- Last edited on February 18, 2021
Alpha 2-adrenergic Agonists
Primer
Alpha-adrenergic agonists are a class of sympathomimetic medications that selectively stimulate the alpha adrenergic receptors.
Mechanism of Action
- Both clonidine and guanfacine are centrally acting alpha 2-adrenergic agonists
- Alpha 2-adrenergic agonists have agonist effects on presynaptic 2- adrenergic autoreceptors, resulting (through negative feedback) in decreased release of norepinephrine (NE), especially in the locus ceruleus and prefrontal cortex
- Clonidine binds to all three alpha 2-adrenergic receptor subtypes (2A, 2B, 2C) and other receptors (a1- and beta- adrenergic, histamine, imidazoline)
- Guanfacine binds more selectively to the alpha 2A receptor.[1]
Indications
- Within child and adolescent psychiatry, there are indications for:
- Tic disorder
- Disruptive/aggressive behaviour
- Insomnia (especially in children taking stimulants), as alpha 2-adrenergic agonists have sedating effects
Side Effects
- Weakness 10%, anorexia, nausea and vomitting, dry mouth (xerostomia) <40%, hypotension (orthostatic) 1-10%