nitroglycerin
Brand: Nitrostat, Nitro-Dur, Tridil
ISMP High Alert Prototype Drug
Drug Class: nitrate
Drug Family: antianginal
Subclass: organic nitrate (NO donor)
Organ Systems: cardiovascular
Mechanism of Action
Enzymatically converted to NO in vascular smooth muscle activating guanylyl cyclase; increases cGMP causing vasorelaxation; predominantly venodilation at low doses reducing preload; arterial dilation at higher doses reducing afterload.
guanylyl cyclase (via NO release)
Indications
- acute angina (SL)
- unstable angina/NSTEMI
- acute pulmonary edema (IV)
- hypertensive emergency with HF
- esophageal spasm (diagnostic)
Contraindications
- hypotension (SBP <90)
- severe aortic stenosis
- concurrent PDE-5 inhibitors (sildenafil/tadalafil/vardenafil)
- right ventricular MI (preload dependent)
- hypertrophic obstructive cardiomyopathy
- closed-angle glaucoma
Adverse Effects
Common
- headache (vasodilation of meningeal vessels)
- hypotension
- tachycardia
- flushing
Serious
- severe hypotension
- methemoglobinemia (IV — high doses/prolonged)
Pharmacokinetics (ADME)
| Absorption | 1% sublingual bioavailability oral; SL bypasses first-pass — ~40% |
| Distribution | large Vd |
| Metabolism | hepatic (high first-pass oral); liver nitrate reductase |
| Excretion | renal |
| Half-life | 1-3 min (SL), 1-2h (patch) |
| Onset | 1-3 min |
| Peak | 4-8 min (SL) |
| Duration | 30-60 min (SL); 12h (patch) |
| Protein Binding | <0% |
| Vd | very large |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| PDE-5 inhibitors (sildenafil, vardenafil, tadalafil) | profound hypotension — absolutely contraindicated | major |
| alcohol | additive vasodilation and hypotension | moderate |
| heparin (IV) | high doses of IV NTG may reduce heparin effect | minor |
Nursing Considerations
- SL: 0.4 mg q5 min × 3 doses; if no relief after 3 doses → call 911
- Advise patient to sit or lie down (hypotension)
- Remove patch at night to prevent tolerance
- IV NTG: use polyethylene (not PVC) tubing — NTG adsorbs to PVC
- CONTRAINDICATED with PDE-5 inhibitors — ask about sildenafil before administration
Clinical Pearls
- Nitrate tolerance: continuous exposure depletes sulfhydryl groups needed for NO formation; prevent with 10-12 hour nitrate-free interval
- PDE-5 inhibitors: absolutely contraindicated — additive cGMP accumulation causes severe hypotension; 24h for sildenafil, 48h for tadalafil
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.