Medical device are provided for delivering a therapeutic agent to a tissue. The medical device has a layer overlying the exterior surface of the medical device. The layer contains a therapeutic agent and an additive. In certain embodiments, the additive has a hydrophilic part and a drug affinity part, wherein the drug affinity part is at least one of a hydrophobic part, a part that has an affinity to the therapeutic agent by hydrogen bonding, and a part that has an affinity to the therapeutic agent by van der Waals interactions. In embodiments, the additive is water-soluble. In further embodiments, the additive is at least one of a surfactant and a chemical compound, and the chemical compound has a molecular weight of from 80 to 750 or has more than four hydroxyl groups.