Evaluation of a novel phase separation technique for the encapsulation of water-soluble drugs in biodegradable...

Biodegradable microcapsules of four water-soluble drugs (pentamidine, captopril, diltiazem, and metoprolol) were prepared using a novel phase separation technique. The microcapsules prepared by this method were irregular in shape. Particle size of the microcapsules was between 60 and 500 microns. The efficiency of encapsulation for all four drugs was more than 40% at 20% drug loading. The encapsulation increased up to 75% or higher when the drug loading was reduced to 5%. The in vitro dissolution was drug dependent. The microcapsules prepared with 5% drug loading showed the minimum dissolution at the end of 24 hr. The initial drug release increased significantly when the drug loading was increased up to 20%. Although the formulations containing 5% drug maintained a sustained-release profile up to 45 days, the formulations containing 10 and 20% drug released more than 50% drug within the first 2 days.