ABSTRACT
Osmotic pressure, like vapor pressure and boiling point, is a colligative property of a solution in which a nonvolatile solute is dissolved in a volatile solvent. In addition to being dependent on the concentration of solute, the osmotic pressure is also affected by the vapor pressure of the pure solvent. Osmotic pressure arises from at least two phases which are moving toward equilibrium. The earliest application of osmotic pressure to drug delivery was by Rose and Nelson in 1955. In this chapter, the authors describe two systems, one that delivered 0.02 ml/day for 100 days, and one that delivered 0.5 ml/day for 4 days, both for use in pharmacologic research. Drug delivery from both systems was dependent on expansion of the osmotic pressure unit, due to the influx of water, which resulted from the osmotic pressure difference between the unit and the environment.
