ISORDIL

What it is

Isordil is isosorbide dinitrate, available as sublingual tablets containing 5 mg and oral tablets containing 10 mg, 30 mg or 40 mg of the active ingredient. Isosorbide dinitrate is an organic nitrate ester. It has a slower time to onset of action but longer duration of action than glyceryl trinitrate.

Approved indications

Sublingual formulation: — Prevention and treatment of angina pectoris and myocardial ischaemia due to ischaemic heart disease. — Acute and chronic left ventricular failure, either alone or as part of the syndrome of congestive heart failure to improve cardiac performance and stabilise the patient's condition. Oral formulation: — Relief of angina pectoris in prophylactic treatment of angina pectoris and myocardial ischaemia due to ischaemic heart disease. — Aid in the management of left ventricular failure, either alone or as part of the syndrome of congestive heart failure.

Dosing overview

A nitrate-free interval of at least 8 hours every 24 hours is recommended to prevent tolerance.

Key safety warnings

Isordil may cause paradoxical side effects in sensitive patients, which may increase ischaemia and may even lead to extension of myocardial damage and advanced congestive heart failure. Care must be taken to avoid the significant risk of a precipitous fall in blood pressure, particularly in patients with severe coronary or cerebral atherosclerosis or renal insufficiency. Isosorbide dinitrate may cause faintness if taken while standing or sitting, and this hazard is of particular importance in patients not previously treated with the drug. Nitrate dependence is a potentially serious problem. In terminating treatment of patients with angina who are receiving isosorbide dinitrate both the dosage and frequency of administration should be gradually reduced over a period of two weeks to prevent potential withdrawal reactions such as increased frequency of angina attacks. Isosorbide dinitrate has been reported to induce haemolytic anaemia in glucose-6-phosphate dehydrogenase-deficient patients. Oral isosorbide dinitrate tablets should not be administered for rapid relief of the pain of angina. Sublingual administration of isosorbide dinitrate tablets offers relatively fast relief.

Contraindications

Confirmed diagnosis of isolated right ventricular failure, particularly in the setting of acute myocardial infarction and due to dominant right ventricular infarction. Known hypersensitivity to isosorbide dinitrate or a known idiosyncratic reaction to organic nitrate drugs. Hypotension or uncorrected hypovolaemia, as the use of isosorbide dinitrate in such states could produce severe hypotension or shock. Constrictive pericarditis and pericardial tamponade. Severe anaemia or arterial hypoxaemia. Intracranial hypertension. Concomitant use with drugs for erectile dysfunction (phosphodiesterase inhibitors) such as sildenafil, tadalafil or vardenafil is contraindicated because concomitant use can cause severe hypotension, syncope or myocardial ischaemia. Acute circulatory failure (shock, vascular collapse). Aortic or mitral valve stenosis and disease associated with raised intra-cranial pressure, for example following head trauma and including cerebral haemorrhage. Hypertrophic obstructive cardiomyopathy (HOCM).

PBS listing

Isordil 5 mg sublingual tablet is listed on the PBS as an unrestricted item with an ex-manufacturer price of A$3.50.

Regulatory history

Isordil sublingual 5 mg tablet was first listed on the ARTG on 19 August 1991. Isordil 10 mg, 30 mg and 40 mg tablets were first listed on the ARTG on 22 July 1992.