Contraindications of Nitroglycerin
Nitroglycerin is absolutely contraindicated in patients with hypotension (systolic blood pressure <90 mm Hg or ≥30 mm Hg below baseline), extreme bradycardia (<50 bpm), tachycardia in the absence of heart failure (>100 bpm), right ventricular infarction, and recent use of phosphodiesterase-5 inhibitors. 1
Absolute Contraindications
Hemodynamic Contraindications
- Systolic blood pressure <90 mm Hg or ≥30 mm Hg below baseline - This represents the most critical contraindication as nitrates cause vasodilation that can precipitate cardiovascular collapse in already hypotensive patients 1
- Right ventricular infarction - These patients are preload-dependent, and nitrate-induced venous dilation can cause catastrophic hemodynamic compromise 1
Heart Rate Abnormalities
- Extreme bradycardia (<50 bpm) - Nitrates can worsen bradycardia and reduce cardiac output 1
- Tachycardia (>100 bpm) in the absence of heart failure - This is a Class III contraindication, though recent research suggests the absolute risk may be lower than previously thought 1, 2
Drug Interactions
- Phosphodiesterase-5 inhibitors within 24 hours (48 hours for tadalafil) - Concomitant use potentiates severe hypotension and has been associated with myocardial infarction and death 1, 3
- Soluble guanylate cyclase stimulator riociguat - Causes severe hypotension when combined with nitrates 3
Other Absolute Contraindications
- Known hypersensitivity or allergy to nitroglycerin 3
- Early myocardial infarction (in specific contexts per FDA labeling) 3
- Severe anemia 3
- Increased intracranial pressure 3
Critical Clinical Considerations
Right Ventricular Infarction Assessment
Obtain a right-sided ECG in all patients with inferior wall STEMI before administering nitroglycerin - Right ventricular involvement requires adequate preload, and nitrates should be administered with extreme caution if at all in these patients 1
Blood Pressure Monitoring
The risk of hypotension correlates linearly with initial systolic blood pressure - lower pre-treatment blood pressures predict higher risk of post-nitroglycerin hypotension 4, 5. Patients with systolic blood pressure >110 mm Hg and heart rate <100 bpm have the lowest risk of adverse events 5.
Tachycardia Nuance
While AHA guidelines list tachycardia >100 bpm as a contraindication 1, recent evidence shows hypotension following nitroglycerin in tachycardic patients occurs in only 3.9% of cases, with an adjusted odds ratio of 1.60 compared to non-tachycardic patients 2. However, the guideline recommendation remains Class III (contraindicated) 1.
Common Pitfalls to Avoid
- Failing to check for PDE-5 inhibitor use - Always specifically ask about sildenafil, tadalafil, and vardenafil use in the preceding 24-48 hours 1
- Administering to inferior STEMI without right-sided ECG - Up to 50% of inferior MIs involve the right ventricle 1
- Ignoring active gastrointestinal hemorrhage - While primarily an aspirin contraindication, this represents relative caution for nitrates in unstable patients 1