Why are drugs prescribed after a myocardial infarction?

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

The drugs are usually taken each day for life. However, the type of drug prescribed for you will depend on such factors as the type of MI you had as well as any other illnesses you may have. Your doctor will discuss the drugs you will need to take in more detail.

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 (indigestion) or heartburn whilst taking aspirin then your should stop your aspirin and see a doctor. These symptoms may indicate a gut problem or a bleed caused by the aspirin.
• Ideally, you should not take anti-inflammatory drugs or steroids if you take aspirin. For example, drugs used to reduce inflammation in arthritis like ibuprofen. Aspirin in addition to these drugs increases the risk of a bleed in your 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.
• A small number of people with asthma cannot take aspirin as it brings on asthma symptoms.

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 any possible side-effects and problems.

Aspirin is usually taken for the rest of your life. Also, you will normally be advised to take the antiplatelet drug clopidogrel in addition to aspirin. However, this is usually only advised for a number of weeks or months, depending on the type and severity of your MI.

Beta-blockers - help to protect the heart

Beta-blockers work by easing the workload of the heart 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 will help to stop you having another MI. Beta-blockers are also used to treat angina and high blood pressure. There are a few beta-blocker drugs for your doctor to chose from.

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:

• 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

One of the actions of an ACE inhibitor (angiotensin converting enzyme inhibitors) 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. There are a few ACE inhibitors for your doctor to chose from.

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 can cause a drop in blood pressure in a few people.
  • If you do feel dizzy, sit or lie down and it will usually ease off.
• 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 and built up to a standard dose over 2-4 weeks.
• A blood test is usually done before starting an ACE inhibitor, and about two weeks 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.

Angiotensin receptor blockers are drugs which have the same effect as ACE inhibitors but are sometimes given as an alternative, for example if you have side effects to an ACE inhibitor.

Statins - to lower the cholesterol level

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 often for your blood cholesterol level to come below 4 mmol/l. If the target is not reached at first, the dose may need to be increased or a different preparation used.

You should have a blood test before starting treatment. This checks the level of cholesterol. It also checks if your liver is working properly. After starting treatment, you should have a blood test within 1-3 months, and again at 12 months. The blood test is to check that the liver has not been affected by the medication. The blood may also be checked to measure the cholesterol level to see how well the statin is working.

Most people who take a statin have no side-effects, or only minor ones. Read the information leaflet that comes with your particular brand for a full list of possible side-effects. These include: headache, pins and needles, abdominal pain, bloating, diarrhoea, feeling sick, and a rash.

Some notable points to remember about statins:

• Tell your doctor if you have any unexpected muscle pains, tenderness, cramps or weakness. This is because a rare side-effect of statins is a severe form of muscle inflammation.
• You should not take a statin if you have active liver disease, if you are are pregnant or intend to be pregnant, or if you are breast-feeding. You should stop a statin if you develop liver disease.
• Do not eat grapefruit or drink grapefruit juice if you are taking a statin. A chemical in grapefruit can increase the level of statin in the bloodstream which can make side-effects from the statin more likely.
• Various other drugs that you may take may interfere with statin drugs. For example, some antibiotics and ciclosporin. The doses of either the statin or the other interacting drug may need to be adjusted. Therefore, if you are prescribed (or buy) another drug, remind the doctor or pharmacist that you are on a statin in case it is one where an interaction may be possible.
• Tell a doctor if you develop chest symptoms such as unexplained dyspnoea (shortness of breath) or cough. This is because, in very rare cases, statins may cause a disease called interstitial lung disease.

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

In addition to taking medication, there are various measures which you can also undertake to help reduce your risk of a future MI occurring.

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.

See separate leaflet called 'After a Myocardial Infarction' which discusses lifestyle changes in more detail .

Further sources of information and help

British Heart Foundation

Greater London House, 180 Hampstead Road, London, NW1 7AW
Tel (Heart Help Line): 0300 330 3311 Web: www.bhf.org.uk

HEART UK (the Hyperlipidaemia Education and Atherosclerosis Research Trust UK)

7 North Road, Maidenhead, Berkshire SL6 1PE
Tel (Helpline): 0845 450 5988 Web: www.heartuk.org.uk

British Cardiac Patients Association

15 Abbey Road, Bingham, Notts, NG13 8EE
Tel (Helpline): 01223 846845 Web: www.bcpa.co.uk

References

• Management of acute myocardial infarction in patients presenting with persistant ST-segment elevation, European Society of Cardiology (November 2008)
• Garas S et al; Myocardial Infarction, eMedicine, Jan 2010
• Myocardial infarction - secondary prevention, Clinical Knowledge Summaries (January 2008)
• Secondary prevention in primary and secondary care for patients following a myocardial infarction, NICE Clinical Guideline (2007)