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

IV. Pharmacokinetics

  1. Renal excretion (unchanged in urine)
    1. Decrease dose in Renal Insufficiency

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. Readily absorbed with 70% bioavailability
    2. Start: 0.2 mg oral load
    3. Titrate 0.1 mg/hour to:
      1. Maximum of 0.7 mg
      2. Diastolic Blood Pressure drops more than 20 mmHg
    4. Activity
      1. Onset in 30-60 min
      2. Duration: 6-10 hours
  2. Clonidine Transdermal Patch
    1. Available in 0.1, 0.2 and 0.3 mg/day dosing
    2. Costs $40-100/month (depending on dose)
    3. Changed every 7 days
    4. Does not reach peak effect for 2-3 days
    5. Once at level, delivers constant Clonidine rate over 7 days
    6. 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. Rebound Hypertension (if abruptly discontinued at higher dose)
    1. See Clonidine Withdrawal
  7. 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

Ontology: Clonidine (C0009014)

Definition (MSH) An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.
Definition (CHV) a hypertension treatment drug
Definition (NCI) An imidazoline derivate and centrally-acting alpha-adrenergic agonist, with antihypertensive activity. Clonidine binds to and stimulates central alpha-2 adrenergic receptors, thereby reducing the amount of norepinephrine (NE) release and thus decreasing sympathetic outflow to the heart, kidneys, and peripheral vasculature. The reduction in sympathetic outflow leads to decreased peripheral vascular resistance, decreased blood pressure, and decreased heart rate. In addition, clonidine binds to imidazoline receptor subtype 1 (I1), which may also contribute to a reduction in blood pressure.
Definition (NCI_NCI-GLOSS) The active ingredient in a drug used to treat high blood pressure. It is also being studied in the treatment of certain types of cancer pain. It blocks the release of chemicals from nerve endings that make blood vessels constrict (get narrower). Clonidine is a type of antihypertensive agent and a type of alpha-adrenergic agonist.
Definition (CSP) alpha-2 adrenergic agonist that crosses the blood-brain barrier; acts centrally by reducing sympathetic tone, resulting in a fall in diastolic and systolic blood pressure and a reduction in heart rate; also acts peripherally.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D003000
SnomedCT 22139009, 372805007, 62782004
LNC LP32548-7, LP14987-9, MTHU002290
English Clofenil, Clonidine, Klofenil, 1H-Imidazol-2-amine, N-(2,6-dichlorophenyl)-4,5-dihydro-, N-(2,6-Dichlorophenyl)-4,5-dihydro-1H-imidazol-2-amine, clonidine, clonidine (medication), Clonidine [Chemical/Ingredient], CLONIDINE, cloNIDine, Clonidine (product), Clonidine (substance)
Swedish Klonidin
Finnish Klonidiini
Russian KHLOFAZOLIN, GEMITON, KATAPRESAN, KLOFELIN, KLONIDIN, ГЕМИТОН, КАТАПРЕСАН, КЛОНИДИН, КЛОФЕЛИН, ХЛОФАЗОЛИН
Japanese クロニジン塩酸塩, カタプレス, クロニジン, 塩酸クロニジン
Croatian KLONIDIN
Polish Klonidyna
Czech clonidin, klonidin
Spanish clonidina (producto), clonidina (sustancia), clonidina, Clonidina
French Clonidine
German Clonidin
Italian Clonidina
Portuguese Clonidina

Ontology: Catapres (C0699881)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D003000
English Catapresan, Catapressan, catapresan, catapres, Catapres