Release Characteristics of the Matrices Prepared from Co-spray-Dried Powders of Theophylline and Ethylcellulose

Abstract

Co-spray-dried powders of theophylline and ethylcellulose were prepared using aqueous ethylcellulose dispersion. Co-spray-dried powders were directly compressed into the matrices and the release characteristics of the prepared matrices were investigated. The co-spray-dried powders exhibited good matrix formations with high hardness at rather low compression force. The concentration of ethylcellulose in the matrices was, as expected, the rate-determining factor in controlling the release rate of the drug. Increasing the weight fractions of ethylcellulose resulted in a corresponding decrease in the drug release rates in both 0.1 N HCl and phosphate buffer pH 6.8. However, at the same level of ethylcellulose content, the drug release in acidic conditions was higher than in alkaline medium. To modify release characteristics of the matrices, PVP K30 and lactose were employed as channeling agents. At concentrations of 5 and 10%, PVP K30 was found to slow the drug release when incorporated into the co-spray-dried powder formulations containing 5% ethylcellulose. Lactose at a concentration of 15% provided an increasing effect on drug release when added in the formulations. But an increase in lactose quantity from 15 to 25% did not exert much more influence on release characteristics. Higuchi plots were found to be best applicable to all release data. Scanning electron microscopic examinations on the surface and cross-section of the matrices before and after subjection to release testing revealed the formation of porous networks within the matrices by the ethylcellulose fibers. Such polymeric networks would account for the controlled diffusion of the drug from the matrices.

Release characteristics of microspheres prepared by co-spray dryingActinobacillus pleuropneumoniaeantigens and aqueous ethyl-cellulose dispersion

“…In this process, encapsulation and ®lm formation occur simultaneously in a spray drying process. It has also been proposed that a hydrophilic agent, such as lactose, sugars, or water soluble polysaccharides, may be selected as a channelling agent to modify the release characteristic of a matrix product (Fites et al 1970, Kulvanich andLeesawat 1996). Therefore, the objectives of the study were to introduce a new application of the process for an oral vaccine delivery in the gastrointestinal tract, and to demonstrate the potential use of microspheres, prepared by a co-spray drying process, as an oral vaccine in the gastrointestinal tract.…”

“…Recently, co-spray-dried microspheres for drugs have been prepared with an ethylcellulose aqueous polymeric dispersion (Kulvanich and Leesawat 1996). In this process, encapsulation and ®lm formation occur simultaneously in a spray drying process.…”

Mycoplasma hyopneumoniae Vaccination Influence on Porcine Reproductive and Respiratory Syndrome Virus and Mycoplasma hyopneumoniae Coinfection

“…The vaccination of piglets in the first group was performed subcutaneously by vaccine that was developed in the Pig Research Institute Taiwan (PRIT) and that contained killed M. hyopneumoniae cells with an aluminium hydroxide adjuvant. The second group received an oral vaccine that was developed also in PRIT and contained killed M. hyopneumoniae cells with enteric-coated polymer microspheres (AQ6) prepared by a co-spray drying procedure (Kulvanich and Leesawat 1996). The third group of piglets received both oral and parenteral vaccines.…”

Protective Effects of Oral Microencapsulated Mycoplasma hyopneumoniae Vaccine Prepared by Co-Spray Drying Method.

“…For antibody quantitative analysis, a standard curve of enzymeimmunoassay values was obtained with dilutions of a swine immunoglobulin reference serum. The 3-fold dilutions (6, 2, 0.6, 0.2, 0.06, 0.02, 0.006 µg/ml of IgG or 1.4, 0.48, 0.14, 0.048, 0.014, 0.0046, 0.0015 µg/ml of IgA) were introduced and coated in triplicate on a plate [15]. Unknown sample values were obtained from the standard curves.…”

“…Disk speed was adjusted to 30,000 rpm and the inlet air temperature was held between 40°C and 50°C for a few seconds, before cooling at 25°C to 35°C. A model L-8 spray dryer (from Ohkawara Kakohki Co., Ltd., Yokohama, Japan) was used as described in a previous report [15].…”