Monoket (Isosorbide Mononitrate): Patient-Friendly Medicine Guide for Australian Patients
Basic Product Information
| International Nonproprietary Name (INN) | Isosorbide mononitrate |
|---|---|
| Australia Brand Names | Monoket, Imdur, Isomil, Duride, Isomonit |
| ATC Code | C01DA14 |
| Available Forms & Strengths | Tablets (10 mg, 20 mg), Modified-release tablets (30 mg, 60 mg, 120 mg) |
| Manufacturers | Bayer, Mylan, Alphapharm, Chemmart, Sandoz |
| Prescription Status | Prescription only (Schedule 4, Rx) |
Mechanism of Action
For Patients:
Monoket works by relaxing and widening the blood vessels in your heart and body. This makes it easier for blood and oxygen to reach your heart, which helps prevent chest pain (angina).
For Healthcare Professionals:
Isosorbide mononitrate is a nitrate-class vasodilator. It releases nitric oxide (NO), stimulating the enzyme guanylate cyclase, which increases cyclic GMP. The result is smooth muscle relaxation, predominantly venodilation, reduction of cardiac preload, and improved myocardial oxygen supply/demand ratio.
Pharmacokinetics
- Absorption: Rapid and complete, oral bioavailability ~100% due to lack of significant first-pass hepatic metabolism.
- Time to peak plasma: ~30-60 minutes (immediate release); 4-6 hours (modified-release)
- Metabolism: Hepatic; mainly to inactive metabolites.
- Elimination: Primarily via urine (mostly as metabolites); renal or hepatic impairment may prolong effect.
- Duration of Action: Immediate release: 4–6 hours; Modified-release: up to 24 hours depending on formulation.
Use in Everyday Life and Best Practices
Typical Use: Monoket is most often used to prevent angina pectoris in adults. It is not suitable for acute relief of chest pain but rather as regular therapy. Your GP or specialist will decide your dose and how often to take it.
- Tablets are usually taken once or twice daily (modified or immediate-release, respectively).
- Follow the exact instructions from your doctor or pharmacist regarding timing and dose.
- Do not stop taking Monoket suddenly without talking to your healthcare provider.
- It is important to take the medicine at the same time(s) each day for best results.
- Carry a record of your angina symptoms to share with your doctor.
Dosing: Morning vs Evening
- Morning Dosing: Modified-release tablets are generally taken in the morning, after waking up. This aligns with the time when angina is more likely and allows a "nitrate-free interval" at night, which helps maintain the medication’s effect and reduces risk of nitrate tolerance.
- Evening Dosing: Not typically recommended unless prescribed, as a nitrate-free interval is needed for effectiveness (nighttime dosing may increase risk of tolerance).
- Tip: Set a daily alarm or reminder for consistent dosing.
- Note: Always check with your pharmacist about dose timings that fit your daily life and sleep patterns in line with Australian lifestyle habits.
Taking with Food or on an Empty Stomach
- Monoket can be taken with or without food.
- Some patients find it easier on the stomach to take with breakfast or a light meal, a common practice in Australia.
- Avoid heavy, high-fat meals around dosing time, as this may delay absorption of modified-release tablets slightly.
- Follow your personal routine for best adherence, as minor variations caused by food are usually not clinically significant.
Interaction Warnings
| Interaction | Details & Action |
|---|---|
| Alcohol | Can increase risk of low blood pressure, dizziness, fainting. Limit or avoid alcohol while on Monoket. |
| Phosphodiesterase-5 Inhibitors | (e.g., sildenafil/Viagra, tadalafil/Cialis, vardenafil/Levitra) Serious risk: Can cause dangerous drops in blood pressure. Never use together! |
| Other Blood Pressure Medications | May increase risk of hypotension. Careful monitoring and dose adjustment needed if used together. |
| Tricyclic Antidepressants, Antipsychotics | Possible additive blood pressure lowering; report any fainting or dizziness. |
| Ergot Alkaloids (migraine meds) | Reduced effectiveness of both medications; discuss alternatives with your doctor. |
| Food | No significant issues, but avoid sudden heavy meals/drinks when starting therapy. |
- Always inform your pharmacist about all prescription, over-the-counter, and herbal products you use.
- Avoid grapefruit or grapefruit juice unless your doctor advises otherwise (very rare interactions but best practice).
Indications
| Indication | Status | Notes |
|---|---|---|
| Prevention of Angina Pectoris | Official (TGA approved) | Primary use in Australia. |
| Heart Failure (adjunct) | Off-label | Occasionally used as add-on for symptom control. |
| Pulmonary Hypertension | Off-label | Under specialist guidance only. |
| Raynaud’s Phenomenon | Off-label | Rare, under specialist care. |
Dosing According to Clinical Indications
| Population | Indication | Starting Dose | Maintenance Dose | Comments |
|---|---|---|---|---|
| Adults | Angina Prevention | 20 mg twice daily (immediate release) or 60 mg once daily (modified-release) | Up to 120 mg/d, as directed | Always follow your doctor's instructions. |
| Elderly | Angina Prevention | Same as adults, or 10 mg twice daily | As tolerated | Start lower if risk of falls/hypotension. |
| Children/Adolescents | Any | Not routinely recommended | N/A | Use only if directed by a paediatric specialist. |
| Heart Failure (Off-label) | Adjunct | 10–20 mg twice daily | As advised by cardiologist | Specialist use only. |
Safety Profile and Side Effects
Most people tolerate Monoket well. If you get side effects, speak to your pharmacist or GP.
| Side Effect | Frequency | Advice |
|---|---|---|
| Headache | Very common | Usually improves with time. Paracetamol may help. |
| Flushing | Common | Benign, usually settles after first few weeks. |
| Dizziness, Light-headedness | Common | Get up slowly from sitting/lying to prevent falls. |
| Low Blood Pressure (Hypotension) | Rare, but serious if occurs | Sit/lie down if faint or dizzy. Contact your doctor. |
| Rapid Heartbeat (Tachycardia) | Less common | Normally mild. See doctor if persistent. |
| Nausea | Uncommon | Take with food, or in divided doses if needed. |
| Severe Allergic Reaction | Very rare | Seek urgent medical help for swelling, rash, difficulty breathing. |
- If pregnant, planning pregnancy, or breastfeeding, consult your doctor before use.
- Not suitable for sudden (acute) chest pain – use your GTN spray or sublingual tablet as prescribed.
- Keep out of children's reach.
Guidelines for Proper Use: Pharmacist & Clinical Advice
- Take Monoket exactly as prescribed, at the same time each day.
- Do not skip or double doses if a dose is missed; take the next dose as scheduled.
- Store below 25°C, protected from moisture, in the original packaging.
- Have regular blood pressure and heart health checks, especially if there are any changes in symptoms.
- Report any new chest pain, worsening angina, or severe dizziness to your GP promptly.
- Let your cardiologist know before any surgery or dental procedure that you are taking Monoket.
Alternative Treatment Options
- Other Nitrates: Glyceryl trinitrate (GTN) oral tablets/sprays (for acute attacks)
- Beta Blockers: E.g., metoprolol, atenolol. Pros: Blood pressure/heart rate control. Cons: May cause fatigue/erectile dysfunction.
- Calcium Channel Blockers: E.g., amlodipine, diltiazem. Pros: Useful alternative/add-on. Cons: May cause oedema/flushing.
- Nicorandil: Similar anti-anginal effects, but with different side effect risks.
- Ranolazine: Specialist use; limited by TGA approval and reimbursement.
- Lifestyle Changes: Smoking cessation, healthy English-style diet (vegetables, fish, lean meat, moderated sodium), regular exercise.
Reimbursement: Many of these alternatives are PBS-listed and subsidised for eligible patients in Australia. Discuss which is best for your health profile and cost needs with your GP or pharmacist.
Legal, Registration & Reimbursement Status in Australia
- TGA Registration: Monoket and generics registered by the Therapeutic Goods Administration (TGA).
- Schedule: Prescription only (Schedule 4).
- PBS Status: Subsidised under the Pharmaceutical Benefits Scheme (PBS) when prescribed for angina or heart failure, subject to relevant clinical criteria and eligibility.
Latest Research and Clinical Guidance (2022–2025)
- ESC & NHFA 2023 Guidelines: Monoket remains “first-line” for stable angina prevention in adults. Use in combination with beta-blockers or calcium channel blockers where required. Nitrate-free intervals are essential to avoid tolerance. (ESC 2023. “Chronic Coronary Syndromes Guideline”)
- Recent Trials: Studies continue to show good effectiveness and safety when used as prescribed. Headaches and hypotension remain the leading concerns, but these are manageable for most patients.
- Australian Cardiovascular Guidelines (2024): Advocates morning dosing and lifestyle modification as part of holistic heart health management. (NHFA/CSANZ Heart Failure Guideline Update 2024)
Availability and Delivery
| Pack Size | Common Strengths | Indicative PBS Price | Delivery Time (Melbourne, Sydney, Brisbane, Perth, Adelaide) |
|---|---|---|---|
| 30 tablets | 20 mg, 60 mg | $7.30 (PBS-eligible), $15–25 (private) | 1–3 business days |
| 60 tablets | 20 mg, 60 mg | $10.60 (PBS-eligible), $28–45 (private) | 1–4 business days |
| 100 tablets | 10 mg, 20 mg | N/A (private only), $40–65 | 2–5 business days |
- Available at all major pharmacy chains and local pharmacies across Australia.
- Online ordering and home delivery possible; consult your pharmacist for next-business day services.
- Always use registered/licensed Australian pharmacies for safety.
Frequently Asked Questions (FAQ)
- Can Monoket be used for chest pain that has already started?
No. Monoket is designed to prevent angina, not to treat angina attacks once they start. For sudden chest pain, use your fast-acting GTN spray or sublingual tablet as prescribed by your doctor. Call 000 if the pain doesn’t improve quickly. - What should I do if I miss a dose?
Take the dose as soon as you remember, unless it’s almost time for your next dose. Do not double up. Just take the next dose at the regular time. - Can I drink alcohol while taking Monoket?
It’s best to avoid alcohol or keep it to a minimum, as it can enhance the blood pressure-lowering effect of Monoket and increase the risk of dizziness or fainting. - How long do side effects like headaches last?
Headaches often improve after a few days to a week. Using paracetamol can help in the meantime. Talk to your pharmacist or doctor if they persist. - Is Monoket safe to use with other heart medicines?
Generally yes, but always inform your doctor or pharmacist about all medications you take, including herbal or over-the-counter products, to avoid interactions and ensure safe management.
If you have any further questions, speak to your pharmacist or GP. This information is intended as a general guide and does not replace personalised medical advice.
