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Sandilya AA, Priya MH. The counteracting influence of 2-hydroxypropyl substitution and the presence of a guest molecule on the shape and size of the β-cyclodextrin cavity. Phys Chem Chem Phys 2024; 26:11531-11544. [PMID: 38323885 DOI: 10.1039/d3cp05354g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
The aqueous solubility of β-cyclodextrin (β-CD), a cyclic carbohydrate comprising seven α-D-glucose molecules, is enhanced by 2-hydroxypropyl (2-HP) substitution of the hydroxyl groups at the CD rims. Our thorough analysis of the structural and solvation properties with different degrees of 2-hydroxypropyl substitution on β-CD using molecular dynamics simulations reveals that the solubility is enhanced at the cost of the structural distortion of the CD cyclic structure. Substitution at the secondary rim predominantly enhances the favourable interactions between CD and water by decreasing CD-CD hydrogen bonding and promoting CD-water hydrogen bonding. However, the effect of substitution at the primary rim on the CD-water interactions is minimal; the hydrogen bonds between water and the primary hydroxyl group in native CD merely get replaced by those between water and 2-HP, since the substitution makes the primary hydroxyl oxygen (O6 atom) inaccessible to water. In contrast, substitution at the primary rim maintains the structural integrity of CD, while substitution at the secondary rim results in structural distortion due to the disruption of the intramolecular hydrogen bond belt, even leading to cavity closure. Certain strategic substitutions of the primary hydroxyl groups can help in the reduction of structural distortion, depending upon the degree of substitution at the secondary hydroxyl rim. A detailed inspection of the simulation trajectory revealed that the tilting of glucose units with the primary hydroxyl oxygen (O6) pointing inward is the primary driver for cavity closure. Even though the dynamics of glucose tilting can influence the kinetics of host-guest complex formation, once the guest is well incorporated into the cavity, glucose tilting is inhibited and the cavity opens up as in native β-CD.
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Affiliation(s)
- Avilasha A Sandilya
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai-600036, India.
| | - M Hamsa Priya
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai-600036, India.
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Zahel P, Bruggink V, Hülsmann J, Steiniger F, Hofstetter RK, Heinzel T, Beekmann U, Werz O, Kralisch D. Exploring Microemulsion Systems for the Incorporation of Glucocorticoids into Bacterial Cellulose: A Novel Approach for Anti-Inflammatory Wound Dressings. Pharmaceutics 2024; 16:504. [PMID: 38675165 PMCID: PMC11054342 DOI: 10.3390/pharmaceutics16040504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/05/2024] [Accepted: 03/20/2024] [Indexed: 04/28/2024] Open
Abstract
The effective pharmacological treatment of inflamed wounds such as pyoderma gangraenosum remains challenging, as the systemic application of suitable drugs such as glucocorticoids is compromised by severe side effects and the inherent difficulties of wounds as drug targets. Furthermore, conventional semi-solid formulations are not suitable for direct application to open wounds. Thus, the treatment of inflamed wounds could considerably benefit from the development of active wound dressings for the topical administration of anti-inflammatory drugs. Although bacterial cellulose appears to be an ideal candidate for this purpose due to its known suitability for advanced wound care and as a drug delivery system, the incorporation of poorly water-soluble compounds into the hydrophilic material still poses a problem. The use of microemulsions could solve that open issue. The present study therefore explores their use as a novel approach to incorporate poorly water-soluble glucocorticoids into bacterial cellulose. Five microemulsion formulations were loaded with hydrocortisone or dexamethasone and characterized in detail, demonstrating their regular microstructure, biocompatibility and shelf-life stability. Bacterial cellulose was successfully loaded with the formulations as confirmed by transmission electron microscopy and surprisingly showed homogenous incorporation, even of w/o type microemulsions. High and controllable drug permeation through Strat-M® membranes was observed, and the anti-inflammatory activity for permeated glucocorticoids was confirmed in vitro. This study presents a novel approach for the development of anti-inflammatory wound dressings using bacterial cellulose in combination with microemulsions.
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Affiliation(s)
- Paul Zahel
- JeNaCell GmbH—An Evonik Company, 07745 Jena, Germany; (P.Z.); (V.B.); (U.B.)
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University, 07743 Jena, Germany; (R.K.H.); (O.W.)
| | - Vera Bruggink
- JeNaCell GmbH—An Evonik Company, 07745 Jena, Germany; (P.Z.); (V.B.); (U.B.)
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University, 07743 Jena, Germany; (R.K.H.); (O.W.)
| | - Juliana Hülsmann
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University, 07745 Jena, Germany; (J.H.); (T.H.)
| | - Frank Steiniger
- Electron Microscopy Center, University Hospital Jena, Friedrich Schiller University, 07743 Jena, Germany;
| | - Robert K. Hofstetter
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University, 07743 Jena, Germany; (R.K.H.); (O.W.)
| | - Thorsten Heinzel
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University, 07745 Jena, Germany; (J.H.); (T.H.)
| | - Uwe Beekmann
- JeNaCell GmbH—An Evonik Company, 07745 Jena, Germany; (P.Z.); (V.B.); (U.B.)
| | - Oliver Werz
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University, 07743 Jena, Germany; (R.K.H.); (O.W.)
| | - Dana Kralisch
- JeNaCell GmbH—An Evonik Company, 07745 Jena, Germany; (P.Z.); (V.B.); (U.B.)
- Evonik Operations GmbH, 45128 Essen, Germany
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Aiassa V, Garnero C, Zoppi A, Longhi MR. Cyclodextrins and Their Derivatives as Drug Stability Modifiers. Pharmaceuticals (Basel) 2023; 16:1074. [PMID: 37630988 PMCID: PMC10459549 DOI: 10.3390/ph16081074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 08/27/2023] Open
Abstract
Cyclodextrins (CDs) are cyclic oligosaccharides that contain a relatively hydrophobic central cavity and a hydrophilic outer surface. They are widely used to form non-covalent inclusion complexes with many substances. Although such inclusion complexes typically exhibit higher aqueous solubility and chemical stability than pure drugs, it has been shown that CDs can promote the degradation of some drugs. This property of stabilizing certain drugs while destabilizing others can be explained by the type of CD used and the structure of the inclusion complex formed. In addition, the ability to form complexes of CDs can be improved through the addition of suitable auxiliary substances, forming multicomponent complexes. Therefore, it is important to evaluate the effect that binary and multicomponent complexes have on the chemical and physical stability of complexed drugs. The objective of this review is to summarize the studies on the stabilizing and destabilizing effects of complexes with CDs on drugs that exhibit stability problems.
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Rawas-Qalaji M, Cagliani R, Al-Hashimi N, Al-Dabbagh R, Al-Dabbagh A, Hussain Z. Microfluidics in drug delivery: review of methods and applications. Pharm Dev Technol 2023; 28:61-77. [PMID: 36592376 DOI: 10.1080/10837450.2022.2162543] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Microfluidics technology has emerged as a promising methodology for the fabrication of a wide variety of advanced drug delivery systems. Owing to its ability for accurate handling and processing of small quantities of fluidics as well as immense control over physicochemical properties of fabricated micro and nanoparticles (NPs), microfluidic technology has significantly improved the pharmacokinetics and pharmacodynamics of drugs. This emerging technology has offered numerous advantages over the conventional drug delivery methods for fabricating of a variety of micro and nanocarriers for poorly soluble drugs. In addition, a microfluidic system can be designed for targeted drug delivery aiming to increase the local bioavailability of drugs. This review spots the light on the recent advances made in the area of microfluidics including various methods of fabrication of drug carriers, their characterization, and unique features. Furthermore, applications of microfluidic technology for the robust fabrication and development of drug delivery systems, the existing challenges associated with conventional fabrication methodologies as well as the proposed solutions offered by microfluidic technology have been discussed in details.HighlightsMicrofluidic technology has revolutionized fabrication of tunable micro and nanocarriers.Microfluidic platforms offer several advantages over the conventional fabrication methods.Microfluidic devices hold great promise in controlling the physicochemical features of fabricated drug carriers.Micro and nanocarriers with controllable release kinetics and site-targeting efficiency can be fabricated.Drug carriers fabricated by microfluidic technology exhibited improved pharmacokinetic and pharmacodynamic profiles.
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Affiliation(s)
- Mutasem Rawas-Qalaji
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates.,Research Institute For Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Dr. Kiran C. Patel College of Allopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Roberta Cagliani
- Research Institute For Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates
| | - Noor Al-Hashimi
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
| | - Rahma Al-Dabbagh
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
| | - Amena Al-Dabbagh
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
| | - Zahid Hussain
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates.,Research Institute For Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates
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Celebioglu A, Uyar T. Hydrocortisone/cyclodextrin complex electrospun nanofibers for a fast-dissolving oral drug delivery system. RSC Med Chem 2020; 11:245-258. [PMID: 33479631 PMCID: PMC7484989 DOI: 10.1039/c9md00390h] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 10/07/2019] [Indexed: 12/29/2022] Open
Abstract
The electrospinning of hydrocortisone/cyclodextrin complex nanofibers was performed in order to develop a fast-dissolving oral drug delivery system. Hydrocortisone is a water-insoluble hydrophobic drug, yet, the water solubility of hydrocortisone was significantly enhanced by inclusion complexation with hydroxypropyl-beta-cyclodextrin (HP-β-CyD). In this study, hydrocortisone/HP-β-CyD complexes were prepared in aqueous solutions having molar ratios of 1/1, 1/1.5 and 1/2 (hydrocortisone/HP-β-CyD). Highly concentrated aqueous solutions of HP-β-CyD (180%, w/v) were used for hydrocortisone/HP-β-CyD systems (1/1, 1/1.5 and 1/2) in order to perform electrospinning without the use of an additional polymer matrix. The turbidity of hydrocortisone/HP-β-CyD (1/1 and 1/1.5) aqueous solutions indicated the presence of some uncomplexed crystals of hydrocortisone whereas the aqueous solution of hydrocortisone/HP-β-CyD (1/2) was homogeneous indicating that hydrocortisone becomes totally water-soluble by inclusion complexation with HP-β-CyD. Nonetheless, the electrospinning of hydrocortisone/HP-β-CyD systems (1/1, 1/1.5 and 1/2) successfully yielded defect-free uniform nanofibrous structures. Moreover, the electrospinning process was quite efficient that hydrocortisone was completely preserved without any loss yielding hydrocortisone/HP-β-CyD nanofibers having the initial molar ratios (1/1, 1/1.5 and 1/2). The structural and thermal characterization of the hydrocortisone/HP-β-CyD nanofibers revealed that hydrocortisone was totally inclusion complexed with HP-β-CyD and was in the amorphous state in hydrocortisone/HP-β-CyD (1/2) nanofibers whereas some uncomplexed crystalline hydrocortisone was present in hydrocortisone/HP-β-CyD (1/1 and 1/1.5) nanofibers. Nevertheless, hydrocortisone/HP-β-CyD (1/1, 1/1.5 and 1/2) complex aqueous systems were electrospun in the form of nanofibrous webs having a free-standing and flexible nature. The hydrocortisone/HP-β-CyD (1/1, 1/1.5 and 1/2) nanofibrous webs have shown fast-dissolving behavior in water or when they were in contact with artificial saliva. Yet, the hydrocortisone/HP-β-CyD (1/2) nanofibrous web dissolved more quickly than the hydrocortisone/HP-β-CyD (1/1 and 1/1.5) nanofibrous webs due to the full inclusion complexation and the amorphous state of hydrocortisone in this sample. In short, the results suggest that polymer-free electrospun nanofibrous webs produced from hydrocortisone/HP-β-CyD could be quite applicable for fast-dissolving oral drug delivery systems.
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Affiliation(s)
- Asli Celebioglu
- Department of Fiber Science & Apparel Design , College of Human Ecology , Cornell University , Ithaca , NY 14853 , USA . ;
| | - Tamer Uyar
- Department of Fiber Science & Apparel Design , College of Human Ecology , Cornell University , Ithaca , NY 14853 , USA . ;
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Raut SY, Manne AS, Kalthur G, Jain S, Mutalik S. Cyclodextrins as Carriers in Targeted Delivery of Therapeutic Agents: Focused Review on Traditional and Inimitable Applications. Curr Pharm Des 2019; 25:444-454. [DOI: 10.2174/1381612825666190306163602] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 02/25/2019] [Indexed: 11/22/2022]
Abstract
The objective of the article is to provide a comprehensive review on the application of cyclodextrin
complexation in the delivery of drugs, bioactive molecules or macromolecules, with more emphasis on targeted
drug delivery. Classically the cyclodextrins have been considered only as a means of improving the solubility of
drugs; however, many attempts have been made to use cyclodextrins as drug delivery carriers. The cyclodextrin
surface can be modified with various ligands for active targeting of drugs. It can also be passively targeted
through various triggering mechanisms like thermal, magnetic, pH dependent, light dependent, ultrasound, etc. A
comprehensive literature review has been done in the area of drug delivery using cyclodextrins. Applications of
inclusion complexes in the drug delivery through various routes with examples are discussed. This review focuses
on receptor mediated active targeting as well as stimuli responsive passive targeting of drugs/genes by using
cyclodextrins. The article provides a detailed insight of the use of cyclodextrins and their derivatives on the targeted
delivery of the drugs/genes.
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Affiliation(s)
- Sushil Y. Raut
- Department of Pharmaceutics, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education (MAHE), Manipal 576104, Karnataka State, India
| | - Alekhya S.N. Manne
- Department of Pharmaceutics, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education (MAHE), Manipal 576104, Karnataka State, India
| | - Guruprasad Kalthur
- Department of Clinical Embryology, Kasturba Medical College, Manipal Academy of Higher Education, Manipal 576104, Karnataka State, India
| | - Sanyog Jain
- Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar (Mohali), Punjab 160062, India
| | - Srinivas Mutalik
- Department of Pharmaceutics, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education (MAHE), Manipal 576104, Karnataka State, India
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Egele K, Samaddar S, Schneider N, Thompson D, Wenz G. Synthesis of the Anionic Hydroxypropyl-β-cyclodextrin:Poly(decamethylenephosphate) Polyrotaxane and Evaluation of its Cholesterol Efflux Potential in Niemann-Pick C1 Cells. J Mater Chem B 2019; 7:528-537. [PMID: 31372225 PMCID: PMC6675466 DOI: 10.1039/c8tb02950d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Niemann-Pick type C disease (NPC) is a lysosomal storage disease that is characterized by a progressive accumulation of unesterified cholesterol in the lysosomes leading to organ damage from cell dysfunction. Hydroxypropyl-β-cyclodextrin (HP-β-CD) is an attractive drug candidate for treating NPC, as it diminishes cholesterol accumulation in NPC cells. Systemic HP-β-CD treatment, however, is limited by rapid renal clearance. We designed a new anionic HP-β-CD polyrotaxane to act as a slow release formulation based on a polyalkylene phosphate core to improve the pharmacokinetics. The polyalkylene phosphate comprises hydrophobic decamethylene spacers linked by biodegradable anionic phosphodiester bonds. HP-β-CD was threaded onto this polymer first and α-CD afterwards to prevent burst release of the threaded HP-β-CD. Our findings show that HP-β-CD was slowly released from the watersoluble polyrotaxane over a 30 days period. The polyrotaxane provided persistently diminished cholesterol levels in NPC1 cells by 20% relative to untreated cells. These results demonstrate the therapeutic potential of this novel HP-β-CD polyrotaxane for the mobilization of aberrantly stored cholesterol in NPC1 cells.
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Affiliation(s)
- Kerstin Egele
- Organic Macromolecular Chemistry, Saarland University, Saarbrücken, Germany
| | | | | | | | - Gerhard Wenz
- Organic Macromolecular Chemistry, Saarland University, Saarbrücken, Germany
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Burgalassi S, Cappello B, Chetoni P, Iervolino M, Monti D, Saettone MF. Rufloxacin Eyedrops: Effect of Different Formulations on Ocular Pharmacokinetics in Rabbits. Eur J Ophthalmol 2018; 16:311-7. [PMID: 16703552 DOI: 10.1177/112067210601600219] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE To evaluate the aqueous humor pharmacokinetics of rufloxacin in rabbits after topical administration of different formulations, and to individuate the ones showing the best pharmacokinetic profile. METHODS Six formulations were instilled in rabbit eyes: two pH 7.2 suspensions of non-salified rufloxacin base, or zwitterion (RUF), one of which was viscosized with tamarind seed polysaccharide (TSP); two pH 7.2 solutions of RUF obtained using hydroxypropyl-beta-cyclodextrin (CD), one of which was viscosized with TSP; and two pH 5.0 solutions of rufloxacin hydrochloride (RUF-HCl ), one of which was viscosized with TSP. At different times after administration, samples of aqueous humor were withdrawn and analyzed by high-pressure liquid chromatography. The main pharmacokinetic parameters of RUF in the aqueous humor produced by the different formulations were calculated and statistical differences were assessed. RESULTS The best results, in terms of aqueous humor bioavailability, were observed with two TSP-viscosized formulations: a solution of the hydrochloride (TSP/RUF-HCl) and a suspension of the base (TSP/RUF), followed by the non-viscosized solution of RUF-HCl. The formulations containing CD-solubilized RUF were much less effective. CONCLUSIONS The present data confirm the significant availability-enhancing properties of tamarind seed polysaccharide, and indicate that solubilization of RUF with hydroxypropyl-beta-cyclodextrin (CD/RUF) results in decreased drug availability with respect to standard formulations. Two of the TSP-viscosized formulations (RUF suspension and RUF-HCl solution) produced aqueous humor RUF concentrations in the range of activity against Enterobacteriaceae and Pseudomonas aeruginosa, thus warranting further studies on applications of rufloxacin in ocular therapy.
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Affiliation(s)
- S Burgalassi
- Department of Bioorganic Chemistry and Biopharmaceutics, University of Pisa, Pisa, Italy.
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Dhall M, Madan AK. Comparison of cyclodextrins and urea as hosts for inclusion of drugs. J INCL PHENOM MACRO 2017. [DOI: 10.1007/s10847-017-0748-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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10
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Loftsson T, Stefánsson E. Cyclodextrins and topical drug delivery to the anterior and posterior segments of the eye. Int J Pharm 2017; 531:413-423. [PMID: 28391041 DOI: 10.1016/j.ijpharm.2017.04.010] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Revised: 04/04/2017] [Accepted: 04/05/2017] [Indexed: 12/31/2022]
Abstract
It is generally believed that it is virtually impossible to obtain therapeutic drug concentrations in the posterior segment of the eye after topical application of aqueous, low viscosity eye drops. Thus, intravitreal drug injections and drug implants are currently used to treat diseases in the posterior segment such as macular edema. Here it is described how, through proper analysis of the drug permeation barriers and application of well-known pharmaceutical excipients, aqueous eye drops are designed that can deliver lipophilic drugs to the posterior segment as well as how such eye drops can maintain high drug concentrations in the anterior segment. Through stepwise optimization, eye drops containing solid drug/cyclodextrin complex microparticles with a mean diameter of 2-4μm, dissolved drug/cyclodextrin complex nanoparticles and dissolved drug molecules in an aqueous eye drop media of low viscosity were designed. After administration of the eye drops the microparticles slowly dissolved and maintained close to saturated drug concentrations in the aqueous tear fluid for several hours. Studies in rabbits and clinical evaluations in humans, using dorzolamide and dexamethasone as sample drugs, show that the eye drops deliver significant amounts of drugs to both the posterior segment and anterior segment of the eye. Clinical studies indicate that the eye drops can replace intravitreal injections and implants that are currently used to treat ophthalmic diseases and decrease frequency of drug administration, both of which can improve patient compliance.
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Affiliation(s)
- Thorsteinn Loftsson
- Faculty of Pharmaceutical Sciences, University of Iceland, Hofsvallagata 53, IS-107 Reykjavik, Iceland.
| | - Einar Stefánsson
- Department of Ophthalmology, Faculty of Medicine, National University Hospital, Eiríksgata 37, IS-101 Reykjavík, Iceland
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Tan L, Li J, Liu Y, Zhou H, Zhang Z, Deng L. Synthesis and characterization of β-cyclodextrin-conjugated alginate hydrogel for controlled release of hydrocortisone acetate in response to mechanical stimulation. J BIOACT COMPAT POL 2015. [DOI: 10.1177/0883911515590494] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Alginate hydrogels are a class of biomaterials that can be used as local release depots for therapeutic agents. A particular drug that can take advantage of alginate hydrogel for controlled release is hydrocortisone acetate. Hydrocortisone acetate is a widely used anti-inflammatory agent, but is limited in application due to poor solubility and lack of controlled delivery. To overcome this limitation, a mechanically responsive β-cyclodextrin-conjugated alginate (Alg-β-CD) hydrogel was synthesized and characterized for enhanced aqueous solubility and controlled release of hydrocortisone acetate. We demonstrated that mono-6-deoxy-6-ethylenediamine-β-cyclodextrin and hydrocortisone acetate formed a 1:1 inclusion complex, thus resulting in marked increase in hydrocortisone acetate solubility, while causing no significant inhibition to the growth of cultured mouse fibroblasts (L929). More importantly, the release of hydrocortisone acetate from the hydrogel system was increasingly sensitive to mechanical compression, and the mechanical responsiveness of hydrocortisone acetate release increased dramatically as the concentration of mono-6-deoxy-6-ethylenediamine-β-cyclodextrin increased from 0% to 46%, whereas the swelling rate and stiffness of the hydrogel decreased as the concentration of mono-6-deoxy-6-ethylenediamine-β-cyclodextrin increased. The mechanical responsiveness of hydrocortisone acetate release was attributable to conformational distortion of mono-6-deoxy-6-ethylenediamine-β-cyclodextrin moieties and deformation of the polymer network. Moreover, we demonstrated that the hydrogel continuously released and accumulated hydrocortisone acetate in the medium when compressed for up to 72 h, which led to increasing suppression of nitric oxide production in the lipopolysaccharide-stimulated mouse macrophages (RAW264.7), indicating desirable anti-inflammatory effect at the cell level. Hence, this hydrogel system may provide a useful platform for drug delivery, such as hydrocortisone acetate release to wound site, by intentionally generated mechanical force.
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Affiliation(s)
- Li Tan
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
- School of Materials Science and Engineering, Changzhou University, Changzhou, China
| | - Jingjing Li
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
| | - Yang Liu
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
| | - Huan Zhou
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
| | - Zhiguo Zhang
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
| | - Linhong Deng
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
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13
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Tártara LI, Quinteros DA, Saino V, Allemandi DA, Palma SD. Improvement of Acetazolamide Ocular Permeation Using Ascorbyl Laurate Nanostructures as Drug Delivery System. J Ocul Pharmacol Ther 2012; 28:102-9. [DOI: 10.1089/jop.2011.0104] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Luis I. Tártara
- Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, UNITEFA-CONICET, Córdoba, Argentina
| | - Daniela A. Quinteros
- Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, UNITEFA-CONICET, Córdoba, Argentina
| | - Verónica Saino
- Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, UNITEFA-CONICET, Córdoba, Argentina
| | - Daniel A. Allemandi
- Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, UNITEFA-CONICET, Córdoba, Argentina
| | - Santiago D. Palma
- Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, UNITEFA-CONICET, Córdoba, Argentina
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Bucolo C, Melilli B, Piazza C, Zurria M, Drago F. Ocular Pharmacokinetics Profile of Different Indomethacin Topical Formulations. J Ocul Pharmacol Ther 2011; 27:571-6. [DOI: 10.1089/jop.2011.0120] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Claudio Bucolo
- Department of Clinical and Molecular Biomedicine, Section of Pharmacology and Biochemistry, University of Catania, Catania, Italy
| | | | | | - Monia Zurria
- Research and Development, AlfaIntes, Casoria, Italy
| | - Filippo Drago
- Department of Clinical and Molecular Biomedicine, Section of Pharmacology and Biochemistry, University of Catania, Catania, Italy
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Microgels formed by electrostatic and hydrophobic interaction of naphthaleneacetic acid with β-cyclodextrin-grafted polyethyleneimine. Colloid Polym Sci 2011. [DOI: 10.1007/s00396-011-2442-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Loftsson T, Brewster ME. Pharmaceutical applications of cyclodextrins: effects on drug permeation through biological membranes. J Pharm Pharmacol 2011; 63:1119-35. [DOI: 10.1111/j.2042-7158.2011.01279.x] [Citation(s) in RCA: 201] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Abstract
Objectives
Cyclodextrins are useful solubilizing excipients that have gained currency in the formulator's armamentarium based on their ability to temporarily camouflage undesirable physicochemical properties. In this context cyclodextrins can increase oral bioavailability, stabilize compounds to chemical and enzymatic degradation and can affect permeability through biological membranes under certain circumstances. This latter property is examined herein as a function of the published literature as well as work completed in our laboratories.
Key findings
Cyclodextrins can increase the uptake of drugs through biological barriers if the limiting barrier component is the unstirred water layer (UWL) that exists between the membrane and bulk water. This means that cyclodextrins are most useful when they interact with lipophiles in systems where such an UWL is present and contributes significantly to the barrier properties of the membrane. Furthermore, these principles are used to direct the optimal formulation of drugs in cyclodextrins. A second related critical success factor in the formulation of cyclodextrin-based drug product is an understanding of the kinetics and thermodynamics of complexation and the need to optimize the cyclodextrin amount and drug-to-cyclodextrin ratios. Drug formulations, especially those targeting compartments associated with limited dissolution (i.e. the eye, subcutaneous space, etc.), should be carefully designed such that the thermodynamic activity of the drug in the formulation is optimal meaning that there is sufficient cyclodextrin to solubilize the drug but not more than that. Increasing the cyclodextrin concentration decreases the formulation ‘push’ and may reduce the bioavailability of the system.
Conclusions
A mechanism-based understanding of cyclodextrin complexation is essential for the appropriate formulation of contemporary drug candidates.
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Affiliation(s)
- Thorsteinn Loftsson
- Faculty of Pharmaceutical Sciences, University of Iceland, Hofsvallagata, Reykjavik, Iceland
| | - Marcus E Brewster
- Pharmaceutical Development and Manufacturing Sciences, Janssen Research and Development, Johnson & Johnson, Scheperstraat, Beerse, Belgium
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Ali HSM, York P, Ali AMA, Blagden N. Hydrocortisone nanosuspensions for ophthalmic delivery: A comparative study between microfluidic nanoprecipitation and wet milling. J Control Release 2010; 149:175-81. [PMID: 20946923 DOI: 10.1016/j.jconrel.2010.10.007] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 09/24/2010] [Accepted: 10/03/2010] [Indexed: 02/07/2023]
Abstract
Recently, drug nanosuspensions have shown a potential for ophthalmic delivery. In this study, a hydrocortisone (HC) nanosuspension (NS) was developed using microfluidic nanoprecipitation as a recent, simple and cost-effective bottom-up technique of drug nanonization. For comparison, a second HC NS was prepared by top-down wet milling procedures. The produced nanosuspensions were characterized for particle size, shape and zeta potential. HC nanosuspensions of approximately 300nm particle size were produced by adjusting experimental conditions of the two processing techniques. Results of X-ray diffraction and differential scanning calorimetry revealed that HC maintained the crystalline structure upon milling, while predominant amorphous particles were generated after precipitation. Ocular bioavailability of HC nanosuspensions was assessed in albino rabbits using HC solution as a control. A sustained drug action was maintained up to 9h for the nanosuspensions compared to 5h for the drug solution. The precipitated and milled NS achieved comparable AUC(0-9h) values of 28.06±4.08 and 30.95±2.2, respectively, that were significantly (P<0.05) higher than that of HC solution (15.86±2.7). After 2 months storage at room temperature, the milled HC NS showed good stability with no discernable changes in particle size, whereas the particle size of the precipitated HC NS increased to 440nm.
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Affiliation(s)
- Hany S M Ali
- Institute of Pharmaceutical Innovation, University of Bradford, Bradford, BD7 1DP, UK.
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18
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Granero GE, Longhi MR. Promising complexes of acetazolamide for topical ocular administration. Expert Opin Drug Deliv 2010; 7:943-53. [DOI: 10.1517/17425247.2010.497536] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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19
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20
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El Maghraby G, Alomrani A. Effects of hydroxypropyl-β-cyclodextrin, gel and in situ gelling systems on the stability of hydrocortisone after gamma irradiation. J Drug Deliv Sci Technol 2010. [DOI: 10.1016/s1773-2247(10)50063-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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21
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Zawko SA, Truong Q, Schmidt CE. Drug-binding hydrogels of hyaluronic acid functionalized with β-cyclodextrin. J Biomed Mater Res A 2008; 87:1044-52. [DOI: 10.1002/jbm.a.31845] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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Zhang J, Wang L, Gao C, Zhang L, Xia H. Ocular Pharmacokinetics of Topically-Applied Ketoconazole Solution Containing Hydroxypropyl Beta-Cyclodextrin to Rabbits. J Ocul Pharmacol Ther 2008; 24:501-6. [DOI: 10.1089/jop.2008.0015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Junjie Zhang
- Pharmaceutic and Pharmacology Department, Henan Eye Institute, Henan Key Laboratory of Keratopathy, Zhengzhou, China
| | - Liya Wang
- Pharmaceutic and Pharmacology Department, Henan Eye Institute, Henan Key Laboratory of Keratopathy, Zhengzhou, China
| | - Changfeng Gao
- Pharmaceutic and Pharmacology Department, Henan Eye Institute, Henan Key Laboratory of Keratopathy, Zhengzhou, China
| | - Li Zhang
- Pharmaceutic and Pharmacology Department, Henan Eye Institute, Henan Key Laboratory of Keratopathy, Zhengzhou, China
| | - Huiyun Xia
- Pharmaceutic and Pharmacology Department, Henan Eye Institute, Henan Key Laboratory of Keratopathy, Zhengzhou, China
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23
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Prabagar B, Yoo BK, Woo JS, Kim JA, Rhee JD, Piao MG, Choi HG, Yong CS. Enhanced bioavailability of poorly water-soluble clotrimazole by inclusion with β-cyclodextrin. Arch Pharm Res 2007; 30:249-54. [PMID: 17366748 DOI: 10.1007/bf02977701] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Clotrimazole, a poorly water-soluble antimycotic agent, is a promising agent for various diseases including cancer and sickle cell anemia. To improve the oral bioavailability of clotrimazole, the inclusion compound of clotrimazole with beta-cyclodextrin was prepared by spray-drying method and characterized by phase solubility, differential scanning calorimetry and dissolution. Furthermore, the pharmacokinetics after oral administration in rats was then performed compared with clotrimazole powder. The solubility of clotrimazole increased linearly as a function of beta-cyclodextrin concentration, resulting in A(L) type phase solubility diagram which revealed a formation of inclusion compound in a molar ratio of 1:2, with the apparent association constant of 230.2 M(-1). The dissolution rate of clotrimazole in the inclusion compound increased greatly compared to clotrimazole powder in pH 7.4 phosphate buffer solution. The inclusion compound gave significantly higher initial plasma concentrations, Cmax and AUC of clotrimazole than did clotrimazole powder when they were administered as suspension form, indicating that the drug from inclusion compound could be more orally absorbed in rats. Thus, the oral bioavailability of clotrimazole could be improved markedly by inclusion complexation, possibly due to an increased dissolution rate.
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24
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Loftsson T, Stefánsson E. Cyclodextrins in ocular drug delivery: theoretical basis with dexamethasone as a sample drug. J Drug Deliv Sci Technol 2007. [DOI: 10.1016/s1773-2247(07)50001-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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25
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Choi HG, Kim DD, Jun HW, Yoo BK, Yong CS. Improvement of Dissolution and Bioavailability of Nitrendipine by Inclusion in Hydroxypropyl-β-cyclodextrin. Drug Dev Ind Pharm 2003; 29:1085-94. [PMID: 14677769 DOI: 10.1081/ddc-120025866] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A significant increase in solubility and dissolution rate of nitrendipine, a slightly soluble calcium channel blocker, was achieved by inclusion complexation with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The inclusion complex was prepared by solvent evaporation method and characterized by phase solubility method, x-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. The solubility of nitrendipine increased linearly as a function of HP-beta-CD concentration, resulting in AL-type phase solubility diagram which revealed a formation of inclusion complex in a molar ratio of 1:1, with the apparent association constant of 108.3M(-1). The in vitro dissolution rate of nitrendipine in pH 7.4 phosphate buffer was in the order of inclusion complex, physical mixture, and nitrendipine powder. These three different forms of nitrendipine were administered orally to rats with a dose of 10 mg/kg equivalent to nitrendipine. The AUC of inclusion complex was significantly larger than that of nitrendipine powder. Tmax of inclusion complex was significantly shorter and Cmax was significantly higher than those of nitrendipine powder. Cmax of physical mixture was higher than that of nitrendipine powder. Tmax of physical mixture, however, remained the same. The results indicated that the bioavailability of nitrendipine could be improved markedly by inclusion complexation, possibly due to an increased dissolution rate.
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Affiliation(s)
- Han-Gon Choi
- College of Pharmacy, Yeungnam University, Gyongsan, Korea
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26
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Maestrelli F, Mura P, Casini A, Mincione F, Scozzafava A, Supuran CT. Cyclodextrin complexes of sulfonamide carbonic anhydrase inhibitors as long-lasting topically acting antiglaucoma agents. J Pharm Sci 2002; 91:2211-9. [PMID: 12226848 DOI: 10.1002/jps.10215] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Complexes of several 1,3,4-thiadiazole-2-sulfonamide derivatives possessing strong carbonic anhydrase (CA) inhibitory properties with beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin were obtained and characterized. Although the investigated CA inhibitors possessed very powerful inhibitory properties against the two CA isozymes involved in aqueous humor production within the eye, i.e., CA II and CA IV, these compounds were topically ineffective as intraocular pressure (IOP) lowering agents in normotensive/hypertensive rabbits, due to their very low water solubility. On the contrary, the cyclodextrin-sulfonamide complexes proved to be effective and long-lasting IOP lowering agents in the two animal models of glaucoma mentioned above.
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Affiliation(s)
- Francesca Maestrelli
- Università degli Studi di Firenze, Dipartimento di Scienze Farmaceutiche, Via Gino Capponi 9, I-50121, Florence, Italy
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27
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Abstract
The leading cause of irreversible blindness is glaucoma, a disease normally characterized by the development of ocular hypertension and consequent damage to the optic nerve at its point of retinal attachment. This results in a narrowing of the visual field, and eventually results in blindness. A number of drugs are available to lower intraocular pressure (IOP), but, occasionally, they are ineffective or have intolerable side-effects for some patients and can lose efficacy with chronic administration. The smoking of marijuana has decreased IOP in glaucoma patients. Cannabinoid drugs, therefore, are thought to have significant potential for pharmaceutical development. However, as the mechanism surrounding their effect on IOP initially was thought to involve the CNS, issues of psychoactivity hindered progress. The discovery of ocular cannabinoid receptors implied an explanation for the induction of hypotension by topical cannabinoid applications, and has stimulated a new phase of ophthalmic cannabinoid research. Featured within these investigations is the possibility that at least some cannabinoids may ameliorate optic neuronal damage through suppression of N-methyl-D-aspartate receptor hyperexcitability, stimulation of neural microcirculation, and the suppression of both apoptosis and damaging free radical reactions, among other mechanisms. Separation of therapeutic actions from side-effects now seems possible through a diverse array of novel chemical, pharmacological, and formulation strategies.
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Affiliation(s)
- Tomi Järvinen
- Department of Pharmaceutical Chemistry, University of Kuopio, Finland.
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28
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Loftsson T, Stefánsson E. Cyclodextrins in eye drop formulations: enhanced topical delivery of corticosteroids to the eye. ACTA OPHTHALMOLOGICA SCANDINAVICA 2002; 80:144-50. [PMID: 11952479 DOI: 10.1034/j.1600-0420.2002.800205.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cyclodextrins are cylindrical oligosaccharides with a lipophilic central cavity and hydrophilic outer surface. They can form water-soluble complexes with lipophilic drugs, which 'hide' in the cavity. Cyclodextrins can be used to form aqueous eye drop solutions with lipophilic drugs, such as steroids and some carbonic anhydrase inhibitors. The cyclodextrins increase the water solubility of the drug, enhance drug absorption into the eye, improve aqueous stability and reduce local irritation. Cyclodextrins are useful excipients in eye drop formulations of various drugs, including steroids of any kind, carbonic anhydrase inhibitors, pilocarpine, cyclosporins, etc. Their use in ophthalmology has already begun and is likely to expand the selection of drugs available as eye drops. In this paper we review the properties of cyclodextrins and their application in eye drop formulations, of which their use in the formulation of dexamethasone eye drops is an example. Cyclodextrins have been used to formulate eye drops containing corticosteroids, such as dexamethasone, with levels of concentration and ocular absorption which, according to human and animal studies, are many times those seen with presently available formulations. Cyclodextrin-based dexamethasone eye drops are well tolerated in the eye and seem to provide a higher degree of bioavailability and clinical efficiency than the steroid eye drop formulations presently available. Such formulations offer the possibility of once per day application of corticosteroid eye drops after eye surgery, and more intensive topical steroid treatment in severe inflammation. While cyclodextrins have been known for more than a century, their use in ophthalmology is just starting. Cyclodextrins are useful excipients in eye drop formulations for a variety of lipophilic drugs. They will facilitate eye drop formulations for drugs that otherwise might not be available for topical use, while improving absorption and stability and decreasing local irritation.
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Affiliation(s)
- Thorsteinn Loftsson
- Faculties of Pharmacy and Medicine, University of Iceland, Reykjavik, Iceland
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29
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Abstract
Cyclodextrins are cyclic oligosaccharides with a hydrophilic outer surface and a somewhat lipophilic central cavity. Cyclodextrins are able to form water-soluble inclusion complexes with many lipophilic water-insoluble drugs. In aqueous solutions drug molecules located in the central cavity are in a dynamic equilibrium with free drug molecules. Furthermore, lipophilic molecules in the aqueous complexation media will compete with each other for a space in the cavity. Due to their size and hydrophilicity only insignificant amounts of cyclodextrins and drug/cyclodextrin complexes are able to penetrate into lipophilic biological barriers, such as intact skin. In general, cyclodextrins enhance topical drug delivery by increasing the drug availability at the barrier surface. At the surface the drug molecules partition from the cyclodextrin cavity into the lipophilic barrier. Thus, drug delivery from aqueous cyclodextrin solutions is both diffusion controlled and membrane controlled. It appears that cyclodextrins can only enhance topical drug delivery in the presence of water.
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Affiliation(s)
- T Loftsson
- Faculty of Pharmacy, University of Iceland, Hofsvallagata 53, PO Box 7210, IS-107, Reykjavik, Iceland.
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30
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Proniuk S, Blanchard J. Influence of degree of substitution of cyclodextrins on their colligative properties in solution. J Pharm Sci 2001; 90:1086-90. [PMID: 11536213 DOI: 10.1002/jps.1062] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The purpose of this study was to investigate the effect of the total degree of substitution (TDS) on the colligative properties of substituted cyclodextrins (CDs; i.e., beta- and gamma-cyclodextrins substituted with sulfobutylether or hydroxypropyl groups) in solution. The osmotic pressure (OP) of aqueous CD solutions was determined over the concentration range 100-350 mmol/kg using vapor pressure osmometry. A chloride ion-selective electrode was used to help determine the possible mechanism for any CD-water interactions that might occur by measuring the chloride-ion activity of a sodium chloride solution containing various CDs. Titration microcalorimetry was used to verify that sodium chloride did not interact with the CDs, thereby permitting the chloride ion activity to be utilized as an indicator of any possible CD-water interaction. The results indicate that CDs with different total degrees of substitution (TDS) exhibit different colligative properties in solution. It was observed that increases in the degree of substitution of the CD produced an increased OP. All substituted CDs exhibited an OP above their theoretical values, whereas the OP of the unsubstituted gamma-CD was below its expected value, likely due to self-association. The results obtained with the chloride-ion selective electrode did not exhibit a consistent trend; however, it was observed that changes in the TDS caused significant changes in the activity of chloride ions in solution. These findings are of interest in using CDs to formulate parenteral and ophthalmic solutions where the OP of the solutions must be considered.
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Affiliation(s)
- S Proniuk
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ 85721, USA
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31
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Abstract
1. Despite the accessibility of the front of the eye, efficient delivery of drug to treat various ocular disorders is a challenge to the formulation scientist. The majority of ophthalmic medications are formulated as eye drops. Due to anatomical constraints, the volume that can be administered is limited to approximately 30 microL. This, together with the efficient clearance system that exists in the front of the eye, makes it difficult to maintain an effective pre-ocular drug concentration for a desired length of time. Various formulation strategies have been used to increase pre-ocular retention of eye drops. The most successful of these has been the inclusion of viscosity enhancing polymers, particularly those able to interact with the mucous layer on the eye surface or those that can undergo a transition from a solution to a gel under the conditions of the pre-ocular area. 2. When the target site is intra-ocular, drug must be absorbed from the pre-ocular region into the eye. The main route for absorption is across the cornea. However, absorption of drug across the cornea is inefficient due to its impermeable nature and small surface area. Thus, the intra-ocular bioavailability of topically administered medications is typically less than 10%. 3. Corneal permeability favours moderately lipophilic compounds. These compounds often have a low aqueous solubility. Problems in ocular drug delivery and formulation are compounded for poorly soluble drugs that must be formulated as suspensions. 4. Reformulation of ophthalmic suspensions as solutions has many advantages. This may be achieved by complexation using cyclodextrins. Solubilization using cyclodextrins can overcome many of the formulation problems. However, it is unclear as to their potential for improving ocular bioavailability, which is seemingly drug dependent and may be influenced by both the physicochemical properties of the drug and the complex formed.
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Affiliation(s)
- N M Davies
- Formulation and Drug Delivery Group, School of Pharmacy, University of Otago, Dunedin, New Zealand.
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Filipović-Grcić J, Voinovich D, Moneghini M, Becirevic-Lacan M, Magarotto L, Jalsenjak I. Chitosan microspheres with hydrocortisone and hydrocortisone-hydroxypropyl-beta-cyclodextrin inclusion complex. Eur J Pharm Sci 2000; 9:373-9. [PMID: 10664477 DOI: 10.1016/s0928-0987(99)00078-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the present study, an inclusion complex composed of hydrocortisone acetate (HC) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was prepared by the spray-drying method. HC alone, HC inclusion complex or HC with HPbetaCD as a physical mixture were incorporated into chitosan microspheres by spray-drying. The inclusion complex and microspheres were characterized by X-ray powder diffractometry and differential scanning calorimetry (DSC). Microspheres were studied with respect to particle size distribution, drug content and in vitro drug release. The results indicate that the HCHPbetaCD inclusion complex is more water soluble than HC alone. The HC release rates from chitosan microspheres were influenced by the drug/polymer ratio in the manner that an increase in the release rate was observed when the drug loading was decreased. However, release data from all samples showed significant improvement of the dissolution rate for HC, with 25-40% of the drug being released in the first hour compared with about 5% for pure HC. The complexation method and microsphere preparation method (spray-drying) is simple with great potential for industrial production.
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Affiliation(s)
- J Filipović-Grcić
- Department of Pharmaceutics, Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovacica 1, 10000, Zagreb, Croatia.
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33
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Siefert B, Pleyer U, Müller M, Hartmann C, Keipert S. Influence of cyclodextrins on the in vitro corneal permeability and in vivo ocular distribution of thalidomide. J Ocul Pharmacol Ther 1999; 15:429-38. [PMID: 10530704 DOI: 10.1089/jop.1999.15.429] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The aim of the present study has been to develop aqueous Thalidomide (THA) eye drops in order to minimize systemic side effects and to improve bioavailability following topical application. Cyclodextrins (CDs), suitable vehicles to improve aqueous solubility of THA, were evaluated with regard to their ability to influence in vitro corneal permeability of THA. Additionally, rabbit eyes received either THA-suspension (0.04%) (THA-SP) or THA (0.04%)/hydroxypropyl-beta-cyclodextrin (HP-beta-CD) (12.5%) solution (THA-CD). In vitro corneal permeation studies demonstrated that the absolute amount of THA permeated could not be increased by means of CDs. The percentile release of THA was extensively decreased using saturated THA/CD solutions. Following loading doses of either THA-CD or THA-SP onto the rabbit eye, significantly increased aqueous humor levels were obtained for THA-CD 30 min (THA-CD:THA-SP=4.6:1) and 60 min (THA-CD:THA-SP=3.1:1) post instillation (p<0.05). In the iris-ciliary body, significantly increased THA levels were obtained using THA suspension (THA-CD(60 min):THA-SP(60 min)=1:6.1) (p<0.05). In the cornea, conjunctiva, vitreous and sclera, differences between the THA tissue levels were not statistically significant. Cyclodextrins might be a useful tool to formulate aqueous THA eye drop solutions and modify intraocular drug bioavailability.
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Affiliation(s)
- B Siefert
- Klinge Pharma GmbH, Technological Development Laboratories, Munich, Germany
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