Dipyridamole is an antiplatelet medicine, or blood thinner. It makes your blood flow through your veins more easily. This means your blood will be less likely to make a dangerous blood clot.

Taking dipyridamole helps to prevent blood clots if you have an increased risk of having them. Your risk is higher if you have or have had:

• a stroke or "mini-stroke"(transient ischaemic attack or TIA)
• an operation on your heart to replace your heart valves

Dipyridamole is only available on prescription.

It comes as tablets and slow-release (called "modified-release") capsules. It is also available as a liquid if you find it difficult to swallow tablets or capsules.

• The usual dose for dipyridamole is 200mg twice a day for slow-release capsules or 300mg to 600mg taken 3 or 4 times a day for tablets or liquid.
• Your doctor may prescribe dipyridamole alone or with daily low dose aspirin.
• The main side effects of dipyridamole are feeling sick (nausea), diarrhoea and being sick (vomiting), headaches, feeling dizzy, or feeling hot and flushed.
• You can drink alcohol with dipyridamole. However, do not drink too much while taking this medicine. It can make you dizzy or lightheaded.
• Dipyridamole is also called by the brand names Attia, Ofcram, Persantin, Persantin Retard and Trolactin. Some products may contain a combination of dipyridamole and low dose aspirin (with the brand names Atransipar and Molita).

Dipyridamole can be taken by adults to prevent strokes and after heart valve replacement surgery.

It is sometimes prescribed for children to treat a rare illness called Kawasaki disease or prevent blood clots after heart surgery.

Dipyridamole isn't suitable for some people. To make sure this medicine is safe for you, tell your doctor if you:

• have had an allergic reaction to dipyridamole or any other medicines in the past
• have angina or other heart problems, or have had a recent heart attack
• have a muscle-weakening disease called myasthenia gravis
• have any bleeding disorders, such as haemophilia or von Willebrand disease
• have low blood pressure
• have migraines
• are trying to get pregnant, are already pregnant or breastfeeding

How much dipyridamole you take depends on what form you have been prescribed.

• Slow-release (modified-release) capsules: these release the medicine slowly in your body over a number of hours. Take 1 capsule twice a day - usually 1 in the morning and 1 in the evening. Take your capsules with or shortly after a meal. Swallow the capsule whole. Do not crush or chew it. Capsules are not prescribed for children.
• Tablets or liquid: your doctor will tell you whether to take your dose 3 or 4 times a day. Take it before meals at the same time each day. Swallow the tablet whole with a glass of water. Dipyridamole liquid comes with a syringe or a spoon to help you take the right amount. If you don't have a syringe or spoon, ask your pharmacist for one.

How much should I take?

The usual dose for slow-release capsules is 200mg twice a day.

The usual dose for tablets and liquid is 300mg to 600mg taken 3 or 4 times a day. Follow your doctor's instructions.

If the doctor prescribes it for your child, they usually need to take it 2 or 3 times a day. The doctor will use your child's weight to work out the right dose.

What if I forget to take it?

If you forget to take dipyridamole, take it as soon as you remember. If it's nearly time for your next dose, skip the missed dose.

Don't take a double dose to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to remember to take your medicines.

What if I take too much?

Accidentally taking 1 or 2 extra doses is unlikely to harm you. However, the amount of dipyridamole that can lead to overdose is different from person to person.

Contact your doctor straight away if you've taken some extra medicine and you get side effects such as:

• a faster heart rate or pain in your chest - these can be signs of a heart problem
• feeling dizzy or lightheaded, especially when you stand up or sit up quickly
• shortness of breath, wheezing and tightening of the chest

Like all medicines, dipyridamole can cause side effects, although not everyone gets them.

Common side effects

These common side effects happen in more than 1 in 100 people. Talk to your doctor or pharmacist if these side effects bother you or don't go away:

• feeling sick (nausea)
• diarrhoea and being sick (vomiting)
• headaches
• feeling dizzy
• feeling hot and flushed

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Call a doctor straight away if:

• you have chest pain, or a fast or uneven heartbeat
• your skin or the whites of your eyes turn yellow - these are signs of a liver problem

Serious allergic reaction

In rare cases, dipyridamole can cause a serious allergic reaction.

These are not all the side effects of dipyridamole. For a full list, see the leaflet inside your medicines packet.

What to do about:

• feeling sick (nausea) - try taking your tablets with or after a meal or snack. It may also help if you don't eat rich or spicy food.
• diarrhoea and being sick (vomiting) - drink plenty of water in small, frequent sips. Speak to a pharmacist if you have signs of dehydration, such as peeing less than usual or having dark, strong-smelling pee. Don't take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor.
• headaches - make sure you rest and drink plenty of fluids. Don't drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if the headaches are severe or last longer than a week.
• feeling dizzy - if dipyridamole makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you don't faint, then sit until you feel better. Don't drive or use tools or machines if you feel dizzy or a bit shaky.
• feeling hot and flushed - try cutting down on coffee, tea and alcohol. It might help to keep the room cool and use a fan. You could also spray your face with cool water or sip cold or iced drinks. The flushing should go away after a few days. If it doesn't, or if it's causing you problems, contact your doctor.

Dipyridamole isn't normally recommended in pregnancy or when breastfeeding. However, your doctor may prescribe it if they think the benefits of the medicine outweigh the risks.

If you're planning a pregnancy or you are already pregnant, talk to your doctor about the benefits and possible harms of taking dipyridamole. These will depend on how many weeks pregnant you are and the reason you need to take it. There may be other treatments that are safer for you.

Dipyridamole and breastfeeding

There is not a lot of information about the safety of dipyridamole if you're breastfeeding. It's not known how much dipyridamole may get into your breast milk.

Talk to your doctor to discuss your choices if you want to breastfeed.

Some medicines interfere with the way dipyridamole works.

Tell your doctor if you're taking these medicines before you start taking dipyridamole:

• medicines to thin blood or prevent blood clots, such as aspirin, warfarin, rivaroxaban or apixaban
• medicines for high blood pressure, such as bisoprolol, ramipril or furosemide
• indigestion medicines, such as ranitidine, proton pump inhibitors like omeprazole, or antacids that contain magnesium or aluminium
• digoxin for heart problems
• medicines used to treat myasthenia gravis

Taking dipyridamole with everyday painkillers

Your doctor may prescribe daily low dose aspirin (75mg tablets) to take together with dipyridamole. Or your doctor may prescribe dipyridamole instead of daily low dose aspirin if you have problems with aspirin.

Do not take aspirin for pain relief (300mg tablets) or ibuprofen while you're taking dipyridamole unless a doctor has said it's OK to. They increase the chance of bleeding.

You can take paracetamol together with dipyridamole.

Taking dipyridamole with indigestion medicines

Some indigestion medicines, such as omeprazole, may reduce the effect of dipyridamole. This is important if you're taking dipyridamole as tablets or liquid, but it's not a problem if you're taking capsules.

If you need to take indigestion medicines, do not take them at the same time of day as dipyridamole. Take them 2 to 3 hours before or after your dose of dipyridamole.

Mixing dipyridamole with herbal remedies and supplements

There might be a problem with taking some herbal remedies and supplements with dipyridamole, especially ones that can affect your blood, for example ginkgo.