BMA Concise Guide to Medicine & Drugs

Dipyridamole

Brand names Persantin, Persantin Retard

Used in the following combined preparation Asasantin Retard

QUICK REFERENCE

Drug group Antiplatelet drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Dipyridamole was introduced in the late 1970s as an anti-angina drug to improve the capability of people with angina to exercise. More effective drugs are now available, but dipyridamole is still prescribed as an antiplatelet drug. It acts by reducing the ability of platelets to stick to each other and to blood vessel walls, which reduces the likelihood of clots forming. This is especially important in people who have had a stroke or transient ischaemic attacks (TIAs) or have undergone heart valve replacement surgery. Dipyridamole is usually given with other drugs such as warfarin or aspirin. The drug can also be given by injection during certain types of diagnostic test on the heart.

Side effects may occur, especially during the early days of treatment. If they persist, your doctor may advise a reduction in dosage.

INFORMATION FOR USERS

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

How taken/used Tablets, capsules, MR capsules, liquid, injection (for diagnostic tests only).

Frequency and timing of doses 3–4 x daily, 1 hour before meals (tablets, capsules, liquid). 2 x daily with food (MR capsules).

Adult dosage range 300–600mg daily (tablets, capsules, liquid); 400mg daily (MR capsules).

Onset of effect Within 1 hour. Full therapeutic effect may not be reached for 2–3 weeks.

Duration of action Up to 8 hours. Up to 12 hours (MR capsules).

Diet advice None.

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

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; withdrawal of the drug could lead to abnormal blood clotting.

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

POSSIBLE ADVERSE EFFECTS

Adverse effects are rare. Possible symptoms include nausea, stomach upsets, diarrhoea, headache, and flushing. Discuss with your doctor if these are severe or if the drug causes dizziness and fainting. If a rash, breathing difficulties, or swollen lips occur, stop taking the drug and consult your doctor promptly. In rare cases, dipyridamole may aggravate angina.

INTERACTIONS

Anticoagulant drugs The effect of these drugs may be increased by dipyridamole, thereby increasing the risk of uncontrolled bleeding. The dosage of the anticoagulant may need to be adjusted accordingly.

Adenosine should not be given to somebody who is taking dipyridamole as the combination can cause a serious drop in blood pressure.

Antihypertensives Dipyridamole may increase the effect of these drugs.

Cholinesterase inhibitors Used to treat myasthenia gravis, the effect of these drugs may be reduced by dipyridamole.

Antacids may reduce the effectiveness of dipyridamole.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have low blood pressure.

· You have a blood clotting disorder.

· You suffer from migraine.

· You have angina or heart valve problems.

· You have myasthenia gravis.

· You have had a recent heart attack.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. 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 Reduced dose necessary.

Over 60 No special problems.

Driving and hazardous work Avoid such activities until you have learned how dipyridamole affects you because the drug may cause dizziness and faintness.

Alcohol Avoid until you have learned how dipyridamole affects you because the drug may cause dizziness and faintness when taken with alcohol.

PROLONGED USE

No known problems.