Tolazoline is a non-selective competitive

Competitive antagonist

A competitive antagonist is a receptor antagonist that binds to a receptor but does not activate the receptor. The antagonist will compete with available agonist for receptor binding sites on the same receptor...

 α-adrenergic receptor

Adrenergic receptor

The adrenergic receptors are a class of metabotropic G protein-coupled receptors that are targets of the catecholamines, especially noradrenaline and adrenaline ....

 antagonist

Receptor antagonist

A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...

. It is a vasodilator that is used to treat spasms of peripheral blood vessels (as in acrocyanosis

Acrocyanosis

Acrocyanosis is persistent blue or cyanotic discoloration of the extremities, most commonly occurring in the hands, although it also occurs in the feet and distal parts of face....

). It has also been used successfully as an antidote to reverse the severe peripheral vasoconstriction which can occur as a result of overdose with certain 5-HT_2A

5-HT2A receptor

The mammalian 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor . This is the main excitatory receptor subtype among the GPCRs for serotonin , although 5-HT2A may also have an inhibitory effect on certain areas such...

 agonist

Agonist

An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

 drugs such as LSD

LSD

Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic psychedelic drug of the ergoline family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an...

, DOB

2,5-Dimethoxy-4-bromoamphetamine

DOB, also known as Brolamfetamine and Bromo-DMA, is a psychedelic hallucinogenic drug and a substituted amphetamine of the phenethylamine class of compounds, which can be used as an entheogen. DOB was first synthesized by Alexander Shulgin in 1967...

 and Bromodragonfly and can lead to gangrene

Gangrene

Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...

 if untreated.

It is however most commonly used in veterinary medicine

Veterinary medicine

Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

, to reverse xylazine

Xylazine

Xylazine is a drug that is used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle and other non-human mammals. An analogue of clonidine, it is an agonist at the α2 class of adrenergic receptor....

-induced sedation

Sedation

Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure...

.

Chemistry

Tolazoline, 2-benzyl-2-imidazoline, is synthesized by the heterocyclation of the ethyl ester of iminophenzylacetic acid with ethylene diamine

Ethylene diamine

Ethylenediamine is the organic compound with the formula C2H42. This colorless liquid with an ammonia-like odor is a strongly basic amine. The liquid fumes upon contact with humid air...

, which forms the desired product. The structure of tolazoline is strikingly similar to α-adrenergic agonists, which are antiedema sympathomimetics.

• A. Sonn, (1939).
• W. Wustrow, P. Herold, (1934).
• M. Hartmann, H.O. Isler, (1938).
• N. Guenter, (1982).