BMA Concise Guide to Medicine & Drugs

Verapamil

Brand names Cordilox, Securon, Univer, Verapress, Vertab, Zolvera

Used in the following combined preparations Tarka

QUICK REFERENCE

Drug group Anti-angina drug, anti-arrhythmic drug, and antihypertensive drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Verapamil belongs to a group of drugs known as calcium channel blockers, which interfere with the conduction of signals in the muscles of the heart and blood vessels. It is used in the treatment of hypertension, abnormal heart rhythms, and angina. It reduces the frequency of angina attacks but does not help relieve pain while an attack is in progress. Verapamil increases the ability to tolerate physical exertion and can be used safely by asthmatics.

Verapamil is also prescribed for certain types of abnormal heart rhythm. It can be administered by injection as well as in tablet form for such disorders.

Verapamil is not generally prescribed for people with low blood pressure, slow heart beat, or heart failure because it may worsen these conditions.

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/capsules, liquid, injection.

Frequency and timing of doses 2–3 x daily (tablets, liquid); 1–2 x daily (SR tablets/capsules).

Adult dosage range 120–480mg daily.

Onset of effect 1–2 hours (tablets); 2–3 minutes (injection).

Duration of action 6–8 hours. During prolonged treatment some beneficial effects may last for up to 12 hours. SR tablets act for 12–24 hours.

Diet advice Avoid grapefruit juice, which may increase blood levels of verapamil.

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 3 hours (tablets, liquid) or 8 hours (SR tablets/capsules), take a single dose now and skip the next.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. Large overdoses may cause dizziness. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

The main adverse effect of verapamil is constipation. It also commonly causes headache, nausea, vomiting, and ankle swelling. Discuss with your doctor if these are severe. Rare side effects include dizziness (which may be due to slowing of the heart rate), rash, and, after prolonged use, breast enlargement in males and an increase in gum tissue. Consult your doctor if you experience any of these effects.

INTERACTIONS

Beta blockers When verapamil is taken with these drugs, there is a slight risk of abnormal heart beat and heart failure.

Carbamazepine, ciclosporin, digoxin, theophylline, sirolimus, and ivabradine The effects of these drugs may be increased by verapamil; their doses may need to be reduced or the combination avoided.

Rifampicin and barbiturates may reduce the effects of verapamil.

Clarithromycin and erythromycin may increase the effects of verapamil.

Simvastatin and atorvastatin There is an increased risk of muscle damage if these drugs are taken with verapamil.

Colchicine Verapamil may increase the effects of colchicine and the combination should be avoided.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have a long-term liver problem.

· You have heart failure.

· You have porphyria.

· You are taking other medicines.

Pregnancy Not usually prescribed. May inhibit labour if taken during later stages of pregnancy. 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 Usually given on specialist advice only. Reduced dose necessary.

Over 60 No special problems.

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

Alcohol Avoid. Alcohol may further reduce blood pressure, causing dizziness or other symptoms.

Surgery and general anaesthetics Verapamil may need to be stopped before surgery. Consult your doctor or dentist.

PROLONGED USE

Rarely, gynaecomastia (breast enlargement in men) or enlargement of the gum tissues may occur with long-term use.