Levorphanol: the forgotten opioid.
BACKGROUND
Levorphanol (levo-3-hydroxy-N-methylmorphinan) is a strong opioid that is the only available opioid agonist of the morphinan series. Levorphanol was originally synthesized as a pharmacological alternative to morphine more than 40 years ago. It is considered a step-3 opioid by the World Health Organization (WHO) and has a greater potency than morphine. Analgesia produced by levorphanol is mediated via its interactions with mu, delta, and kappa opioid receptors. Levorphanol is also an N-methyl-D-aspartate (NMDA) receptor antagonist. There is evidence that levorphanol may inhibit uptake of norepinephrine and serotonin. Similar to morphine, levorphanol undergoes glucuronidation in the liver, and the glucuronidated products are excreted in the kidney. Levorphanol can be given orally, intravenously, and subcutaneously.


OBJECTIVE
This article reviews the pharmacodynamics, pharmacology, and clinical efficacy for this often overlooked step-3 opioid.


CONCLUSIONS
The long half-life of the drug increases the potential for drug accumulation. Levorphanol has clinical efficacy in neuropathic pain.
Prommer
Eric
E
VIP Palliative Care Program, Greater Los Angeles Healthcare, Division of Hematology/Oncology, UCLA School of Medicine, 11301 Wilshire 111-H, Los Angeles, CA, USA. eric.prommer@med.va.gov
D000284:Administration, Oral; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use*; D004334:Drug Administration Schedule; D006801:Humans; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D007981:Levorphanol / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use*; D009369:Neoplasms / Q000150:complications; D010146:Pain / Q000188:drug therapy / Q000209:etiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000187:drug effects; D011957:Receptors, Opioid / Q000819:agonists / Q000187:drug effects; D013810:Therapeutic Equivalency
D000701:Analgesics, Opioid; D016194:Receptors, N-Methyl-D-Aspartate; D011957:Receptors, Opioid; D007981:Levorphanol