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CAS Number
PubChem CID
E number{{#property:P628}}
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Chemical and physical data
Molar mass433.494 g/mol

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Levallorphan (INN) (Lorfan) is a drug which acts as an opioid mixed agonist-antagonist, with mainly antagonist effects. It is derived from the morphinan family of drugs.

Levallorphan used to be widely used in general anaesthesia, mainly to reverse the respiratory depression produced by the opioid analgesics and barbiturates which are used for induction of surgical anaesthesia, although it is now less common as the newer drug naloxone tends to be used instead. It was also used in combination with opioids to reduce their side effects, mainly in obstetrics, and when a very small dose of levallorphan is used alongside an opioid full agonist this can in fact produce greater analgesia than when the agonist is used by itself.[1] The combination of levallorphan with pethidine (meperidine) was indeed used so frequently that a standardised formulation was made available, known as "Pethilorfan".[2]


  1. Bullough J. Use of premixed pethidine and antagonists in obstetrical analgesia; with special reference to cases in which levallorphan was used. British Medical Journal. 1959 Oct 31;2(5156):859-62. PMID 13805887
  2. Williams G, Cope I. An evaluation of a combination of pethidine and levallorphan ("pethilorfan") in labour. Medical Journal of Australia. 1962 Sep 29;49(2):499-503. PMID 14000851