Definition Levorphanol is a synthetic opioid analgesic used for the management of moderate to severe pain.
Overview Levorphanol tartrate is a centrally acting opioid agonist approved by the U.S. Food and Drug Administration (FDA) for the relief of severe pain when a continuous, long-term opioid analgesic is necessary and when alternative pain treatments are inadequate. It functions primarily as a mu-opioid receptor agonist, though it also interacts with kappa- and delta-opioid receptors. Additionally, levorphanol exhibits activity as an NMDA receptor antagonist, a property thought to contribute to its analgesic efficacy and potential utility in managing neuropathic pain.
It is considered a potent opioid, with an analgesic potency approximately 4 to 8 times that of morphine when administered parenterally. The drug is administered orally or by injection and has a relatively long half-life, ranging from 12 to 16 hours, which allows for less frequent dosing compared to some other opioids.
Levorphanol is classified as a Schedule II controlled substance in the United States due to its high potential for abuse and dependence.
Etymology/Origin The name "levorphanol" is derived from its chemical structure and stereochemistry. The prefix "levo-" indicates the levorotatory (left-rotating) isomer of the compound oripavine, a derivative of thebaine, which is one of the naturally occurring alkaloids in the opium poppy (Papaver somniferum). "Morphanol" refers to the morphinan class of opioids to which it belongs.
Characteristics
- Chemical Class: Morphinan
- Molecular Formula: C17H23NO
- Mechanism of Action: Acts primarily as an agonist at mu-, kappa-, and delta-opioid receptors; also a non-competitive antagonist of the NMDA receptor
- Pharmacokinetics: Long elimination half-life (12–16 hours); undergoes hepatic metabolism via glucuronidation and N-demethylation
- Routes of Administration: Oral, intramuscular, intravenous
- Clinical Uses: Management of moderate to severe acute and chronic pain; occasionally considered in complex pain syndromes due to its NMDA antagonism
- Side Effects: Typical opioid-related adverse effects, including respiratory depression, sedation, constipation, nausea, dizziness, and risk of dependence or addiction
Related Topics
- Opioid analgesics
- NMDA receptor antagonists
- Chronic pain management
- Opioid use disorder
- Morphine
- Methadone
- Thebaine derivatives
- Controlled Substances Act (U.S.)
Levorphanol remains a less commonly prescribed opioid compared to others like oxycodone or morphine, largely due to its long half-life and complex pharmacokinetics, which can increase the risk of accumulation and toxicity, especially in elderly or renally impaired patients. However, its dual mechanism of action continues to be of clinical interest for refractory pain conditions.