Degree of clinically quantified tolerance to the desired effects of and adverse drug reactions to the full mu opiod receptor agonist morphine, methadone and fentanyl and to the partial agonist buprenorphine during opioid maintenance and analgesic treatment

Mu opioid analgesics like the full mu opioid receptor agonists morphine, methadone and fentanyl or the partial agonist buprenorphine have remained the mainstay in the treatment of moderate to severe pain. During chronic treatment, the development of tolerance to their antinociceptive effects presents a considerable therapeutic challenge, especially in opioid maintenance patients who, to complicate matters, may or may not abuse opioids on the side. In opioid-based maintenance patients, it is desirable to assess the actual degree of tolerance to effectively treat withdrawal symptoms while avoiding illegal diversion of surplus quantities of the prescribed mu opioid agonist. As a further complication, the degree of tolerance may vary considerably among different opioid effects.