III. Mechanism

  1. See Alpha Adrenergic Central Agonist
  2. See Alpha Adrenergic Receptor
  3. Central Acting Adrenergic Agonists
    1. Activates alpha-2 receptors that inhibit CNS preganglionic sympathetic signals, lowering Blood Pressure
    2. Results in increased parasympathetic effects and side effects (e.g. sedation)
  4. Peripheral Adrenergic Nerve terminal activity
    1. Depletes Norepinephrine stores

IV. Pharmacokinetics

  1. Renal and Hepatic Clearance
  2. Adjust dose for renal or hepatic Impairment

V. Dosing: Guanfacine (Tenex)

  1. Adults and children age >12 years
    1. Start 1 mg orally at bedtime
    2. Most effective dose is 1 mg
      1. May increase to 2-3 mg at bedtime after 3-4 weeks (as needed)
      2. Maximum: 3 mg/day

VI. Dosing: Guanabenz (Wytensin)

  1. Listed for historical purposes only (discontinued in U.S. outside of use in horses)
  2. Adult: 2 to 4 mg orally twice daily (up to 32 mg twice daily)
  3. Child (over age 12): 0.25 to 1 mg orally twice daily (up to 2 to 12 mg orally twice daily)

VII. Adverse Effects

  1. Dry Mouth
  2. Sedation
  3. Rebound Hypertension
    1. Less than with Clonidine

VIII. Drug Interactions

IX. Safety

  1. See Alpha Adrenergic Central Agonist
  2. Pregnancy Category B (Guanfacine)
  3. Unknown Safety in Lactation

XI. References

  1. Olson (2020) Clinical Pharmacology, MedMaster, Miami, p. 64-5
  2. Hamilton (2010) Tarascon Pocket Pharmacopeia, Jones and Bartlett, p. 76

Images: Related links to external sites (from Bing)

Related Studies

Cost: Medications

guanfacine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
GUANFACINE 1 MG TABLET Generic $0.39 each
GUANFACINE 2 MG TABLET Generic $0.56 each
GUANFACINE HCL ER 1 MG TABLET Generic $0.21 each
GUANFACINE HCL ER 2 MG TABLET Generic $0.22 each
GUANFACINE HCL ER 3 MG TABLET Generic $0.22 each
GUANFACINE HCL ER 4 MG TABLET Generic $0.24 each

Ontology: Guanabenz (C0018312)

Definition (MSH) An alpha-2 selective adrenergic agonist used as an antihypertensive agent.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D006143
SnomedCT 372867002, 82951001
English 2,6-Dichlorobenzylideneaminoguanidine, Guanabenz, 2,6 Dichlorobenzylideneaminoguanidine, Hydrazinecarboximidamide, 2-((2,6-dichlorophenyl)methylene)-, guanabenz, Guanabenz [Chemical/Ingredient], GUANABENZ, Guanabenz (product), Guanabenz (substance)
Swedish Guanabenz
Czech guanabenz
Finnish Guanabentsi
Russian GUANABENZ, ГУАНАБЕНЗ
Japanese グアナベンツ, グアナベンズ
Polish Guanabenz
Spanish guanabenz (producto), guanabenz (sustancia), guanabenz, Guanabenzo
French Guanabenz
German Guanabenz
Italian Guanabenzo
Portuguese Guanabenzo

Ontology: Wytensin (C0018313)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D006143
English Wyeth-Ayerst of Guanabenz Acetate, Wyeth Ayerst of Guanabenz Acetate, Acetate Wyeth-Ayerst, Guanabenz, Guanabenz Acetate Wyeth-Ayerst, Wytensin

Ontology: Guanfacine (C0079466)

Definition (MSH) A centrally acting antihypertensive agent with specificity towards ADRENERGIC ALPHA-2 RECEPTORS.
Definition (NCI) A centrally acting adrenergic agonist with non-stimulant and antihypertensive property. Guanfacine selectively stimulates alpha-2 adrenergic receptors in the central nervous system, thereby resulting in inhibition of sympathetic nervous system outflow. Used alone or in combination with other drugs, this agent causes reduction of peripheral and renal vascular resistance, and lowers both systolic and diastolic blood pressure and heart rate.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D016316
SnomedCT 108553003, 372507007
English Guanfacine, Benzeneacetamide, N-(aminoiminomethyl)-2,6-dichloro-, Guanfacine [Chemical/Ingredient], guanFACINE, GuanFACINE, guanfacine (medication), guanfacine, GUANFACINE, Guanfacine (product), Guanfacine (substance)
Swedish Guanfacin
Czech guanfacin
Finnish Guanfasiini
Russian GUANFATSIN, ГУАНФАЦИН
Japanese グアンファシン
Polish Guanfacyna
Spanish guanfacina (producto), guanfacina (sustancia), guanfacina, Guanfacina
French Guanfacine
German Guanfacin
Italian Guanfacina
Portuguese Guanfacina

Ontology: Tenex (C0242580)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D016316
English tenex, Tenex