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Controlled drug release from gels using surfactant aggregates: I. Effect of lipophilic interactions for a series of uncharged substances
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: Journal of Pharmaceutical Sciences, ISSN 0022-3549, E-ISSN 1520-6017, Vol. 90, no 9, 1216-1225 p.Article in journal (Refereed) Published
Abstract [en]

Gels are often used for the delivery of drugs because they have rheological properties that will give a long residence time. Most pharmaceutical gels consist of approximately 99% water and a polymer matrix that will not hinder the release of drugs with a small molecular weight. To fully take advantage of the residence time, it is necessary to have a sustained drug release. In this paper it is suggested that surfactant micelles can be used to control the release from gels. The in vitro release under physiological conditions of five parabens from four different poly(acrylic acid) gels (Carbopol 934, 940, 1342) and one gellan gum (Gelrite) gel was measured using a USP dissolution bath modified for gels, and the diffusion coefficients were calculated. The diffusion coefficient of uncharged parabens was generally lower in gels with lipophilic modifications, such as C1342, and the greatest effect was seen for butylparaben, with a diffusion that was 25% lower than that in C934 (lacking lipophilic modification). Addition of surfactant micelles to gels delayed the release of all the uncharged drugs in all types of gels studied. The slowest release was seen for butylparaben in a lipophilically modified gel with micelles present. The diffusion coefficient in such a system was almost 30 times smaller than that in C934 without micelles.

Place, publisher, year, edition, pages
2001. Vol. 90, no 9, 1216-1225 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-89520DOI: 10.1002/jps.1075PubMedID: 11745775OAI: oai:DiVA.org:uu-89520DiVA: diva2:161061
Available from: 2001-11-15 Created: 2001-11-15 Last updated: 2014-12-30
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.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 0282-7484 ; 259
Pharmacy, FARMACI
National Category
Pharmaceutical Sciences
Research subject
urn:nbn:se:uu:diva-1493 (URN)91-554-5173-X (ISBN)
Public defence
2001-12-07, B42, BMC, Uppsala, 09:15
Available from: 2001-11-15 Created: 2001-11-15 Last updated: 2013-06-12Bibliographically approved

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