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)

IV. Pharmacokinetics

  1. Renal excretion (unchanged in urine)
    1. Decrease dose in Renal Insufficiency, including starting dose
    2. Observe for adverse effects (Bradycardia, Hypotension)
  2. Oral Dosing
    1. Readily absorbed with 70% Bioavailability
    2. Activity
      1. Onset in 30-60 min
      2. Duration: 6-10 hours

V. Precautions

  1. See Clonidine Withdrawal
  2. Acute withdrawal risk with rebound Hypertension
    1. Do not stop suddenly (esp. if Clonidine dose >1.2 mg per day)

VI. Preparations

  1. Clonidine (Catapres) Tablet
    1. Hypertension (adults)
      1. Start 0.1 mg orally twice daily
      2. Titrate dose weekly, modifying total daily dose 0.1 mg/day to typical dose of 0.2 to 0.6 mg/day divided twice daily
      3. Maximum total daily dose: 2.4 mg/day
    2. Hypertensive Urgency (adults, other agents are preferred for Hypertensive Urgency )
      1. Start: 0.2 mg oral load
      2. Titrate 0.1 mg/hour to:
        1. Maximum of 0.7 mg
        2. Diastolic Blood Pressure drops more than 20 mmHg
    3. Hypertension (children)
      1. Start 5 to 7 mcg/kg/day orally divided every 6 to 12 hours
      2. Titrate dose weekly, modifying total daily dose 5-25 mcg/kg/day in divided doses (maximal dose 0.9 mg/day)
    4. Hot Flushes
      1. Start 0.1 mg orally at bedtime (or transdermal patch)
      2. May titrate up to 0.2 mg orally twice daily
  2. Clonidine Transdermal Patch (Catapress-TTS)
    1. Not recommended for use in children
    2. Available in 0.1, 0.2 and 0.3 mg/day patches (may combine patches up to two of the 0.3 mg/day patches)
    3. Start with a 0.1 mg/day patch
      1. Titrate to effective dose, up to maximum effective dose of 0.6 mg/day (two of the 0.3 mg/day patches)
    4. Costs $40-100/month (depending on dose)
    5. Changed every 7 days
    6. Does not reach peak effect for 2-3 days
    7. Once at level, delivers constant Clonidine rate over 7 days
    8. Transition from oral to patch
      1. Day 1
        1. Apply transdermal Clonidine
        2. Take full oral Clonidine dose
      2. Day 2
        1. Take 50% of oral Clonidine dose
      3. Day 3
        1. Take 25% of oral Clonidine dose
        2. Discontinue oral Clonidine
  3. Other forms
    1. Clonidine IV
    2. Epidural Clonidine (for Chronic Pain)

VII. Adverse Effects

  1. See Clonidine Overdose
  2. Somnolence
  3. Headache
  4. Dry Mouth
  5. Constipation
  6. Bradycardia
    1. Risk of Sinus Node Dysfunction and Atrioventricular Block
    2. Increased risk when combined with Digoxin, Beta Blockers, nondihydropyridine Calcium Channel Blockers
  7. Hypotension
  8. Rebound Hypertension (if abruptly discontinued at higher dose)
    1. See Clonidine Withdrawal
    2. Risk increases with total daily doses >0.7 mg/day (esp. >1.2 mg/day)
    3. Slowly taper dose every 3 to 7 days to prevent rebound Hypertension
    4. Continue in Clonidine in the perioperative period
  9. Sodium and water retention
    1. Reflex renin release in response to excessive Clonidine and renal hypoperfusion

VIII. Drug Interactions

  1. Tricyclic Antidepressants
    1. Decreased Clonidine antihypertensive effect
  2. CNS Depressants (e.g. Alcohol, Benzodiazepines, Barbiturates)
    1. Increase Clonidine related CNS effects (e.g. Somnolence)

IX. Resources

X. References

  1. Mishler and Lovecchio (2017) Crit Dec Emerg Med 31(11): 15-20
  2. Olson (2020) Clinical Pharmacology, MedMaster, Miami, p. 64-5

Images: Related links to external sites (from Bing)

Related Studies

Cost: Medications

Clonidine (on 6/18/2017 at Walmart.com)
Clonidine 0.1mg #30 tablets for $4.00 $0.13 each
Clonidine 0.1mg #90 tablets for $10.00 $0.11 each
Clonidine 0.2mg #30 tablets for $4.00 $0.13 each
Clonidine 0.2mg #90 tablets for $10.00 $0.11 each
clonidine (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
CLONIDINE 0.1 MG/DAY PATCH Generic $14.73 each
CLONIDINE 0.2 MG/DAY PATCH Generic $23.62 each
CLONIDINE 0.3 MG/DAY PATCH Generic $28.02 each
CLONIDINE HCL 0.1 MG TABLET Generic $0.02 each
CLONIDINE HCL 0.2 MG TABLET Generic $0.04 each
CLONIDINE HCL 0.3 MG TABLET Generic $0.05 each
CLONIDINE HCL ER 0.1 MG TABLET Generic $2.98 each
catapres (on 1/4/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
CATAPRES 0.2 MG TABLET Generic $0.04 each
CATAPRES-TTS 1 PATCH Generic $14.73 each
CATAPRES-TTS 2 PATCH Generic $23.62 each
CATAPRES-TTS 3 PATCH Generic $28.02 each