Encapsulation of theophylline in waxes/fat microspheres: preparation, characterization and release kinetics of microspheres

ABSTRACT

The objectives of the present study is to prepare waxes/Tat microspheres loaded with Theophylline, [TP] a well known xanthine bronchodilator, was entrapped into gastro-resistant, biodegradable waxes such as beeswax [BW], cetostearyl alcohol [CSA], spermaceti [SC] and fat cetyl alcohol [CA] microspheres using meltable emulsified dispersion cooling induced solidification technique utilizing wetting agents. Solid, discrete, reproducible free flowing microspheres were obtained converting the liquid drug droplets into solid materials. Prepared waxes/fat microspheres are spherical in shape, have smooth surfaces with free flowing and good packing properties, as evidenced by scanning electron microscope [SEM]. The microspheres were characterized for their particle size, micromeritic properties and encapsulation efficiency. Size of the obtained waxes/fat microspheres ranged between 115 to 850 micro m. Molecular level drug distribution and compatibility of the drug after encapsulation in the waxes/fat microspheres was confirmed by differential scanning calorimetry [DSC] and FT1R spectral studies. The prepared microspheres were analyzed quantitatively for the amount of encapsulated drug. Maximum yield was produced by TP loaded in beeswax [AT] and minimum amount of TP was encapsulated into cetyl alcohol [DT] microspheres. The release of drug was controlled for more than 8 hours. Intestinal discharge of TP from waxes/fat microspheres was studied and compared with the oral formulation of TP [Unieontin[R]-n-400]. Among all the systems studied, TP loaded in cetostearyl alcohol [BT] have shown fastest release whereas slowest release by TP loaded in spermaceti [CT]. The release kinetics followed different transport mechanisms. The release performance was greatly affected by the materials used in microspheres preparations, which allows maximum absorption in the intestine