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Clonidine chemical structure

IUPAC name
CAS number
ATC code

C02AC01 ., .

Chemical formula C9H9Cl2N3
Molecular weight 230.093 g/mol
Bioavailability 75-95%
Metabolism Hepatic to inactive metabolites
Elimination half-life 12-16 hours
Excretion {{{excretion}}}
Pregnancy category C US
Legal status Rx-only
Routes of administration oral, transdermal

Clonidine is a direct-acting adrenergic agonist prescribed historically as an anti-hypertensive agent. It has found new uses, including treatment of some types of neuropathic pain, opioid detoxification, and, off-label, to counter the side effects of stimulant medications such as methylphenidate or Adderall. It is becoming a more accepted treatment for insomnia, because clonidine is less addictive than most prescription sleep aids. Clonidine is increasingly used in conjunction with stimulants to treat attention-deficit hyperactivity disorder (ADHD), where it's given in late afternoon and/or evening for sleep, and because it sometimes helps moderate ADHD-associated impulsive and oppositional behavior, and may reduce tics.[1] Clonidine can also be used in the treatment of Tourette syndrome.[2]

Mechanism of action

Clonidine is a centrally-acting alpha-2 agonist. It selectively stimulates receptors in the brain that monitor catecholamine levels in the blood. These receptors close a negative feedback loop that begins with descending sympathetic nerves from the brain that control the production of catecholamines (epinephrine, also known as adrenaline, and norepinephrine) in the adrenal medulla. By fooling the brain into believing that catecholamine levels are higher than they really are, clonidine causes the brain to reduce its signals to the adrenal medulla, which in turn lowers catecholamine production and blood levels. The result is a lowered heart rate and blood pressure, with side effects of dry mouth and fatigue. If clonidine is suddenly withdrawn the sympathetic nervous system will revert to producing high levels of epinephrine and norepinephrine, higher even than before treatment, causing rebound hypertension. Rebound hypertension can be avoided by slowly withdrawing treatment.

Clonidine for opiate withdrawals

Clonidine is regularly prescribed to opiate addicts to help alleviate their withdrawals. It is mainly used to combat the dopesickness in the first couple days of withdrawals. It helps take away the sweating, hot/cold flashes, and general restlessness. The sedation effect is also useful.

Clonidine tablets and transdermal patch


Clonidine is typically available as tablets (Catapres®, Dixarit®), as a transdermal patch (Catapres-TTS®), or as an injectable form to be given epidurally, directly to the central nervous system.


  1. National Institute of Neurological Disorders and Stroke (2002). "Methylphenidate and Clonidine Help Children With ADHD and Tics".
  2. Schapiro NA. "Dude, you don't have Tourette's": Tourette's syndrome, beyond the tics. Pediatr Nurs. 2002 May-Jun;28(3):243-6, 249-53. PMID 12087644

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