Implantable drug delivery devices include a housing having a closed drug reservoir lumen bounded by a first wall structure and a hydrophilic second wall structure, and a drug contained in the drug reservoir lumen, wherein the first wall structure is impermeable to the drug and the second wall structure is permeable to the drug. Methods of providing controlled release of drug to a patient include deploying a drug delivery device in the patient releasing a drug from the drug reservoir lumen via diffusion through the second wall structure.
