Direct Measurements of Osmotic Pressure in Remotely Controlled Implantable Drug Delivery Devices

Long-acting drug delivery systems have gained widespread popularity due to their numerous advantages over conventional methods of drug administration. These systems offer several benefits, including reduced dosing frequency, improved patient compliance, minimized side effects, and the ability to maintain therapeutic drug levels for extended durations. Reservoir-based systems, such as polymeric implants, osmotic pumps, and electromechanical systems, are commonly employed as long-acting drug delivery mechanisms. However, these devices are susceptible to the accumulation of osmotic pressure within the drug reservoir, which can compromise their integrity and affect the efficacy of drug release. Various techniques, such as the Van't Hoff equation, freezing point determination, or vapor pressure osmometry, are currently utilized to estimate the osmotic pressure generated by drug delivery systems. However, these methods have limitations and may not accurately reflect the actual behavior of the devices. Moreover, investigations into osmotic phenomena are presently confined to in vitro experimentation, further restricting our understanding of the real-world dynamics. To overcome these limitations, we have developed an innovative subcutaneous implant for remotely controlled drug delivery that allows for direct measurement of osmotic pressure in vivo. The implant utilizes Bluetooth connectivity to establish real-time communication and accurately transmit pressure data. We conducted in vitro experiments using sucrose and glycerin solution to measure the osmotic pressure. The results revealed a pressure increase of up to 20 bar, followed by a gradual decrease over a 10-day period. Further, we conducted in vivo studies in rats, which confirmed the stability of remote communication. While lower pressure values were reached in vivo, the overall trend of a rapid pressure increase, followed by a plateau and a slow decrease, remained consistent. By enabling direct measurement of osmotic pressure within the reservoir, our approach has the potential to revolutionize the development of more effective long-acting drug delivery systems. This capability is critical for optimizing drug release efficacy and patient safety, paving the way for enhanced therapeutic outcomes.