A system for delivering an active substance has sustained release of the active substance in the intestinal tract. This delivery system is especially useful for an active substance such as a .beta.-lactam antibiotic which preferably has minimal exposure to the acidic environment of the stomach. Particles...http://www.google.com.au/patents/US5160742?utm_source=gb-gplus-sharePatent US5160742 - System for delivering an active substance for sustained release
