US Patent 7066904 Triggered release hydrogel drug delivery system

The invention features a method for triggering release of a drug from a hydrogel polymer to tissue at a desired location of the body using a catheter. A portion of the catheter is coated on its outer surface with a polymer having the capacity to incorporate a predetermined substantial amount of drug which is immobilized in the polymer until released by a triggering agent or condition that is different from physiological conditions. Upon contact with a triggering agent or condition, the polymer reacts, e.g., swells or contracts, such that the drug is delivered to the desired body tissue. A balloon catheter is shown in which the hydrogel is carried on the exterior surface of the balloon.