Drug delivery to the brain using polymers.

The delivery of drugs to the brain has been a major challenge to the scientist developing drugs designed for central nervous system (CNS) activity. One of the obstacles to the progress is the transport of drug through the blood brain barrier (BBB). The criteria for effective drug delivery to the CNS include the following: (a) the drug must have access to the brain, (b) the effect of the drug should be localized, (c) the drug must be stable, and (d) the effective dose should be sustained and controlled. To meet some of the above criteria, two approaches have been used: systemic administration of drugs, and direct delivery of drugs into the brain. The systemic administration of drugs relies on passive diffusion of drug through the BBB, formation of lipid soluble prodrugs and the use of monoclonal antibodies for targeting the drug to the CNS. The other approach includes the use of implantable polymer systems and infusion pumps. Both of the approaches have some advantages and disadvantages. Because of the enormous amount of literature on drug delivery to the brain, the following review focuses on the use of polymer-based implantable systems. The review includes nondegradable and biodegradable polymer implants from the conceptual phase to the clinic.

A biologic comparison of polyglactin 910 and polyglycolic acid synthetic absorbable sutures.

Two synthetic absorbable sutures were implanted in rats for a comparative evaluation of breaking strength, tissue reaction and absorption. Polyglactin 910 suture was stronger than polyglycolic acid suture in both sizes tested and at all time periods from zero to 35 days. Both suture types elicited minimal tissure response. Based upon histologic examination, virtually all remnants of the polyglactin 910 were absorbed by 90 days, while considerable quantities of polyglycolic acid persisted at 120 days. The difference in absorption rates was a highly significant feature of the comparative biologic profiles of the two suture materials.