How does it work?
ALZET pumps operate because of an osmotic pressure difference.
The rate of delivery by an ALZET pump is controlled by the water permeability
of the pump’s outer membrane. Thus, the delivery profile of the
pump is independent of the drug formulation dispensed. Drugs of various
molecular configurations, including ionized drugs and macromolecules,
can be dispensed continuously in a variety of compatible vehicles at
controlled rates. The molecular weight of a compound, or its physical
and chemical properties, has no bearing on its rate of delivery by ALZET
pumps.
The volume delivery rate of ALZET pumps is fixed at manufacture. ALZET osmotic pumps are available with a variety of delivery rates between 0.11 and 10 µL/hr and delivery durations between 1 day and 6 weeks. While the volume delivery rate of the pump is fixed, different dosing rates can be achieved by varying the concentration of agent in the solution or suspension used to fill the pump reservoir.
A more complete and technical explanation of the operation of ALZET osmotic pumps can be found in the following reference.
Theeuwes F and Yum SI. Principles of the design and operation of generic osmotic pumps for the delivery of semisolid or liquid drug ormulations. Ann Biomed Eng 1976, 4(4): 343-353.
