国生 国生 Characteristics of a reservoir systems 国Osmotic pump systems ·Advantages .The osmotic pump system contains an osmotic Zero-order delivery is possible .Release rate variable with polymer type agent that acts to imbibe water from the ·Disadvantages surrounding medium via a semipermeable Bad for high-molecular weight compounds membrane. ·Expensive The drug is forced out of an orifice in the device Potential toxicity if system fails by the osmotic pressure generated within the device 国生一 国生 ④Osmotic pump systems ®Osmotic pump systems The rate of water imbibition the amount of drug released at time t 出-华a-△n d 婴出网 dt dV/dt is the rate of water flow When the hydrostatic pressure difference is negligible, k is the hydraulic permeability and there is an excess of solid (saturated solution)in the ·A is the membrane area device ·I is the thickness dM=k△S ·△t is the osmotic pressure difference ·△P is the hydrostatic pressure difference .Therefore,the drug release rate remains constant, delivering a volume equal to the volume of water uptake. 国生一 国秋生 Characteristics of osmotic pump systems ©Osmotic pump systems ·Advantages Zero-order release is obtainable ·one-chamber system Release of drug is independent of environment of the system ·two-chamber system ·Disadvantages requires specialized equipment and complex processes higher cost,longer development time delayed onset of drug release Bare operation quality control is more extensive 55 Shanghai Jiao Tong University Characteristics of a reservoir systems • Advantages • Zero-order delivery is possible • Release rate variable with polymer type • Disadvantages • Bad for high-molecular weight compounds • Expensive • Potential toxicity if system fails Shanghai Jiao Tong University Osmotic pump systems • The osmotic pump system contains an osmotic agent that acts to imbibe water from the surrounding medium via a semipermeable membrane. • The drug is forced out of an orifice in the device by the osmotic pressure generated within the device. Shanghai Jiao Tong University Osmotic pump systems • The rate of water imbibition • dV/dt is the rate of water flow • k is the hydraulic permeability • A is the membrane area • l is the thickness • Δπ is the osmotic pressure difference • ΔP is the hydrostatic pressure difference Shanghai Jiao Tong University Osmotic pump systems • the amount of drug released at time t • When the hydrostatic pressure difference is negligible, and there is an excess of solid (saturated solution) in the device • Therefore, the drug release rate remains constant, delivering a volume equal to the volume of water uptake. Shanghai Jiao Tong University Osmotic pump systems • one-chamber system • two-chamber system Shanghai Jiao Tong University Characteristics of osmotic pump systems • Advantages • Zero-order release is obtainable • Release of drug is independent of environment of the system • Disadvantages • requires specialized equipment and complex processes • higher cost, longer development time • delayed onset of drug release • quality control is more extensive