Naloxone
Naloxone may be mixed with a number of opioids like buprenorphine.  (Buprenorphine mixed with naloxone is called Suboxone.)  Buprenorphine is used to decrease cravings for opiates.  When buprenorphine and naloxone are mixed, and taken by mouth, only buprenorphine has an effect.  But if a person misuses Suboxone by injecting it or taking large doses, the naloxone blocks the effect of the opioid. This combination is used to try to prevent abuse.