An oil-in-water buprenorphine formulation including buprenorphine and a surfactant that emulsifies the buprenorphine in oil, wherein the drug release is controlled by varying the oil concentration and/or pH. A buprenorphine aqueous suspension formulation including a free base buprenorphine and a suspension stabilizer. A buprenorphine oil formulation including a buprenorphine salt suspended in a pharmaceutically acceptable oil. Methods of providing sustained release of buprenorphine over a period of time.