|Systematic (IUPAC) name|
|oral, intravenous, subcutaneous, intramuscular|
|Bioavailability||70% (oral); 100% (IV)|
|Biological half-life||11-16 hours|
|CAS Registry Number|
|Molecular mass||257.371 g/mol|
Levorphanol (Levo-Dromoran) is an opioid medication used to treat moderate to severe pain. Chemically it is (−)-3-hydroxy-N-methyl-morphinan. It is the levorotatory stereoisomer of the synthetic morphinan (Dromoran) and a pure opioid agonist, first described in Germany in 1948 as an orally active morphine-like analgesic. It has been in clinical use in the U.S. since the 1950s. Levorphanol has opioid, NMDA antagonist and monoamine reuptake inhibitor activity; it binds strongly to the mu opioid receptor and less strongly to the kappa and delta opioid receptors but lacks complete cross-tolerance with morphine. It possesses greater intrinsic activity at the MOR than morphine. The duration of action is generally long compared to other comparable analgesics and varies from 4 hours to as much as 15 hours. For this reason levorphanol is useful in palliation of chronic pain and similar conditions. Levorphanol has an oral to parenteral effectiveness ratio of 2:1, one of the most favourable of the strong narcotics. Its NMDA actions, similar to those of the phenylheptylamine open-chain narcotics such as methadone or the phenylpiperidine ketobemidone, make levorphanol useful for types of pain that other analgesics may not be as effective against, such as neuropathic pain.
Levorphanol is listed under the Single Convention On Narcotic Drugs 1961 and is regulated like morphine in most countries. In the United States it is a Schedule II Narcotic controlled substance with a DEA ACSCN of 9220 and 2013 annual aggregate manufacturing quota of 4.5 kilos. The salts in use are the tartrate (free base conversion ratio 0.58) and hydrobromide (0.76) 
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