MICROENCAPSULATED EUDRAGIT(R) RS30D-COATED CONTROLLED-RELEASE PELLETS- THE INFLUENCE OF DISSOLUTION VARIABLES AND TOPOGRAPHICAL EVALUATION

The air suspension technique was employed to prepare Eudragit(R) RS30D -coated controlled-release pellets of salbutamol. Drug release in diss olution studies can be dependent on the dissolution method and medium used. Thus, the aim of this study was to investigate the influence of various dissolution methods and dissolution medium pH values on drug r elease from a batch of pellets which displayed controlled drug-release characteristics over an 8-h period in deionized water using the rotat ing basket method. In vitro testing using the official USP XXII (rotat ing basket and rotating paddle) and nonofficial (rotating bottle) meth ods showed drug release to be independent of the method used. The prep ared pellets displayed pH-dependent drug-release characteristics when tested in hydrochloric acid (pH 1.5), phosphate buffer (pH 6.8) and de ionized water (pH 7.2). Also, in vitro testing, which exposed the pell ets to a changing pH gradient that simulated the gastrointestinal pH c onditions following oral administration, was used to confirm the drug- release characteristics. The results showed controlled-release charact eristics to be maintained, with the drug being released over an 8-h pe riod. Scanning electron microscopic evaluation proved useful in the el ucidation of the physical characteristics of the controlled-release pe llets as well as in the identification of a possible mode of drug tran sfer into the dissolution medium.