Angina Pectoris: Treatment

A. Treatment of Acute Attack
Sublingual nitroglycerin is the drug of choice; it acts in about 1-2 minutes. Nitrates decrease arteriolar and venous tone, reduce preload and afterload, and lower the oxygen demand of the heart. Nitrates may also improve myocardial blood flow by dilating collateral channels and, in the presence of increased vasomotor tone, coronary stenoses. As soon as the attack begins, one fresh tablet is placed under the tongue. This may be repeated at 3- to 5-minute intervals. The dosage (0.3, 0.4, or 0.6 mg) and the number of tablets to be used before seeking further medical attention must be individualized. Nitroglycerin buccal spray is also available as a metered (0.4 mg) delivery system. It has the advantage of being more convenient for patients who have difficulty handling the pills and of being more stable. Nitroglycerin should also be used prophylactically before activities likely to precipitate angina. Pain not responding to three tablets or lasting more than 20 minutes may represent evolving infarction, and the patient should be instructed to seek immediate medical attention.

B. Prevention of Further Attacks
1. Aggravating factors - Angina may be aggravated by hypertension, left ventricular failure, arrhythmia (usually tachycardias), strenuous activity, cold temperatures, and emotional states. These factors should be identified and treated or avoided where possible.

2. Nitroglycerin - Nitroglycerin, 0.3-0.6 mg sublingually or 0.4-0.8 mg translingually by spray, should be taken 5 minutes before any activity likely to precipitate angina. Sublingual isosorbide dinitrate (2.5-10 mg) is only slightly longer-acting than sublingual nitroglycerin.

3. Long-acting nitrates - A number of longer-acting nitrate preparations are available. These include isosorbide dinitrate, 10-40 mg orally three times daily; isosorbide mononitrate, 10-40 mg orally twice daily or 60-120 mg once daily in a sustained-release preparation; oral sustained-release nitroglycerin preparations, 6.25-12.5 mg two to four times daily; nitroglycerin ointment, 6.25-25 mg applied two to four times daily; and transdermal nitroglycerin patches that deliver nitroglycerin at a predetermined rate (usually 5-20 mg/24 h). The main limitation to chronic nitrate therapy is tolerance, which occurs to some degree in most patients. The degree of tolerance can be limited by utilizing a regimen which includes a minimum 8- to 10-hour period per day without nitrates. Isosorbide dinitrate given three times daily, with the last dose after dinner, is the most commonly used approach, but longer-acting isosorbide mononitrate is becoming more popular. Because it is the active metabolite of the dinitrate, isosorbide mononitrate has more consistent bioavailability. Transdermal nitrate preparations should be removed overnight in most patients.