Drug delivery devices and methods are provided for modulating the microenvironmental pH surrounding the device. One embodiment of a drug delivery device includes an elongated annular body formed of a matrix system containing a drug dispersed in a biocompatible polymer and a pH modifier disposed in the lumen of the body, wherein the device is configured to release in vivo (i) the drug by diffusion from the annular body and (ii) the pH modifier by diffusion through the annular body. Methods in clude inserting into the patient a device and releasing the drug and pH modifier therefrom by diffusion.
