What is it used for?

• Angina pectoris.
• High blood pressure (hypertension).
• Irregular heart beats (arrhythmias).
• Reducing irregular heartbeats and the risk of further heart attacks immediately after a heart attack (myocardial infarction) and improving survival.
• Reducing the symptoms of an overactive thyroid gland (thyrotoxicosis).
• Preventing migraines.

How does it work?

• Metocor tablets contain the active ingredient metoprolol, which is a type of medicine called a beta-blocker. 
• Beta-blockers work by blocking beta receptors that are found in various parts of the body, including the heart. Blocking the beta receptors prevents the action of two hormones that are produced naturally by the body, called noradrenaline and adrenaline. These hormones are often referred to as the 'fight or flight' chemicals, because they are responsible for the body's reaction to stressful situations.
• Metocor blocks beta receptors that are found in the heart. This reduces the action of adrenaline and noradrenaline on the heart, causing it to beat more slowly and with less force. In turn, this reduces the pressure at which the blood is pumped out of the heart and around the body, which helps to reduce blood pressure. Metocor can therefore be used to lower high blood pressure.
• Metocor action in slowing the rate and force of the heartbeat also reduces the energy used by the heart to pump blood around the body. This reduces the heart's need for oxygen, which means that metoprolol can also be used in the management of angina. Angina is chest pain that occurs because the heart does not get enough oxygen to meet demand, for example during exercise. This is usually as a result of hardening or narrowing of the arteries that supply blood to the heart. Metoprolol reduces the workload of the heart and so decreases the amount of oxygen that it needs to pump blood around the body. This helps to prevent attacks of angina.
• Metocor action on the heart also means it can be used to control irregular heartbeats (arrhythmias, and in particular fast irregular heartbeats known as tachyarrthmias). This is because the slowed heart rate tends to allow the electrical signals in the heart to fire more regularly and thus the heart to beat more regularly.
• Metocor is also used for this reason in the period immediately after a heart attack. It has been shown to reduce irregular heartbeats and the risk of further heart attacks, and thus improve survival. Metoprolol is given by injection immediately after the heart attack, and then as tablets.
• In addition to these heart related uses, metoprolol can also be used to control symptoms that are associated with an overactive thyroid gland (thyrotoxicosis), such as a racing pulse, sweating and tremor.
• Metocor is also used to prevent migraines in people who get frequent attacks of these severe headaches. It is not fully understood how metoprolol works in this area.

Use with caution in

• Elderly people.
• Severely decreased liver function.
• People with a history of heart failure or a weak heart.
• Slowed conduction of electrical messages between the chambers of the heart (1st degree heart block).
• A severe form of chest pain not caused by exertion (Prinzmetal's or variant angina).
• Conditions involving poor blood circulation in the arteries of the extremities, eg hands and feet (peripheral arterial disorders such as Raynaud's syndrome or intermittent claudication).
• Diabetes (this medicine may mask the symptoms of low blood sugar, such as increased heart rate and tremor, and the dose of your diabetes medicine may need adjusting).
• Overactive thyroid gland (this medicine may mask the symptoms of a thyroid storm or thyrotoxicosis).
• History of asthma, wheezing or any other breathing difficulties.
• People with a history of allergies (beta-blockers may increase sensitivity to allergens and result in more serious allergic reactions; they may also reduce the response to adrenaline used to treat anaphylactic shock).
• Psoriasis.

Not to be used in

• Allergy to other beta-blocker medicines, eg propranolol, atenolol.
• Low blood pressure (hypotension).
• Serious defect in the heart's electrical message pathways resulting in decreased function of the heart (2nd or 3rd degree heart block).
• Uncontrolled heart failure.
• Very slow heart rate (bradycardia) of less than 45 beats per minute.
• A problem common in the elderly, related to poor control of the working of the heart (sick sinus syndrome).
• Failure of the heart to maintain adequate circulation of blood around the body (cardiogenic shock).
• Severe problems with blood circulation in the arteries of the extremities, eg hands and feet.
• People with an increase in the acidity of the blood (metabolic acidosis).
• Untreated tumour of the adrenal gland (phaeochromocytoma). If you are being treated for phaeochromocytoma you will be given another medicine called an alpha-blocker in combination with this one.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

• This medicine should not be used during pregnancy unless considered essential by your doctor. Beta-blockers reduce blood flow to the placenta, which could increase the chance of premature delivery or death of the foetus. They may also slow the baby's heart beat, cause its blood sugar to drop, or restrict its growth in the womb. However, beta-blockers are sometimes used in the third trimester to control high blood pressure in the mother. If you think you could be pregnant while taking this medicine, or want to try for a baby, it is important to seek medical advice from your doctor. It is important that you don't stop taking this medicine suddenly.
• This medicine may pass into breast milk in small amounts. As this could potentially cause the baby's heart rate to slow down or its blood sugar to fall, this medicine should be used with caution in breastfeeding mothers and only if the expected benefit to the mother is greater than any possible risk to the baby. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Common (affect between 1 in 10 and 1 in 100 people)

• Fatigue.
• Dizziness (particularly when standing up, which may sometimes cause fainting).
• Headache.
• Slower than normal heart beat (bradycardia).
• Feeling short of breath with physical exertion.
• Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

• Cold hands and feet.
• Awareness of your heartbeat (palpitations).
• Depression.
• Difficulty sleeping (insomnia).
• Nightmares.
• Problems with concentration.
• Pins and needles sensations.
• Feeling sleepy.
• Worsening of heart failure.
• Problems with the electrical pathways that control the pumping action of the heart (heart block).
• Rash.
• Breathing difficulties due to a narrowing of the airways (bronchospasm).
• Muscle cramps.

Very rare (affect less than 1 in 10,000 people)

• Weight gain.
• Increased sweating.
• Sexual problems such as impotence.
• Anxiety or nervousness.
• Visual disturbances.
• Dry or irritated eyes.
• Dry mouth.
• Hair loss.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

Metoprolol is likely to have an additive effect with other medicines that decrease blood pressure, particularly medicines that are used to treat high blood pressure (antihypertensives). This may cause dizziness, which can usually be relieved by lying down until the symptoms pass. If you feel dizzy while taking this medicine in combination with other medicines that can lower blood pressure you should let your doctor know, as your doses may need adjusting.

Other medicines that decrease blood pressure include the following:

• ACE inhibitors, eg enalapril.
• aldesleukin.
• alpha-blockers such as prazosin.
• alprostadil.
• angiotensin II receptor antagonists such as losartan.
• antipsychotics such as chlorpromazine.
• benzodiazepines, eg temazepam, diazepam.
• baclofen.
• other beta-blockers such as propranolol.
• calcium-channel blockers such as verapamil, nifedipine. (If metoprolol is taken with calcium channel blockers such as verapamil, nifedipine or diltiazem, there may also be an increased risk of slow heart rate and heart failure. Verapamil must not be given as an injection into a vein (intravenously) to people being treated with metoprolol.)
• clonidine. (If metoprolol is taken in combination with clonidine there is also a risk of a rebound increase in blood pressure if the clonidine is suddenly stopped. If you are taking both these medicines it is important to keep taking both of them unless otherwise directed by your doctor. When stopping treatment, the metoprolol should be stopped several days before slowly stopping the clonidine.)
• diazoxide.
• diuretics, eg furosemide, bendroflumethiazide.
• dopamine agonists, eg bromocriptine, apomorphine.
• hydralazine.
• levodopa.
• MAOI antidepressants, eg phenelzine.
• methyldopa.
• minoxidil.
• moxonidine.
• moxisylyte.
• nicorandil.
• nitrates, eg glyceryl trinitrate.
• tizanidine.

This medicine may reduce the blood sugar lowering effect of some medicines used to treat diabetes. People with diabetes should carefully monitor their blood sugar while taking this medicine, as metoprolol can also mask some of the signs of low blood sugar, such as increased heart rate and tremor.

There may be an increased risk of slow heart rate and heart block if metoprolol is used in combination with the following medicines:

• digoxin
• medicines for irregular heartbeats (antiarrhythmics), eg amiodarone, flecainide, quinidine.

There may be an increased risk of coldness, numbness or tingling of the hands and feet if ergot derivatives such as ergotamine or methysergide (used to treat migraines) are taken in combination with metoprolol.

Adrenaline injections used to treat anaphylactic shock (a severe allergic reaction) may be less effective in people treated with beta-blockers such as metoprolol.

Metoprolol may increase the blood level of lidocaine, which could increase the risk of its side effects.

The following medicines may reduce the breakdown of metoprolol by the liver and so could increase its blood level and risk of side effects. Your doctor may prescribe you a lower dose of metoprolol if you are taking any of these medicines:

• cimetidine
• hydralazine
• propafenone
• SSRI antidepressants such as citalopram, escitalopram or paroxetine.

The following medicines may increase the breakdown of metoprolol by the liver and so could decrease its blood level and make it less effective. Your doctor may prescribe you a higher dose of metoprolol if you are taking any of these medicines:

• barbiturates such as amobarbital or phenobarbital
• rifampicin.
• Non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin may reduce the blood pressure lowering effect of metoprolol.

References:

http://www.netdoctor.co.uk/medicines/heart-and-blood/a7037/lopresor-metoprolol/

https://www.drugs.com/international/metocor.html

https://www.epharmapedia.com/medicine/profile/128622/Metocor.html?lang=en&tab=druginfo

https://www.medicines.org.uk/emc/medicine/18110