If additional doses are necessary, they should be taken at 5-minute intervals, for a maximum dose of #1.2 mg within 15 minutes. During this timeframe, if relief does not occur, Fihn et al Stable Ischemic Heart Disease: Full Text e409 the patient should seek immediate medical attention. These products are also effective for prevention of effort-induced angina when administered 5 to 10 minutes before activity, with relief lasting approximately 30 to 40 minutes. The tablets must be kept in the manufacturer s bottle (loss of potency can occur in a few hours if out of the bottle) and should be stored in a cool, dry place but should not be refrigerated. The tablets should not be used 6 to 12 months after opening the bottle. Patients usually are able to detect when tablets have lost potency by the absence of a burning sensation beneath the tongue. Nitroglycerin ointment also may be used for short-term relief of angina. Applied to the chest in doses of 0.5 to 2.0 inches, with a delay in relief of 30 minutes, this preparation can be effective for 4 to 6 hours. Absorption can be increased by rotating the application sites, covering the paste with plastic, or not applying the ointment continuously (ie, maintenance of a nitrate-free interval).879 881 All short-acting nitrate preparations can cause hypotension, sometimes severe, and headaches that limit adherence to these agents. Patients should be counseled about these ad- verse effects and advised to seek medical treatment if syncope or resistant chest pain occurs. The ointment can cause permanent discoloration of clothing. 