Table of Contents

Alpha 2-adrenergic Agonists

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:
- Attention-deficit/hyperactivity disorder (ADHD)
- 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%

¹⁾ Alamo, C., López-Muñoz, F., & Sánchez-García, J. (2016). Mechanism of action of guanfacine: a postsynaptic differential approach to the treatment of attention deficit hyperactivity disorder (ADHD). Actas Esp Psiquiatr, 44(3), 107-12.