Levallorphan

Overview
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. The combination of levallorphan with pethidine (meperidine) was indeed used so frequently that a standardised formulation was made available, known as "Pethilorfan".