title: Development of a simple method for the preparation of a silica gel based controlled delivery system with a high drug content.
abstract: Silica gel was used as core particles to design a simple preparation for controlled delivery system with a high drug content. Drug loading was carried out by immersing the silica gel in a pre-heated drug solution or suspension. HPLC, SEM, DSC, PXRD analysis and N2 adsorption studies evaluated the drug-loading process. In the next step, the drug-loaded silica gel was coated with hydroxypropyl methylcellulose (HPMC) and an aqueous dispersion of ethylcellulose (Aquacoat) to control the drug release. The release profile was determined using a dissolution test. The results showed that silica gel could adsorb great quantities of the drug, up to about 450 mg/g, by repetition of the loading process. Evaluation of the drug-loading process indicates that drug deposition in the pores occurs during the loading process and the drug-loading efficacy is strongly related to the drug solubility. On the other hand, the dissolution test showed that the drug release could be controlled by polymer coating the drug-loaded silica gel. An HPMC undercoating effectively suppresses the drug release, as it smoothes the drug-loaded core surface and aids in the formation of a continuous Aquacoat coating film. The floating property was also observed during the dissolution test.
authors.affiliation: Pharmaceutical Research Laboratories, Toray Industries Inc., 1111 Tebiro, Kamakura, Kanagawa 248-8555, Japan. Kotoe_Ota@nts.toray.co.jp
authors.forename: Kotoe Machida
authors.initials: KM
authors.lastname: Ohta
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Fuji
authors.forename: Takashi
authors.initials: T
authors.lastname: Takei
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Chikazawa
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers / Q000737:chemistry*; D004355:Drug Stability; D005782:Gels; D008747:Methylcellulose / Q000031:analogs & derivatives; D011092:Polyethylene Glycols / Q000737:chemistry; D016062:Porosity; D058428:Silica Gel; D012822:Silicon Dioxide; D012995:Solubility; D013501:Surface-Active Agents / Q000737:chemistry; D013806:Theophylline / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors
chemical_list: D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005782:Gels; D013501:Surface-Active Agents; D011092:Polyethylene Glycols; D058428:Silica Gel; D012822:Silicon Dioxide; C013517:ethyl cellulose; D002482:Cellulose; D008747:Methylcellulose; D013806:Theophylline