Drug release from Kollicoat SR 30D-coated nonpareil beads: evaluation of coating level, plasticizer type, and curing condition

A newly available polyvinylacetate aqueous dispersion, Kollicoat SR 30D, was evaluated with respect to its ability to modulate the in vitro release of a highly water-soluble model compound (diphenhydramine hydrochloride) from nonpareil-based systems. Kollicoat SR 30D premixed with a selected plasticizer (10% wt/wt propylene glycol, 2.5% triethyl citrate, or 2.5% dibutyl sebacate), talc, and red #30 lake dye was coated onto the drug beads in an Aeromatic Strea I fluid-bed drier with a Wurster insert using bottom spray. With propylene glycol as the plasticizer, increases in polymer coating level retarded drug release from beads in a stepwise fashion along with apparent permeability, indicating a consistent release mechanism. Stability studies at 40 degrees C/75% RH revealed gradual decreases in dissolution rate, and additional curing studies further confirmed the dependence of release kinetics on curing condition. Furthermore, the type of plasticizer was found to play a key role. Unplasticized formulations exhibited the fastest dissolution, followed by formulations plasticized with triethyl citrate, propylene glycol, and dibutyl sebacate. All 4 formulations (unplasticized and plasticized), nevertheless, revealed a marked difference between uncured and cured dissolution profiles. Kollicoat SR 30D has, thereby, been demonstrated to effectively retard drug release from nonpareil-based systems. However, selected plasticizer type and subsequent curing condition play important roles in controlling drug release from such a system.