| 摘要 |
<p>A method for the controlled release of a biologically active agent wherein the agent is released from a hydrophobic, pH-sensitive polymer matrix is disclosed and claimed. In one embodiment, the polymer matrix swells when the environment reaches pH 8.5, releasing the active agent. A polymer of hydrophobic and weakly acidic comonomers is disclosed for use in the controlled release system. In another embodiment, weakly basic comonomers are used and the active agent is released as the pH drops. Further disclosed is a specific embodiment in which the controlled release system may be used. The pH-sensitive polymer is coated onto a latex catheter used in ureteral catheterization. A common problem with catheterized patients is the infection of the urinary tract with urease-producing bacteria. In addition to the irritation caused by the presence of the bacteria, urease produced by these bacteria degrade urea in the urine, forming carbon dioxide and ammonia. The ammonia causes an increase in the pH of the urine. Minerals in the urine begin to precipitate at this high pH, forming encrustations which complicate the functioning of the catheter. A ureteral catheter coated with a pH-sensitive polymer having an antibiotic or urease inhibitor trapped within its matrix releases the active agent when exposed to the high pH urine as the polymer gel swells. Such release can be made slow enough so that the drug remains at significant levels for a clinically useful period of time. Other uses for the methods and devices of this invention include use in gastrointestinal tubes, respiratory trap lines and ventilation tubes, dye releasing pH-sensitive sutures, active agent release from contact lenses, penile implants, heart pacemakers, neural shunts, food wraps, and clean room walls.</p> |
