An implantable medical device (10) comprises reservoirs (30) for receiving a water-soluble active agent or medicament (36) in the form of a solid deposit and at least one biocompatible and biodegradable protecting/retaining layer (38) for protecting the active agent or medicament (36) until it reaches its site of implantation, said biocompatible and biodegradable protecting layer (38) comprising at least one biocompatible and biodegradable film-forming agent, and at least one hydrophobic, biocompatible, agent for controlling the disintegration rate of the protecting/retaining layer. The invention provides better protection of the active agent or medicament and better control of the disintegration rate of the protecting/retaining layer.