BMA Concise Guide to Medicine & Drugs

Metoprolol

Brand names Betaloc, Betaloc-SA, Lopresor, Lopresor SR

Used in the following combined preparations None

QUICK REFERENCE

Drug group Beta blocker

Overdose danger rating High

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Metoprolol is a cardioselective beta blocker used to prevent the heart from beating too quickly in conditions such as angina, arrhythmias, and hyperthyroidism. It is also used to prevent migraine attacks and protect the heart from further damage after a heart attack. The drug is also used to treat hypertension (high blood pressure) but is not usually used to initiate treatment. It is less likely than non-cardioselective beta blockers to provoke breathing difficulties. However, it should be avoided in people with asthma. It may also slow the body’s response to low blood sugar in diabetics on insulin.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, SR tablets, injection.

Frequency and timing of doses 1–2 x daily (hypertension); 2–3 x daily (angina/arrhythmias); 4 x daily for 2 days, then 2 x daily (heart attack prevention); 2 x daily (migraine prevention); 4 x daily (hyperthyroidism).

Adult dosage range 100–200mg daily.

Onset of effect 1–2 hours.

Duration of action 3–7 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Do not stop taking the drug without consulting your doctor. Stopping suddenly may lead to worsening of the underlying condition.

OVERDOSE ACTION

Seek immediate medical advice in all cases. Take emergency action if breathing difficulties, collapse, or loss of consciousness occur.

POSSIBLE ADVERSE EFFECTS

Metoprolol’s adverse effects are common to most beta blockers and tend to diminish with long-term use. All adverse effects should be reported to your doctor. The most common effects are lethargy, fatigue, and cold hands and feet. Less common side effects include nausea, vomiting, nightmares or vivid dreams, rash, dry eyes, and visual disturbances. If you experience palpitations or fainting (which may be a sign that the drug has slowed the heart excessively), breathlessness, or wheezing, you should stop taking the drug and seek immediate medical attention.

INTERACTIONS

Antihypertensive drugs Metoprolol may enhance the blood-pressure-lowering effect.

Calcium channel blockers may cause low blood pressure, a slow heartbeat, and heart failure if used with metoprolol.

Non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the antihypertensive effect of metoprolol.

Cardiac glycosides (e.g. digoxin) may increase the heart-slowing effect of metoprolol.

Antidiabetic drugs Taken with metoprolol, these drugs may increase the risk of low blood sugar or mask its symptoms.

Antacids may increase the effects of metoprolol.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have liver or kidney problems.

· You have asthma, bronchitis, or emphysema.

· You have heart problems.

· You have diabetes.

· You have psoriasis.

· You have phaeochromocytoma (a type of adrenal gland tumour).

· You are taking other medicines.

Pregnancy Not usually prescribed. May affect the baby. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Not recommended.

Over 60 Reduced doses necessary. There may be an increased risk of adverse effects.

Driving and hazardous work Avoid such activities until you have learned how metoprolol affects you because the drug can cause fatigue, dizziness, and drowsiness.

Alcohol Avoid excessive intake. Alcohol may increase the blood-pressure-lowering effects of metoprolol.

Surgery and general anaesthetics Occasionally, metoprolol may need to be stopped before you have a general anaesthetic; but only do this after discussion with your doctor or dentist.

PROLONGED USE

No special problems.