A nitrate for angina
Isosorbide dinitrate
A nitrate used to prevent and relieve angina by widening blood vessels; it must never be combined with erection medicines (PDE5 inhibitors).
What is Isosorbide dinitrate?
Isosorbide dinitrate is a nitrate used to prevent and relieve the chest pain of angina. It widens blood vessels, which reduces the work of the heart and improves blood flow to it. It must never be taken with erection medicines such as sildenafil, tadalafil or vardenafil, as the combination can cause a dangerous drop in blood pressure.
Education and reference only. This is a plain-language guide to Isosorbide dinitrate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Isosorbide dinitrate is a long-acting nitrate used in the UK to prevent and relieve angina (chest pain caused by reduced blood flow to the heart). It is also sometimes used in heart failure. It works by widening blood vessels, easing the heart's workload. It is taken regularly to prevent angina, and the most important safety points are to allow a nitrate-free period each day to keep it working, and never to combine it with certain erection medicines.
How it works
Isosorbide dinitrate is converted in the body to nitric oxide, a natural substance that relaxes the muscle in blood-vessel walls. This widens veins and arteries, so less blood returns to the heart and the heart has to work less hard, while blood flow through the heart's own arteries improves. Together this reduces the chest pain of angina. The widening of blood vessels also explains the headaches and flushing that are common when starting.
Company & origin
Originated / developed by: Available in the UK from several manufacturers as a generic and as branded products such as Isoket..
Isosorbide dinitrate is a long-acting nitrate, related to glyceryl trinitrate, long used to prevent and relieve angina and marketed in the UK under names including Isoket.
Practical use
How to take Isosorbide dinitrate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it regularly to prevent angina, following the timing your prescriber sets.
- Keep to the spacing advised so you have a daily nitrate-free period (often overnight), which stops the medicine losing its effect.
- Expect headaches when you first start; these usually settle and can be helped with simple painkillers if advised.
- Never take it with erection medicines such as sildenafil, tadalafil or vardenafil.
- Stand up slowly, as it can cause dizziness or light-headedness.
- Do not stop it suddenly without advice, as your angina may get worse.
Weighing it up
Advantages & disadvantages of Isosorbide dinitrate
Advantages
- It is effective at preventing and relieving the chest pain of angina.
- It is long established and widely used, and comes in several forms to suit different needs.
- It eases the heart's workload, which can also help in heart failure.
Disadvantages
- It must never be combined with erection medicines (PDE5 inhibitors), as this can cause a dangerous drop in blood pressure.
- Headaches are common, especially when starting.
- It can lose its effect if taken around the clock, so a nitrate-free period is needed.
- It can cause dizziness and light-headedness, and should not be stopped suddenly.
Practical use
Good to know
Isosorbide dinitrate is taken regularly to prevent angina rather than only when pain strikes. To keep it working, a nitrate-free period (usually overnight) is built into the day, because taking nitrates around the clock leads the body to stop responding (tolerance). Headaches are common when starting and usually settle. It must never be taken with erection medicines (PDE5 inhibitors such as sildenafil, tadalafil or vardenafil), as together they can cause a dangerous fall in blood pressure. It should not be stopped suddenly, as angina can worsen.
Who should not take it / use with caution
- People taking erection medicines (PDE5 inhibitors such as sildenafil, tadalafil or vardenafil).
- People with very low blood pressure, certain heart valve or muscle conditions, or severe anaemia.
- People who have recently had a heart attack with low blood pressure, or raised pressure in the head, used with caution.
Monitoring
- Reviewing how well angina symptoms are controlled.
- Checking that the nitrate-free period is maintained so the medicine keeps working.
- Watching for dizziness, low blood pressure and troublesome headaches.
Side effects
- Headache, especially when starting.
- Flushing and dizziness or light-headedness.
- A fast heartbeat.
- Feeling faint, particularly when standing up quickly.
Key interactions
- Erection medicines (PDE5 inhibitors such as sildenafil, tadalafil and vardenafil) — never combine, as this can cause a dangerous drop in blood pressure.
- Other blood-pressure-lowering medicines and alcohol, which add to its effect.
- Riociguat (a medicine for certain lung blood-pressure conditions), which must not be combined with nitrates.
Available as: Tablets, modified-release tablets, a spray and an injection used in hospital.
Answers
Isosorbide dinitrate: frequently asked questions
Can I take isosorbide dinitrate with Viagra or similar?
No — never. Nitrates such as isosorbide dinitrate must not be combined with erection medicines (PDE5 inhibitors) like sildenafil (Viagra), tadalafil or vardenafil, as together they can cause a dangerous drop in blood pressure. Tell any prescriber you take a nitrate.
Why do I get headaches on isosorbide dinitrate?
Headaches happen because the medicine widens blood vessels. They are common when you first start and usually settle after a short while. Simple painkillers can help if your prescriber agrees.
What is a nitrate-free period and why does it matter?
Taking nitrates around the clock leads the body to stop responding (tolerance). A daily nitrate-free period, usually overnight, lets the medicine keep working. Follow the timing your prescriber advises.
Can I stop isosorbide dinitrate suddenly?
No — do not stop it suddenly, as your angina may get worse. If you want to stop, speak to your prescriber, who will guide any change.
Why do I feel dizzy on isosorbide dinitrate?
By widening blood vessels it can lower blood pressure and make you feel light-headed, especially when standing up quickly. Rise slowly and tell your prescriber if the dizziness is troublesome.
The wider class
About Nitrates
Isosorbide dinitrate belongs to the nitrates class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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