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| {{drugbox
| | #REDIRECT [[Clonidine#Pharmacology]] |
| | IUPAC_name = ''N''-(2,6-dichlorophenyl)-4,5-dihydro-1''H''-imidazol-2-amine
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| | image = clonidine structure.png
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| | width = 188
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| | CAS_number = 4205-90-7
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| | ATC_prefix = C02
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| | ATC_suffix = AC01
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| | ATC_supplemental = {{ATC|N02|CX02}}, {{ATC|S01|EA04}}
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| | PubChem = 2803
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| | DrugBank = APRD00174
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| | C=9 | H=9 | Cl=2 | N=3
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| | molecular_weight = 230.093 g/mol
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| | bioavailability = 75-95%
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| | protein_bound = 20-40%
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| | metabolism = [[Hepatic]] to inactive [[metabolite]]s
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| | excretion = urine (40-50%)
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| | elimination_half-life = 12-33 hours
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| | pregnancy_US = C
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| | legal_status = Rx-only
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| | routes_of_administration = oral, [[transdermal]]
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| }}
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| {{CMG}}
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| '''Clonidine''' is a direct-acting [[alpha-2 adrenergic receptor|α2]] [[adrenergic agonist]] prescribed historically as an [[antihypertensive]] agent. It has found new uses, including treatment of some types of [[neuropathy|neuropathic pain]], [[opioid]] [[detoxification]], [[sleep hyperhydrosis]], [[anaesthetic]] use, and [[off-label]], to counter the side effects of [[stimulant]] medications such as [[methylphenidate]] or [[amphetamine]]. It is becoming a more accepted treatment for [[insomnia]], as well as for relief of menopausal symptoms. Clonidine is increasingly used in conjunction with stimulants to treat attention-deficit hyperactivity disorder ([[ADHD]]), for which it is administered in late afternoon or evening for sleep, and because it sometimes helps moderate ADHD-associated impulsive and oppositional behavior, and may reduce [[tic]]s.<ref>
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| National Institute of Neurological Disorders and Stroke (2002). [http://www.ninds.nih.gov/news_and_events/news_articles/news_article_adhd.htm "Methylphenidate and Clonidine Help Children With ADHD and Tics".]</ref> Clonidine can also be used in the treatment of [[Tourette syndrome]].<ref name=dude>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</ref>
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| ==Indications==
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| The main use for this medication is to treat high blood pressure. It works by stimulating certain brain receptors (alpha adrenergic type) which results in the relaxing of blood vessels in other parts of the body, causing them to widen. It has specificity towards the presynaptic alpha-2 receptors in the vasomotor center in the CNS. This binding inhibits the production of [[norepinephrine]] (NE), thus decreasing sympathetic outflow. The parasympathetic activity predominates.
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| [[Image:Clonidine_pills_and_patch.jpg|thumb|left|200px|Clonidine tablets and transdermal patch]]<br clear="left">
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| Clonidine is typically available as [[tablet]]s (Catapres, Dixarit), as a [[transdermal patch]] (Catapres-TTS), or as an [[Injection (medicine)|injectable]] form to be given [[epidural]]ly, directly to the [[central nervous system]].
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| ===FDA approved uses===
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| This medication may also be used to ease withdrawal symptoms associated with the long-term use of [[narcotic]]s, [[Alcoholic beverage|alcohol]] and [[nicotine]] (smoking). In addition, clonidine has also been used for [[migraine]] headaches, hot flashes associated with menopause, attention deficit hyperactivity disorder.<ref name="Web MD">{{cite web | title=Clonidine Oral Uses |url=http://www.webmd.com/drugs/drug-11754-Clonidine.aspx?drugid=11754&drugname=Clonidine |publisher=Web MD}}</ref><ref>{{cite web |title=Clonidine |url=http://www.drugs.com/clonidine.html |publisher=Drugs.com}}</ref>
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| Clonidine is regularly prescribed to [[opiate]] addicts to help alleviate their withdrawal symptomology. It is mainly used to combat the [[sympathetic nervous system]] response to opiate withdrawal, namely [[tachycardia]] and [[hypertension]], in the first couple days of withdrawals.<ref>. AJ Giannini. Drugs of Abuse--Second Edition. Los Angeles, Practice Management Information Corporation,1997.</ref> It helps take away the sweating, hot/cold flashes, and general restlessness. The sedation effect is also useful although its side effects can include insomnia, thus exacerbating an already common feature of opiate withdrawal.<ref> AJ Giannini, I. Extein,MS Gold, ALC Pottash, S. Castellani. Clonidine in mania. Drug Development Research. 3:101-105,1983. </ref>
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| ==Adverse effects==
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| This drug may cause drowsiness, lightheadedness, dry mouth, dizziness, or constipation. Clonidine may also cause [[hypotension]],Clonidine can also cause inhibition of orgasm in women.<ref>{{cite journal | author = Hossmann V | coauthors = Maling TJ, Hamilton CA, Reid JL, Dollery CT. | year = 1980 | month = Aug | title = Sedative and cardiovascular effects of clonidine and nitrazepam | journal = Clin Pharmacol Ther. | volume = 28 | issue = 2 | pages = 167–76 | pmid = 7398184 }}</ref> Sucking on sugarless hard candy or ice chips, chewing sugarless gum, drinking water, and using a saliva substitute may help relieve dry mouth.
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| ==Pharmacodynamics==
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| Clonidine is a centrally-acting α-[[adrenergic agonist|adrenergic receptor agonist]] with more affinity for [[Alpha-2 receptor|α<sub>2</sub>]] than [[alpha-1 receptor|α<sub>1</sub>]]. 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 gland|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.
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| ===Clonidine suppression test===
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| Clonidine's effect on reducing circulating epinephrine by a central mechanism was used in the past as an investigatory test for [[pheochromocytoma]], which is a catecholamine-synthesizing tumor, usually of the adrenal medulla. In a '''clonidine suppression test''' plasma catecholamines levels are measured before and 3 hours after a 0.3 µg/kg oral test dose has been given to a patient. A positive test occurs if there is no decrease in plasma levels. | |
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| ==Footnotes==
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| {{reflist|2}}
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| {{Adrenergic agonists}}
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| {{Antihypertensives and diuretics}}
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| {{Antimigraine preparations}}
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| {{Antiglaucoma preparations and miotics}}
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| {{Drugs used in addictive disorders}}
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| [[Category:Antihypertensive agents]]
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| [[Category:Imidazolines]]
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| [[de:Clonidin]]
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| [[es:Clonidina]]
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| [[fr:Clonidine]]
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| [[hr:Klonidin]]
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| [[it:Clonidina]]
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| [[nl:Clonidine]]
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| [[ja:クロニジン]]
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| [[pl:Klonidyna]]
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| [[ru:Клонидин]]
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| {{WH}}
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| {{WS}}
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