Nitroglycerin is converted in vascular smooth muscle to nitric oxide, which activates guanylate cyclase, increasing intracellular cGMP. This produces vasodilation - venous at lower doses (reduces preload, the primary therapeutic mechanism in angina), arterial at higher doses (reduces afterload, useful in heart failure). Coronary artery vasodilation contributes modestly to angina relief; the main benefit is reduced myocardial oxygen demand through preload reduction. Tolerance develops with continuous exposure (the basis for nitrate-free intervals in chronic dosing).

• Acute coronary syndrome (unstable angina, NSTEMI, STEMI) - chest pain relief
• Acute decompensated heart failure with pulmonary edema
• Hypertensive emergency (IV infusion)
• Esophageal spasm
• Anal fissure (topical, rarely in tactical settings)

• Phosphodiesterase-5 inhibitor use within 24 to 48 hours (sildenafil/Viagra, tadalafil/Cialis, vardenafil/Levitra) - fatal hypotension can result
• Severe hypotension (SBP under 90 mmHg or 30 mmHg below baseline)
• Severe bradycardia or tachycardia
• Right ventricular MI (preload-dependent state)
• Severe aortic stenosis
• Hypertrophic obstructive cardiomyopathy
• Increased intracranial pressure
• Known hypersensitivity to nitrates

Common: headache (very common, often severe and dose-limiting), flushing, dizziness, orthostatic hypotension, palpitations. Cardiovascular: hypotension (the main safety concern), reflex tachycardia, methemoglobinemia at very high doses. Tolerance with continuous exposure - requires nitrate-free interval of 10 to 12 hours per 24 hours for chronic dosing. Drug interactions: PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) - absolute contraindication due to severe hypotension; antihypertensives - additive hypotension; alcohol - additive vasodilation. Pregnancy Category C. Compatible with lactation in acute use. Pediatric use rare; not standard. Always ask about ED medications before administering nitroglycerin in any chest pain patient - this is a critical pre-administration question. Riociguat (Adempas, for pulmonary hypertension) is also contraindicated. Check blood pressure before each dose; hold if SBP under 100 mmHg.

Not standard in pediatric tactical EMS.

Peak Effect: SL: 4 to 8 minutes. IV: 1 to 2 minutes. Topical: 1 to 2 hours.

Duration: SL: 20 to 30 minutes. IV: 3 to 5 minutes after infusion stopped. Topical ointment: 4 to 8 hours. Transdermal patch: 12 to 14 hours (with nitrate-free interval).

Store at room temperature (15 to 25 degrees C). Protect from light, moisture, and heat. SL tablets in original glass bottle with tight cap - they degrade rapidly in plastic or with cotton padding; discard 6 months after opening even if not expired. SL spray more stable than tablets and increasingly preferred for field use. IV solution: use glass bottles or non-PVC plastic bags and non-PVC tubing. Topical and patch formulations stable in standard EMS conditions.

Reconstitution:

SL tablets and spray: ready to use, no reconstitution. IV: dilute concentrate to 100 to 400 mcg/mL in NS or D5W in glass bottle or non-PVC bag. Standard mix: 25 mg in 250 mL D5W (100 mcg/mL); 50 mg in 250 mL D5W (200 mcg/mL). Topical ointment: applied with dose-measuring paper directly to skin; do not rub in.

Nitroglycerin is not in the TCCC core trauma formulary - TCCC focuses on hemorrhage, airway, and acute trauma management. Nitroglycerin appears in tactical EMS protocols for management of acute coronary syndrome in non-trauma patients (operators experiencing chest pain from acute MI, for example, or civilian medical emergencies encountered during tactical operations). In TECC for active threat civilian response, nitroglycerin appears in the medical emergency component for patients with concurrent cardiac events. By definition the patient is non-mission-capable once requiring nitroglycerin.