Isosorbide Shortage: What Providers and Prescribers Need to Know in 2026

Isosorbide mononitrate (ISMN) and isosorbide dinitrate (ISDN) have been prescribed for decades to manage stable angina due to coronary artery disease. In 2026, supply disruptions — particularly for ISMN 10 mg and 20 mg immediate-release tablets — are creating challenges for prescribers and their patients. This guide provides clinical context, therapeutic alternatives, and practical steps for practices managing this shortage.

What Is the Current Supply Situation?

Isosorbide mononitrate is now entirely off-patent with all brand-name products (Imdur, Monoket, ISMO) discontinued. The generic market is served by a limited number of manufacturers, which creates supply fragility. The FDA drug shortages database and Drugs.com have tracked active shortage notices for ISMN tablets.

On April 8, 2026, ANI Pharmaceuticals received FDA approval and launched ISMN tablets USP 10 mg and 20 mg, adding a new generic manufacturer. This is a positive development but distribution to individual pharmacies takes time, and the shortage is expected to persist unevenly across regions for the near term.

Clinical Impact: Why This Shortage Is High Stakes

Unlike some medications where brief interruptions are clinically tolerable, abrupt discontinuation of isosorbide mononitrate can lead to rebound angina — particularly in patients with significant coronary artery disease who depend on the medication's preload and afterload reduction for daily symptom control. Industrial studies have documented withdrawal events (including chest pain and potential MI) with abrupt nitrate cessation after chronic use.

Practices should proactively identify patients on chronic isosorbide therapy and develop a plan before they run out — not after they call in distress from the pharmacy.

Therapeutic Alternatives: A Clinical Framework

When isosorbide is unavailable, the following therapeutic substitution pathways are generally appropriate, depending on patient factors:

Option 1: Switch Between Isosorbide Formulations

If ISMN immediate-release (10 or 20 mg) is unavailable, consider:

• ISMN extended-release (30–120 mg once daily): Often has different availability than immediate-release. Built-in nitrate-free interval when dosed in the morning. Easier once-daily compliance.
• Isosorbide dinitrate (5–40 mg TID): Less predictable bioavailability due to first-pass effect; must ensure adequate nitrate-free interval. May have different stock availability than ISMN.

Option 2: Nitroglycerin Transdermal Patch

Transdermal nitroglycerin (e.g., Nitro-Dur, Minitran) at 0.1–0.8 mg/hr, applied for 12–14 hours/day with a patch-free interval, is a reasonable substitute for chronic nitrate therapy. Patches are widely available and have a different supply chain than oral isosorbide. Oral nitroglycerin extended-release capsules (Nitro-Time) are another option.

Option 3: Beta-Blockers (First-Line Antianginal)

Per ACC/AHA guidelines, beta-blockers are first-line for stable angina prevention. If a patient is not already on a beta-blocker, this may be the ideal time to add or optimize one:

• Metoprolol succinate ER (Toprol-XL generic): 25–200 mg once daily; first-line for angina and systolic heart failure.
• Atenolol: 25–100 mg once daily; inexpensive, widely available.
• Carvedilol: 3.125–25 mg twice daily; appropriate when heart failure with reduced EF coexists.

Option 4: Calcium Channel Blockers

Dihydropyridine CCBs (amlodipine 2.5–10 mg once daily) and non-dihydropyridine CCBs (diltiazem, verapamil) are effective antianginals. Amlodipine is generally well-tolerated and is a reasonable substitute or add-on. Note that combining CCBs with nitrates can cause additive hypotension — monitor BP accordingly if using concurrently.

Option 5: Ranolazine (Ranexa)

Ranolazine 500–1000 mg twice daily is FDA-approved for chronic angina as add-on or monotherapy. It does not affect heart rate or blood pressure significantly, making it an option for patients with borderline BP or bradycardia. Note: Ranolazine prolongs the QT interval — screen for QT-prolonging comedications and obtain a baseline ECG.

Communication Strategies for Your Practice

Proactive communication prevents after-hours calls and patient anxiety. Consider these approaches:

• Send a proactive message to all patients on chronic isosorbide therapy explaining the shortage and providing a contact number if they need assistance finding their medication.
• Create a standard response protocol for pharmacy callbacks about isosorbide — this reduces staff burden.
• Educate patients never to stop isosorbide without calling first, even if their pharmacy runs out.
• Recommend medfinder to patients who are struggling to locate their medication — this service calls pharmacies on behalf of patients and identifies which ones have their specific prescription in stock.

How medfinder Can Help Your Patients

medfinder is a service that calls pharmacies near a patient to identify which ones can fill their specific prescription. This eliminates the time patients spend calling around — a particular burden for older adults with coronary artery disease who may have limited mobility. Providers can refer patients to medfinder.com/providers to learn more about supporting your patients through medication access challenges.