Last reviewed 2026-04-20 · How we verify

Tenex (GUANFACINE)

Tenex works by stimulating alpha-2 adrenergic receptors in the brain, which helps to reduce the activity of certain nerve cells.

Tenex (Guanfacine) is a central alpha-2 adrenergic agonist developed by Promius Pharma, targeting Nischarin. It was FDA-approved in 1986 for attention deficit hyperactivity disorder and hypertensive disorder. As an off-patent medication, Tenex is available from multiple generic manufacturers. Key safety considerations include its potential to cause dizziness, fatigue, and dry mouth. Tenex has a half-life of 15 hours and bioavailability of 81%.

At a glance

Mechanism of action

Guanfacine is central alpha2A-adrenergic receptor agonist. Guanfacine is not central nervous system (CNS) stimulant. The mechanism of action of guanfacine in ADHD is not known.

Approved indications

• Attention deficit hyperactivity disorder
• Hypertensive disorder

Common side effects

• Somnolence
• Abdominal Pain
• Fatigue
• Irritability
• Nausea
• Dizziness
• Vomiting
• Hypotension
• Decreased Appetite
• Enuresis
• Headache

Key clinical trials

• ACE-D Aim 3 Clinical Cognitive Trial to Enhance Translation in Depression (PHASE2)
• Mechanistic Evaluation of Guanfacine on Drinking Behavior in Women and Men With Alcohol Use Disorders (PHASE2)
• Maximizing trEatment of Neurological Dysfunction Using INtravenous Guanfacine Study (PHASE2)
• Guanfacine for Hyperactivity in Children With Down Syndrome (HYPEbeGONE_DS) (PHASE2)
• Treating Young Children With Attention Deficit Hyperactivity Disorder (PHASE4)
• Effect of Guanfacine on the Reversal of Opioid-induced Hyperalgesia (OIH) (NA)
• Effect of Guanfacine on Opioid-induced Hyperalgesia (OIH) and Tolerance (PHASE4)
• AWARE: Management of ADHD in Autism Spectrum Disorder (PHASE4)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.