an implantable medical device includes a substrate , a drug - impregnated layer deposited over the substrate , and a barrier layer at least partially covering the drug - impregnated layer . the barrier layer may be a biodegradable metal , biodegradable metal oxide , or biodegradable metal alloy , such as , magnesium , a magnesium oxide or a magnesium alloy . the drug - impregnated layer includes a therapeutic substance , such as , antineoplastic , anti - inflammatory , antiplatelet , anticoagulant , fibrinolytic , thrombin inhibitor , antimitotic , antiallergic , and antiproliferative substances .