Medicine & USMLE


Cardio Drugs - Blood Pressure
  1. ACE Inhibitors
  2. Angiotensin II Receptor Blockers (ARBs)
  3. Beta Blockers: Drug Names and Selectivity
  4. Beta Blockers: Mechanisms and Clinical Uses
  5. Beta Blockers: Side Effects
  6. DHP Calcium Channel Blockers
  7. Hydralazine
  8. Aliskiren
  9. Nitroprusside
  10. Alpha-1 Blockers
  11. Centrally Acting Alpha-2 Agonists


Clonidine is a medication that is primarily used to lower blood pressure and treat hypertension. Clonidine should not be stopped abruptly, as sudden discontinuation of the drug can lead to rebound hypertension. Other side effects of clonidine include the 3 D’s - dizziness, drowsiness, and dry mouth.

Key Points

  • Mechanism of Action (Saunders, Mictlan)
    • Stimulates alpha-2-receptors
      • Decreases sympathetic response, inhibiting vasoconstriction
      • Reduces blood pressure and heart rate
    • Metabolized by the liver
    • Clinical Use (Saunders)
      • Hypertension
        • Can be given orally or as a transdermal patch
          • Apply transdermal patch to a dry, hairless area on the upper arm or chest
          • Patch must be replaced every 7 days, rotate sites with each new patch
          • Wash hands before and after application
      • Opiate withdrawal
      • Severe pain in cancer patients
      • ADHD
    • Side Effects and Adverse Reactions (Saunders)
      • Severe rebound hypertension if abruptly discontinued
        • Due to the rapid surge of catecholamine secretion that was suppressed during therapy
        • The patch should never be taken off abruptly; must be tapered off over 2-4 days
        • Can lead to a hypertensive crisis
      • Dry Mouth
        • Medical term is xerostomia
        • Can use hard candy, chewing gum, or over-the-counter moisturizers to relieve dry mouth
      • Drowsiness
        • Avoid use with alcohol, opioids, and other CNS depressants
        • More common initially, will lessen with time
      • Dizziness
        • Dry mouth, drowsiness, and dizziness are often called the “3 D’s” of clonidine
      • Hypotension
        • Due to reduced sympathetic stimulation
        • Carefully monitor blood pressure and avoid giving concurrently with diuretics
      • Bradycardia
        • Due to reduced sympathetic stimulation
      • Abuse potential
        • Not recommended for patients with a history of opioid dependence
      • Teratogenic
        • Not recommended for pregnant women