title: Coated formulations: new insights into the release mechanism and changes in the film properties with a novel release cell.
abstract: The effect of the blend ratio of water-insoluble ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC-LF), on the properties of sprayed films and on the drug release mechanism of formulations coated with the material was investigated. When the original HPC-LF content exceeded 22%, both the amount of HPC-LF leached out and the water permeability of the films increased drastically when they were immersed in a phosphate buffer solution. The release mechanism of potassium nitrate through EC/HPC-LF films containing 20, 24 and 30% HPC-LF was elucidated in a new release cell equipped with a manometer to measure the pressure build-up inside the cell. A lag phase in the release accompanied by a pressure build-up was observable in all the experiments showing that all the films were initially semi-permeable to KNO3. However, pressure data revealed that films with 30% HPC-LF became permeable to KNO3 during the release process due to HPC-LF leaching. Importantly, the blend ratio influenced not only the release rate (which increased as the amount of HPC-LF increased), and the lag time (which increased as the amount of HPC-LF decreased), but also the release mechanism, which changed from osmotic pumping to diffusion as the amount of HPC-LF increased.
authors.affiliation: Department of Chemical Engineering, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Marucci
authors.forename: Johan
authors.initials: J
authors.lastname: Hjärtstam
authors.forename: Gert
authors.initials: G
authors.lastname: Ragnarsson
authors.forename: Frida
authors.initials: F
authors.lastname: Iselau
authors.forename: Anders
authors.initials: A
authors.lastname: Axelsson
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D004058:Diffusion; D004304:Dosage Forms; D009566:Nitrates / Q000737:chemistry; D009995:Osmosis; D010539:Permeability; D017680:Potassium Compounds / Q000737:chemistry; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D004304:Dosage Forms; D009566:Nitrates; D017680:Potassium Compounds; D014867:Water; C013517:ethyl cellulose; D002482:Cellulose; C008079:hydroxypropylcellulose; C023844:potassium nitrate