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Controlled drug release from gels using surfactant aggregates: II. Vesicles formed from mixtures of amphiphilic drugs and oppositely charged surfactants
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2001 (English)In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 18, no 11, 1585-1591 p.Article in journal (Refereed) Published
Abstract [en]

URPOSE:

The aim of this study was to control the release of charged drugs from gels by adding surfactants that can interact with the drug and polymer matrix.

METHODS:

The in vitro release from gels was measured by using 6-mL gel holders immersed in 250 mL of simulated tear fluid and detecting the ultraviolet absorbance on-line. Gels were characterized by using a controlled rate rheometer, and surfactant aggregates were characterized by using cryo-transmission electron microscopy.

RESULTS:

The diffusion coefficient of alprenolol was 2.8 x 10(-6) cm2/s in a lipophilically modified poly(acrylic acid) gel without surfactants present and 0.14 x 10(-6) cm2/s when formulated with 1% sodium dodecyl sulfate. For fluvastatin, the diffusion coefficient changed from 3.0 x 10(-6) cm2/s to 0.07 x 10(-6) cm2/s in the presence of 0.2% benzyldimethyldodecyl-ammonium bromide. Alprenolol, betaxolol, metoprolol, diphenhydramine, and fluvastatin formed vesicles with oppositely charged surfactants in physiologic salt conditions.

CONCLUSIONS:

In this article we show that it is feasible to control the release of charged drugs from gels by using surfactants. Vesicles are generally formed when surface active drugs are mixed with oppositely charged surfactants in physiologic conditions. The strongest effects on the release rate are seen for lipophilically modified polymer gels in which the drug and the oppositely charged surfactant form vesicles, but systems with micelles also give a slower release.

Place, publisher, year, edition, pages
2001. Vol. 18, no 11, 1585-1591 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-89521DOI: 10.1023/A:1013086632302PubMedID: 11758767OAI: oai:DiVA.org:uu-89521DiVA: diva2:161062
Available from: 2001-11-15 Created: 2001-11-15 Last updated: 2014-12-30Bibliographically approved
In thesis
1. Controlled Release Gel Formulations for Mucosal Drug Delivery
Open this publication in new window or tab >>Controlled Release Gel Formulations for Mucosal Drug Delivery
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drug delivery to nasal or ocular mucosa for either local or systemic action faces many obstacles – these routes are protected by effective mechanisms. Gel formulations with suitable rheological and mucoadhesive properties increase the contact time at the site of absorption. However, drug release from the gel must be sustained if benefits are to be gained from the prolonged contact time.

The work presented here is the characterization of gels and the determination of the mucoadhesive properties of polymers using rheology. Gelrite gels were formed in simulated tear fluid at concentrations of polymer as low as 0.1%, and it was shown that sodium was the most important gel-promoting ion in vivo. Rheology, although it may be a questionable technique for evaluating mucoadhesive properties of polymers, showed that interactions between mucin and polymers were most likely to be seen with weak gels.

It was possible to control the release of uncharged drug substances by including surfactants that form micelles in the gel. This release depended on lipophilic interactions between the drug and the polymer and/or the micelles. Controlled-release formulations of charged drugs could be designed by mixing the drugs with oppositely charged surfactants in certain ratios. In this way, vesicles in which the drug and surfactant constituted the bilayer formed spontaneously. The vesicle formation was affected by the presence of polymer, and very small vesicles that gave a slow release rate were formed when a lipophilically modified polymer was used.

The gels were also evaluated in the Ussing chamber using porcine nasal mucosa. The rate of transport of drugs through the mucosa could be controlled by the rate of release from the formulation. Furthermore, the Ussing chamber could be used to evaluate the potential toxicity of formulations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2001. 52 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 0282-7484 ; 259
Keyword
Pharmacy, FARMACI
National Category
Pharmaceutical Sciences
Research subject
Pharmaceutics
Identifiers
urn:nbn:se:uu:diva-1493 (URN)91-554-5173-X (ISBN)
Public defence
2001-12-07, B42, BMC, Uppsala, 09:15
Opponent
Available from: 2001-11-15 Created: 2001-11-15 Last updated: 2013-06-12Bibliographically approved

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