Levorphanol is a potent μ agonist (approximately sixfold greater than morphine), and its uses, side
effects, and physical dependence liability are like those of oxymorphone or hydromorphone.
Levorphanol is available in oral, subcutaneous, and intravenous dosage forms. The oral dose of
levorphanol is approximately twice the parenteral dose. This drug is unique among the μ agonists
in that its analgesic duration of action is 4 to 6 hours, whereas its clearance half-life is 11.4 hours.
Thus, effective analgesic doses of this agent can lead to a buildup of the drug in the body and
result in excessive sedation.
