Clonidine
Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal (alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and certain pain conditions. The drug is often prescribed off-label for tics. It is used orally (by mouth), by injection, or as a transdermal skin patch. Onset of action is typically within an hour with the effects on blood pressure lasting for up to eight hours.
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Pronunciation | /ˈklɒnədiːn/ |
Trade names | Catapres, Kapvay, Nexiclon, others |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682243 |
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Routes of administration | Oral, epidural, intravenous (IV), transdermal, topical |
Drug class | Centrally acting α2A-agonist hypotensive agent |
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Bioavailability | 70–80% (oral), 60–70% (transdermal) |
Protein binding | 20–40% |
Metabolism | Liver to inactive metabolites, 2/3 CYP2D6 |
Onset of action | IR: 30–60 minutes after an oral dose |
Elimination half-life | IR: 12–16 hours; 41 hours in kidney failure, 48 hours for repeated dosing |
Excretion | Urine (72%) |
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ECHA InfoCard | 100.021.928 |
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Formula | C9H9Cl2N3 |
Molar mass | 230.09 g·mol−1 |
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Common side effect include dry mouth, dizziness, headaches, hypotension, and sleepiness. Severe side effects may include hallucinations, heart arrhythmias, and confusion. If rapidly stopped, withdrawal effects may occur. Use during pregnancy or breastfeeding is not recommended. Clonidine lowers blood pressure by stimulating α2 receptors in the brain, which results in relaxation of many arteries.
Clonidine was patented in 1961 and came into medical use in 1966. It is available as a generic medication. In 2021, it was the 80th most commonly prescribed medication in the United States, with more than 8 million prescriptions.