[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Centrally acting antihypertensives](https://durgical.com/en/pharmacology/classes/centrally-acting-antihypertensives/) › Clonidine [Pharmacology](https://durgical.com/en/pharmacology/) · [Centrally acting antihypertensives](https://durgical.com/en/pharmacology/classes/centrally-acting-antihypertensives/) # Clonidine A blood pressure medicine that calms the sympathetic nervous system from the brainstem. Stopping it suddenly can make blood pressure rebound. Updated 2026-11-01 - Class: [Centrally acting antihypertensives](https://durgical.com/en/pharmacology/classes/centrally-acting-antihypertensives/) - Receptor: Alpha-2A adrenergic receptor - ATC code: C02AC01 ◎**Alpha-2A adrenergic receptor**Clonidine ⓘ No structure of clonidine bound to its receptor is available; the figure shows noradrenaline in the same binding site of the human alpha-2A adrenergic receptor. **Target in 3D:** Alpha-2A adrenergic receptor. PDB structure 7EJ0 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/7EJ0) · Drag to rotate · pinch to zoom ## Mechanism of action Clonidine is an alpha-2 adrenergic agonist. In the brainstem it reduces sympathetic outflow, so peripheral and renal vascular resistance, heart rate and blood pressure fall. The same central action explains sedation, dry mouth and its use in withdrawal states and attention deficit hyperactivity disorder. - Clonidine stimulates alpha-2 receptors in the brainstem - Sympathetic outflow to heart, vessels and kidneys falls - Heart rate, resistance and blood pressure fall ## Pharmacokinetics **Absorption** Oral bioavailability about 70 to 80 percent (label); also given as a skin patch **Elimination** Kidneys: about half of the absorbed dose appears unchanged in urine; little is removed by haemodialysis **Half-life** Elimination half-life about 12 to 16 hours, longer in severe kidney failure (label) ## Indications - High blood pressure [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/) - Attention deficit hyperactivity disorder, alone or with other medicines - Other uses: opioid or alcohol withdrawal symptoms, menopausal hot flushes ## Adverse effects ### Common - Dry mouth - Drowsiness and sedation - Dizziness and orthostatic symptoms - Constipation - Fatigue and headache ### Serious (rare, important) - Rebound hypertension after abrupt withdrawal, with agitation, headache and tremor - Bradycardia and AV block - Severe sedation and respiratory depression in overdose, especially in children ## Contraindications - Hypersensitivity to clonidine ## Key interactions **Alcohol, sedatives and other CNS depressants** More sedation **Tricyclic antidepressants** The fall in blood pressure may be weakened **Beta blockers, digoxin and calcium channel blockers** Bradycardia and AV block; with a beta blocker, withdrawal reactions are worse **Other antihypertensives** Additive fall in blood pressure ## What is monitored - Blood pressure, lying and standing - Heart rate - Sedation - Blood pressure during dose reduction or after missed doses ## Nursing care - Teach that the drug is not stopped suddenly; doses are reduced gradually under medical supervision. - If a beta blocker is also being stopped, the beta blocker is withdrawn several days before clonidine is tapered. - Warn about drowsiness and dizziness; rise slowly from lying or sitting. - Dry mouth can be eased with water, sugar-free gum or saliva substitutes. ## Pregnancy and breastfeeding Clonidine crosses the placenta and adequate human studies are lacking; it is used only if the benefit justifies the risk. ## Memory aid CLONidine CLOses the sympathetic faucet; turn it off fast and the pressure floods back. ## Test yourself Think of the answer, then tap the question to see it. ## What happens if clonidine is stopped abruptly? Rebound hypertension with nervousness, agitation, headache and tremor, from a surge in sympathetic activity. ## Why is the beta blocker stopped first when a patient takes both a beta blocker and clonidine? Withdrawal reactions are worse if the beta blocker continues: unopposed alpha stimulation by the catecholamine surge raises pressure further. ## Which central effects explain the common adverse effects of clonidine? Alpha-2 stimulation in the brain causes sedation and drowsiness, and reduced salivary secretion causes dry mouth. ## Which non-cardiovascular uses does clonidine have? Attention deficit hyperactivity disorder; it is also used for opioid or alcohol withdrawal symptoms and menopausal hot flushes. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/clonidine/) ## Related drugs - [Methyldopa](https://durgical.com/en/pharmacology/methyldopa/) - [Propranolol](https://durgical.com/en/pharmacology/propranolol/) ## Related conditions - [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/) [← Back to the class: Centrally acting antihypertensives](https://durgical.com/en/pharmacology/classes/centrally-acting-antihypertensives/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - CLONIDINE HYDROCHLORIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cf493e6a-1603-4c7d-a442-69a119bec843) (DailyMed (U.S. National Library of Medicine), 2026); [Clonidine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682243.html) (MedlinePlus (U.S. National Library of Medicine), 2024); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C02AC01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 14 (McGraw Hill, 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/clonidine/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/clonidine/