For severe hypertension, should clonidine or hydralazine be ordered?

Hydralazine is Preferred Over Clonidine for BP 192/93

For severe hypertension with BP 192/93, hydralazine is preferred over clonidine due to its more favorable safety profile and the fact that clonidine is generally reserved as a last-line agent. 1

Rationale for Choosing Hydralazine

Medication Classification and Role

• Hydralazine: Direct vasodilator with established efficacy in severe hypertension

  • Usual dose: 100-200 mg/day divided in 2-3 doses 1
  • Can effectively lower blood pressure in severe hypertension
  • Works through direct arterial smooth muscle relaxation

• Clonidine: Central alpha-2 agonist

  • Generally reserved as last-line therapy due to:
    • Significant CNS adverse effects (sedation, dizziness)
    • Risk of rebound hypertension with abrupt discontinuation
    • Need for careful tapering when discontinuing 1

Key Considerations

1. Guideline Recommendations:

   • Current guidelines specifically state that central alpha-2 agonists like clonidine are "generally reserved as last-line because of significant CNS adverse effects, especially in older adults" 1
   • Hydralazine is positioned as a direct vasodilator that can be considered before central-acting agents 1

2. Safety Concerns:

   • Clonidine risks:

     • Rebound hypertension if doses are missed 2
     • Sedation and CNS effects that may impair functioning 2
     • Must be tapered to avoid hypertensive crisis 1

   • Hydralazine considerations:

     • Requires co-administration with a beta-blocker to prevent reflex tachycardia 1
     • Risk of drug-induced lupus-like syndrome at higher doses (>150 mg daily) 1
     • Sodium and water retention (requires diuretic) 1

Implementation Algorithm

1. For BP 192/93 (Stage 2 Hypertension):

   • Start hydralazine 25 mg orally three times daily
   • Ensure patient is also on:
     • A diuretic (to counter sodium retention)
     • A beta-blocker (to prevent reflex tachycardia)

2. Monitoring:

   • Check BP within 1-2 hours after first dose
   • Titrate dose upward as needed (maximum 200 mg/day)
   • Monitor for headache, palpitations, or tachycardia

3. When to consider clonidine instead:

   • If patient has documented intolerance to hydralazine
   • If lupus-like symptoms develop on hydralazine
   • As a fifth-line agent after other options have failed 1

Important Precautions

• Hydralazine precautions:

  • Do not exceed 150 mg daily long-term to avoid drug-induced lupus 1
  • Always use with a beta-blocker to prevent reflex tachycardia
  • Use with caution in coronary artery disease 3

• If clonidine must be used:

  • Start with 0.1-0.2 mg orally
  • Never discontinue abruptly
  • Be aware of sedation and potential for orthostatic hypotension
  • Monitor for rebound hypertension if doses are missed 2

Special Considerations

• In heart failure patients, hydralazine (combined with nitrates) has shown mortality benefit in African American patients 1
• In the newest 2024 ESC guidelines, hydralazine is still positioned before centrally-acting medications like clonidine in the treatment algorithm 1

Remember that both medications are considered secondary agents, and first-line therapy for hypertension typically includes ACE inhibitors, ARBs, calcium channel blockers, and thiazide diuretics. The current BP of 192/93 requires prompt intervention, and hydralazine offers a better safety profile than clonidine for this purpose.