Provided are uses of a transmucosal drug delivery device comprising buprenorphine in the manufacture of a medicament for treating chronic pain with a low incidence of adverse effects. The device comprises a bioerodable mucoadhesive layer comprising buprenorphine disposed in a buffered polymeric diffusion environment, wherein the polymeric diffusion environment is a buffered environment having a pH of between about 4 and about 6, and a backing layer buffered to a pH of between about 4.0 and about 4.8 and that does not include an opioid antagonist.
