NITRONAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NITRONAL (NITRONAL).
Nitronal (nitroglycerin) is a vasodilator that works by releasing nitric oxide, which activates guanylate cyclase and increases cyclic guanosine monophosphate (cGMP) in vascular smooth muscle, leading to relaxation and dilation of peripheral arteries and veins, predominantly venous dilation.
| Metabolism | Nitroglycerin is extensively metabolized in the liver by glutathione S-transferases and also in erythrocytes and vascular smooth muscle cells via denitration to dinitrates and mononitrates, which are further conjugated. |
| Excretion | Renal: ~60% as inactive metabolites; fecal: ~35% via bile; unchanged drug: <1%. |
| Half-life | Terminal elimination half-life is 1-4 minutes (due to rapid hepatic metabolism via glutathione S-transferase). Clinical context: necessitates continuous IV infusion for sustained effect. |
| Protein binding | ~60% bound to plasma proteins (albumin). |
| Volume of Distribution | 3.3 L/kg (large Vd due to high lipophilicity; indicates extensive tissue distribution). |
| Bioavailability | Sublingual: ~40-60% (first-pass hepatic metabolism); oral: <10% (extensive first-pass); topical: ~100% (minimal first-pass). |
| Onset of Action | IV: 1-3 minutes; sublingual spray: 2-5 minutes; topical ointment: 15-30 minutes. |
| Duration of Action | IV: 3-5 minutes after infusion stops; sublingual: up to 30 minutes; topical: up to 6 hours (tolerance develops with prolonged use). |
Initial intravenous infusion of 5 mcg/min, titrated by 5 mcg/min every 3-5 minutes to clinical effect; typical maintenance 10-200 mcg/min.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | Severe hepatic impairment (Child-Pugh class C): reduce dose by 50% and monitor closely. |
| Pediatric use | Intravenous infusion: 0.25-0.5 mcg/kg/min, titrate as needed; maximum 5 mcg/kg/min. |
| Geriatric use | Initiate at lower end of dosing range (5 mcg/min) due to increased sensitivity; titrate slowly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NITRONAL (NITRONAL).
| Breastfeeding | Excreted in breast milk in small amounts; M/P ratio unknown. Potential for infant methemoglobinemia and hypotension. Caution advised; consider alternative therapy or monitor infant for signs of cyanosis or hypotension. |
| Teratogenic Risk | FDA Category C. First trimester: Risk of teratogenicity cannot be ruled out; animal studies show fetal abnormalities at high doses. Second/third trimester: Risk of fetal nitrite toxicity (methemoglobinemia), fetal bradycardia, and reduced uteroplacental blood flow. Use only if maternal benefit outweighs fetal risk. |
■ FDA Black Box Warning
None explicitly required by FDA for nitroglycerin products; however, caution is advised due to risk of severe hypotension and syncope.
| Serious Effects |
["Hypersensitivity to nitrates","Severe hypotension (systolic BP <90 mmHg)","Cardiac tamponade","Constrictive pericarditis","Increased intracranial pressure (e.g., head trauma, cerebral hemorrhage)","Concomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)"]
| Precautions | ["Hypotension","Tachycardia","Headache","Methemoglobinemia (rare with high doses)","Tolerance development with prolonged use"] |
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| Fetal Monitoring |
| Monitor maternal blood pressure and heart rate continuously during infusion; fetal heart rate monitoring; assess for maternal methemoglobinemia (pulse oximetry, co-oximetry if prolonged use); monitor for signs of fetal distress (bradycardia). |
| Fertility Effects | No human data on fertility effects; animal studies at high doses showed impaired fertility and fetal anomalies. Not recommended in patients attempting conception unless no safer alternative. |