Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NITROL vs ISMO
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
NITROL (nitroglycerin) is a vasodilator that relaxes vascular smooth muscle via the release of nitric oxide (NO), which activates guanylate cyclase and increases cyclic guanosine monophosphate (c GMP) levels, leading to vasodilation.
Isosorbide mononitrate is a nitrate that dilates coronary arteries and peripheral veins. It acts by releasing nitric oxide, which activates guanylate cyclase, increasing c GMP levels, leading to smooth muscle relaxation and vasodilation.
Treatment of acute angina pectoris,Prophylaxis of angina pectoris (pre-exertional use),Management of acute myocardial infarction (FDA-approved),Congestive heart failure (off-label, in acute settings)
Prevention of angina pectoris due to coronary artery disease,Off-label: Treatment of acute angina (immediate-release forms)
Sublingual: 0.3-0.6 mg every 5 minutes as needed for angina, up to 3 doses in 15 minutes. Translingual spray: 1-2 sprays (0.4 mg/spray) under tongue every 5 minutes as needed, max 3 doses in 15 minutes. Transdermal: 0.2-0.8 mg/hour patch applied daily for 12-14 hours. Intravenous: Initial 5 mcg/min, titrate by 5 mcg/min every 3-5 minutes until response, usual range 10-200 mcg/min.
20 mg orally twice daily, 7 hours apart (e.g., 8 AM and 3 PM) to minimize nitrate tolerance.
1-4 minutes for nitroglycerin; clinical effect disappears within 30-60 minutes due to rapid metabolism and redistribution.
Terminal elimination half-life is approximately 5-6 hours. In elderly patients or those with hepatic impairment, half-life may be prolonged (up to 8-10 hours), warranting dose adjustment.
Primarily metabolized by nitrate reductase in the liver; also undergoes denitration by glutathione-dependent organic nitrate reductase and by hemoglobin in red blood cells.
Primarily metabolized in the liver by denitration; minor metabolism via glucuronidation. Metabolites are inactive.
Renal: minimal, <1% unchanged; extensive metabolism by liver, metabolites excreted renally. Biliary/fecal: negligible.
Primarily renal; 80-90% of the dose is excreted as inactive metabolites (isosorbide mononitrate and isosorbide dinitrate) in urine. Less than 1% is excreted unchanged. Fecal excretion is minimal.
Approximately 60% bound to albumin.
Approximately 30% bound to plasma proteins, primarily albumin.
3.3 L/kg, indicating extensive distribution into tissues.
Vd is 0.6-0.9 L/kg, indicating distribution into total body water. Higher Vd may be observed in patients with heart failure.
Sublingual: ~40-60% (first-pass metabolism); Oral: <10% due to high first-pass; Transdermal: ~20-30% with continuous delivery; Intravenous: 100%.
Oral: 90-100% (sustained-release formulations). Sublingual: high but variable; generally effective due to extensive absorption.
No specific adjustment for GFR; monitor for hypotension and methemoglobinemia in severe impairment. Use with caution in dialysis patients.
No dose adjustment required for GFR ≥30 m L/min. For GFR <30 m L/min, consider reducing dose to 10 mg twice daily due to potential accumulation of active metabolite.
Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50% and titrate carefully. Child-Pugh C: Avoid use or use with extreme caution, consider alternative therapy.
No dose adjustment in Child-Pugh A or B. For Child-Pugh C, reduce dose to 10 mg twice daily and monitor for hypotension.
Sublingual/translingual: 5 mcg/kg/dose every 5-10 minutes as needed for acute angina, max 4 doses. IV: Start 0.25-0.5 mcg/kg/min, titrate by 0.5-1 mcg/kg/min, max 5 mcg/kg/min. Not recommended for neonates due to risk of methemoglobinemia.
Safety and efficacy not established; no standard dosing recommendations.
Start at low end of adult dose (sublingual 0.3 mg, transdermal 0.2 mg/hr, IV 5 mcg/min). Titrate slowly due to increased sensitivity and risk of hypotension. Monitor for orthostatic hypotension.
Start at 10 mg twice daily with gradual titration based on tolerance and renal function. Monitor for hypotension and dizziness.
Contraindicated in patients with erectile dysfunction who are using phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, tadalafil) due to risk of severe hypotension.
Do not use with phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, tadalafil) due to risk of severe hypotension.
Risk of severe hypotension and syncope, especially in volume-depleted patients or those with low systolic blood pressure; tolerance and cross-tolerance with other nitrates may develop; abrupt cessation may precipitate angina; caution in patients with hypertrophic obstructive cardiomyopathy.
Hypotension and reflex tachycardia may occur,Caution in patients with volume depletion or hypotension,May cause headaches; tolerance may develop with prolonged use,Abrupt withdrawal may increase angina frequency
Hypersensitivity to nitroglycerin or any component; severe anemia; increased intracranial pressure (e.g., head trauma, cerebral hemorrhage); concurrent use with PDE-5 inhibitors; right ventricular infarction; constrictive pericarditis; cardiac tamponade.
Concurrent use of PDE-5 inhibitors,Severe anemia,Closed-angle glaucoma,Hypersensitivity to isosorbide mononitrate or nitrates,Acute myocardial infarction with low filling pressures
Alcohol can exacerbate hypotensive effects and should be avoided. No specific food restrictions; however, high-fat meals may delay sublingual absorption but not clinically significant.
Alcohol may enhance hypotension risk. Avoid high-fat meals if extended-release formulation, as they may affect absorption. No other significant food interactions.
FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, nitroglycerin has been shown to be embryotoxic in rats and rabbits at doses 20 times the human dose. Use in first trimester only if clearly needed. During second and third trimesters, may be used for management of preterm labor or pregnancy-induced hypertension, but monitor for maternal hypotension and fetal bradycardia.
ISMO (isosorbide mononitrate) is categorized as FDA Pregnancy Category C. In animal studies, reduced fetal survival and growth retardation were observed at high doses. No adequate human studies exist. Use only if potential benefit justifies risk. First trimester: Theoretical risk of hemodynamic effects; avoid unless necessary. Second/third trimester: May cause fetal hypoxia due to maternal hypotension; monitor fetal heart rate. Peripartum: May exacerbate uterine relaxation and postpartum hemorrhage if used near delivery.
Not known if nitroglycerin is excreted in human milk. M/P ratio not available. Because of potential for serious adverse reactions in nursing infants, discontinue nursing or discontinue drug, taking into account importance of drug to mother. Use with caution if breastfeeding; avoid high doses or continuous exposure.
Excretion into human milk is unknown. Due to risk of infant methemoglobinemia and hypotension, caution is advised. M/P ratio: Not available. American Academy of Pediatrics considers nitrate derivatives compatible with breastfeeding, but monitor infant for cyanosis and lethargy.
No specific dose adjustments recommended for pregnancy-related PK changes. However, increased plasma volume and cardiac output in pregnancy may require higher doses for therapeutic effect. Start at lowest effective dose and titrate based on clinical response and blood pressure. For intravenous use in pregnancy, standard non-pregnant doses may be used but with careful titration.
No specific dose adjustments for ISMO in pregnancy are established due to lack of pharmacokinetic studies. However, pregnancy-induced hemodynamic changes (increased plasma volume, cardiac output) may reduce efficacy; consider dose titration based on clinical response. Avoid doses >60 mg/day to minimize hypotensive risk. Use immediate-release formulations for flexible dosing if needed.
Nitrol (nitroglycerin) is a potent vasodilator used primarily for angina pectoris. Sublingual tablets should be administered at first sign of attack; patient should be sitting to prevent syncope from hypotension. If pain persists after 3 doses 5 minutes apart, seek emergency care. Tolerance develops with sustained use; avoid long-acting formulations for acute episodes. Monitor for orthostatic hypotension and headache, common side effects. Contraindicated with concurrent use of PDE-5 inhibitors (e.g., sildenafil) due to risk of severe hypotension.
ISMO (isosorbide mononitrate) is a nitrate used for angina prophylaxis, not for acute attacks. Tolerance develops with sustained use; maintain a 10-12 hour nitrate-free interval to prevent tolerance. Do not use with phosphodiesterase-5 inhibitors (e.g., sildenafil) due to risk of profound hypotension. Contraindicated in severe anemia, increased intracranial pressure, or hypertrophic obstructive cardiomyopathy. Discontinue if blurred vision or dry mouth occurs.
Take sublingual nitroglycerin at the first sign of chest pain; do not swallow. Place tablet under tongue and allow to dissolve.,Sit down before taking to avoid fainting due to drop in blood pressure.,If pain is not relieved after 1 dose, take a second dose after 5 minutes. If not relieved after 3 doses, call 911 immediately.,Store tablets in original glass container, tightly closed, away from light and heat. Replace every 6 months as potency decreases.,Avoid alcohol and erectile dysfunction drugs (e.g., Viagra, Cialis) as they can cause severe hypotension.,Common side effects include headache, dizziness, and flushing. Headache may indicate effectiveness.
Take as prescribed to prevent angina; do not use for acute attacks.,May cause headache, dizziness, or hypotension; rise slowly from sitting.,Avoid taking erectile dysfunction drugs (e.g., sildenafil, tadalafil) as severe blood pressure drop can occur.,Do not stop abruptly to avoid rebound angina.,Store in original container away from light and moisture.
No interactions on record
"Bosentan, a dual endothelin receptor antagonist and an inducer of CYP3A4 and CYP2C9, reduces systemic exposure to vismodegib, a Hedgehog pathway inhibitor primarily metabolized by CYP3A4. This interaction leads to decreased serum concentrations of vismodegib, potentially diminishing its antitumor efficacy in patients with advanced basal cell carcinoma. Concomitant use may require vismodegib dose adjustment or alternative therapies to avoid therapeutic failure."
"Vismodegib inhibits CYP3A4, which is the primary enzyme responsible for metabolizing nilotinib. Concomitant administration may lead to increased nilotinib plasma concentrations, elevating the risk of QT interval prolongation, torsades de pointes, hepatotoxicity, and myelosuppression. Clinical vigilance is warranted due to the narrow therapeutic index of nilotinib."
"Vismodegib, a hedgehog pathway inhibitor, is a moderate inhibitor of CYP2C9, the primary enzyme responsible for metabolizing tolbutamide. Concomitant use can significantly decrease tolbutamide clearance, leading to elevated plasma concentrations and prolonged hypoglycemic effects. This increases the risk of severe hypoglycemia, especially in diabetic patients, and may require dose adjustment of tolbutamide."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about NITROL vs ISMO, answered by our medical review team.
NITROL is a Nitrate Vasodilator that works by NITROL (nitroglycerin) is a vasodilator that relaxes vascular smooth muscle via the release of nitric oxide (NO), which activates guanylate cyclase and increases cyclic guanosine monophosphate (c GMP) levels, leading to vasodilation.. ISMO is a Nitrate Vasodilator that works by Isosorbide mononitrate is a nitrate that dilates coronary arteries and peripheral veins. It acts by releasing nitric oxide, which activates guanylate cyclase, increasing c GMP levels, leading to smooth muscle relaxation and vasodilation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NITROL and ISMO depend on the specific clinical indication. These are both Nitrate Vasodilator agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of NITROL is: Sublingual: 0.3-0.6 mg every 5 minutes as needed for angina, up to 3 doses in 15 minutes. Translingual spray: 1-2 sprays (0.4 mg/spray) under tongue every 5 minutes as needed, max 3 doses in 15 minutes. Transdermal: 0.2-0.8 mg/hour patch applied daily for 12-14 hours. Intravenous: Initial 5 mcg/min, titrate by 5 mcg/min every 3-5 minutes until response, usual range 10-200 mcg/min.. The standard adult dose of ISMO is: 20 mg orally twice daily, 7 hours apart (e.g., 8 AM and 3 PM) to minimize nitrate tolerance.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between NITROL and ISMO in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. NITROL is classified as Category C. FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, nitroglycerin has been shown to be embryotoxic in rats and rabbits at doses 20 times the human d. ISMO is classified as Category C. ISMO (isosorbide mononitrate) is categorized as FDA Pregnancy Category C. In animal studies, reduced fetal survival and growth retardation were observed at high doses. No adequate . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.