Caffeine has been an ingredient in both OTC and prescription drug products for many decades. Medical research has demonstrated that caffeine is a safe and effective addition to the combination of acetaminophen and aspirin in medications for relief of pain when used at the appropriate dose. The acetaminophen-aspirin-caffeine combination is approved and clinically proven to be effective and well-tolerated for the relief of both migraine and tension-type headache pain, but as always, you should follow package directions. The recommended dose of this product contains about as much caffeine as a cup of coffee. Limit the use of caffeine-containing medications, foods, or beverages while taking this product because too much caffeine may cause nervousness, irritability, sleeplessness, and, occasionally, rapid heartbeat.