Release Mechanism Between Ion Osmotic Pressure and Drug Release in Ionic-Driven Osmotic Pump Tablets (I).

The objective of this study was to develop an authentic ionic-driven osmotic pump system and investigate the release mechanism, simultaneously exploring the in vitro and in vivo correlation of the ionic-driven osmotic pump tablet. A comparison of the ionic-driven and conventional theophylline osmotic pump, the influence of pH and the amount of sodium chloride on drug release, the relationship between the ionic osmotic pressure and the drug release, and the pharmacokinetics experiment in beagle dogs were investigated. Consequently, the similarity factor (f ₂ ) between the novel and conventional theophylline osmotic pump tablet was 60.18, which indicated a similar drug-release behavior. Also, the release profile fitted a zero-order kinetic model. The relative bioavailability of the ionic-driven osmotic pump to the conventional osmotic pump calculated from the AUC _(0-∞) was 93.6% and the coefficient (R = 0.9945) confirmed that the ionic-driven osmotic pump exhibited excellent IVIVC. The driving power of the ionic-driven osmotic pump was produced only by ions, which was strongly dependent on the ion strength, and a novel formula for the ionic-driven osmotic pump was derived which indicated that the drug-release rate was proportional to the ionic osmotic pressure and the sodium chloride concentration. Significantly, the formula can predict the drug-release rate and release characteristics of theophylline ionic-driven osmotic pumps, guiding future modification of the ionic osmotic pump.