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Active ingredient: Clonidine - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

  • Sympatholytics
  • Antihypertensive Agents
  • Analgesics
  • Central Alpha-Agonists

Dosage Forms

  • Tablet
  • Patch

Brands / Synonyms

Adesipress; Catapres; Catapres-TTS; Catapresan; Catapressan; Catarpres; Catarpresan; Chlornidinum; Clonidin; Clonidine HCl; Clonidinhydrochlorid; Clonidinum [Inn-Latin]; Clonistada; Clorpres; Dixarit; Duraclon; Duraclont; Ipotensium; Isoglaucon; ST 155BS; Tenso-Timelets

Indications

For the treatment of hypertension and maybe used in prophylaxis of migraine or recurrent vascular headache; Menopausal flushing

Pharmacology

Clonidine is an antihypertensive agent and an epidural agent for refractory cancer pain. Similar to guanabenz in mechanism of action, clonidine is used in the treatment of hypertension, opiate and nicotine withdrawal, vascular headaches, diabetic diarrhea, glaucoma, ulcerative colitis, Gilles de la Tourette's syndrome, menopause symptoms, severe pain in cancer patients refractory to opiate agonists, and neuropathic pain and in the diagnosis of pheochromocytoma.

Mechanism of Action

Clonidine acts as an agonist at presynaptic alpha(2)-receptors in the nucleus tractus solitarius of the medulla oblongata. Stimulation of these receptors results in the supression of efferent sympathetic pathways and the subsequent decrease in blood pressure and vascular tone in the heart, kidneys, and peripheral vasculature. Clonidine is also a partial agonist at presynaptic alpha(2)-adrenergic receptors of peripheral nerves in vascular smooth muscle.

Absorption

Well absorbed following oral administration. Bioavailability following chronic administration is approximately 65%.

Toxicity

Oral LD50 is 150 mg/kg in rat and 30 mg/kg in dog. Symptoms of overdose include constriction of pupils of the eye, drowsiness, high blood pressure followed by a drop in pressure, irritability, low body temperature, slowed breathing, slowed heartbeat, slowed reflexes, and weakness.

Biotrnasformation / Drug Metabolism

Hepatic. Metabolized through minor pathways. The major metabolite, p-hydroxyclonidine, is present in concentrations less than 10% of those of unchanged clonidine in urine.

Contraindications

Tablet

None known.

Epidural Injection

Clonidine HCl is contraindicated in patients with a history of sensitization or allergic reactions to clonidine. Epidural administration is contraindicated in the presence of an injection site infection, in patients on anticoagulant therapy, and in those with a bleeding diathesis. Administration of epidural clonidine HCl above the C4 dermatome is contraindicated since there are no adequate data to support such use

Drug Interactions

Tablet

If a patient receiving clonidine hydrochloride is also taking tricyclic antidepressants, the effect of clonidine may be reduced, thus necessitating an increase in dosage. Clonidine hydrochloride may enhance the CNS-depressive effects of alcohol, barbiturates or other sedatives. Amitriptyline in combination with clonidine enhances the manifestation of corneal lesions in rats

Epidural Injection

Clonidine may potentiate the CNS-depressive effect of alcohol, barbiturates or other sedating drugs. Narcotic analgesics may potentiate the hypotensive effects of clonidine. Tricyclic antidepressants may antagonize the hypotensive effects of clonidine. The effects of tricyclic antidepressants on clonidine's analgesic actions are not known.

Beta blockers may exacerbate the hypertensive response seen with clonidine withdrawl. Also, due to the potential for additive effects such as bradycardia and AV block, caution is warranted in patients receiving clonidine with agents known to affect sinus node function or AV nodal conduction (e.g., digitalis, calcium channel blockers, and beta-blockers.)

There is one reported case of a patient with acute delirium associated with the simultaneous use of fluphenazine and oral clonidine. Symptoms resolved when clonidine was withdrawn and recurred when the patient was rechallenged with clonidine.

Epidural clonidine may prolong the duration of pharmacologic effects of epidural local anesthetics, including both sensory and motor blockade.

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