|Systematic (IUPAC) name|
|Legal status||℞ Prescription only|
|Mol. mass||283.4079 g/mol|
| (what is this?)
Levallorphan (Lorfan, Naloxiphan) is a drug of the morphinan family which is used as an opioid antidote or antagonist. It acts as an antagonist on μ-opioid receptor and agonist on kappa receptors hence called partial agonist, and as a result, blocks the effects of stronger agents with greater intrinsic activity such as morphine or endogenous β-endorphin.
Levallorphan was formerly 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. The combination of levallorphan with pethidine (meperidine) was indeed used so frequently that a standardized formulation was made available, known as Pethilorfan.
See also 
- Swiss Pharmaceutical Society (2000). Index Nominum 2000: International Drug Directory (Book with CD-ROM). Boca Raton: Medpharm Scientific Publishers. ISBN 3-88763-075-0.
- Goodman & Gilman. The Pharmacological Basis of Therapeutics (10th ed.). McGraw Hill Medical Publishing. p. 602. ISBN 978-0-07-135469-1.
- Codd, E. E.; Shank, R. P.; Schupsky, J. J.; Raffa, R. B. (September 1995). "Serotonin and norepinephrine uptake inhibiting activity of centrally acting analgesics: structural determinants and role in antinociception". The Journal of Pharmacology and Experimental Therapeutics 274 (3): 1263–1270. PMID 7562497.
- Bullough, J. (1959). "Use of premixed pethidine and antagonists in obstetrical analgesia; with special reference to cases in which levallorphan was used" (pdf). British Medical Journal 2 (5156): 859–862. PMC 1990381. PMID 13805887.
- Williams, G.; Cope, I. (1962). "An evaluation of a combination of pethidine and levallorphan ("pethilorfan") in labour". The Medical Journal of Australia 49 (2): 499–503. PMID 14000851.