An implantable device such as a stent is formed from a biocompatible metallic material such as a magnesium alloy. The magnesium alloy implantable medical device may be designed to degrade over a given period of time. In order to control the degradation time, the device may be coated or otherwise have affixed thereto one or more coatings, one of which comprises a material for controlling the degradation time and maintain a pH neutral environment proximate the device. The coating is formed from a blend of a high molecular weight acidic polymer and a low molecular weight acidic polymer. Additionally, therapeutic agents may be incorporated into one or more of the coatings on the implantable medical device.
