyclodextrin

A dihydropyridine pyridinium salt redox carrier-based chemical delivery system for benzylpenicillin (1) was complexed with 2-hydroxypropyl--cyclodextrin (HPCD). The solubility of the lipophilic 1, which is incompatible with aqueous formulations, was dramatically increased and showed a linear dependency on the HPCD concentration. The degree of incorporation was 20 mg of 1 per g of complex. The stability study of 1 in various pH buffers indicated the base-catalyzed hydrolysis of the acyloxyalkyl linkage and the hydration of the 5,6 double bond of the dihydropyridine as the main degradation processes. The overall loss of 1, which follows first-order kinetics, was not influenced by changes in ionic strength and elimination of oxygen from the reaction medium. The HPCD complex of 1, which has a stability constant of 720–940 M ^–1, stabilized the chemical delivery system. The influence of the temperature on the stability of 1 is also discussed.     

Aqueous hydrocortisone mouthwash solution: clinical evaluation

Patients often experience difficulties in applying topical steroids in orabase to the oral mucosa, particularly when large areas need to be covered. An aqueous hydrocortisone mouthwash solution has been developed, one that was anticipated to be more acceptable to patients. The solution contains hydrocortisone (0.3% w/v) in a 4.5% (w/v) 2-hydroxypropyl-β-cyclodextrin solution. Hydroxypropylmethylcellulose (0.5% w/v) was used to increase the viscosity of the solution and to promote the hydrocortisone±cyclodextrin complex. One hundred and two patients with aphthous ulceration, lichen planus, and other mucosal conditions used the mouthwash in an open clinical efficacy study. Most patients reported some or considerable improvement following a 2-week course of treatment with the mouthwash: 26 of 33 (78.8%) patients with aphthous ulceration were `much better', as were 26 of 54 (48.1%) patients with lichen planus and 5 of 16 (31.3%) patients with other mucosal lesions. No serious side effects were reported. Aqueous mouthwash solutions offer a potential vehicle for topical steroid therapy of oral mucosal lesions.     

Cyclodextrins: structure,physicochemical properties and pharmaceutical applications

Since their discovery over 100 years ago cyclodextrins (CDs) have been the subject of numerous scientific publications. In 2016 alone CDs were the subject of over 2200 research articles published in peer-reviewed journals and mentioned in over 2300 patents and patent applications, many of which were on pharmaceutical applications. Natural CDs and their derivatives are used as enabling pharmaceutical excipients that enhance aqueous solubility of poorly soluble drugs, increase drug permeability through biological membranes and improve drug bioavailability. Unlike conventional penetration enhancers, their hydrophilic structure and high molecular weight prevents them from penetrate into lipophilic membranes leaving biological membranes intact. The natural CDs and some of their derivatives have monographs in pharmacopeias and are also commonly used as food additives and in toiletry products. CDs form inclusion complexes with lipophilic moieties of hydrophobic drugs. Furthermore, CDs are able to form non-inclusion complexes and self-assembled aggregates; small and large complex aggregates with micellar-like structures that can enhance drug solubility. Excipients commonly used in pharmaceutical formulations may have additive or inhibiting effect on the CD solubilization. Here various methods used to investigate CD aggregate formation are reviewed as well as techniques that are used to increase the solubilizing effects of CDs; methods that enhance the apparent intrinsic solubility of drugs and/or the complexation efficacy and decrease the amount of CD needed to develop CD-containing pharmaceutical formulations. It will be explained how too much or too little CD can hamper drug bioavailability, and the role of CDs in solid dosage forms and parenteral formulations, and examples given on how CDs can enhance drug delivery after ocular, nasal and pulmonary administration.     

Encapsulation of Drug Molecules into Calix[n]arene Nanobaskets. Role of Aminocalix[n]arenes in Biopharmaceutical Field

Calix[n]arenes (CAs) are supramolecular compounds able to form guest-host inclusion complexes with metal ions, small organic molecules, and small moieties of larger molecules. Although the CA literature is extensive, relatively few publications deal with water-soluble CAs, especially those containing nitrogen-based functionality. These CAs possess antibacterial and antifungal activity. Because of their molecular structure, they are surface active and also able to form water-soluble drug complexes, giving additional potential as enabling pharmaceutical excipients. This article provides an overview of the published data regarding synthesis, physicochemical properties, and pharmaceutical application of water-soluble CAs with emphasis on those that contain nitrogen-based substituents in their structure, particularly aminoCAs. In particular, it describes state-of-the-art in complexation of water-soluble CAs with pharmaceutically relevant ions and organic molecules up to amino acids, DNA, and proteins.     

Methazolamide 1% in cyclodextrin solution lowers IOP in human ocular hypertension

PURPOSE: To formulate aqueous eye drops containing methazolamide 1% in cyclodextrin solution and to evaluate their effect on intraocular pressure (IOP) in a double-blind randomized trial in humans. Methazolamide, a carbonic anhydrase inhibitor (CAI), has been used in oral doses in the treatment of glaucoma but hitherto has not been successfully formulated in eye drops. In this study the effects of methazolamide are compared with those of dorzolamide (Trusopt). METHODS: Methazolamide 1% was formulated in a 2-hydroxypropyl-beta-cyclodextrin with hydroxypropyl methylcellulose in aqueous solution. Eight persons with ocular hypertension were treated with the methazolamide-cyclodextrin eye drops and eight persons with dorzolamide (Trusopt), both groups at dosages of three times a day for 1 week. IOP was measured before treatment was begun and on days 1, 3, and 8 at 9 AM (peak) and 3 PM (trough). RESULTS: After 1 week of treatment, the peak IOP in the methazolamide group had decreased from 24.4 +/- 2.1 mm Hg (mean +/- SD) to 21.0 +/- 2.0 mm Hg, which is a 14% pressure decrease (P: = 0.006). In the dorzolamide group, the peak IOP decreased from 23.3 +/- 2.1 mm Hg to 17.2 +/- 3.1 mm Hg, which is a 26% pressure decrease (P: < 0.001). On average, the IOP declined 3.4 +/- 1.8 mm Hg after methazolamide administration and 6.1 +/- 3.6 mm Hg after dorzolamide. CONCLUSIONS: Through cyclodextrin complexation, it is possible to produce topically active methazolamide eye drops that lower IOP. This is the first double-blind clinical trial that demonstrates the efficacy of the classic CAIs in eye drop formulation.     

Studies of curcumin and curcuminoids. XXVII. Cyclodextrin complexation: solubility,chemical and photochemical stability

Cyclodextrin complexes of the natural compound curcumin were prepared in order to improve the water solubility and the hydrolytic and photochemical stability of the compound. Complex formation resulted in an increase in water solubility at pH 5 by a factor of at least 10(4). The hydrolytic stability of curcumin under alkaline conditions was strongly improved by complex formation, while the photodecomposition rate was increased compared to a curcumin solution in organic solvents. The cavity size and the charge and bulkiness of the cyclodextrin side-chains influenced the stability constant for complexation and the degradation rate of the curcumin molecule.     

Self-association and cyclodextrin solubilization of drugs

Phase-solubility diagrams are frequently used to calculate stoichiometry of drug/cyclodextrin complexes. Linear diagrams (A(L)-type systems) are thought to indicate that the complexes are first order with respect to cyclodextrin and first or higher order with respect to the drug. Positive deviation from linearity (A(P)-type systems) are thought to indicate formation of complexes that are first order with respect to the drug but second or higher order with respect to cyclodextrin. The phase solubility of several different compounds, i.e., cholesterol, ibuprofen, diflunisal, alprazolam, 17beta-estradiol and diethylstilbestrol, and various charged and uncharged cyclodextrins was investigated. Phase-solubility diagrams of cholesterol in aqueous cyclodextrin solutions were all of A(P) type. However, the phase-solubility diagrams obtained with charged cyclodextrins could not be fitted to complexes of second or higher order with respect to cyclodextrin. The phase-solubility diagrams of ibuprofen and diflunisal were of A(L) type with slope greater than unity indicating formation of 2:1 drug/cyclodextrin complexes. However, Job's plots and space filling docking studies indicated that 1:1 complexes were formed. These and other observations show that stoichiometry of drug/cyclodextrin complexes cannot be derived from simple phase-solubility studies. Furthermore, the results indicate that drug/cyclodextrin complexes can self-associate to form water-soluble aggregates, which then can further solubilize the drug through non-inclusion complexation.     

Comparison of topical 0.7% dexamethasone–cyclodextrin with 0.1% dexamethasone sodium phosphate for postcataract inflammation

Background To compare 0.7% dexamethasone–cyclodextrin aqueous eye drop solution applied once daily with 0.1% dexamethasone sodium phosphate eye drops applied three times a day for the control of postoperative inflammation after cataract surgery.Methods Twenty cataract patients who underwent phacoemulsification and intraocular lens implantation were randomly divided into two postoperative treatment groups. Postoperative medication in group I included 0.1% dexamethasone sodium phosphate eye drops three times daily and in group II 0.7% dexamethasone–cyclodextrin eye drop solution once daily. Testing of visual acuity, biomicroscopic examination, applanation tonometry and laser flare cell meter (LFCM) examination were carried out before operation and days 1, 3, 7 and 21 after surgery.Results Preoperative and postoperative visual acuity, aqueous flare and cells in biomicroscopic examination, and the mean intraocular pressure did not show any statistically significant differences between the treatment groups. LFCM examination showed that the mean postoperative photon count values (P=0.032) and the median cell count values on the 1st (P=0.014), 3rd (P=0.031), 7th (P=0.034), and 21st (P=0.0097) postoperative days in group I were more elevated than in group II.Conclusions 0.7% dexamethasone–cyclodextrin eye drops applied once daily is a more effective postoperative anti-inflammatory medication than 0.1% dexamethasone sodium phosphate applied three times a day. In both groups, 3 weeks after the operation the mean visual acuity was normal and intraocular pressure significantly lower than before operation. The use of 0.7% dexamethasone–cyclodextrin eye drops may be useful especially in elderly people who cannot apply themselves the eye drops onto the eye.