Last reviewed 2026-04-22 · How we verify

Clonidine Pill

Clonidine is an alpha-2 adrenergic agonist that reduces sympathetic nervous system activity by stimulating alpha-2 receptors in the brain and periphery.

Clonidine is an alpha-2 adrenergic agonist that reduces sympathetic nervous system activity by stimulating alpha-2 receptors in the brain and periphery. Used for Hypertension, Attention-deficit/hyperactivity disorder (ADHD), Opioid withdrawal.

At a glance

Mechanism of action

Clonidine binds to alpha-2 adrenergic receptors in the central nervous system, particularly in the locus coeruleus, which decreases the release of norepinephrine and reduces overall sympathetic outflow. This leads to decreased heart rate, blood pressure, and peripheral vascular resistance. The drug also has peripheral alpha-2 agonist effects that contribute to its antihypertensive action.

Approved indications

• Hypertension
• Attention-deficit/hyperactivity disorder (ADHD)
• Opioid withdrawal
• Menopausal hot flashes

Common side effects

• Dry mouth
• Drowsiness
• Dizziness
• Constipation
• Sedation
• Headache
• Rebound hypertension (upon discontinuation)

Key clinical trials

• Treatment of Orthostatic Intolerance (PHASE1, PHASE2)
• Repurposing Low-Dose Clonidine for PTSD in Veterans (PHASE3)
• Mitigating the Pro-inflammatory Phenotype of Obesity (PHASE1)
• Anxiety-mediated Impairments in Large Elastic Artery Function and the Autonomic Nervous System (PHASE4)
• Sensorial and Physiological Mechanism-based Assessments of Perioperative Pain (PHASE3)
• The Role of Stress Neuromodulators in Decision Making Under Risk (Part II) (NA)
• Clonidine is Better Than Zopiclone for Insomnia Treatment in Chronic Pain Patients
• PET Study of a2a Agonist Effects on the Ventricular CSF Clearance of [11C]Butanol (EARLY_PHASE1)

Primary sources

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