Development of a simple method for the preparation of a silica gel based controlled delivery system with a high drug content

• Published in: European journal of pharmaceutical sciences Vol. 26; no. 1; pp. 87 - 96
• Main Authors: Ohta, Kotoe Machida, Fuji, Masayoshi, Takei, Takashi, Chikazawa, Masatoshi
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01.09.2005; Elsevier
• Subjects: Biological and medical sciences; Cellulose - analogs & derivatives; Cellulose - chemistry; Chemistry, Pharmaceutical - methods; Coating; Controlled release; Delayed-Action Preparations; Dose-Response Relationship, Drug; Drug Carriers - chemistry; Drug Stability; Gels; General pharmacology; Medical sciences; Methylcellulose - analogs & derivatives; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Polyethylene Glycols - chemistry; Pore; Porosity; Silica Gel; Silicon Dioxide; Solubility; Surface-Active Agents - chemistry; Theophylline; Theophylline - chemistry; Theophylline - metabolism; Time Factors; Silica gel; Coating; Pore; Controlled release; Theophylline; Drug; Delivery system; Pharmaceutical technology; Controlled release form; Bronchodilator; Antiasthma agent; Respiratory analeptic; Preparation; Content; Dosage form; Xanthine derivatives
• ISSN: 0928-0987; 1879-0720
• DOI: 10.1016/j.ejps.2005.05.002

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 N 2 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.