Does nitroglycerin (nitro) paste need to be removed before starting Cardene (nicardipine)?

Nitroglycerin Paste Removal Before Starting Nicardipine

Nitroglycerin paste should be removed before starting nicardipine to prevent potential additive hypotensive effects that could lead to significant cardiovascular decompensation. 1

Rationale for Removing Nitroglycerin Paste

The combination of nitroglycerin and nicardipine presents several hemodynamic concerns:

1. Additive vasodilatory effects: Both medications cause vasodilation through different mechanisms:

   • Nitroglycerin primarily causes venodilation with some arterial dilation 2
   • Nicardipine is a calcium channel blocker that causes arterial vasodilation 3

2. Risk of significant hypotension:

   • The American Heart Association guidelines note that "the venodilating and arterial dilating effects of nitroglycerin are mimicked by some anesthetic agents, so the combination could lead to significant hypotension" 1
   • This concern extends to other vasodilating agents like nicardipine

3. Unpredictable absorption:

   • Topical nitroglycerin (paste/patch) may have uneven absorption, making its effects difficult to predict when combined with another vasodilator 2

Hemodynamic Differences Between Agents

When choosing between these agents, it's important to understand their different hemodynamic profiles:

• Nitroglycerin:

  • Decreases cardiac output (-21%)
  • Significantly reduces preload (pulmonary artery wedge pressure -49%)
  • Greater effect on small vessels (<2mm²) 4
  • Reduces right atrial pressure 4

• Nicardipine:

  • Increases cardiac output (+13%)
  • Moderately reduces preload (pulmonary artery wedge pressure -26%)
  • Dilates both small and large arterial segments equally
  • Significantly decreases systemic vascular resistance 4

Clinical Decision Algorithm

1. Assess current blood pressure:

   • If SBP <90 mmHg or ≥30 mmHg below baseline: Remove nitroglycerin paste immediately before starting nicardipine 1
   • If SBP is stable but patient requires transition to nicardipine: Remove nitroglycerin paste before initiating nicardipine

2. Monitor closely after transition:

   • Check blood pressure within 15-30 minutes after removing nitroglycerin and starting nicardipine
   • Be prepared to adjust nicardipine dosing based on response

3. Consider clinical indication:

   • For hypertensive acute heart failure: Nicardipine may be more effective than nitroglycerin (shorter time to optimal BP control, shorter infusion duration) 5
   • For coronary vasodilation: Both agents are effective but have different hemodynamic profiles 4

Important Precautions

• Establish IV access before making medication changes to ensure prompt treatment of potential hypotension 1
• Monitor vital signs frequently during the transition between agents 1
• Have fluid boluses readily available to counteract potential hypotension
• Consider the patient's volume status before administering either agent, as hypovolemia can exacerbate hypotensive effects 2

Common Pitfalls to Avoid

1. Overlapping administration: Allowing both agents to be active simultaneously increases hypotension risk
2. Inadequate monitoring: Failing to monitor blood pressure closely during transition
3. Not accounting for nitroglycerin's residual effect: Even after paste removal, effects may persist for 30-60 minutes
4. Inappropriate dosing: Starting nicardipine at too high a dose after nitroglycerin removal

By removing nitroglycerin paste before starting nicardipine, you can minimize the risk of significant hypotension while maintaining effective blood pressure control.