Guanfacine
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Guanfacine
Intuniv (extended-release), Tenex (immediate-release)
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Summary
Common uses
Attention-deficit/hyperactivity disorder (monotherapy or adjunct to psychostimulants, ages 6-17)0, Tic disorders / Tourette syndrome (off-label)0, Opioid withdrawal adjunct (off-label)0, PTSD-associated nightmares and hyperarousal (off-label, selected populations)0, Hypertension (historical indication, largely supplanted by other classes)0
Pharmacy
Starting dose
Intuniv ER 1 mg PO once daily; titrate by 1 mg/week as tolerated to clinical response
Preparations
Extended-release tablets 1, 2, 3, 4 mg (Intuniv); immediate-release tablets 1, 2 mg (Tenex)
US FDA Max
7 mg/day in children and adolescents; weight-based ceiling (~0.12 mg/kg/day) applies in smaller patients
Pharmacology
Routes
Oral
Onset
Gradual; full clinical effect over 2-4 weeks of titration
Duration
~24 hours (ER formulation supports once-daily dosing)
Half-life
~17-18 hours (Intuniv ER); ~17 hours (immediate-release)[1]
Bioavailability
~58% (extended-release); ~80% (immediate-release)[1]
Pregnancy
Limited human data. Animal studies show fetal effects at maternally toxic doses; use only if benefits justify the potential risk.[citation needed]
Legal status
Purported mechanism
Selective postsynaptic α2A-adrenergic receptor agonist. In the prefrontal cortex, α2A activation on pyramidal-neuron dendritic spines strengthens working-memory and attention-regulation circuits by closing HCN channels and reducing cyclic-AMP-driven "noise" from competing inputs. The peripheral antihypertensive effect (the historical indication) reflects α2 agonism in brainstem sympathetic outflow regions.0 Sedation and hypotension are the dose-limiting effects; gradual titration and bedtime or split dosing mitigate both. Abrupt discontinuation can precipitate rebound hypertension, particularly with long-standing use[1].
References
- ↑ 1.0 1.1 1.2 1.3 FDA Prescribing Information, Intuniv (guanfacine extended-release), Shire/Takeda, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/022037s009lbl.pdf