Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NITROMIST vs ISMO
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Nitroglycerin is a prodrug that releases nitric oxide (NO) which activates guanylyl cyclase, increasing c GMP in smooth muscle cells, leading to vasodilation primarily of venous capacitance vessels and coronary arteries.
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.
Acute angina pectoris,Prophylaxis of angina pectoris,Acute coronary syndrome (off-label),Heart failure with preserved ejection fraction (off-label),Anal fissure (off-label)
Prevention of angina pectoris due to coronary artery disease,Off-label: Treatment of acute angina (immediate-release forms)
1-2 sprays (0.4-0.8 mg) sublingually or intraorally at onset of angina, may repeat every 5 minutes up to 3 doses. Prophylaxis: 1 spray (0.4 mg) 5-10 minutes before activity.
20 mg orally twice daily, 7 hours apart (e.g., 8 AM and 3 PM) to minimize nitrate tolerance.
2–3 minutes for nitroglycerin; rapid metabolism results in short terminal half-life. Clinically, effects dissipate within 30 minutes of discontinuation.
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 hepatic via glutathione S-transferases (GST) and possibly cytochrome P450 (CYP3A4) to inactive metabolites.
Primarily metabolized in the liver by denitration; minor metabolism via glucuronidation. Metabolites are inactive.
Renal excretion of inactive metabolites accounts for >80% of elimination; biliary/fecal excretion is minimal (<15%).
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 plasma proteins (albumin).
Approximately 30% bound to plasma proteins, primarily albumin.
3.3 L/kg; large Vd indicates extensive tissue distribution, especially to vascular smooth muscle.
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% (due to first-pass metabolism); transdermal: variable (~10–30%); intravenous: 100%.
Oral: 90-100% (sustained-release formulations). Sublingual: high but variable; generally effective due to extensive absorption.
No dose adjustment required for renal impairment.
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.
Use with caution in severe hepatic impairment (Child-Pugh C); consider dose reduction due to increased bioavailability.
No dose adjustment in Child-Pugh A or B. For Child-Pugh C, reduce dose to 10 mg twice daily and monitor for hypotension.
Not recommended for use in pediatric patients due to lack of safety and efficacy data.
Safety and efficacy not established; no standard dosing recommendations.
Initiate with lower doses (e.g., 1 spray = 0.4 mg) due to increased sensitivity and higher risk of hypotension.
Start at 10 mg twice daily with gradual titration based on tolerance and renal function. Monitor for hypotension and dizziness.
None.
Do not use with phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, tadalafil) due to risk of severe hypotension.
Hypotension,Hypovolemia,Increased intracranial pressure,Hypertrophic cardiomyopathy,Severe anemia,Tolerance with continuous use,Contraindicated use with phosphodiesterase-5 inhibitors (e.g., sildenafil)
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,Severe hypotension (SBP <90 mm Hg),Cardiac tamponade,Constrictive pericarditis,Hypertrophic cardiomyopathy with left ventricular outflow tract obstruction,Concurrent use with phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil),Increased intracranial pressure (e.g., head trauma, cerebral hemorrhage),Severe anemia
Concurrent use of PDE-5 inhibitors,Severe anemia,Closed-angle glaucoma,Hypersensitivity to isosorbide mononitrate or nitrates,Acute myocardial infarction with low filling pressures
Avoid alcohol consumption as it may enhance the hypotensive effects of nitroglycerin. No specific food restrictions, but a high-fat meal may delay absorption if taken orally; however, Nitromist is a sublingual spray, so food interactions are minimal.
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 X. Nitroglycerin is contraindicated in pregnancy due to risk of fetal bradycardia and hypotension. First trimester: Risk cannot be ruled out; use only if clearly needed. Second and third trimesters: Increased risk of maternal hypotension leading to decreased placental perfusion. Not recommended.
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.
Nitroglycerin is excreted into breast milk in small amounts; M/P ratio is approximately 0.55. American Academy of Pediatrics considers it compatible with breastfeeding. However, use caution in nursing mothers due to potential for infant hypotension.
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.
Standard dosing may be used but with caution due to increased plasma volume in pregnancy potentially altering pharmacokinetics. No specific dose adjustments recommended; start at lowest effective dose and titrate based on maternal response and fetal status.
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.
Nitromist (nitroglycerin lingual spray) is indicated for acute relief of angina pectoris. Onset of action is 1-3 minutes. Administer 1-2 sprays onto or under the tongue at the first sign of an attack; may repeat every 5 minutes up to 3 doses in 15 minutes. Do not shake canister. Avoid use with phosphodiesterase-5 inhibitors (e.g., sildenafil) due to risk of severe hypotension. Hypotension, reflex tachycardia, and headache are common. Tolerance may develop with frequent use; a nitrate-free interval of 10-12 hours can minimize tolerance.
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.
Use one or two sprays under or on the tongue at the first sign of chest pain; do not swallow. If no relief after 5 minutes, call 911.,Store at room temperature; do not expose to heat or open flame.,Do not shake the canister before use.,Sit down when using this medication to avoid dizziness or fainting.,Avoid alcohol and erectile dysfunction drugs (e.g., Viagra) while using this medication.
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 NITROMIST vs ISMO, answered by our medical review team.
NITROMIST is a Nitrate Vasodilator that works by Nitroglycerin is a prodrug that releases nitric oxide (NO) which activates guanylyl cyclase, increasing c GMP in smooth muscle cells, leading to vasodilation primarily of venous capacitance vessels and coronary arteries.. 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 NITROMIST 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 NITROMIST is: 1-2 sprays (0.4-0.8 mg) sublingually or intraorally at onset of angina, may repeat every 5 minutes up to 3 doses. Prophylaxis: 1 spray (0.4 mg) 5-10 minutes before activity.. 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 NITROMIST 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. NITROMIST is classified as Category C. FDA Pregnancy Category X. Nitroglycerin is contraindicated in pregnancy due to risk of fetal bradycardia and hypotension. First trimester: Risk cannot be ruled out; use only if cle. 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.