III. Mechanism

  1. See Alpha Adrenergic Central Agonist
  2. See Alpha Adrenergic Receptor
  3. Central Acting Adrenergic Agonists
    1. Activate alpha-2 receptors that inhibit CNS sympathetic signals
    2. Results in increased parasympathetic effects and side effects
  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: Guanabenz (Wytensin)

  1. Adult: 2 to 4 mg orally twice daily (up to 32 mg twice daily)
  2. Child (over age 12): 0.25 to 1 mg orally twice daily (up to 2 to 12 mg orally twice daily)

VI. Dosing: Guanfacine (Tenex)

  1. Adults and children >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

VII. Adverse Effects

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

VIII. Drug Interactions

  1. Thiazide Diuretics
    1. Increased antihypertensive effect (Hypotension risk)

IX. 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 6/18/2017 at Walmart.com)
Guanfacine 1mg #30 tablets for $4.00 $0.13 each
Guanfacine 1mg #90 tablets for $10.00 $0.11 each
guanfacine (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
GUANFACINE 1 MG TABLET Generic $0.07 each
GUANFACINE 2 MG TABLET Generic $0.10 each
GUANFACINE HCL ER 1 MG TABLET Generic $0.58 each
GUANFACINE HCL ER 2 MG TABLET Generic $0.54 each
GUANFACINE HCL ER 3 MG TABLET Generic $0.58 each
GUANFACINE HCL ER 4 MG TABLET Generic $0.63 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