Osmotically controlled drug delivery system ALZET & DUROS Osmotic pump @ Mrs. Arti Majumdar

The osmotic pump system is similar in construction to a reservoir device but contains an osmotic agent that acts to imbibe water from the surrounding medium via a semipermeable membrane which is permeable to water but impermeable to drug. Such a device, called the elementary osmotic pump (EOP), was first described by Theeuwes and Higuchi in 1975. he delivery of the active agent from the device is controlled by water influx across the semipermeable membrane. The drug is forced out of an orifice in the device by the osmotic pressure generated by the device. The size of the orifice is designed to minimize solute diffusion, while preventing the build-up of a hydrostatic pressure head that has the effect of decreasing the osmotic pressure and changing the volume of the device.
Osmotic pumps (ALZET) are generally implanted subcutaneously or intraperitoneally and used for systemic administration in mice and rats. Many active agents have been delivered by the Alzet® system (e.g., amino acids, anesthetics, antibiotics, antibodies, anticancer agents, anticoagulants, anti-epileptics, antigens, antihypertensives, anti-parasitic agents, anti-Parkinson agents, ascitic fluid, catecholamines, chelators, cholinergics, central nervous system acting agents, enzyme inhibitors, and gastrointestinal modulators).
DUROS®, a long-term zero-order drug delivery system designed by Alza, was the first implantable osmotic pump to be used in humans (Figure 6.11). It is a small pump (4 mm diameter × 45 mm length) composed of a titanium alloy cylinder and capped on one side by a rate-controlling semipermeable membrane (polyurethane polymer), and on the other by a plug with a hole for active agent delivery. Only water can permeate the membrane. A piston made of elastomeric materials is located on the side of the pump, separating the osmotic site (normally containing sodium chloride) from the active agent reservoir. The extracellular body fluids activate the osmotic engine and the piston displaces, resulting in delivery of the active agent.