1. Introduction
Isosorbide mononitrate is a nitrate vasodilator used primarily to prevent and manage angina pectoris (chest pain) and heart failure. It works by relaxing blood vessels, reducing the heart’s workload, and improving oxygen delivery to the heart.
2. Indications
- Approved Indications:
- Prevention of angina pectoris (chronic stable angina).
- Heart failure (as part of combination therapy).
- Off-Label Uses:
- Esophageal spasm (rare cases).
3. Dosage
- Adults:
- Chronic Angina Prevention:
- Immediate-release: 20 mg twice daily, with doses 7 hours apart to prevent tolerance.
- Extended-release: 30–60 mg once daily in the morning, titrated up to 120 mg if needed.
- Heart Failure:
- 20–40 mg twice daily, or as prescribed by a cardiologist.
- Chronic Angina Prevention:
- Elderly:
- Use standard adult doses, but monitor for hypotension and dizziness.
4. Administration
- Take orally with water.
- Extended-release tablets should be swallowed whole, not crushed or chewed.
- Immediate-release tablets should be taken at the same time(s) daily, ensuring a nitrate-free interval of 10–12 hours to avoid tolerance.
5. Forms Available
- Tablets (immediate-release): 10 mg, 20 mg.
- Extended-release tablets: 30 mg, 60 mg, 120 mg.
6. Side Effects
6.1. Common Side Effects
- Headache (common during initiation).
- Dizziness or light-headedness.
- Flushing.
6.2. Less Common Side Effects
- Nausea.
- Fatigue.
6.3. Rare but Serious Side Effects
- Severe hypotension.
- Syncope (fainting).
- Paradoxical angina.
7. Warnings
- Tolerance: Continuous use without a nitrate-free interval can lead to reduced efficacy.
- Hypotension: Increased risk in volume-depleted patients or those on antihypertensives.
- Interaction with Phosphodiesterase Inhibitors: Avoid use with sildenafil, tadalafil, or vardenafil, as this can cause life-threatening hypotension.
8. Precautions
- Use cautiously in patients with:
- Severe hypotension.
- Hypertrophic obstructive cardiomyopathy (may worsen symptoms).
- Severe anaemia.
- Cerebrovascular disease (increased risk of syncope).
9. Interactions
- Drug-Drug Interactions:
- Phosphodiesterase inhibitors (e.g., sildenafil): Severe hypotension risk.
- Alcohol: Increased risk of dizziness and hypotension.
- Antihypertensives: Additive blood pressure-lowering effects.
- Drug-Food Interactions:
- No significant interactions, but avoid alcohol to reduce side effect risks.
10. Monitoring Parameters
- Frequency and severity of angina episodes.
- Blood pressure (watch for hypotension).
- Signs of adverse effects (e.g., headache, dizziness).
11. Use in Children
- Not recommended, as safety and efficacy have not been established in children.
12. Use in Pregnancy
- Category C: Use only if the potential benefit justifies the risk. Limited human data are available, but animal studies show possible risks.
13. Use in Elderly
- Safe for use but monitor closely for hypotension and dizziness. Start with lower doses if necessary.
14. Use in Kidney Disease
- No dose adjustment is required, as isosorbide mononitrate is metabolised in the liver.
15. Use in Liver Disease
- Use cautiously in severe liver impairment due to potential changes in drug metabolism.
16. Patient Counselling Points
- Take isosorbide mononitrate exactly as prescribed, ensuring a nitrate-free interval of 10–12 hours to prevent tolerance.
- Headaches are common when starting treatment and usually improve over time. Use paracetamol if needed for relief.
- Avoid alcohol, as it may worsen dizziness or flushing.
- Do not stop taking this medication suddenly without consulting your doctor.
- If you experience severe dizziness, fainting, or increased chest pain, seek medical attention immediately.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Imdur (extended-release) | AstraZeneca | $25–50 (30 tablets, 60 mg) |
Monoket (immediate-release) | Lannett | $20–40 (30 tablets, 20 mg) |
Generic Isosorbide Mononitrate | Various manufacturers | $5–15 (30 tablets, 20 mg) |
18. FAQs (15 Questions)
- What is isosorbide mononitrate used for?
It is used to prevent angina and, in some cases, manage heart failure. - How does isosorbide mononitrate work?
It relaxes blood vessels, reducing the workload on the heart and improving blood flow. - How long does isosorbide mononitrate take to work?
The immediate-release form starts working within 30–60 minutes, while the extended-release form works gradually over the day. - Can isosorbide mononitrate cause headaches?
Yes, headaches are a common side effect, especially at the beginning of treatment. - What is the difference between immediate-release and extended-release forms?
Immediate-release forms provide quick relief, while extended-release forms offer prolonged protection throughout the day. - Can I take isosorbide mononitrate with food?
Yes, it can be taken with or without food. - What should I do if I miss a dose?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - Can isosorbide mononitrate cause low blood pressure?
Yes, it may cause hypotension, especially in dehydrated patients or those taking other blood pressure medications. - Can I drink alcohol while taking isosorbide mononitrate?
Avoid alcohol, as it can worsen dizziness and flushing. - Is isosorbide mononitrate safe during pregnancy?
Use only if the benefits outweigh the risks. Consult your doctor. - Can isosorbide mononitrate be used for acute angina?
No, it is not suitable for immediate relief of acute angina. Use sublingual nitroglycerin instead. - Does isosorbide mononitrate interact with other medications?
Yes, it interacts with phosphodiesterase inhibitors (e.g., sildenafil) and antihypertensives, increasing the risk of hypotension. - Can isosorbide mononitrate cause dizziness?
Yes, dizziness is a common side effect, particularly when starting treatment. - How should I store isosorbide mononitrate?
Store at room temperature, away from moisture and heat. - Is isosorbide mononitrate the same as nitroglycerin?
No, they are both nitrates but are used differently. Isosorbide mononitrate is for long-term prevention, while nitroglycerin is for acute relief.