<unk>  is a morphinan-type synthetic agonist–antagonist opioid analgesic developed by Bristol-Myers.<unk>  is most closely structurally related to levorphanol.<unk>  is available as the tartrate salt in injectable, tablet, and intranasal spray formulations. The tablet form is only used in dogs, cats and horses due to low bioavailability in humans. It was patented in 1971 and approved for medical use in 1979.
Butorphanol
Levorphanol
Morphine
Oxymorphol
Hydromorphone
Oxymorphone
Noroxycodone
Nalorphine