Clonidine

Clonidine is a medication that stimulates alpha-2 adrenergic receptors. It is used to treat hypertension, attention-deficit/hyperactivity disorder, withdrawal symptoms, and other conditions.

Alpha-2 adrenergic receptor: A G-protein-coupled receptor activated by norepinephrine and epinephrine that regulates neurotransmitter release and autonomic activity. Clonidine activates this receptor, especially in brainstem pathways that reduce sympathetic outflow.
Hypertension: Persistently elevated arterial blood pressure that increases the risk of cardiovascular and kidney disease. Clonidine is an antihypertensive option, generally reserved for situations where other choices are unsuitable.
Guanfacine: A selective alpha-2A adrenergic receptor agonist used for hypertension and attention-deficit/hyperactivity disorder. It shares clonidine's central mechanism but is more alpha-2A selective and often less sedating.
Bradycardia: A slower-than-normal heart rate, commonly defined in adults as fewer than 60 beats per minute. Reduced sympathetic drive from clonidine can slow the heart, especially in susceptible patients.
Oral administration: Delivery of a medicine by swallowing it for absorption through the gastrointestinal tract. Oral tablets and extended-release products are common ways to take clonidine.
Locus coeruleus: A brainstem nucleus and major source of norepinephrine projections throughout the brain. Clonidine's suppression of norepinephrine release here contributes to sedation and withdrawal relief.
Attention deficit hyperactivity disorder: A neurodevelopmental disorder characterized by persistent inattention, hyperactivity, and impulsivity. Extended-release clonidine can reduce ADHD symptoms, alone or alongside stimulant medication.
Methyldopa: An antihypertensive drug converted in the body to a central alpha-2 adrenergic receptor agonist. Both reduce sympathetic activity centrally, but methyldopa is especially associated with pregnancy treatment.
Orthostatic hypotension: A sustained fall in blood pressure after standing, which can cause dizziness or fainting. Clonidine can lower blood pressure enough to cause symptoms on standing.
Transdermal patch: A medicated adhesive system that delivers a drug through the skin into the bloodstream over time. Clonidine patches provide sustained delivery and are changed on a weekly schedule.

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Adrenergic receptorRelated: It lowers sympathetic outflow through an inhibitory adrenergic receptor subtype.