Guanfacine
Guanfacine, sold under the brand name Tenex (immediate-release) and Intuniv (extended-release) among others, is an oral alpha-2a agonist medication used to treat attention deficit hyperactivity disorder (ADHD) and high blood pressure. Guanfacine is FDA-approved for monotherapy treatment of ADHD, as well as being used for augmentation of other treatments, such as stimulants. Guanfacine is also used off-label to treat tic disorders, anxiety disorders, and post-traumatic stress disorder (PTSD).
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| Trade names | Estulic, Intuniv, Tenex, others |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a601059 |
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| Routes of administration | By mouth |
| Drug class | Centrally acting α2A- adrenergic receptor agonist |
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| Bioavailability | 80–100% (IR), 58% (XR) |
| Protein binding | 70% |
| Metabolism | CYP3A4 |
| Elimination half-life | IR: 10–17 hours; XR: 17 hours (10–30) in adults & adolescents and 14 hours in children |
| Excretion | Kidney (80%; 50% [range: 40–75%] as unchanged drug) |
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| ECHA InfoCard | 100.044.933 |
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| Formula | C9H9Cl2N3O |
| Molar mass | 246.09 g·mol−1 |
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Common side effects include sleepiness, constipation, and dry mouth. Other side effects may include low blood pressure and urinary problems. The FDA has categorized Guanfacine as "Category B" in pregnancy, which means animal-reproduction studies have not demonstrated a fetal risk or an adverse effect during pregnancy or breastfeeding. It appears to work by activating α2A-adrenergic receptors in the brain, thereby decreasing sympathetic nervous system activity.
Guanfacine was first described by 1974 and was approved for medical use in the United States in 1986. It is available as a generic medication. In 2021, it was the 231st most commonly prescribed medication in the United States, with more than 1 million prescriptions.