Tolazoline is a non-selective competitive α2-adrenergic receptor antagonist. It is a vasodilator that is used to treat spasms of peripheral blood vessels (as in acrocyanosis). It has also been used (in conjunction with sodium nitroprusside) successfully as an antidote to reverse the severe peripheral vasoconstriction which can occur as a result of overdose with certain 5-HT2A receptor agonist drugs such as 25I-NBOMe, DOB, and Bromodragonfly.
History
Tolazoline was first used in the 1980s as an alternative reversal agent for
xylazine.
Use
Tolazoline is used in large animal medicine to reverse the effects of α
2-adrenergic receptor agonists, typically
xylazine. Large doses of
intravenous tolazoline in cattle can cause
hyperesthesia and
opisthotonos and other routes such as
intramusucular are preferred.
Pharmacology
Tolazoline binds to the a
2 adrenergic receptor at a ratio of 4:1, the lowest of all a
2 adrenergic receptor antagonists. Tolazoline activates the imidazoline receptor.
IV tolazoline has slow elimination and a large distribution in the horse.