Prescription drugs dominate many people’s lives, but the advent of controlled-release delivery systems is set to change all that. Examples already in the marketplace include time-release pills that reduce the number of doses required for pain relievers and antidepressants, and contraceptive patches and implants. In the November issue of Nature Materials, Robert Langer and colleagues report a novel polymer-based pulsed drug delivery system designed to release accurate doses of drugs from an implant at predetermined times.
The drug delivery system is based on a microchip formed from poly(L-lactic acid), which is a slowly degrading polyester. The drug solutions are injected into reservoirs on the chip surface, and sealed by biodegradable polymer membranes with different degradation rates. By varying the composition and molecular weight of each polymer membrane, Langer and colleagues are able to tightly control the degradation rate (and thus drug release time) over a wide range.
The new polymer-based system is capable of releasing a variety of different drugs at well-controlled times. So far, the researchers have demonstrated that heparin -- a common anticoagulant -- remains bioactive after incorporation and release from the system over periods up to 140 days. Given the high biocompatibility and superb performance of the polymer-based system, clinical demonstration should not be too far off.
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