Conorphone (TR5109) is an opioid of mixed agonist-antagonist analgesic class. In animal models, conorphone demonstrated an analgesic activity in the same range as morphine, and lack of addiction liability. Conoprphone was evaluated in a clinical trial for postoperative pain in the oral surgery model and in patients with postepisiotomy pain. The 40 mg dose of conorphone resulted in a significant incidence of side effects such as drowsiness, dizziness, nausea, and vomiting.