It is possible that fasting is required before the procedure. You will receive instructions from your doctor on how long you should withhold food and liquids. During pharmacologic myocardial perfusion scans, theophylline and caffeine-containing medications must be avoided. The consumption of coffee, even decaffeinated coffee, is prohibited since it contains caffeine. It is possible for asthma medications to contain theophylline. Ensure that your doctor is aware of your asthma. 48 hours before the test, theophylline medications should be stopped. Food and drinks containing caffeine and all medications that contain caffeine should be held for 12 to 24 hours. A number of over-the-counter medications contain caffeine, including Anacin, Excedrin, and NoDoz. Specific instructions should be obtained from your physician.