title: In vitro evaluation of a hydroxypropyl cellulose gel system for transdermal delivery of timolol.
abstract: In this work, the development of a gel reservoir for a timolol (TM) transdermal iontophoretic delivery system is investigated. TM gel is prepared using hydroxypropyl cellulose (HPC) and the permeability of TM from the gel through an artificial membrane (Polyflux) and pig stratum corneum (SC) is studied. For a constant TM donor concentration, the TM transport across the Polyflux membrane alone decreases when the concentration of the gel increases due to increase of the gel viscosity. For constant gel concentration, however, the TM permeation across the membrane increases when the TM donor concentration increases. In addition, no effect of the electrical current (iontophoresis, current density 0.5 mA cm-2) on the TM permeation is found. For the combination of the Polyflux membrane with pig SC, the TM transport is much lower than for the membrane alone and the SC fully controls the TM delivery. In this case, the application of electrical current enhances the TM delivery 13-15 times in comparison to passive (no current) transport. According to our estimation, the daily TM dose (10-60 mg) can be delivered by an iontophoretic patch with Polyflux membrane area of 6-36 cm2 containing 20% (w/w) HPC gel and 15 mg cm-3 of TM.
authors.affiliation: Membrane Technology Group, University of Twente, Faculty of Science and Technology, PO Box 217, NL-7500 AE Enschede, The Netherlands. d.stamatialis@utwente.nl
authors.forename: D F
authors.initials: DF
authors.lastname: Stamatialis
authors.forename: H H M
authors.initials: HH
authors.lastname: Rolevink
authors.forename: M
authors.initials: M
authors.lastname: Gironès
authors.forename: D C
authors.initials: DC
authors.lastname: Nymeijer
authors.forename: G H
authors.initials: GH
authors.lastname: Koops
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000737:chemistry / Q000493:pharmacokinetics; D000818:Animals; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D004058:Diffusion; D004305:Dose-Response Relationship, Drug; D005782:Gels; D066298:In Vitro Techniques; D007478:Iontophoresis / Q000379:methods; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D010539:Permeability; D016062:Porosity; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D012996:Solutions / Q000737:chemistry / Q000493:pharmacokinetics; D013552:Swine; D013999:Timolol / Q000737:chemistry / Q000493:pharmacokinetics*; D014783:Viscosity
chemical_list: D000319:Adrenergic beta-Antagonists; D005782:Gels; D008567:Membranes, Artificial; D012996:Solutions; D013999:Timolol; D002482:Cellulose; C008079:hydroxypropylcellulose