histamine agonist

{{Short description|Drug to increase activity at histamine receptors}}

A histamine agonist is a drug which causes increased activity at one or more of the four histamine receptor subtypes.

H₁ agonists promote wakefulness.{{cite book | last1=Sakai | first1=N. | last2=Nishino | first2=S. | title=Encyclopedia of Sleep | chapter=Wake-Promoting Medications | publisher=Elsevier | date=2013 | isbn=978-0-12-378611-1 | doi=10.1016/b978-0-12-378610-4.00126-1 | pages=627–633|quote=Although centrally injected histamine or histaminergic H1 agonists promote wakefulness, the systemic administration of these compounds induces various unacceptable side effects via peripheral H1 receptor stimulation.}}

H₂: Betazole and Impromidine are examples of agonists used in diagnostics to increase histamine.

H₃: Betahistine is a weak Histamine₁ agonist and a very strong antagonist of the Histamine₃ autoreceptor. Antagonizing H₃ increases histaminergic tone.