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How it Works

Drug pellets are coated with semi-permeable polymers and injected into muscle tissue.  Water then diffuses through the polymer and dissolves the drug core (D), creating a saturated solution inside the drug implant (C) and essentially sink conditions outside the implant (c).  This concentration gradient drives a constant (zero order) release of the drug from the drug implant, as long as there is some drug core remaining to maintain a saturated solution.  The period of release can be tuned by altering the permeability of the polymer coating.