NITRONAL
Clinical safety rating
cautionComprehensive 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). |
| Molecular Weight | 227.09 |
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 | Associated with congenital malformations, particularly Ebstein's anomaly and neural tube defects; should be avoided unless no alternative and risk-benefit justifies use in life-threatening conditions. |
| 2nd trimester | Increased risk of maternal hypotension and fetal hypoxia; may cause fetal bradycardia and decreased uteroplacental blood flow; use only if clearly needed. |
| 3rd trimester | Risk of maternal hypotension and fetal distress; may inhibit uterine contractions and prolong labor; avoid near term unless necessary for hypertensive emergencies. |
Clinical note
Comprehensive clinical and safety monograph for NITRONAL (NITRONAL).
| Placental transfer | Nitroglycerin crosses the placenta; studies indicate rapid transfer with fetal concentrations approximately 10-15% of maternal levels. |
| Breastfeeding | NITRONAL (nitroglycerin) is excreted into breast milk in low amounts; however, due to potential for adverse effects in the infant (e.g., hypotension), caution is advised. Usually considered compatible if maternal therapy is essential, but monitor infant for signs of vasodilation. |
| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| 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. |
■ 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 nitroglycerin or any componentConcurrent use with phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil) due to risk of severe hypotensionSevere anemiaIncreased intracranial pressure (e.g., head trauma, cerebral hemorrhage)Constrictive pericarditisPericardial tamponadeAcute myocardial infarction with low filling pressuresRight ventricular infarction
| Precautions | Hypotension, Tachycardia, Headache, Methemoglobinemia (rare with high doses), Tolerance development with prolonged use |
| Food/Dietary | Avoid alcohol consumption as it may enhance hypotensive side effects. No specific food restrictions. |
| Clinical Pearls | Nitroglycerin is used for acute angina and perioperative hypertension. Administer sublingually for rapid onset; avoid in patients with hypertrophic obstructive cardiomyopathy, severe aortic stenosis, or concurrent phosphodiesterase-5 inhibitor use. Monitor for hypotension and reflex tachycardia. Tolerance develops with continuous exposure; use intermittent dosing schedules. Intravenous formulations require non-PVC tubing due to drug adsorption. |
| Patient Advice | Place tablet under tongue or spray onto oral mucosa; do not swallow. · Sit or lie down when using to prevent fainting from low blood pressure. · If chest pain persists after 5 minutes, call emergency services immediately. · Store in original container, tightly closed, away from heat and moisture. · Do not use if taking erectile dysfunction medications like sildenafil within the past 24-48 hours. |
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