Pulsatile drug release from an insoluble capsule body controlled by an erodible plug

Purpose. The objective of this study was to develop and evaluate a pulsatile drug delivery system based on an impermeable capsule body filled with drug and an erodible plug placed in the opening of the capsule body. Methods. The erodible plugs were either prepared by direct compression followed by placing the tablets in the capsule opening or by congealing a meltable plug material directly within the capsule opening, The disintegration/erosion properties of these plugs were determined and optimized for the final delivery system. In order to assure rapid drug release of the capsule content after erosion of the plug, various excipients (fillers, effervescent agents) and drugs with different solubilities were evaluated. The lag time prior to drug release and the subsequent drug release were investigated as function of capsule content, plug composition, plug preparation technique, plug hardness, weight, and thickness. Results. The erosion time of the compressed plugs increased with increasing molecular weight of the hydrophilic polymer (e.g. hydroxypropyl methylcellulose, polyethylene oxide), decreasing filler (lactose) content and decreased with congealable lipidic plugs with increasing HLB-value and inclusion of surfactants. For complete and rapid release of the drug from the capsule body, effervescent agents had to be included in the capsule content. The drug delivery system showed typical pulsatile release profiles with a lag time followed by a rapid release phase. The lag time prior to the pulsatile drug release correlated well with the erosion properties of the plugs and, besides the composition of the plug, could be controlled by the thickness (weight) of the plug. Conclusions. A single-unit, capsular-shaped pulsatile drug delivery system was developed wherein the pulsatile release was controlled by the erosion properties of a compressed or congealed plug placed within the opening of the capsule opening.