Centrally Acting Sympatholytics: Clonidine



Common side effect include dry mouth, dizziness, headaches, and sleepiness.[7] Severe side effects may include seeing or hearing things that other people do not, heart arrhythmias, and confusion.[8] If rapidly stopped, withdrawal effects may occur.[7] Use during pregnancy or breastfeeding is not recommended.[8] Clonidine lowers blood pressure by stimulating α2 receptors in the brain, which results in relaxation of many arteries.[7]
Clonidine was patented in 1961 and came into medical use in 1966.[9][10][11] It is available as a generic medication.[7] As of 2019 a month of medication costs the NHS about £8.[8] In the United States this amount costs about US$2.70 as of 2019.[12] In 2016 it was the 76th most prescribed medication in the United States with more than 10 million prescriptions.[13]

Medical usesEdit

Clonidine tablets and transdermal patch

Clonidine is used to treat high blood pressure, attention deficit hyperactivity disorder (ADHD), drug withdrawal (alcohol, opioids, or smoking), menopausal flushing, diarrhea, and certain pain conditions.[7]

Resistant hypertensionEdit

Clonidine may be effective for lowering blood pressure in people with resistant hypertension.[14]
Clonidine works by slowing the pulse rate and exert a reduction of serum concentrations of renin, aldosterone and catecholamines.[15]

Attention deficit hyperactivity disorderEdit

Clonidine may improve symptoms of attention deficit hyperactivity disorder in some people but causes many adverse effects and the beneficial effect is modest.[16] In Australia, clonidine is an accepted but not approved use for ADHD by the TGA.[17] Clonidine along with methylphenidate has been studied for treatment of ADHD.[18][19][20] While not as effective as methylphenidate in treating ADHD, clonidine does offer some benefit;[21] it can also be useful in combination with stimulant medications.[22] Some studies show clonidine more sedating than guanfacine, which may be better at bed time along with an arousing stimulant at morning.[23][24]

Drug withdrawalEdit

Clonidine may be used to ease drug withdrawal symptoms associated with abruptly stopping the long-term use of opioids, alcohol, benzodiazepines and nicotine (smoking).[25] It can alleviate opioid withdrawal symptoms by reducing the sympathetic nervous system response such as tachycardia and hypertension, as well as reducing sweating, hot and cold flashes, and general restlessness.[26] It may also be helpful in aiding smokers to quit.[27] The sedation effect is also useful. However, its side effects can include insomnia, thus exacerbating an already common feature of opioid withdrawal.[28] Clonidine may also reduce severity of neonatal abstinence syndrome in infants born to mothers that are using certain drugs, particularly opioids.[29] In infants with neonatal withdrawal syndrome, clonidine may improve the neonatal intensive care unit Network Neurobehavioral Score.[30]
Clonidine has also been suggested as a treatment for rare instances of dexmedetomidine withdrawal.[31]

OtherEdit

Clonidine also has several off-label uses, and has been prescribed to treat psychiatric disorders including stress, sleep disorders, and hyperarousal caused by post-traumatic stress disorder, borderline personality disorder, and other anxiety disorders.[32][33][34][35][36][37][38][39] Clonidine is also a mild sedative, and can be used as premedication before surgery or procedures.[40] Its epidural use for pain during heart attack, postoperative and intractable pain has also been studied extensively.[41] Clonidine can be used in restless legs syndrome.[42] It can also be used to treat facial flushing and redness associated with rosacea.[43] It has also been successfully used topically in a clinical trial as a treatment for diabetic neuropathy.[44] Clonidine can also be used for migraine headaches and hot flashes associated with menopause.[45][46] Clonidine has also been used to treat refractory diarrhea associated with irritable bowel syndrome, fecal incontinence, diabetes, diarrhea associated with opioid withdrawal, intestinal failure, neuroendocrine tumors and cholera.[47] Clonidine can be used in the treatment of Tourette syndrome (specifically for tics).[48]
Injection into the knee joint space of α2 receptor agonists, including clonidine, may reduces the severity of knee pain after arthroscopic knee surgery.[49]

Clonidine suppression testEdit

The reduction in circulating norepinephrine by clonidine was used in the past as an investigatory test for phaeochromocytoma, which is a catecholamine-synthesizing tumour, usually found in the adrenal medulla.[50] In a clonidine suppression test plasma catecholamine levels are measured before and 3 hours after a 0.3 mg oral test dose has been given to the patient. A positive test occurs if there is no decrease in plasma levels.[50]

Pregnancy and breastfeedingEdit

Clon

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