| Recently, a new class of drug delivery system, called electrorheological (ER) dosage forms, has been investigated. These systems are capable of delivering drugs to the body at rates that can be adjusted after the dose has been administered.; The primary aim of this research is to design a system in which the rate of drug release is not necessarily zero-order, but instead can be altered while the drug is releasing, to study the mechanism of drug release, to investigate the effects of the filler particle size and volume fraction on drug release in the presence and in the absence of an applied electric field (E-field), to study the effects of temperature on drug release, with and without applied E-fields, and to develop a theoretical model to facilitate analysis of the experimental release data.; To study ER drug delivery systems, a model system consisting of different filler particles suspended in a solution of benzocaine (BZN) in olive oil was used. The volume fraction of the filler particles ranged from ∼0.1–80%, and the filler particle sizes ranged from ∼0.2–90 μm. The drug release patterns from these systems were studied by varying different parameters such as particle size, filler fraction, temperatures and E-field strengths. Two different experimental set-ups were designed to study the drug release from the ER systems. In the first design, acrylic cells were used for the donor and receiver. In the second set-up, modified Franz diffusion cells were used for the release experiments. Fick's Laws of diffusion were modified to forms that are applicable to these two-phase ER systems and were solved to derive equations describing the mass vs. time-release profiles. These equations were then evaluated by two numerical simulation methods—random walk and finite differences.; The experimental data show that the filler particles have significant effect on tortuosity, which increases with increasing filler volume fraction. For symmetrical filler particles, the tortuosity increased as the particle size decreased. Although models in the literature indicate that the correlating factor for tortuosity is the filler volume fraction, it was found in this study that the total surface area is the fundamental correlating factor. Drug release from the ER systems can be controlled (enhanced) by the application of a static external electric field. The E-field strengths used in the current study ranged from 0–18 V/mm.; A promising prototype device has been designed which works at much lower E-fields. This design is convenient in the sense that the E-field does not have to straddle, which brings the applicability of these systems much closer to reality. Further studies are being conducted to optimize and fine-tune these systems for programmable drug delivery. (Abstract shortened by UMI.)... |
