Butorphanol
Butorphanol is levorphanol in which a hydrogen at position 14 of the morphinan skeleton is substituted by hydroxy and one of the hydrogens of the N-methyl group is substituted by cyclopropyl. A semi-synthetic opioid agonist-antagonist analgesic, it is used as its (S,S)-tartaric acid salt for relief or moderate to severe pain. It has a role as an opioid analgesic, a mu-opioid receptor agonist, a kappa-opioid receptor agonist and an antitussive.