BMA Concise Guide to Medicine & Drugs

Isosorbide Dinitrate/Mononitrate

Brand names [dinitrate] Angitak, Cedocard, Isodur, Isoket, and many others; [mononitrate] Chemydur, Elantan, Imdur, Isib, Ismo, Isodur, Isotard, Modisal, Monomax, Monomil XL, Monosorb, and many others

Used in the following combined preparations None

QUICK REFERENCE

Drug group Nitrate vasodilator and anti-angina drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed No (some preparations); yes (other preparations and injection)

Available as generic No

GENERAL INFORMATION

Isosorbide dinitrate and mononitrate are vasodilator drugs similar to glyceryl trinitrate. They are usually used to treat patients suffering from angina, and are also used in some cases of heart failure.

Unlike glyceryl trinitrate, however, both isosorbide dinitrate and isosorbide mononitrate are stable and can be stored for long periods without losing their effectiveness.

Headache, flushing, and dizziness are common side effects during the early stages of treatment; small doses of the drug given in the initial stages can help to minimize these symptoms. The effectiveness of isosorbide dinitrate and mononitrate are reduced if the drugs are taken continuously. To minimize this, formulations are often designed to give a drug-free period when taken once daily.

INFORMATION FOR USERS

Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Dinitrate Tablets, SR tablets, injection, spray. Mononitrate Tablets, SR tablets, SR capsules.

Frequency and timing of doses Relief of angina attacks As required (spray). Heart failure/prevention of angina 2–4 x daily; 1–2 x daily (SR tablets, capsules).

Adult dosage range Prevention of angina 30–120mg daily (in divided doses). Treatment of angina 1–3 doses under the tongue (spray). Heart failure 40–240mg daily (in divided doses).

Onset of effect 2–3 minutes (spray); 20–30 minutes (SR tablets, capsules).

Duration of action 4–6 hours (dinitrate tablets); 8–10 hours (mononitrate tablets); up to 17 hours (SR tablets); up to 10 hours (SR capsules); 1–2 hours (spray).

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; stopping the drug may lead to worsening of the underlying condition.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large doses may cause dizziness, headache, or shortness of breath. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

Flushing and headache are common adverse effects. The most serious adverse effect is excessively lowered blood pressure, which may cause dizziness, fainting, or weakness and may need to be monitored regularly. If these symptoms occur or if your heart rate is unusually fast or slow, discuss with your doctor. Regular use of the drug and/or dosage adjustment may improve initial adverse effects.

INTERACTIONS

Sildenafil, tadalafil, and vardenafil The blood-pressure-lowering effect of nitrates is significantly enhanced by these drugs; they should not be used together.

Antihypertensives A further lowering of blood pressure occurs when such drugs are taken with nitrates.

SPECIAL PRECAUTIONS

Be sure to consult your doctor or pharmacist before taking this drug if:

· You have long-term liver or kidney problems.

· You have any blood disorders or anaemia.

· You have glaucoma.

· You have low blood pressure.

· You have ever had a heart attack.

· You have an underactive thyroid.

· You have G6PD deficiency.

· You have had a recent head injury.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding Safety not established. Discuss with your doctor.

Infants and children Not usually prescribed.

Over 60 No special problems.

Driving and hazardous work Avoid such activities until you have learned how isosorbide dinitrate or mononitrate affects you because these drugs can cause dizziness.

Alcohol Avoid. Alcohol may further lower blood pressure, depressing the heart and causing dizziness and fainting.

PROLONGED USE

The initial adverse effects may disappear with prolonged use. The effects of the drug become weaker as the body adapts. This may be overcome by a change in the dose to allow a drug-free period during each day.