Pharm

Guanfacine

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Guanfacine, Tenex, Guanabenz, Wytensin

  • See Also
  1. Alpha Adrenergic Central Agonist
  2. Clonidine
  3. Methyldopa
  • Indications
  1. Hypertension
  2. Attention Deficit Disorder
  3. Motor Tic Disorder
  • 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
  • Pharmacokinetics
  1. Renal and Hepatic Clearance
  2. Adjust dose for renal or hepatic Impairment
  • 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
  • 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)
  • Adverse Effects
  1. Dry Mouth
  2. Sedation
  3. Rebound Hypertension
    1. Less than with Clonidine
  • Drug Interactions
  1. Thiazide Diuretics
    1. Increased Antihypertensive effect (Hypotension risk)
  • Safety
  1. See Alpha Adrenergic Central Agonist
  2. Pregnancy Category B (Guanfacine)
  3. Unknown Safety in Lactation
  • Resources
  1. Guanfacine (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=d9fdc4b4-5b00-46dd-8700-6e36ceaafb0e
  • References
  1. Olson (2020) Clinical Pharmacology, MedMaster, Miami, p. 64-5
  2. Hamilton (2010) Tarascon Pocket Pharmacopeia, Jones and Bartlett, p. 76