Levallorphan (brand name Lorfan), is an opiate antagonist of morphine family. Levallorphan was formerly used in general anesthesia, mainly to reverse the respiratory depression produced by opioid analgesics and barbiturates used for induction of surgical anaesthesia whilst maintaining a degree of analgesia. Levallorphan was also used in combination with opioid analgesics to reduce their side effects, mainly in obstetrics. The combination of levallorphan with pethidine was used so frequently, a standardized formulation was made available, known as Pethilorfan, by Roche Products Ltd in later 1950s. Is known to be used for narcotic overdose. Levallorphan is similar to naloxone but differs from naloxone in that it also possesses some agonist properties. It acts as an antagonist and partial agonist of the mu opioid receptor (MOR). Levallorphan can produce severe mental reactions at sufficient doses including hallucinations, dissociation, and other psychotomimetic effects, dysphoria, anxiety, confusion, dizziness, disorientation, derealization, feelings of drunkenness, and bizarre, unusual, or disturbing dreams.