Floating or pulsatile drug delivery systems based on coated effervescent cores.

The objective of this study was to develop and evaluate floating and pulsatile drug delivery systems based on a reservoir system consisting of a drug-containing effervescent core and a polymeric coating. Preliminary studies identified important core and coating properties for the two systems. The mechanical properties (puncture strength and elongation) of acrylic (Eudragit RS, RL or NE) and cellulosic (cellulose acetate, ethyl cellulose) polymers, which primarily determined the type of delivery system, were characterized with a puncture test in the dry and wet state. For the floating system, a polymer coating with a high elongation value and high water- and low CO(2) permeabilities was selected (Eudragit RL/acetyltributyl citrate 20%, w/w) in order to initiate the effervescent reaction and the floating process rapidly, while for the pulsatile DDS, a weak, semipermeable film, which ruptured after a certain lag time was best (ethyl cellulose/dibutyl sebacate 20%, w/w). With the floating system, the polymeric coating did not retard the drug release. A polymer (cellulose acetate or hydroxypropylmethylcellulose) was added to the core to control the drug release. The time to flotation could be controlled by the composition (type of filler, concentration of effervescent agents) and hardness of the tablet core and the composition (type of polymer and plasticizer) and thickness of the coating. For the pulsatile system, a quick releasing core was formulated in order to obtain a rapid drug release after the rupture of the polymer coating. The lag time prior to the rapid drug release phase increased with increasing core hardness and coating level.