FIG. 2.

The osmotic mini-pump is placed in the subdermal space. Interstitial fluid flows consistently and predictably through the semipermeable membrane into the osmotic engine compartment that contains NaCl tablets. Mixing of the salt with fluid causes expansion of the osmotic engine compartment that pushes a piston resulting in formulated drug being expelled through the diffusion moderator into the SC space where drug is absorbed into the systemic circulation. NaCl, sodium chloride; SC, subcutaneous.