Educational use only. Drug cards are AI-assisted study material for NCLEX preparation.
Mechanism of action
Releases nitric oxide, which activates guanylyl cyclase and dilates vascular smooth muscle — predominantly venous at low doses (reducing preload), arterial at higher doses (reducing afterload), and coronary arteries throughout. The result is reduced cardiac oxygen demand and improved coronary perfusion. Used for acute angina, ACS, hypertensive emergency, and acute heart failure with pulmonary edema.
Adverse effects
Life-threatening / NCLEX-tested
- Severe hypotension — especially in volume-depleted, inferior MI/RV infarct, or with PDE5 inhibitors
- Reflex tachycardia
- Methemoglobinemia (rare, with high-dose IV)
- Tolerance with continuous use — needs a 10–14 hour nitrate-free interval daily
- Increased ICP (relative contraindication in head injury)
Side effects
Common — what to teach
- Pounding headache (very common — reassure that it usually improves with continued use)
- Flushing
- Dizziness, lightheadedness
- Orthostatic hypotension
- Burning under the tongue with SL form (still potent — does not mean it's working or not)
Food & drug interactions
PDE5 inhibitors (sildenafil, tadalafil, vardenafil) cause life-threatening hypotension — absolute contraindication within 24 hours (48 h for tadalafil). Riociguat is also contraindicated. Antihypertensives, alcohol, and tricyclic antidepressants amplify hypotension. Sublingual tablets must be stored in the original dark glass container — they degrade with light, heat, and moisture; replace every 6 months once opened.
Nursing implications
Assessment, monitoring, patient teaching
- For chest pain: place 1 sublingual tablet under the tongue (or 1 spray) at the first sign — sit or lie down before taking
- If pain not relieved after 1 dose in 5 minutes, CALL 911 (per AHA guidance), then may repeat every 5 minutes for up to 3 total doses
- Check BP before and after each dose; hold if SBP < 90
- ALWAYS confirm no PDE5 use in the last 24 hours before giving NTG
- Topical/transdermal: rotate sites, wear gloves to avoid self-dosing, allow a 10–14 h nitrate-free interval (often overnight)
- Store SL tablets in original brown bottle, not in pill organizers; teach the burning/tingling sensation is normal and not a potency check
When to hold / contraindications
- SBP < 90 mmHg
- Severe bradycardia or marked tachycardia
- Right ventricular infarct or inferior MI with hemodynamic instability
- PDE5 inhibitor in last 24 h (48 h for tadalafil)
- Severe head injury or increased ICP
Memory anchor
"Sit, take, wait 5, call 911" — new AHA guidance: don't wait for three doses if symptoms persist. Never with Viagra/Cialis. Rotate transdermal sites; respect the nitrate-free interval.
Practice Nitroglycerin questions
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