Simultaneous In Vitro Release of Levodopa and Carbidopa from Biocompatible Core-in-Cup Implants

Abstract

Most implantable drug delivery systems do not release drug at a zero-order rate of release due to their geometry of a decreasing releasing surface. Microcapsules which can release drug at a zero-order rate are very difficult to produce and are prone to dose dumping. The purpose of this study was to test the in vitro release of levodopa and carbidopa from a new core-in-cup bioerodible implantable tablet. Core-in-cup implantable tablets with cups of Resomer® 207, and cores of Resomer RG 746 and Resomer RG 858 were tested. The core-in-cup implantable tablets were tested as to whether they released levodopa or carbidopa at a zeroorder rate. Their rate and extent of erosion in normal saline were also examined. The results indicate that levodopa and carbidopa were released at a zero-order rate in vitro for up to 100 days depending on the inherent viscosity of the polymer used in the core of the implant. It was also found that the rate and extent of erosion of the cup portion of the core-in-cup implantable tablet did not adversely affect the zero-order release of the drugs.