DEVIATION OF THE RATIO OF DRUGS IN A 2-COMPONENT MIXTURE ENCAPSULATEDIN CELLULOSE PHTHALATE MICROSPHERES

Microspheres were formed when a solution of cellulose phthalate was ex truded into 30% glacial acetic acid solution. Sulphonamides entrapped in such microspheres leached into the hardening solution because they dissolved freely in the acetic acid solution. This resulted in poor lo ading efficiency of the sulphonamides in the microspheres. When mixtur es of sulphaguanidine and sulphathiazole in various drug ratios were m icroencapsulated by this method, the observed drug ratios were found t o be markedly changed. This was attributed to the difference in solubi lity of the two sulphonamides in acid such that their extent of diffus ion into the hardening solution was not similar. NSAIDS such as ibupro fen and mefenamic acid which are acidic and more hydrophobic in nature are less soluble in acetic acid. These drugs were retained better in the microspheres during the hardening process and the loading efficien cy was consequently improved. In cases where mixture of the NSAIDS wer e encapsulated, the drug ratios showed little deviation from the theor etical values. This study shows that loading of the CAP microspheres i s dependent on the solubility of the drugs in acetic acid. When more t han one drug is required to be microencapsulated, the drug ratio may c hange if the drugs have different solubility in acetic acid.