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Alpha-2A agonist

Alpha-2A agonist (1/3)

• Presynaptic autoreceptor activation → ↓ locus coeruleus firing → sympatholytic (quiets fight-or-flight)
• Decreased BP via central negative feedback; rebound HTN if stopped abruptly
• Improves prefrontal cortex tuning by reducing NE “noise”→ better attention/impulse control
• Sedation at higher doses

Alpha-2A agonist (2/3)

• Analgesia via spinal nociceptive suppression
• Dry mouth
• Decreased sweating (helps hyperhidrosis)
• Peripheral vasoconstriction
• ↓ aqueous humor and ↑ uveoscleral outflow

Alpha-2A agonist (3/3)

• Less vascular impact than α2A (minimal BP lowering)
• Dry mouth +

Drugs with this mechanism (17)

• Brimonidine — Alpha-2 agonist for glaucoma and rosacea redness.
• Clonidine — Central alpha-2 agonist for hypertension, ADHD and withdrawal; sedation and rebound.
• Clonidine ER — Extended-release central alpha-2 agonist for ADHD; sedation and rebound hypertension limit it.
• Dexmedetomidine — Alpha-2 agonist sedative giving cooperative sedation without respiratory depression.
• Dexmedetomidine sublingual — Sublingual dexmedetomidine film for acute agitation in schizophrenia or bipolar disorder.
• Guanabenz — Central alpha-2 agonist antihypertensive, now rare.
• Guanfacine — Alpha-2A agonist; non-stimulant ADHD agent, also for tics; sedation, hypotension.
• Guanfacine ER — Long-acting alpha-2A agonist for ADHD; less sedating than clonidine but still hypotensive.
• Lofexidine — Alpha-2 agonist for opioid-withdrawal symptoms.
• α-methyl­ norepinephrine — Active methyldopa metabolite; central alpha-2 agonism reduces sympathetic outflow and blood pressure.
• Moxonidine — Central imidazoline I1 agonist for hypertension in some countries; dry mouth and dizziness, with avoidance in heart failure.
• Norepinephrine — Endogenous catecholamine; the first-line vasopressor for shock.
• Clonidine ER suspension — Extended-release clonidine liquid for ADHD; sedation and rebound hypertension shape use.
• Oxymetazoline — Topical alpha agonist decongestant; rebound congestion with overuse.
• Rilmenidine — Central imidazoline I1 agonist used for hypertension outside the U.S.; reduces sympathetic activity, with dry mouth and dizziness.
• Tizanidine — Short-acting alpha-2 agonist for spasticity; hypotension and CYP1A2 interactions.
• Xylazine — Veterinary alpha-2 sedative ("tranq") now adulterating street fentanyl.

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