Medication After a Myocardial Infarction

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Why are drugs prescribed after a myocardial infarction?

• To reduce the chance of having another myocardial infarction (MI).
• To help prevent heart disease from getting worse.

Aspirin - helps to prevent blood clots

Aspirin works by reducing the 'stickiness' of platelets. Platelets are tiny particles in the blood that help the blood to clot if a blood vessel is cut. However, if a blood clot forms inside a blood vessel that takes blood to the heart muscle, it blocks the flow of blood and can cause an MI. Therefore, aspirin reduces the chance of blood clots forming within blood vessels, which reduces the chance of a further MI.

If you cannot take aspirin (for example, if you are allergic to it) then another anti-platelet drug called clopidogrel may be used instead.

It is best to read the leaflet that comes with the drug packet for a full list of instructions and possible side-effects. Some main points about aspirin include the following:

• The usual dose of aspirin is 75 mg per day. This is a low dose (anti-platelet dose) compared to the dose of aspirin used to ease pains and headaches.
• Side-effects are uncommon. An important side-effect is bleeding in the gut that occurs in some people. If you have ever had a stomach or duodenal ulcer, or a bleed from your gut, you must tell your doctor. Extra care is needed when taking aspirin. For example, if you have had any of these conditions and take aspirin you may be advised to take another tablet that reduces stomach acid to protect the gut.
• If you develop dyspepsia whilst taking aspirin (abdominal pains) then stop the aspirin and see a doctor. Dyspepsia may indicate a gut problem or a bleed caused by aspirin.
• Ideally, you should not take anti-inflammatory drugs or steroids if you take aspirin. For example, drugs used to reduce inflammation in arthritis, and in particular, ibuprofen. Aspirin plus these drugs increases the risk of a bleed in the gut. However, some people need these drugs. In this case, your doctor may advise another drug to reduce stomach acid to lower the risk of a bleed in the gut.
• Rarely, aspirin may cause a bleed in another part of the body such as into the brain to cause a stroke. In particular, do not take aspirin if you have a bleeding disorder such as haemophilia.
• A small number of people are allergic to aspirin. If you are allergic to aspirin you may get breathing difficulties, wheezing or a swollen face and tongue if you take aspirin. If any of these symptoms occur, stop taking the aspirin and see a doctor.
• Some people with asthma cannot take aspirin as it brings on asthma symptoms.
• You should not take aspirin if you also take a drug called methotrexate.

The above list may sound alarming but most people who take aspirin do not have any problems or side-effects. Also, the benefits of taking aspirin following an MI usually greatly outweigh the risk of side-effects and problems.

Beta-blockers - help to protect the heart

There are a few beta-blocker drugs to chose from. They ease the workload of the heart. They work by blocking the beta receptors on heart muscle cells. A receptor is a tiny part on the wall of certain cells. There are different types of receptors throughout the body. The beta receptors on heart muscle cells are stimulated by the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). When the beta receptors are stimulated, they make the heart muscle cells work harder which increases the heart rate and blood pressure.

Beta-blocker drugs 'sit' on beta receptors, and block them from being stimulated. This prevents the heart rate from going too fast, reduces blood pressure, and helps to stabilise the electrical activity of the heart. Beta-blockers are also used to treat angina and high blood pressure.

It is best to read the leaflet that comes with the drug packet for a full list of instructions and possible side-effects. Some main points about beta-blockers include the following:

• You should not take a beta-blocker if you have asthma or chronic obstructive pulmonary disease (COPD) with an asthmatic component.
• Beta-blockers are not used in people with certain types of heart problems. For example, people with a very slow pulse, sick sinus syndrome, or second or third degree atrioventricular (AV) block.
• Most people do not develop any side-effects. However, tell your doctor if you have any side-effects. The most common are: cool hands and feet, sleeping problems, impotence, pins and needles, and tiredness. A change in dose or preparation may help if you develop any troublesome side-effects.

ACE inhibitors - help to protect the heart

There are a few ACE inhibitors (Angiotension Converting Enzyme Inhibitors) to chose from. One of their actions is to interfere with the enzyme (chemical) found in the bloodstream called angiotensin. Blocking this enzyme widens blood vessels, and lowers the blood pressure, which eases the burden on the heart. ACE inhibitors also appear to have a direct action on the heart which has a protective effect.

It is best to read the leaflet that comes with the drug packet for a full list of instructions and possible side-effects. Some main points about ACE inhibitors include the following:

• After the very first dose, on the first day you start an ACE inhibitor:
  • Stay indoors for about four hours as occasionally some people feel dizzy. This is because the very first dose causes a large drop in blood pressure in a few people, and may cause a faint.
  • If you do feel dizzy, sit or lie down and it will usually ease off.
  • If you become very dizzy, contact your doctor immediately.
• Your body quickly becomes used to the new drug. After the first dose on the first day of treatment, there is no need to take any special precautions.
• A low dose is usually started at first, but built up to a standard dose over 2-4 weeks.
• A blood test is usually done before starting an ACE inhibitor, and about 7-10 days after the first dose. This checks the function of the kidneys. (The kidneys are affected in a small number of people who take an ACE inhibitor.) A blood test at least every year is then usual.

Statins - to lower the cholesterol level

There are a few statin drugs to chose from. Statins work by reducing the amount of cholesterol that is made in the liver. Cholesterol contributes to the build up of atheroma. Patches of atheroma are like 'fatty lumps' that build up on the inside lining of blood vessels. A build up of atheroma can lead to heart disease, strokes and other blood vessel problems. In general, the lower the cholesterol level, the better. Most people who have an MI are advised to take a statin.

Your GP or practice nurse will give you a target cholesterol level to aim for. This is usually for your blood cholesterol level to come below 5 mmol/l or to be reduced by 20-25% from your original level, whichever is lower. You will need a blood test before starting a statin, and 4-12 weeks later. This checks if the cholesterol level has come down, and that your liver is not affected. A blood test every so often may then be advised to keep a check on your cholesterol level. The dose may be increased until your target level is reached.

It is best to read the leaflet that comes with the drug packet for a full list of instructions and possible side-effects. Some main points about statins include the following:

• You should not take a statin if you have liver disease, are pregnant or are breastfeeding.
• Most people do not get any side-effects. A minor stomach upset is the most common side-effect, but rarely requires treatment to stop.
• Tell a doctor urgently if you develop muscle pains. A muscle problem is a rare but serious side-effect.
• It is best to take your statin at bedtime as more cholesterol tends to be made by the liver at night than during the day.

Other drugs - are sometimes advised

Some people take fish oil supplements. There is some evidence that eating oily fish (or taking fish oil supplements) helps to protect the heart and reduces the risk of having a further MI.

This leaflet is about drugs that are commonly prescribed if you have had an MI. However, it is not a substitute for advice from your doctor. You may be advised differently if you have other diseases, develop complications, or have allergies or side-effects to certain drugs. For example, if you develop angina or heart failure after an MI you may be advised to take other drugs.

Self help measures - are also important

Drugs are used in addition to any relevant lifestyle changes which also help to prevent heart disease from getting worse. These include:

• stop smoking if you are a smoker.
• take regular exercise (unless advised otherwise by your doctor).
• lose weight if you are overweight.
• eat a healthy diet, including oily fish at least 2-3 times a week.
• drink alcohol in moderation.

Lifestyle changes are discussed in more detail in another leaflet called 'After a Myocardial Infarction'.

Further sources of information and help

British Heart Foundation
14 Fitzhardinge Street, London, W1H 4DH
Heart Information Line: 0845 070 8070 (Mon-Fri 9am-5pm)
Web: www.bhf.org.uk

© EMIS and PIP 2006   Updated: February 2006   PRODIGY Validated

The authors and editors of this article are employed to create accurate and up to date content reflecting reliable research evidence, guidance and best clinical practice. They are free from any commercial conflicts of interest. Find out more about updating.

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