Levallorphan is a drug

Drug

A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...

 of the morphinan

Morphinan

Morphinan is the base chemical structure of a large chemical class of psychoactive drugs, consisting of opioid analgesics, cough suppressants, and dissociative hallucinogens, among others.- Chemical Derivatives :Immediate derivatives of morphinan include:...

 family which is used as an opioid

Opioid

An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...

 antidote

Antidote

An antidote is a substance which can counteract a form of poisoning. The term ultimately derives from the Greek αντιδιδοναι antididonai, "given against"....

 or antagonist

Opioid antagonist

An opioid antagonist is a receptor antagonist that acts on opioid receptors.Naloxone and naltrexone are commonly used opioid antagonist drugs which are competitive antagonists that bind to the opioid receptors with higher affinity than agonists but do not activate the receptors...

. It acts as an antagonist on μ-opioid receptor and agonist on kappa receptors [hence called [partial agonist]], (Reference : p 602, Goodman & Gilman's The Pharmacological Basis of Therapeutics, ed. 10 from McGraw Hill Medical Publishing Division)and as a result, blocks the effects of stronger agents with greater intrinsic activity

Intrinsic activity

Intrinsic activity or efficacy refers to the relative ability of a drug-receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its molecular target, and the EC50, which is a measure of the...

 such as morphine

Morphine

Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...

 or endogenous

Endogenous

Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...

 β-endorphin.

Levallorphan was formerly widely used in general anaesthesia

General anaesthesia

General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

, mainly to reverse the respiratory depression produced by the opioid analgesic

Analgesic

An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

s and barbiturate

Barbiturate

Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

s which are used for induction of surgical anaesthesia, although it is now less common as the newer drug naloxone

Naloxone

Naloxone is an opioid antagonist drug developed by Sankyo in the 1960s. Naloxone is a drug used to counter the effects of opiate overdose, for example heroin or morphine overdose. Naloxone is specifically used to counteract life-threatening depression of the central nervous system and respiratory...

 tends to be used instead.

It was also used in combination with opioids to reduce their side effect

Side effect

In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequences of the use of a drug.Occasionally, drugs are...

s, mainly in obstetrics

Obstetrics

Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...

, 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

Pethidine

Pethidine or meperidine Pethidine (INN) or meperidine (USAN) Pethidine (INN) or meperidine (USAN) (commonly referred to as Demerol but also referred to as: isonipecaine; lidol; pethanol; piridosal; Algil; Alodan; Centralgin; Dispadol; Dolantin; Mialgin (in Indonesia); Petidin Dolargan (in Poland);...

(meperidine) was indeed used so frequently that a standardized formulation was made available, known as Pethilorfan.